NTT Technical Review

January 2022 Vol. 20 No. 1

Front-line Researchers
 Toshikazu Hashimoto, Senior Distinguished Researcher, NTT Device Technology Laboratories
Rising Researchers Yosuke Todo, Distinguished Researcher, NTT Social Informatics Laboratories
Feature Articles: NTT Research: Open Collaboration to Upgrade Reality
 Opening Up about Our Collaboration Strategy
 Making the Blockchain Ecosystem Secure, Scalable, and Sustainable
 The Future of Problem Solving: The Coherent Ising Machine Approach Bio Digital Twin Research Update
 A New Lab Exploring Emergent Matter from Light
Feature Articles: Research and Development of Security in the IOWN Era
 Security as Driving Force of the Future Secure Optical Transport Network
 Cryptographic Circuit Technology Consisting of Optical Logic Gates
 Trusted Data Space for Creating Value from Data in a Chain Reaction Manner
Feature Articles: Olympic and Paralympic Games Tokyo 2020 and NTT R&D—Technologies
that Colored Tokyo 2020 Games Initiatives toward a New Way of Experiencing and Supporting the Torch Relay
 Torch Relay Commemorative Photography × Ultra-realistic Communication Technology
Kirari!
 Direction for Supporting Torchbearers × Swarm Communication Control Technology
 Stage Production for Celebration of Torch Relay × Ultra-realistic Communication Technology
Kirari!
 Torch Relay Regional Event × Voice-recognition Communication Technology
Feature Articles: Olympic and Paralympic Games Tokyo 2020 and NTT R&D—Technologies
that Supported Tokyo 2020 Games High-efficiency Wi-Fi Technologies
 Network Security
Global Standardization Activities
 Report on ITU-T SG2 Standardization of Telecommunication Numbering
External Awards/Papers Published in Technical Journals and Conference Proceedings

Front-line Researchers

Think about Your Definition of aGood Idea and Believe in Your Idea
Toshikazu Hashimoto
Senior Distinguished Researcher,
NTT Device Technology Laboratories
Abstract
Today, everything is digitalized. In the creative process, however, not only digital thinking but also analog thinking, which
captures events as they are, is considered important. Toshikazu
Hashimoto, a senior distinguished researcher at NTT Device
Technology Laboratories, is researching and developing opticalcircuits to enable new information processing using the analog
characteristics of light. We interviewed him about the progress of
his research activities and his attitude as a researcher.
Keywords: optical circuits, planar lightwave circuit, quantum
teleportation

Optical circuits for new information processing
by manipulating light waves—Tell us about the research you are currently working on.
I am researching optical circuits that enable a new
type of information processing by manipulating lightas waves. What I mean by “manipulating light aswaves” is to use the analog nature of light. In the caseof digital computation, for example, it is necessary to
use two values (bits), “1” or “0,” in a sequence suchas “010110...” to represent a number. In analog computation, however, it is only necessary to use a single
value, for example, “0.10110...” (i.e., the number
itself). If we use analog computation skillfully, we
may be able to conduct calculations faster, reduce thenumber of calculation steps, and save the labor
involved in calculations. However, as you can easily
imagine, when a number is represented by an analog
signal such as light intensity, the last digit after the
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Vol. 20 No. 1 Jan. 2022

decimal point would lose its information due to noise.
Information processing using analog computation,
which is susceptible to noise, is difficult to scale up
and has not been applied to computing.
Despite the above-mentioned drawback, for computations to extract properties independent of minor
differences, as is the case with artificial intelligence(AI), or computations by using the superposition ofmany quantum states while suppressing noise in thequantum state, as required with quantum computers,
analog computation is more significant because it ispossible to execute many calculations at once, albeit
at the expense of accuracy, or manipulate quantum
states without destroying them. In other words, rather
than exceeding the limit of digital-information-processing capacity by using analog computation, we
carry out a different type of processing using analog
computation for information with different quantityand quality than before. This is the “new” information processing using light waves that I am aimingfor. To make such information processing a reality,
1Front-line Researchers

Optical-waveguide circuit

Application example: High-performance
universal optical quantum circuit(a) Light paths fabricated through microfabrication

Multi
mode

Single mode

Optical circuit with complicated patternSingle mode

Application example: Lossless multi-mode
wavelength multiplexers/demultiplexers(b) Example of an optical circuit device that controls light waves (also using scattered light)

Fig. 1. Newly designed, ultra-low-loss optical device technology.

we are proceeding with research and development(R&D) with a focus on the following two technologies.
The first technology is newly designed, ultra-lowloss optical device technology (Fig. 1). It might seem
contradictory to what I said earlier, but as noise
becomes lower, the calculation performance
improves, so the first step is to minimize loss—whichconstitutes noise—in an optical circuit as much as
possible. Therefore, we are working on a new device
design that enables significantly reducing the loss andsignal processing by capturing the light scattering of
the optical circuit that causes the loss. The opticalcircuit technology that I am researching targets optical fiber communications, and I have been pursuing
low-loss characteristics so that the optical signal does
not weaken. However, I am aiming for technologythat reduces losses by an order of magnitude andenables large-scale circuits and high-performance
optical circuits.
The second technology is light-wave computing
technology, which uses light waves for computations(Fig. 2). The challenge is to devise a computational
method for exploiting the advantages of light asphysical light. We are proposing light-wave information-processing technology using optical device techNTT Technical Review

Vol. 20 No. 1 Jan. 2022

nology. To develop the world’s first and highest-performance computing technology using light waves,
we are attempting to demonstrate the basic operationof optical information processing using technology
based on the light paths (optical waveguides) in current devices.
Of course, lowering the loss of optical circuits alsoreaches a limit, and electrical control is essential to
fully use light waves; accordingly, it is important tocreate new optical circuit technology by combining
the features of both digital and analog computations.
One example application of this new type of information-processing technology using light waves is alarge-scale, fault-tolerant universal optical quantum
computer, which is expected to be developed around2050. A quantum computer capable of large-scale,universal computation is expected to enable thedevelopment of innovative materials and the designof chemical reactions that have been difficult to carryout with conventional supercomputers. It is also
expected to contribute to solving global issues such asenergy problems. As a participant in one of theMoonshot Research and Development Programs of
the Japan Science and Technology Agency, whichstarted in 2020, we are developing optical-circuit
device technology for quantum information processing
2

Front-line Researchers

Manipulation of quantum statesby using optical circuits
Squeezed light 1

90 deg.

Squeezed light 2

A circuit that manipulates quantum stateswith waves of light(a) Continuum-quantum optical quantum information-processing circuit (quantum teleportation circuit)

Weighting by optical circuit m(t)Output m(t)u(t)Input u(t)Circuit that executes time-division multiplexing andweighting using the frequency of light(b) Optical-frequency-domain-weighted up-sampling processing circuit

Fig. 2. Example of light-wave computing technology.

to enable a large-scale, fault-tolerant and universal
quantum computer that exploits the properties of light
as a wave and can operate at room temperature.
—It is fascinating that your research on optical circuit technology could contribute to achieve largescale quantum computers. Can you tell us about oneof your achievements in other applications?
The optical circuit that I am researching is called aplanar lightwave circuit (PLC). As a component technology for optical fiber communications, a PLC integrates an optical-waveguide circuit (namely, a path oflight) on a silicon substrate. The application of PLC
includes optical branch circuits and wavelength multiplexers/duplexers. Developing PLC technology tocreate optical circuits with even higher performance
was the essence of my research. This high-performance optical circuit technology can control lightwith wavelengths less than half that of the light used
for optical fiber communications (visible light). It istherefore being applied not only to optical computation but also to ultra-compact RGB (red, green, and
NTT Technical Review

Vol. 20 No. 1 Jan. 2022blue) laser light sources for smart glasses. Semiconductor lasers using the three RGB primary colors are
beginning to be used in a variety of situations as single-color lasers; however, to combine them and create
an RGB light source, it is important to devise an
optical system (optical circuit) technology that uses
the characteristics of the laser light by means of interference and other phenomena. Conventionally, theoptical system was made up of lenses and mirrors,
which are bulky and difficult to assemble. We havetherefore applied our visible-light PLC technology
for those parts and created the world’s smallest optical system that forms the basis of an ultra-compact
light-source module that fits in the temples of smart
glasses.
Making sure that the limits of my imagination do
not become the limits of my research—How do you find research themes?
Optical circuit technology—which is the basis of
my research—has matured as a device technology for3

Front-line Researchers

optical fiber communications, so it can be said that itis difficult to propose new ideas. Therefore, I started
to think that what type of light to input into an opticalcircuit is more important than what type of opticalcircuit is possible. This way of thinking is the same as
I mentioned at the beginning of this interview, namely, it is important to know what kind of information tohandle to take advantage of the characteristics ofanalog computation. By inputting visible light, which
has a different wavelength from that used for opticalcommunications, into an optical circuit, we would be
able to consider applications such as RGB lightsources. Also, by devising ways to put information on
optical signals, analog computation with optical circuits becomes possible. We might also be able to create an optical quantum computer by inputting quantaof light (photons) into an optical circuit. I believe that
inputting new light into an optical circuit is the sourceof creating a new optical circuit.
To foster different perspectives, I am paying attention to the trends of deep-tech ventures involved inAI, quantum computers, and so on. Although it is a
mixture of good and bad, the ability of such venturecompanies to quickly commercialize basic technology (such as AI and quantum computers) is remarkable. Collaboration is also important because throughcollaboration, it will be possible to apply the opticaldevice technology we have developed thus far tocompletely different fields. I have been greatly stimulated by collaboration with other researchers andcompanies, which is true joy of research.
—Do you feel that you have any advantage as a
researcher working at NTT laboratories? In addition,
could you tell us about the attitude that you value inyour research activities?
I think that various applications and collaboration
are possible only with outstanding optical circuit
technology that is difficult for others to imitate. The
optical-component technology of the research laboratory to which I belong represents research results
accumulated for half a century. With such a foundation, adding a little more value or doing somethingslightly different will lead to top-notch research
results. (Of course, there have been many cases inwhich our approach has not worked.) We also have afull range of research facilities that are necessary for
manufacturing, and such an environment is a hugeadvantage in regard to advancing device research. To
put that another way, I believe that NTT researchers
have the mission to develop the technologies that we
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have developed thus far and implement them in society. Through such efforts, we will be able to consolidate various technologies and create the direction oftechnology trends.
Of course, it is not possible to conduct research by
only using the advantages of our laboratories; youneed to create value on your own accord. One of themost important points that I keep in mind is to makesure that the limits of my imagination do not become
the limits of my research. For example, the study of
optical circuits deals with the natural phenomenon of“light.” Natural phenomena are far beyond my imagination, and many unexpected things can happen. I
think it is important to start your research with themindset “It would be great if that happened” insteadof “This is a natural phenomenon, so anything otherwise cannot happen.” The design method shown in
Fig. 1(b) was developed on the basis of this mindset.
That is, by using light scattering, we can design optical circuits with desired characteristics. The conventional idea behind optical circuits is to minimize as
much scattering as possible because scattering usually results in loss. Instead of adopting that mindset asa starting point, we devised the design method shownin the figure by first thinking about how to create an
optical circuit with the desired characteristics. Even if
you take this attitude, it does not mean it is always theright way; even so, I think that is okay. I believe that
it is okay to make mistakes without hesitation because
natural phenomena will correct our wrong ideas after
we conduct calculations and experiments. Instead ofthinking about what is correct, it is important to think
hard about what you wish would happen.
First, let’s consider the definition of a“good idea”—What are some of the challenges you face as a
researcher?
It is normal for research to go wrong and forresearchers to struggle, so I tend to think positively
and try to persevere. I think that has always been thecase. My first research theme was hybrid optical integration of optical waveguides and semiconductor
lasers, which is a technology for assembling opticalcomponents. Since such integration involved combining multiple optical components, it was necessarythat all the components were aligned and fixed properly. At first, it looked like it would be easy to do it in
my mind because it was like putting together building
blocks; however, it did not go well, and I struggled for4Front-line Researchers

over a month. I researched the cause of the problem,
thought about it thoroughly, and corrected it. When I
was finally able to assemble all components properly,
I let out a shout with tears swelled up, and I would
have surprised anyone if they had been around.
Although it may have been a minor success, I remember how happy I was to think that I was the first person in the world to know that I have achieved this.
Since having such experiences, I have come tobelieve that rather than just trying to do what you can
do to break free of difficulties, it is better to face thosedifficulties and think carefully about them. To do that,
it is important to be persistent in thinking things
through and optimistic in finding the right way forward. If that approach still does not solve the problem, I try not to get stuck by changing my interpretations or assumptions and stay optimistic. For example, I try to find value and meaning in work that I
dislike by viewing it from a different perspective. I
believe that there is a lot to learn by doing so, and by
expanding my work in this way, I will be able to meet
more people and come into contact with a wider variety of ideas.

er about my ideas for finding research themes. I thinkthat person was just trying to come up with a newresearch theme. I answered, “The idea itself is natural, and you will come up with some sort of idea
soon,” and I still wonder if that was good advice.
Now, I think I would answer, “First, think about thedefinition of a ‘good idea’.” The definition of a goodidea varies from person to person; for example, agood idea may be one that can make money frompatents or can be cited in many other studies. My
definition of a good idea is one that I like. If you
deeply like an idea, you can discuss it with otherswith passion and can overcome difficulties to make it
happen. If you define ideas in this way, I think it isimportant to think things through in your own way
and have your own conviction, even if you cannot
prove or explain the idea fully; in other words, believe
in your ideas, without worrying about the results orwhat people around you think.
My message to young researchers would be that if
you keep your original intentions in mind and passionately discuss good ideas with others, you will
surely enjoy your research.

—Would you say a word to future generations ofresearchers?
I joined NTT and was assigned to a research laboratory, and since then I have been mostly engaged in
R&D. Along the way, there were times when I did notknow what I wanted to do as a researcher, and sometimes I felt that research was “just a job.” More than
20 years have passed, and sometimes I look back on
those early days. I feel that I have come to understandthe joy of research a little more by going back to myoriginal intentions and approaching my research fromthat standpoint. I think it is very effective to go backto your beginning from time to time to look at yourself objectively.
In the past, I have been asked by a young research-

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Interviewee profile
Toshikazu Hashimoto received a B.S. and M.S.
in physics from Hokkaido University in 1991 and1993. He joined NTT Photonics Laboratories in1993 and has been researching hybrid integrationof semiconductor lasers and photodiodes on silica-based PLCs and conducting theoreticalresearch and primary experiments on the wavefront-matching method. He is a member of theInstitute of Electronics, Information andCommunication Engineers and the PhysicalSociety of Japan.

5

Rising Researchers

Pioneering a Next-generation Basic
Theory and Purpose-specific
Cryptography toward the Future of
Symmetric-key Cryptography
Yosuke Todo
Distinguished Researcher, NTT Social
Informatics Laboratories
Abstract
Cryptography is an essential technology for secure information
communications. Types of cryptography include public-key cryptography and symmetric-key cryptography. Here, we’re talking to
Yosuke Todo, a distinguished researcher who is working on building a basic theory for symmetric-key cryptography and researching purpose-specific cryptography.
Keywords: symmetric-key cryptography, purpose-specific cryptography, tamper resistance

Symmetric-key cryptography: Using a common
key for encryption and decryption—What is symmetric-key cryptography?
In information communications, hiding and protecting your information hinges on encryption.
Encryption can be thought of as the “gears,” thesmallest parts composing the larger system of security. A missing or broken gear can affect the entire
system, and may lead directly to safety issues. As
such, you could think of cryptography research as
pursuing the creation of highly secure, high-performance gears.
Cryptography uses separate keys for encryption
and decryption, and within that there is public-key
cryptography, which uses a public encryption key,and symmetric-key cryptography, which uses the
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same key for encryption and decryption (Fig. 1).
Public-key cryptography can be compared to a padlock on a shed. Anyone can lock a padlock, but theyneed a key to open it. Public-key cryptography is amechanism where there are many distributed “padlocks,” but they can only be opened by the personwith the corresponding key. To reproduce this digitally, the system is contrived to make use of mathematical problems that are difficult to solve, such as
integer factoring, discrete logarithmic problems, andlattice problems. And so, just as with solving these
difficult math problems, encryption and decryption
require complex computer-based calculations.
On the other hand, symmetric-key cryptography
can be compared to a safe in a hotel room. You entera particular number when you lock it, and then enter
the same number again to unlock it. Unlike publickey cryptography, symmetric-key cryptography is
6

Rising Researchers

Public-key cryptography

Symmetric-key cryptography• Like a padlock• Separate keys used forencryption and decryption• Complex math calculations
required• Like a safe
• Same key used for encryption
and decryption• Created through efficient
calculations

Fig. 1. Public-key cryptography and symmetric-key cryptography.

based on the concept of making efficient calculations
based on the environment in which it is used. As aresult, symmetric-key cryptography is 100 to 1000
times faster than public-key cryptography, and so iswell suited for encrypting large amounts of information.
I work with symmetric-key cryptography, and mycurrent research topics are “A Basic Theory for Nextgeneration Symmetric-key Cryptography” in themedium to long term, and “Purpose-specific Cryptography and Solutions” in the short, medium, andlong term.
—What kind of research is “A Basic Theory for Nextgeneration Symmetric-key Cryptography”?
Unlike public-key cryptography, symmetric-key
cryptography isn’t based on difficult mathematicalproblems, so there are important questions about
whether or not the encryption itself is really secure,and how to ensure that security.
For example, the Caesar cipher, used by ancient
Roman politician Julius Caesar, could be considereda symmetric-key cipher that shifts each letter of theunencrypted text (the plaintext) a certain number of
positions in the alphabet; however, it is very easily
attacked. In general, symmetric-key ciphers can becreated by anyone, but the drawback is that they canquickly be broken by someone without any special
equipment. Nearly half a century has passed since theemergence of cryptographers specializing in symmetric-key cryptography, and nowadays there aremany ciphers that are considered difficult to crack.
However, even if you can ensure a cipher is secure bytesting it with various attacks, you cannot guarantee
it will be safe against the attempts of a future cryptographical genius.
The basic theory of symmetric-key cryptography is
to discover new methods of attack and analysis, andto explore measures that ensure absolute safety
against existing methods of attack and analysis. Of
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course, it’s hard to create truly secure encryption, andin practice it’s more like working toward encryptionthat is absolutely secure against a particular kind of
attack, going some way to ensuring overall security.
In a way, this is the defining goal of all cryptographers, and ever since joining the company I have been
focusing on an attack method known as “integral
cryptanalysis,” and studying the complexity of cryptography—phrased more technically, I have been
researching the vulnerabilities of attacks that involve
accurately estimating algebraic degrees. And to put it
simply, it’s research that aims to get to grips with theupper bounds of the security of an encryption: knowing that if the encryption is attacked, the security will
be lower than a certain level at best. As a result, in2015 I was the first Japanese person to receive theBest Paper Award at Crypto, the premier international
conference in the field of encryption, and in 2020 I
became the third ever person to win the award twice.
Recently, I have also been working on research where
the lower bounds of the security are considered, i.e.,
where you know that security is higher than a certain
level, at least.
—What kind of research is “Purpose-specific
Cryptography and Solutions”?
We compared encryption to gears earlier, and gears
are generally manufactured without the creators
knowing where the gears are going to be used. We’retherefore trying to create gears that are as safe andhigh-performance as possible. However, of course
there will be special gears out there that are only used
for certain products.
And like these gears, the same approach can beused in creating custom-made ciphers to suit specificapplications, which is the topic of my research on“Purpose-specific Cryptography and Solutions.” Inrecent times, Internet of Things devices and smart
cards are increasingly handling sensitive data such as
personal information, and so more devices require
7

Rising Researchers

encryption. In response to this, I am working on lightweight encryption that can be implemented on devices with less computing power than personal computers.
Designing purpose-specific, custom-made ciphers—In what fields can you use symmetric-key cryptography research?
My research into “A Basic Theory for Next-generation Symmetric-key Cryptography” will potentiallycreate a generic standard cipher; It will combine
research from the perspective of the attacker, understanding the upper bounds of the security of an
encryption, and research from the perspective of thedesigner, understanding the lower bounds of theencryption’s security, and ensuring high security of atleast a certain level. The foundation of today’s
encryption was developed 40 years ago, so if a newgeneric standard cipher is built, it could become thefoundation for the next generation of encryption,
increase security, and find applications in all sorts offields.
One type of purpose-specific cryptography is ultralow-energy encryption, which is expected to be useful in the medical field. For example, consider a
medical device, implanted in a person, that collects
and transmits a variety of vital data to a medical institution. Such sensitive vital data should, of course, be
encrypted to prevent plagiarism and tampering. However, it is quite the ordeal to have surgeries every timethe device’s battery is depleted. So the device needs
to run for a long time on a small battery, and theencryption also needs to consume as little energy as
possible.
Previous approaches to cryptography have beenquite all-purpose, balancing all elements and improving overall performance. However, if you make acompromise in one area you can ramp up the performance in another to suit the application, and this iswhat I aim to do with purpose-specific cryptography.
In addition, various types of encryption may be possible depending on the application. For example,
minimizing the circuit size using small sensors, orminimizing the communication latency between thecentral processing unit and the memory.
I think it would be interesting to ask organizations
that deal with confidential data and personal information about how their data are used, and then create
new, specific encryption methods to meet thoseneeds.
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—What are your plans for future research?
First, we are aiming for ultimate tamper resistance.
Current cryptographic safety studies assume that theplaintext and ciphers will be seen by third parties, butthat the intermediate stage, during the actual encryption process, will not be seen. However, there havebeen instances of a type of attack called a “sidechannel attack,” which figures out encryption keys
using information such as the power consumption of
hardware and electromagnetic wave leakage. It canbe even more serious in the case of software, withinstances of reverse engineering being used to extract
the algorithms in the encrypted portion of an app
downloaded to a smartphone. The strength to withstand these attacks on the encryption process is called“tamper resistance.”
Given that the encryption process itself is being
exposed, we are now focusing on research areas suchas “white box cryptography” and “gray box cryptography” that, while they may not currently be 100%
secure, are safe in the event of an encryption algorithm being leaked.
—What is special about your current research environment?
NTT’s strength is that it has many talented people.
When I joined the company ten years ago, I didn’tknow about symmetric-key cryptography, how towrite papers, or how to conduct research, but I
received a lot of guidance from my senior colleagues.
We do have to create new research fields ourselves,
but when you’re just getting to grips with the basics
of research, you have the advantage that you canincrease the speed and quality of your learning byfollowing the paths skillfully carved out by your8

Rising Researchers

senior colleagues, rather than by studying alone.
I also think it’s valuable to have several distinguished researchers in the same laboratory working
on the common field of encryption. I think that having multiple distinguished researchers working in thesame area will create diversity in research, which willin turn lead to the creation of new technologies.
Above all, young researchers who are under the guidance of distinguished researchers will also be promoted if they get important results, which I think will
be encouraging for them.

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Interviewee profile
Yosuke Todo joined NTT in 2012 as a master’s
graduate, and worked for NTT Secure Platform
Laboratories. He received the Crypto Best Paper
Award in 2015, completed a Ph.D. at Kobe
University in 2017, was a visiting researcher at
Ruhr-University Bochum from July 2019 to
October 2020, and received the Crypto Best
Paper Award in 2020. He has been a distinguishedresearcher at NTT Secure Platform Laboratories
since April 2021, and is currently a distinguishedresearcher at NTT Social Informatics Laboratories.

9Feature Articles: NTT Research: Open Collaboration toUpgrade Reality

Opening Up about Our Collaboration
Strategy
Hideaki Ozawa
Abstract

There are several means of conducting scientific research. Corporations have traditionally adopted aproprietary approach. The academic world, by contrast, conducts research in a more open and collaborative manner. This article compares these two approaches in the context of basic and applied research;
explains why NTT Research, a private company, has adopted an Open Lab model; and reviews how thisis working out in practice.
Keywords: Open Lab, research strategy, research community

1. Proprietary vs. open models
Until a few decades ago, corporations typicallyconducted research using internal resources alone.
One classic example was Bell Telephone Laboratories. Originating from engineering departments
within the American Telephone & Telegraph (AT&T)
and Western Electric companies, and now known as
Nokia Bell Labs, this famous research organization
was responsible for many breakthrough technologies,
including the electronic transistor. These results,
including thousands of patents, were the outcome ofbasic and applied physics research conducted by Bell
Labs’ employees. Another example on a smaller scale

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is that of a former Bell Labs engineer, Chester Carlson, who patented a dry photocopy technique known
as Xerography that he developed in his laboratory.
Each technology, the transistor and Xerography, grew
into very big businesses in the 20th century.
However, many companies in the U.S. are now
focusing on applied research for their products orservices, such as autonomous driving, artificial intelligence based on deep neural networking, etc., rather
than on basic research. Basic research has tended tobe the domain of universities, not corporations, andthis remains the case today. This kind of research has
the potential for various future products and services,
but these beneficial outcomes require very long leadtimes and the assumption of many types of risks.
In addition to established laboratories in Japan,
NTT founded NTT Research in the U.S. with thetransformational vision of “Upgrade Reality.” NTTbelieves exploring basic research is also a means tocreate brand-new business value in the future. In
theory, by hiring the right mix of scientists, NTT
Research could try to gain a monopoly on any new
knowledge acquired in this pursuit, along with therights of invention. However, the founders of NTT
Research chose another path. We realized that manyof the challenges facing our current and future generations are extremely complex and closely intertwined. For example, one of the goals of medical careis to enable patients to recover from illness and
10

Feature Articles

maintain their health more easily. Everyone has a different constitution, so we believe it is necessary toprovide precise medical care suited to the individual.
When we explore precise medical care, we need not
only medical and biological knowledge but knowledge related to drug discovery, sensing, big data analytics, treatment materials, etc. To achieve precise
medical care, we believe we need to improve upon
the accuracy of these technologies.
To gather as much insight, experience, and wisdom
as possible, as well as to manage our risk in precision
medical care and other research areas, we decided
that an Open Lab strategy was the better way to go.
This Open Lab approach is more akin to academic
and government-sponsored research, rather thancorporate research, which on the whole aims for
short-term product development. Research universities pursue scientific discovery in the open, withresults shared and evaluated by peers. Foundational
knowledge is often the common goal. Governmentdirected research may have more specific goals, but it
is also a collective effort for social benefit. The U.S.
Defense Advanced Research Project Agency(DARPA), famously responsible for creating theInternet by collaborating with several universities, isa case in point.
The NTT Research executive team and board havetaken the lead in establishing the vision “Upgrade
Reality,” and setting goals such as a cardiovascularbio digital twin and a quantum computing system
based on optical technologies. Our vision and goals
are connected to resolving parts of social problems,for instance: precise medical care through the bio
digital twin or drug discovery through a new kind ofquantum computing. Because our high aspirations
are beyond the reach of any single company, we haveadopted an Open Lab strategy that faces outward,
predominantly through joint research projects withother worldwide research organizations. We contribute our new knowledge, results, and findings in the
public as papers or as joint patents with collaborators.
We also see ourselves as a venue for discussion, seeking various viewpoints to expand upon the ideas ofany individual researcher.

munity expands, attracting developers of not only
core software but also applications. The knowledge
and ideas proposed by community members improves
the code, which in turn increases its value.
The Coherent Ising Machine (CIM) research groupwithin our Physics and Informatics Laboratories (PHI
Lab) has a comparable record. Starting with just several internal employees, within our first year the CIM
group gained eight joint research partners, covering
theoretical and hardware research of optical-based
quantum computers. In our second year, this hasgrown to 13 organizations and over 60 members,
including collaborators. We are now achieving new
breakthroughs as we gain employees and collaborators, including scientists who are researching CIM
applications, such as compressed sensing, drug discovery, and artificial/biological brain science.
Like the PHI Lab, our Medical and Informatics
Laboratories (MEI Lab) has a clear and visionary
lead product—the aforementioned bio digital twin, avirtual replica of individuals in cyberspace. In theinitial phase, we are focused on the cardiovascularsystem. The MEI Lab is also engaged in research on
implantable electrodes and remote sensing that cancapture many types of vital information from theactual human body. Like the PHI Lab, the MEI Lab
can subdivide its research, with collaborators taking
on parts of the agenda. The National Cerebral andCardiovascular Center in Japan and the Technical
University of Munich in Germany, for instance, havebecome key partners.
Measured in terms of contributions to leading academic conferences, our Cryptography and Information Security Laboratories (CIS Lab) has become aworld leader in its field. While the CIS Lab has established several joint research agreements, its members
also collaborate with peers on a less formal, topical

2. Open-source and NTT Research operations
In certain ways, our method resembles that of opensource software development. In that model, an individual or small community first approaches a coding
project with a vision and goal. When more developers
and users realize the value of the initiative, the comNTT Technical Review

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Feature Articles

basis. The cryptography team’s research is more academic and theoretical, whereas the blockchain team’s
work is more applied, with implications in law, privacy, and other practical concerns. Theoreticalresearch within cryptography is deepened by discussions between researchers who have the same interestin a target topic. It resembles the kind of small community that initiates an open-source project. Members of an open-source community might write codeand documents as their goal. Our CIS Lab researchers
write scientific papers.
Across all three labs, we might adjust our strategy
if some topics shift from basic research into productdevelopment. Regarding basic research, where discoveries should become public assets, the Open Lab
strategy is a sound method.
3. Open Lab requirements
To succeed, an Open Lab strategy needs to meetseveral requirements. Funding is key, as it can clearly

accelerate research activity. However, without a clear
vision, strong leadership, and an effective team, funds
are likely to be inefficiently distributed. Of all
requirements, vision is the most important.
About 40 excellent researchers have gatheredaround our “Upgrade Reality” vision over the past
two years. We hope to improve upon today’s “Reality,” addressing social and industrial problems thatface the current and next generations. With a clear
vision, the direction of research proceeds in the rightmanner. However, this is not necessarily without
detours, which are often associated with trial anderror. Basic research, especially involving multiple
laboratories, contains a natural element of surprise.
Therefore, we need to allow for some flexibility as
well. Because basic research involves unknown facts
and brand-new technology, it also carries risk. By
subdividing and distributing tasks, the Open Lab
strategy helps to manage that risk and increase thelikelihood of success.

Hideaki Ozawa

Chief Operations Officer and Chief Technology Officer, NTT Research, Inc.
He received a Ph.D. in engineering from the
Graduate School of Science and Technology,
Keio University, Kanagawa, in 1992. He joined
NTT in 1991. After engaging in research andpractical application of multimedia processing
technologies at NTT Human Interface Laboratories and Cyber Solution Laboratories, he joined
NTT WEST (seconded to Walkerplus, Inc.) in
2000, where he was involved in the provision of
local multimedia information. He then joined
NTT Resonant Inc. in 2004, where he worked on
the development and management of “goo”
Internet services including its search engine andthe establishment of mobile-search business andbecame head of the Search Business Division in
2011. After serving concurrently as president of
NTT Resonant Technology, Inc. from 2013, hebecame vice president, head of NTT Media Intelligence Laboratories in 2015 and head of the
Global Business Promotion Office at NTT TechnoCross Corporation in 2018. He assumed his
current position in June 2019.

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Making the Blockchain Ecosystem
Secure, Scalable, and Sustainable
Shin’ichiro Matsuo
Abstract

In place of the centralized computation of the Internet’s current architecture, blockchain could be used
to implement self-resilient or self-operating systems, as it upkeeps states with highly resilient mechanisms by design. Despite blockchain’s potential to correct problems associated with the current Internet
ecosystem, there are several issues that need addressing within the blockchain ecosystem. These include
security; the tradeoff between scalability and decentralization; and sustainability.
Keywords: blockchain ecosystem, smart contract, proof-of-work mechanism

1. Potential and issues regarding theblockchain ecosystem
Whether you are interested in blockchain or not,there are several reasons for engaging with it. Cryptocurrency, smart contracts, and non-fungible tokens(NFTs) rely upon this distributed ledger-based technology, and it could have revolutionary implications
for global networking and information technology(IT) companies, and the Internet at large.
The Internet, for instance, was originally designed
to achieve global networking without a single point of

failure (SPOF). However, the current problem for the
ecosystem over the Internet is that tech giants have in
effect become such SPOFs. Hence, there is a continued need for extensible trust without these risky
flaws. In place of the centralized computation of theInternet’s current architecture, blockchain could be
used to implement self-resilient or self-operating systems, as it upkeeps states with highly resilient mechanisms by design.
Despite blockchain’s potential to correct problems
associated with the current Internet ecosystem, there
are several issues that need addressing within theblockchain ecosystem. These include security, broadly understood; the tradeoff between scalability anddecentralization; and sustainability.
2. Security and cryptography
Studies conducted on the formalization of blockchain security requirements have largely neglected toconsider the entire technology and all its systems.
While this does not necessarily imply insecurities, itmeans we are unable to demonstrate that blockchain
does not contain vulnerabilities.
The presence of risk applies not only to blockchain
specifications but also to its implementation. The
attack in 2016 on a decentralized autonomous organization illustrated the possibility of exploiting vulnerabilities in the Ethereum blockchain code. Because of

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the pervasive role that blockchain is expected to play
as a social infrastructure tool, the impact of security
incidents could increase dramatically. This means
there is a need for vulnerability-handling procedures
to ensure the quality of code and respond to attacks
when they occur.
There also needs to be a standard operating model
regarding the use of cryptography. When the IT
industry transitioned from secure hash algorithm(SHA)-1 to SHA-2 several years ago, following areported compromise of SHA-1, the Bitcoin andblockchain engineering community for the most partlacked the experience, mechanisms, and operations to
do likewise.
With quantum computing looming as a long-term
threat, the digital signature schemes used in blockchain technologies could also become insecure.
Efforts to develop post-quantum cryptographic techniques are underway. The U.S. National Institute ofStandards and Technology (NIST), for instance, has
selected post-quantum finalists covering public-key
encryption and digital signatures. Because long-term
operations are assumed with blockchain applications,
it is important to transition to equally long-term,
secure cryptographic techniques. Cryptographic agility, which means a level of flexibility when the underlying cryptography is compromised, should be implemented into blockchain technology, operations, andgovernance mechanisms.
3. Scalability vs. decentralization
The blockchain ledger is processed according to a
specified rule of processing speed. (In the case of
Bitcoin, 1-MB block of data is added every 10 minutes.) This upper bound on the maximum number oftransactions per unit time effectively puts a limit on
scalability, which advancing computing power canNTT Technical Review

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not overcome.
One solution is to increase the size of the block bychanging its specifications. However, this would
increase the amount of data stored at all user nodes.
This could result in only wealthy individuals or parties having the resources to operate the nodes, which
in turn decreases their number. A solution involving
fewer nodes would therefore contradict the original“decentralization” philosophy of permission-lessblockchain, making such blockchains less secure.
The trade-off between scalability and decentralization is related to design philosophy. Reducing thenumber of nodes or setting multiple nodes in the samecloud computer (to achieve greater scalability) may
destroy one of the prime merits of public blockchain,
namely, the removal of centralized operators. It is,therefore, crucial to consider the cost-merit balanceof introducing such a semi-decentralized blockchain
when we expand its applications.
4. Sustainability
From an environmental perspective, there is concern about whether the proof-of-work (POW) blockchain consensus mechanism used by Bitcoin is sustainable given the tremendous amount of energy
consumed in mining these digital assets. The alternative proof-of-stake (POS) mechanism is much moreenergy-efficient; however, POS faces numerous implementation challenges, including confirmation delays.
From a business perspective, public blockchain
systems such as Bitcoin are considered self-resilient
because their protocols implement fees for operations
through self-issuing crypto assets. A capital growththeory analysis indicates that blockchain systems areusually sustainable, although stakeholders unconstrained by certain standard rules of business (such as
those involving taxes, energy costs, or risk of bankruptcy) could undermine a chain’s viability. Similarly, if we were to see a so-called selfish mining attackon the POW mechanism, it could lead to the collapseof a chain, another limit on sustainability. It is also
worth mentioning that the use of blockchain by itself,
for instance in NFTs or self-executing contracts, does
not guarantee outcomes that could be characterized
as fair. Achieving fair outcomes calls for appropriate
design considerations.
What that also means is that in addition to further
analysis, we are likely to need regulations in thisfield. If we are interested in a new type of public, selfresilient Internet infrastructure mentioned at the startof this article, we may need to upgrade blockchain.
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Feature Articles

Shin’ichiro Matsuo

Senior Scientist, Head of blockchain research,
Cryptography and Information Security Laboratories, NTT Research, Inc.
He is the head of blockchain research at NTT
Research. He is also a research professor at
Georgetown University, Washington, D.C., USA,and works as a director and blockchain researchlead of CyberSMART research center at Georgetown University. He has been engaged inresearch on cryptography and cryptographic
protocols for over 23 years. He was a program
chair of Scaling Bitcoin workshop 2019 andprogram committee member of many blockchain-related academic conferences such as
IEEE Security & Privacy on the Blockchain,
International Workshop on Cryptocurrencies andBlockchain Technology (CBT), Stanford Blockchain Conference and Crypto Economics andSecurity Conference. He is also a co-founder ofBSafe.network, which is the global and neutral
academic research testbed dedicated to blockchain research. As editor and project leader, heoversees two technical reports on the security ofblockchain technology at ISO TC307.

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The Future of Problem Solving: The
Coherent Ising Machine Approach
Yoshihisa Yamamoto
Abstract

Several new computing models tackle combinatorial optimization problems. These include adiabatic
quantum computation, also known as quantum annealing, and the coherent Ising machine (CIM). The
Physics and Informatics Laboratories at NTT Research launched a CIM initiative, and NTT Basic
Research Laboratories built large-scale CIM prototypes. This article reviews the CIM approach, results
to date, and future research agenda.
Keywords: coherent Ising machine, optimization problems, optical parametric oscillator

1. Introduction
The current computing model, composed of processing, communication, and memory units, is morethan 70 years old. To overcome the inherent limitations of this model, over the past few decades, physicists, computer scientists, and technology companies
have been exploring a range of new approaches. A
common goal with these alternative models, which
use a mix of analog, digital, classical, and quantum
technologies, is to solve extremely difficult computational challenges with reduced energy cost.
Such challenges commonly target non-deterministic polynomial-time (NP)-hard or NP-complete problems. There are several types of NP-hard problems.
One type targets combinatorial optimization, i.e.,
finding an optimal solution from a large set of candidates. One of the earliest described combinatorial
optimization problems was determining the minimum total distance in a journey to N number of cities.
Calculated by factorials, the number of combinations
becomes astronomically high as N increases.
Several new computing models tackle combinatorial optimization problems. These include adiabatic
quantum computation, also known as quantum
annealing (QA), and a coherent Ising machine (CIM).
The Physics and Informatics Laboratories (PHI Lab)of NTT Research launched a CIM initiative, and NTT
Basic Research Laboratories built large-scale CIM
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prototypes. This article reviews the CIM approach,results to date, and future research agenda.
2. Definition of terms
To understand the CIM approach and why it is a
type of quantum/classical hybrid computing, let us
define some terms, starting with Ising then turning tocoherent. The proper name refers to Ernst Ising, aGerman physicist linked to a mathematical model
created in the 1920s to describe magnetic orders.
The Ising model originally consisted of a onedimensional set of discrete variables representing N
magnetic moments of atomic spins, each of which
has two possible states (+1 or –1). Its energy was
expressed in terms of the sum of pair-wise (twobody) interaction, Hamiltonian. Solving the model
involves finding its ground state, which is the lowest
energy state. If a spin-spin coupling configuration is
not simple and cannot be described by planar graphs,
finding the ground state of an Ising Hamilton falls
into the NP-hard category of computational complexity.
The most important active component in a CIM isan optical parametric oscillator (OPO). First demonstrated in 1965, about five years after the invention of
the laser, the OPO is a coherent light source. It isdistinct from the laser because it produces a quantum
state of light (squeezed state). While the Ising model,
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which evolved from a one- or two-dimensional latticeframework, mathematically represents the atomic
spins in any complex configuration, the OPO-based
CIM creates a universe of artificial spins, which canthen be mapped to a real-world combinatorial optimization problem through an N x N coupling matrix.
The solution corresponds to an optimum configuration of spins that minimize their energy function.
This system is doubly coherent in the following
sense. When one photon is eliminated from a pumppulse sequence at frequency 2ω, two photons (calleda photon-pair or biphoton) are generated simultaneously in a signal pulse sequence at frequency ω. If a
CIM consists of two OPOs, a single photon pairexists simultaneously in two OPOs as linear superposition. If the CIM consists of N OPOs, a single photon
pair exists simultaneously in N OPOs as linear superposition. Therefore, the elementary excitation of theCIM coherently spreads in an entire machine consisting of N OPOs.
This fact means that each OPO state simultaneously
exists in a vacuum state with a zero-photon state witha large probability and two-photon state with a small
probability. Because of this coherent superposition
nature, each OPO state occupies 0-phase (down spin)and π-phase (up spin) states even if there is one andonly one photon pair in an entire machine. Therefore,a prerequisite for quantum computation, linear superposition of two states, is naturally satisfied in a CIM[1].
3. Two CIM types
In practice, there are two types of CIMs: one using
an optical delay line (ODL) and the other using measurement feedback (MFB) to introduce the coupling
matrices. As mentioned above, the OPO absorbs one
photon from the pump field and emits two photons
into the signal field simultaneously. As a result ofinterference among the zero- and two-photon states,
the electromagnetic field is stretched into a squeezed

above threshold (eitheror)(OPO)2(OPO)1

1

N

2

below threshold (linear superposition of

NTT Technical Review(OPO)Nand)Vol. 20 No. 1 Jan. 2022

vacuum state or a linear superposition of up- anddown-spin states. If the pump amplitude is further
increased, the stretched noise is finally split apart into
the two states with positive and negative average
amplitudes.
That splitting point marks a transition from quantum to classical mechanics. The quantum region
below the threshold is represented by a linear superposition of up- and down-spin states and above it, bya classical up or down spin, but not both simultaneously. It is the states of photon pulses that change a
CIM from quantum to classical, allowing for readingout final answers with high accuracy [2].
Regarding the MFB-CIM, following the OPO’s
generation of two photons, an optical beam splittercreates a quantum correlation between the internaland external (measured) fields. The use of homodyne
detection, which extracts information encoded as anamplitude of an external signal field, induces state
reduction for the internal field [3]. (The measurementof a quantum system induces, via “wave-function collapse”, a completely new state.)
In the ODL-CIM, optical mutual coupling creates
the quantum correlation (entanglement) among
OPOs, while in the MFB-CIM, the original quantum
correlation is converted to classical correlation
among OPOs via measurement feedback. The difference between the two CIMs, which both involve
quantum-to-classical transitions, is that the separation or breaking of symmetry occurs through quantum correlation for the ODL-CIM and classical correlation for the MFB-CIM.
The two machines also have different histories andtradeoffs. The CIM was originally demonstratedusing an ODL, but for the past five years, MFB has
predominated. While an ODL is more difficult toimplement, once set up, it promises higher operational speed and lower energy consumption.
4. CIM performance
How has a CIM performed to date? Two tests, one
experimental and the other mathematical, indicate a
CIM’s unique computational power.
In a 2019 benchmark study between the MFB-CIM
and QA [4], the success probability (time to solution)of this CIM outperformed QA by an ever-widening
gap as the problem size increased. For a dense MaxCut problem of N = 55, for instance, the MFB-CIM
determined a solution seven orders of magnitude
faster than did QA from D-Wave, Inc. For a problem
size of 100, the differential was estimated as 21
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orders of magnitude.
These extremely large differentials derive fromdesign. Whereas the MFB-CIM had all-to-all connections among its 2000 spins, QA was connected only
locally. This resulted in a divergence in the number ofspin-spin couplings: 4 million (CIM) vs. 8 thousand(QA). Ultimately, the difference can be traced back tothe basic hardware platforms. QA consists of localized spins and requires real wiring to connect qubits(the basic unit of quantum information). By contrast,
a CIM is based on a de-localized harmonic oscillator
field, in which mutual spin coupling can be implemented at any place in the machine.
In a mathematical comparison with an ideal QC
machine [5], the MFB-CIM also outperformed it. In
this comparison, the ideal QC exhibited no decoherence, no energy dissipation, no gate error, and all-toall qubit coupling—conditions that are far from being
actualized. Even so, the time-to-solution (TTS) for
discrete adiabatic quantum computation (dAQC) and
the Grover search, an optimum quantum algorithm
for unstructured search, fell far behind. The TTS for
Grover search and dAQC scaled in accordance withthe exponential of problem size n, and the TTS for the
MFB-CIM scaled in accordance with the sub-exponential of n, an increasingly small number.
In this case, system design again matters. The unitary QC machines are limited to linear amplitude
amplification at best, while a dissipative CIM canincrease in this regard exponentially. It can do so
because the operating principle of the quantum-toclassical transition enables the stimulated emission ofphotons above the OPO threshold.
In the latest numerical simulation study [6, 7], theCIM with amplitude error correction feedback can becompetitive also against state-of-the-art digital heuristics such as Breakout Local Search (BLS) and
Simulated Bifurcation Machine (SBM).

Chicago, Cornell University, Harvard University,
University of Michigan, Massachusetts Institute ofTechnology (MIT), NASA Ames Research Center,
University of Notre Dame, Swinburne University ofTechnology, Tokyo Institute of Technology, The University of Tokyo, University of Waterloo, and 1QBit.
These joint research projects with 25 principal investigators cover a wide range of topics, including quantum optics and information, neural network and brain
science, nonlinear photonics, combinatorial optimization, and machine learning.
To be on the edge of new knowledge can be exhilarating. First, there are pressing, real-world problems
that a CIM could solve in areas such as operations
and scheduling, drug discovery, wireless communications, finance, integrated circuit design, compressedsensing, and machine learning. Then there is therange of interdisciplinary viewpoints that impinge
upon this research, which arguably amount to a new
field of study. Neuroscience may be one of the mostsignificant of these areas of knowledge.
Compared with the static nature of the long-standing
legacy computing model, the new paradigm, which
includes CIMs, is shifting toward more brain-likefunctionality, a point captured in our PHI Lab slogan:“Quantum Physics meets Brain Science on Optical
Platform.”
References
[1]
[2]
[3]
[4]

5. Future research agenda
Notwithstanding the strong results from CIM prototypes and mathematical studies, there remains
much from a theoretical perspective to understandabout how they perform. This situation contrasts withthe prevailing scenario in the QC domain, whereexperimental results lag far behind the theory.
To remedy this knowledge deficit, NTT Researchlaunched an ambitious, long-range collaborative
exercise with 14 institutions: Stanford University,
California Institute of Technology, The University of

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Vol. 20 No. 1 Jan. 2022

[5]

[6]

[7]

Y. Yamamoto, T. Leleu, S. Ganguli, and H. Mabuchi, “Coherent Ising
Machines—Quantum Optics and Neural Network Perspectives,”
Appl. Phys. Lett., Vol. 117, No. 16, 160501, 2020.
Y. Inui and Y. Yamamoto, “Entanglement and Quantum Discord in
Optically Coupled Coherent Ising Machines,” Phys. Rev. A, Vol. 102,
No. 6, 062419, 2020.
S. Kako, T. Leleu, Y. Inui, F. Khoyratee, S. Reifenstein, and Y. Yamamoto, “Coherent Ising Machines with Error Correction Feedback,”
Adv. Quant. Technol., Vol. 3, No. 11, 2000045, 2020.
R. Hamerly, T. Inagaki, P. L. McMahon, D. Venturelli, A. Marandi, T.
Onodera, E. Ng, C. Langrock, K. Inaba, T. Honjo, K. Enbutsu, T.
Umeki, R. Kasahara, S. Utsunomiya, S. Kako, K. Kawarabayashi, R.
L. Byer, M. M. Fejer, H. Mabuchi, D. Englund, E. Rieffel, H. Takesue,and Y. Yamamoto, “Experimental Investigation of Performance Differences between Coherent Ising Machines and a Quantum Annealer,”
Sci. Adv., Vol. 5, No. 5, eaau0823, 2019.
K. Sankar, A. Scherer, S. Kako, S. Reifenstein, N. Ghadermarzy, W.
B. Krayenhoff, Y. Inui, E. Ng, T. Onodera, P. Ronagh, and Y. Yamamoto, “Benchmark Study of Quantum Algorithms for Combinatorial
Optimization: Unitary versus Dissipative,” arXiv:2105.03528, 2021.
T. Leleu, Y. Yamamoto, P. L. McMahon, and K. Aihara, “Destabilization of Local Minima in Analog Spin Systems by Correction of
Amplitude Heterogeneity,” Phys. Rev. Lett., Vol. 122, No. 4, 040607,
2019.
S. Reifenstein, S. Kako, F. Khoyratee, T. Leleu, and Y. Yamamoto,“Coherent Ising Machines with Optical Error Correction Circuits,”
Adv. Quant. Technol., Vol. 4, No. 9, 2100077, 2021.

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Yoshihisa Yamamoto

Director, Physics and Informatics Laboratories, NTT Research, Inc.
He received a Ph.D. from the University ofTokyo in 1978 and joined NTT Basic ResearchLaboratories. He became a professor of applied
physics and electrical engineering at Stanford
University in 1992. He also became a professor
at the National Institute of Informatics (NII) in
2003. He is currently a professor (emeritus) at
Stanford University and NII, and an NTT R&D
Fellow. He received many distinctions for his
work, including the Carl Zeiss Award (1992),
Nishina Memorial Prize (1992), IEEE/LEOS
Quantum Electronics Award (2000), Medal with
Purple Ribbon (2005), Hermann A. Haus Lecturer of MIT (2010), Okawa Prize (2011), andWillis E. Lamb Award (2022). His research
focuses on quantum information processing,quantum optics, and mesoscopic physics, especially quantum neural networks and coherent
Ising machines.

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Bio Digital Twin Research Update
Joe Alexander
Abstract

The mission of the Medical and Health Informatics Laboratories at NTT Research is to make advancements in the medical and health sciences that will improve an individual’s overall wellness and healthoutcomes. Our bio digital twin initiative aims to create digital replicas of patients that physicians canthen use to simulate various treatments to enable optimal and patient-specific therapeutics. This article
provides recent updates on our projects and team members.
Keywords: bio digital twin, cardiovascular disease

1. Introduction
The mission of the Medical and Health Informatics
Laboratories at NTT Research is to make advancements in the medical and health sciences that will
improve an individual’s overall wellness and healthoutcomes. Our bio digital twin initiative aims to create digital replicas of patients that physicians can thenuse to simulate various treatments to enable optimaland patient-specific therapeutics. In the initial phaseof this project, we at the MEI Lab are developing a
cardiovascular bio digital twin (CV BioDT). We aretargeting the cardiovascular system in part because ofthat system’s prominent role in global mortality rates
and the relatively high availability of data required
for modeling.
Over the past year, the MEI Lab has made significant progress on several fronts. In December 2020,

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we signed a research agreement with Japan’s National Cerebral and Cardiovascular Center (NCVC) tojointly develop cardiovascular disease-related computational models, implement them on a bio digitaltwin platform, and develop applications for use byphysicians and patients. In the first half of 2021, we
made two key hires, Dr. Jon Peterson, newly promoted to a distinguished scientist, and Iris Shelly as ascientist.
2. NCVC joint research
The two-and-a-half-year project with the NCVC istitled “The Development of Human Hemodynamics
Mapping and Autonomous Multimodal Therapeutics
Systems.” It involves research at both organizations.
The principal investigator (PI) for the joint research
agreement on the NCVC side is Dr. Keita Saku, laboratory chief of NCVC’s Department of Cardiovascular Dynamics. I have the PI role on the NTT Researchside.
The agreement calls for the NCVC to develop integrated computational models to support multimodal
closed-loop interventions for acute myocardial
infarction (AMI) and acute heart failure (Acute HF).
In parallel, the MEI Lab will be implementing thesemodels into a bio digital twin platform and developing physician- and patient-oriented applications to
support physician clinical decision making andpatient self-care.
The NCVC is a semi-independent national institution. Its government affiliation is through the Japan20

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Ministry of Health, Labor and Welfare, the counterpart to the U.S. Department of Health and Human
Services. The NCVC focuses on intramural cardiovascular clinical practice and dedicated cardiovascular research. As such, it resembles the National Heart,
Lung and Blood Institute (NHLBI) of the U.S.
National Institutes of Health. Unlike the NHLBI,
however, the NCVC is not a cardiovascular researchfunding agency.
Near-term goals for the joint project include thedevelopment and validation of models representing
heart and vascular dynamics, particularly as they
relate to AMI and Acute HF. Heart and vascular models that include neural control of circulation, as wellas heart energetics, will be fundamental to computational platforms for determining optimal therapies forheart conditions. New models that Dr. Saku is developing in support of the CV BioDT will help determine optimal interventions for AMI and Acute HF
across multiple therapeutic modalities such as medications, medical devices, and neuromodulation. The
longer-term goal is to achieve patient-specific CV
BioDTs to enable patient-specific therapeutics.
The MEI Lab entered this partnership with Dr. Saku
and the NCVC because of their internationally recognized expertise in cardiovascular regulation andadvanced technologies relating to closed-loop automated therapeutic interventions for conditions suchas heart failure and mechanical circulatory support.
This exciting project has also benefited from the
instrumental support of Dr. Kenji Sunagawa, professor emeritus in the Department of Cardiovascular
Medicine at Kyushu University and founder of the
Department of Cardiovascular Dynamics at the
NCVC Research Institute. Dr. Sunagawa trained bothDr. Saku and myself (in my case, at Johns Hopkins
University, Kyushu University and NCVC) andhelped orchestrate this agreement. Going forward, hewill play a leadership role in this project for the MEILab.
By February 2021, the MEI Lab had already conducted two proof-of-concept studies to establish
requirements and frame the initial bio digital twin
platform architecture. The CV BioDT models developed through this joint research agreement will need
to be validated in further studies before subsequentvalidation in preclinical human studies. These tests
will be conducted at NCVC hospitals. During laterstages of the CV BioDT validation and rollout, additional organ systems will be added towards the goalof an overall bio digital twin. In a noteworthy development, interfaces with the renal, respiratory, pulmoNTT Technical Review

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nary and some neural systems are advancing sooner
than expected.
3. New staff scientists
In February 2021, it was announced that Dr. Jon
Nels Peterson had joined the MEI Lab, then as asenior scientist. Dr. Peterson is a biomedical engineer
with both academic and medical device industry
experience. He had most recently been principal
clinical systems engineer at Micro Systems Engineering, Inc., where he was the lead systems engineer fora family of implantable cardiac monitors. He alsopreviously held research and engineering positions at
Boston Scientific CRM and Creare, Inc. and was a
research assistant professor at the University of Vermont College of Medicine. Dr. Peterson’s background as a research scientist and clinical systems
engineer, with experience in hardware, firmware, andsoftware subsystems, his talent for mathematicalmodeling and simulation, and his understanding ofphysiological control systems, as well as pathophysiological states such as heart failure, all bear directlyon the MEI Lab’s agenda.
In June 2021, it was announced that Iris Shelly had
joined the MEI Lab as a scientist. An applied researchengineer with expertise in biomedical signal processing and low-power devices, Shelly was most recently
a senior applied research engineer at Micro Systems
Engineering, Inc., where she designed, developed,and validated cardiac arrhythmia detection algorithms. She is initially working on model architecture
and the interface for the CV BioDT. Her algorithm
design experience and attention to detail, honed
through years of experience in medical device
research and software verification, are vital skills insupport of model development for the CV BioDT.

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4. Leadership shift
Taken together, the partnerships with the NCVC
and new hires represent significant progress for the
MEI Lab’s bio digital twin initiative, which I have ledsince joining NTT Research in 2020. Before closing,
I should mention another notable development: myappointment as director of the MEI Lab in July 2021,
where I succeeded Dr. Hitonobu Tomoike, who has
assumed the position of research professor at the

NTT Basic Research Lab.
In this new position, I will continue to lead the CV
BioDT group but now with Dr. Peterson as co-lead. I
have also been engaged in harmonizing other MEI
Lab projects, namely those involving implantableelectrodes and remote sensing, within an overarchingstrategy that aligns with NTT Research and thebroader NTT Group. It is an honor to follow in Dr.
Tomoike’s footsteps and continue to advance the MEI
Lab’s ambitious “moonshot” goals.

Joe Alexander

Director, Medical and Health Informatics
Laboratories, NTT Research, Inc.
After graduating with a degree in chemicalengineering from Auburn University, he studied
medicine as a fellow of the Medical Scientist
Training Program (MSTP) at Johns Hopkins
Medical School, where he received both an MD
and PhD. His PhD is in biomedical engineering,where he specialized in cardiovascular dynamics,
training with Dr. Kenji Sunagawa in the laboratory of the late Dr. Kiichi Sagawa. Immediately
afterwards, he completed a fellowship in researchcardiology at Albert Einstein College of Medicine before additional training as a Japan Society
for Promotion of Science (JSPS) Fellow at
Kyushu University. He then took academic faculty positions in biomedical engineering and in
medicine at Vanderbilt University while simultaneously completing a residency in internal medicine at Vanderbilt Hospital. During that time, hehelped train astronauts such as Dr. Chiaki Mukai
for the Neurolab Spacelab Mission. He likewise
collaborated with The National Cerebral andCardiovascular Center as a visiting researcher
supported by the Science and Technology Agency of Japan. Following academia, he entered
Pharma – first Merck then Pfizer. During his 18
years at Pfizer, he worked in various capacities
including roles in R&D, Business Development,
and Medical Affairs. In Pharma as in academia,
his passion for modeling and simulation wasevident throughout his work and extended acrosstherapeutic areas. He is credited with creating
several Pharma modeling platforms including
The Lyrica Virtual Lab, The Neuropathic and
Neuropathic-like Pain Virtual Lab, and The Pulmonary Vascular Disease Virtual Lab. He is afellow of the American College of Cardiology(FACC) and is very interested in heart failure,pulmonary hypertension, and medical devices.

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Vol. 20 No. 1 Jan. 2022

22

Feature Articles: NTT Research: Open Collaboration toUpgrade Reality

A New Lab Exploring Emergent
Matter from Light
Michael D. Fraser
Abstract

In September 2021, NTT Research unveiled its new smart workspace in Sunnyvale, California, called
the NTT OneVision building. It is one of the first office buildings in Silicon Valley built for a post-pandemic vision of the workplace with collaboration-focused spaces, state-of-the-art health monitoring
capabilities, and new layouts. The 35,100 square foot office building also contains a new optical laboratory for the NTT Research Physics & Informatics Laboratories (PHI Lab).
The Sunnyvale optical lab supports multiple users and research themes. One specific design focus
when planning the new lab was to provide ways to experimentally create and study many-body states oflight, a specific example of which is the engineering of a bosonic fractional quantum Hall state using
light. This article provides a brief review of our research agenda on quantum many-body states of lightand details of the new lab.
Keywords: optical lab, quantum many-body states, fractional quantum Hall effect

1. Research agenda
In traditional condensed matter platforms, the interactions between large ensembles of particles (such as
electrons or atoms) lead to the emergence of fascinating new physical phenomena such as superconductivity, superfluidity and the fractional quantum Hall
effect. Key to the most exotic of these emergent
phases of matter is strong interactions between theconstituent particles. While photons (particles oflight) do not typically interact, advances in opticalmaterials and hybrid-optical structures can also
induce very strong non-linearity between photons.
Furthermore, the ability to control photons to very
precise, even single photon levels, in addition to more
recent discoveries such as topological states of light,
make optical platforms extremely exciting for the
exploration of fundamentally new states of matter.
Pursuing new optical platforms that strategicallycombine these and other properties, we aim to create
and explore new many-body quantum states of light.
In optics, there are many experimental platforms
we might use, each of which has distinct features andadvantages. Exciton-polaritons (bosonic half-light,
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half-matter quasi-particles in a semiconductor microcavity), for example, have the advantage of relatively
strong interactions, a result of hybridizing cavity
photons with interacting electronic excitations. This
platform may be fabricated using a variety of materials and structures, also with spatial structuring andeven topological phases. Meanwhile, implementationof topological models in a time-multiplexed opticalresonator network (a similar geometry to the coherent
Ising machine) is a distinct methodology with theunique feature of being able to engineer non-local
interactions, which makes this also an exciting platform to study in the context of lattice bosonic quantum Hall effects.
The breadth of photonic-platform exploration isenhanced by strategic partnerships with external
institutions, including California Institute of Technology, Massachusetts Institute of Technology, Stanford
University and RIKEN – a major scientific research
institute in Japan. Of course, much of our work willtake place at Sunnyvale. Some of the fundamental
problems we are seeking to initially explore in the
new optical lab include the following:
1.	How can photons be made to interact (very)
23

Feature Articles

strongly – to the level at which strong correlations and new physical phenomena result?
2.	How can we induce a large artificial magnetic
field for neutral photons, and use this to create
topological states of light?
3.	What new quantum states of matter and otherphenomena might result from highly non-linear,structured photonic systems?
Pursuing our research agenda requires precise optical control, extreme conditions, including low temperatures and large magnetic fields, as well as
advances in materials and innovative device design.
Our Sunnyvale laboratory is uniquely positioned toapproach these challenges, combining in the same
space advanced material and device fabrication withultra-low temperatures, high magnetic fields, andnew schemes for optical manipulation and measurement.
2. Optical lab features and capabilities
The main lab area is about 35 feet x 33 feet, with avery high ceiling, which is useful for installing andoperating larger equipment, such as our 11-foot-tall
dilution fridge. The room is divided into three parts
with retractable optical blackout curtains separating
the sections. Two sections, which may each be independently and completely blacked out, are host to two
distinct experimental research themes, while theother room will always be lit and used for discussions, data analysis, sample preparation, etc.
There were many design requirements incorporating a range of Physics & Informatics Laboratories(PHI Lab) experiments, and it was necessary to makenumerous accommodations. The combination of

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research projects together had strict requirements,
necessitating design of custom HVAC (heating, ventilation, and air conditioning) systems, noise isolation
for pumps and compressors, and removal of all magnetic materials from sections of the room. Some of
the lab’s notable features and capabilities include thefollowing:•	Precise optical control: In the context of ourexperiments, this initially means being able tocreate and drive optical phenomena on micron or
smaller scales with high spatial precision andreproducibility. It will eventually become more
stringent, where we will need to have such precise spatial and temporal control at a single photon level of quantum objects.
•	Temperature range: Certain experiments arebeing conducted at room temperature, which isone of the advantageous features of optics experiments in general. Other experiments are conducted at significantly using materials anddevices cooled to much lower temperatures. We
will have two helium refrigerators as part of thelab infrastructure. One is compact and fast to use
and operates at around 4 K. This is a sufficiently
low temperature to study, iterate new materials
and structures in detail, and reveal new physics
of these samples. The other refrigerator, known
as a dilution fridge, may reach about 5 mK(about 60,000 times colder than room temperature) and is a highly customized apparatus. Such
low temperatures are desired because quantum
states of matter (many-body states, in particular)
are typically revealed only at very low temperatures. Even if a given many-body quantum state
can be observed (or engineered to appear) at

24

Feature Articles

higher temperatures, lowering the temperature
gives robustness to this quantum state. The fractional quantum Hall effect in its traditional electronic manifestation is paradigmatic of a system
requiring and benefitting from both criteria. Bothfridges have optical excitation and imaging
access with low vibration and high spatial resolutions.
•	
Large magnetic field: A magnetic field can beused to strongly modify the properties andbehavior of electronic and magnetic materials. In
two-dimensional (2D) electronic materials, astrong magnetic field applied to samples at low
temperature quenches the kinetic energy leading
to the formation of topological bands and anenhanced importance of interactions, the necessary ingredients to create an electronic fractional
quantum Hall effect. We will be studying the
emergence of such states in new monolayer optical semiconductors in which optical techniques(not just electronic) can be used for measurement
and control. Hybridizing with other monolayermaterials may also be used to create new functionality and control.
•	Fabrication tools: It is atypical for an optics lab
to have sample fabrication integrated into a single facility, but in doing so, we hope to be able torapidly iterate the process of design, fabrication,and measurement of new samples, along with afast turnaround of testing new materials andincorporating new ideas and refinements into
updated sample structures. Whereas traditionally, complex semiconductor structures need to be‘grown’ in large chemical reactors run by teamsof people, newer materials including van der
Waals materials may be assembled manually
layer-by-layer using a compact but precise set of
fabrication tools. In our laboratory, we have an
inert atmosphere glove box housing a state-ofthe-art 2D material transfer station capable ofconstructing these structures with atomic level
precision in addition to an atomic force microscope for structural characterization. The glove
box maintains an oxygen-, water-, and otherimpurity-free atmosphere (down to the level ofparts per billion) for clean sample fabrication.
•	
Optical measurement and control: Part of thedesign feature set of the laboratory is to be able
to fabricate and characterize new materials andstructures. Another is the ability to opticallypump and measure the dynamics of electronic
and optical excitations in these devices. Our
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cryogenic capabilities were chosen such that we
can measure with sub-micrometer levels ofvibration for precise excitation and imaging. We
also work with very narrow-linewidth stablelaser sources across several wide frequency
bands (including ultraviolet, visible, and nearinfrared) which will be combined with spatial
light modulators to drive structured spatial andtemporal dynamics of these excitations.
3. Flexible and focused
As with any new experimental optics laboratory, we
needed to make sure the Sunnyvale lab was not too
specific to be flexible with the exploratory nature andchanging directions of the research projects. We havea well-balanced set of complimentary and cuttingedge equipment and apparatus, the combination ofwhich is unique and offers us the ability to conduct
entirely new experiments and work with as-yet
unstudied but promising materials, of which only thisapparatus is capable.
For the specific themes discussed in this article, theexploration and creation of quantum many-bodystates in optical platforms is enabled through thedevelopment of new techniques, new materials, newtheory, and by innovative design of experiments. We
are gradually building a toolbox of experimental
techniques, materials and device designs that will
give us further opportunities to create fundamentallynew states of matter with optics.

Michael D. Fraser

Senior Research Scientist, Physics and Informatics Laboratories, NTT Research, Inc.
He received a B.Sc. in physics and physicalmathematics and B. Eng. in microelectronics
engineering from Griffith University in 2002 andPh.D. from the Australian National University in2010. He joined the PHI Lab in 2019, where hefocuses on condensed matter physics using
optics. He has co-authored numerous papers with
PHI Lab Director Yoshihisa Yamamoto, whom he
met while a Fulbright Fellow at Stanford University. He concurrently holds a position as a senior
visiting scientist at RIKEN, Japan.

25

Feature Articles: Research and Development ofSecurity in the IOWN Era

Security as Driving Force of the
FutureShinichi Hirata and Katsumi Takahashi
Abstract

This article describes research and development (R&D) of security in the Innovative Optical and Wireless Network (IOWN) era to create a prosperous and enriching society. We seek to change the role ofsecurity to activating people and ideas. This new form of security will solve diverse problems related tosecurity motivation in individuals, organizations, and society, convert ideas and computing resources
directly into work, and ensure continuous security. We will achieve this through R&D based on the threepillars of theory, data-driven approach, and communication.
Keywords: security, IOWN, R&D

1. Driving force of the future
We have been studying communication and information security continuously for more than 30 years.
During this time, the Internet came into being as ameans of communicating safely no matter where one
may be through cryptography; similarly, the web andcloud came into being as means of safely storing
information anywhere through security measures.
However, while our daily lives have thus far beenprotected by such security measures, it cannot be
overlooked that there is still much anxiety over security threats; thus, the need for giving full attention tosecurity measures.
The Innovative Optical and Wireless Network(IOWN) era will make life more enriching and satisfying through information and communications technology (ICT) that exceeds the limits of conventional
technology. It is our goal to make security the driving
force behind this transformation.
There is no debate as to the need for security. The
security by design approach is being increasingly
adopted, which points to the inherent need for security in achieving healthy individual and social activities. However, keywords, such as security cost andsecurity fatigue, have appeared, reflecting the common feeling that anything that is needed to ensure
healthy activities must be obligatory and troubleNTT Technical Review

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some. We disagree with this mode of thinking. Simply put, security should bring about a bright future.
It is our intent to change the current belief that security technology is necessary but difficult throughresearch and development (R&D) on the basis of thefollowing viewpoints:•	Security is widely useful for all types of workand lifestyles (extended).
•	Security can convert ideas and computing
resources directly into work (efficient).
•	Security is ongoing (continuous).
In this article, we explain the concept of security
R&D in the IOWN era from the viewpoints of extended, efficient, and continuous security and outline thesecurity technologies that we will target (Fig. 1). The
type of security discussed in this article is information security that, while not intended for maintaining
public peace and order, includes peripheral fields
such as privacy and ethics.
2. Extended security
It had been generally believed that security is for aparticular system to be unbreakable. Since we see
security as being useful for all types of work and lifestyles, we would like to drive the evolution of security R&D from the two viewpoints of security targets
and security motivation.
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Extended

Security

Efficient

Continuous

Fig. 1. Concept of security R&D in the IOWN era.

2.1 Extended 1: Security targets
In addition to particular systems (information
assets) as targets of protection by security, we would
like to include companies and organizations, people,
and society.
2.1.1 Information assets
The target of security has been called information
assets, which means a company’s customer information, sales information, technical information, etc.
The protection of information assets depends on theform of their records or storage, so the means of storing these information assets will also be a target ofprotection. Typical formats include files; media, suchas paper; disk storage; transmission channels; hardware systems, such as smartphones and computers;
and software systems, such as email, databases, andartificial intelligence (AI) services. We can add Internet of Things (IoT) devices such as drones and industrial robots.
2.1.2 Extension to companies and organizations
The targets of security are expected to change
greatly in parallel with changes in the activities ofcompanies and organizations. For example, determining the form of information assets will become
difficult. Information assets may be placed in storage
equipment outside the company or under the management of a separate organization through inter-compaNTT Technical Review

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ny transactions. In future companies, the data generated by others in a procurement or supply chain may
become an information asset of those companies. The
introduction of IoT devices, however, will make theform of information assets all the more fluid.
2.1.3 Extension to people
If people were to be regarded as a medium of information assets, they could be called a medium requiring a very high degree of confidentiality. While it issaid that facial expressions reflect a person’s feelings,
it is not the case that customer information could be
leaked from facial expressions. People can be easily
deceived, and in some cases, they can betray others.
Corporations deal with such situations by training
their employees and establishing rules and regulations. There is also posting in social networking services (SNSs) as a medium of people’s activities not
limited to those of corporations. Information security
incidents via SNSs include information leaks, copyright infringements, and flaming. However, such
incidents are mostly left as a matter of personal
responsibility. When it comes to security targetingpeople, there is a limit as to what safety managementthat treats people as systems can accomplish.
2.1.4 Extension to society
There is currently no established opinion on whether society can be set as a target of security. Autonomous
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car and surveillance-camera systems, for example,
are in the process of becoming systemized at a social
level. In a smart city, such systems will have basic
conventions (policies) with regard to security, so thiscan be thought of as an extension of a conventional
security target, though it depends on the system scale.
A specific example is how a pandemic should be dealt
with. Measures, such as contact-tracing apps, operate
under clear policies, but the rules of behavior behindthe operation of many other measures tend to beagreed upon by consensus through voluntary andspontaneous exchanges of information. It is thoughtthat society as a whole operates in this manner. Suchrules of behavior are sometimes referred to as ethics
or customs, and dealing with them requires a new
approach.
2.2 Extended 2: Security motivation
We believe that the reasons (motivation) security isnecessary are wide-ranging going beyond preventing
information leaks. They also include the existence ofincidents, system quality, laws, ethics, customs, andsocial objectives.
2.2.1 Incidents
The most known motivation for security is preventing information leaks. It is common knowledge that
this motivation drives measures for blocking a varietyof threats such as unauthorized access, malicious
software, and unauthorized entry and exit. However,
we believe that it is important not to think of such
incidents as infringing upon confidentiality, integrity,
and availability. For example, incidents involving
privacy (flaming) should also be given attention.
Instead of being a matter of information leaking, they
have been thought of as a peripheral security problem
that arises due to inadequate explanation of information access, purpose of use, etc. or violation of rules.
We should also think about whether abnormal AI
operations are peripheral security problems. The
results of AI operations have not traditionally been
considered a security problem. We consider thatproblems requiring attention should not be treatedwithin the conventional security framework but be
extended to include any problems brought about bycomputers or problems related to privacy, AI, etc.
2.2.2 System quality
In fields such as critical infrastructures, a high levelof security is required beforehand in system development. This need produces some of the motivation for
security. Yet, there are also systems in which security
is just a tacit requirement. In such a case, the level of
security required is also tacitly expressed, and proNTT Technical Review

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viding for security is simply regarded as a development cost. This is a problem that cannot be ignored.
Security is an inherent requirement of a system, so
any deviation from that requirement due to a lack ofmotivation must be fundamentally solved startingwith its cause.
2.2.3 Laws
Observing laws and regulations is also a security
motivation. In Japan, the Basic Act on Cybersecurity
calls for the people of the nation to make securityrelated efforts. For companies, this means security
premised on such laws as the Act on the Protection of
Personal Information and Unfair Competition Prevention Act. We believe that it is not simply a matterof scrutinizing the security-related legal system andapplying it to R&D but something that must be
actively participated in through discussions on what
the legal system should be.
2.2.4 Ethics, customs, and social objectives
There are cases in which security would still be felt
necessary even if there were no fear of incidents,
quality was kept constant, and laws were compliedwith. This feeling is based on values and fears thatpeople hold within themselves that can be expressedin terms of ethics, customs, and social objectives. We
believe their existence should be treated as elements
providing some of the motivation for security.
3. Efficient security as a driving force
Unfortunately, security has the possibility of being
treated as a business cost, but we would like to change
this perception by introducing the concept of security
efficiency. Efficiency relates to (1) ideas and (2) computing resources. Maximizing both these aspects will
maximize the efficiency of security.
3.1 E
 fficiency 1: Converting ideas directly intowork
We are investigating security that does not hinder
the implementation of ideas and supports people inchallenging themselves. When implementing an idea,
security requirements and methods of achieving themmust be determined. Minimizing this process leads toefficiency, and ideally, the security required at thetime of system development would be built-in without having to worry about it.
Determining requirements normally consists ofanalyzing all the elements described above under
security motivation, legal compliance assuming theoccurrence of incidents, etc. Next, in determining amethod for satisfying these requirements, it should be28

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noted that constructing security measures fromscratch is seldom done. The typical approach is tosurvey available components (in a library) and use thesecurity functions needed.
We are now investigating minimizing and automating both processes. The automation of security isextremely difficult, but the problems involved can besolved through a theoretical approach and the datadriven approach described later. In addition, if best
coupling of security requirements and implementation methods can be provided through a development
environment and user interface, a shortcut to solving
these problems should be achieved.
3.2 E fficiency 2: Converting computing resources
directly into work
In current web applications, for example, no one isreally concerned about the fact that security processing generates overhead and slows down communications and screen displays. However, in the IOWN era
in which a massive amount of devices in urban, transport, and other social infrastructures are connected to
the network, this cannot be ignored. In the context ofcarbon-neutral initiatives, security processing thatcan make full use of computing and communication
resources is desirable. For this reason, we are investigating security that can exploit the special features ofadvanced hardware represented with the All-Photonics Network of IOWN and maximize our experience
with information communications.
4. Continuous security
Security must be continuously maintained. Security
attacks and defensive measures evolve along withongoing progress in information processing technology, so our R&D efforts in this area are ongoing to beprepared for that evolution. There is another reason
continuity in security R&D is necessary. The core of
security technology is theory and data. An example ofthe former is cryptography and an example of the latter is whitelisting/blacklisting in which theory anddata, respectively, must be continually built up. In
contrast to the continuity of security technology, thearrival of discontinuous changes in the form of quantum
computers is predicted. We are therefore investigating
the development of technology based on continuity
that can withstand even major changes.
5. Three new pillars of security R&D
To achieve extended, efficient, and continuous
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security, we are promoting R&D focused on the following three pillars (Fig. 2).
5.1 Guaranteeing security through theory
Cryptography guarantees the confidentiality of
applied data through theory. Given a software modulethat is theoretically guaranteed to be safe, there is noneed to worry about the security of that module. If asystem should be constructed by correctly interconnecting only theoretically safe modules, that system
can be evaluated as being entirely secure. Increasing
the number of theoretically safe modules will clearly
contribute to achieving system security. While cryptography is typical of theory that can guarantee security, mathematics, including cryptography, cryptographic protocols, and formal methods, forms thefoundation of this theory. Attention is also being
given to physics. If quantum information processing
becomes possible, we can expect the prevention of
new forms of eavesdropping and data alteration to befound not only in communications but in data processing.
5.2 G uaranteeing security by using a data-driven
approach
Theoretically guaranteeing the security of all targets is difficult, so it is necessary to guarantee certain
items in a data-driven manner. For example, given an
infrastructure system consisting of multiple devices,
one approach is to record the state of all constituent
devices and evaluate risk. This work would be carriedout throughout a supply chain and its operations. The
records of these states constitute data, and their evaluation is called a data-driven approach. Those parts ofan evaluation result that can be used at other times
and in other environments can be reformatted andreused. This data-driven approach can be applied toany security target in addition to infrastructure systems. We call such data for conducting re-evaluations
trust data, which includes both positive and negativeevaluations with regard to safety. Using trust data
enables a data-driven type of security guarantee.
Trust data are not intended to be absolute overall but
rather local and fair.
5.3 C ommunication for a consensus of securitylevel
In addition to the theoretical and data-driven continuous approaches, there is the communication
approach in relation to forming agreements that wehave come to recognize as being extremely necessary.
We noticed that we have to consider how to establish
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Extended

Security

Continuous

Efficient

TheoryDatadriven
approachCommunication

Fig. 2. Three pillars of security R&D.

a security policy, which is a precondition of executing
security measures, by considering what is safe to do,
and what should be done so that people can live theirlives to the fullest without anxiety. To establish a
policy that confirms a security motivation, we believethat forming agreements through communication
between the parties concerned becomes important
while extending security in the narrow sense to ethics, customs, and social objectives. We are studying amechanism for forming agreements on security decisions by concerned parties and a mechanism forevaluating whether operations can actually be carried

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out according to the agreed-upon decision.
6. Conclusion
In this article, we reorganized the direction of security R&D in the IOWN era from the viewpoints ofextended, efficient, and continuous security and outlined the security technologies that we will target by
the three pillars of theory, data-driven approach, andcommunication. We aim to create a society withoutanxiety regarding security with high ethical standards
and technologies.

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Shinichi Hirata

Vice President, Head of NTT Social Informatics Laboratories.
He received a B.S. in mathematics from Hokkaido University in 1990. He joined NTT thesame year and has been engaged in R&D of
cryptography, IC card technology, and authentication systems.

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Vol. 20 No. 1 Jan. 2022

Katsumi Takahashi

Executive Research Scientist, Chief Security
Scientist, NTT Social Informatics Laboratories.
He received a B.S. in mathematics from Tokyo
Institute of Technology in 1988 and Ph.D. in
information science and technology from the
University of Tokyo in 2006. He joined NTT in1988 and has studied information processing
technologies including security and privacy.

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Feature Articles: Research and Development ofSecurity in the IOWN Era

Secure Optical Transport Network
Tetsuya Okuda, Koji Chida, Daisuke Shirai,
Sakae Chikara, Tsunekazu Saito, Misato Nakabayashi,
Kazuki Yamamura, Yuri Tanaka, Katsuyuki Natsukawa,
and Koichi Takasugi
Abstract

The implementation of an optical transport network, especially between datacenters, has been progressing. Similar to the Internet, communications on the optical transport network are protected bypublic-key cryptography and symmetric-key cryptography, but there are concerns that advances in the
research and development of quantum computers will pose a risk to current cryptographic systems,
public-key cryptography and key exchange in particular. In response to this problem, researchers at NTT
Social Informatics Laboratories and NTT Network Innovation Laboratories are engaged in the researchand development of safe key-exchange schemes to counter the cryptographic risks posed by quantum
computers. They are also engaged in architecture design and tests with actual equipment with the aim ofapplying such key-exchange schemes to the optical transport network.
Keywords: optical transport network, quantum key distribution, post-quantum cryptography

1. Background
1.1 What does “transport” mean?
“Transport” is often defined as “carrying” (as inphysical distribution) or “transmission” (as in communications). In other words, it generally refers tocorporate distribution and transport services and tocommunication and transmission services. To make iteasy to imagine the features of a secure optical transport network as a technology affixed with the label“transport,” we begin our discussion using distribution and transport services as an example (Fig. 1).
What are the features of distribution and transport
services by truck? Various images may come to mind,
such as the carrying of many goods at one time andthe prompt delivery of goods after orders are placed.
We take up such features from the five viewpoints
listed in Table 1.
First, in distribution and transport services, large
capacity and low delay are features that are mostimportant to customers and that give value to these
services. Large capacity means a large number oftrucks and low delay means short truck queuing time.
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From the viewpoint of running a distribution andtransport business, efficient operations are essential,
which can be expressed as the optimization of distribution and the economical management of daily
operations. Many questions are now being asked
about the social impact of services, so concerns about
environmental load and safety have also become service features. Environmental load means low levelsof exhaust gas/carbon dioxide (CO 2) and safetymeans correct delivery of goods and few traffic accidents.
What do these features mean in communication andtransmission services? Large capacity and low delay
are also the features that are the most important tocustomers and that give value to these services. Using
terms from the field of communications, large capacity means high throughput and low delay means low
latency. From the viewpoint of running a communication and transmission enterprise, efficient operations
are likewise essential, which can be expressed as
network efficiency in providing communication andtransmission services. Finally, it is also true in thecommunications industry that the social impact of32

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Distribution site A(communicationssite A)

Distribution site B(communicationssite B)

Fig. 1. What does “transport” mean?

Table 1. Comparison of distribution/transport and communication/transmission services.
Distribution/transport services

Communication/transmission services

Large capacity

Service features

Number of trucks

Throughput

Low delay

Truck queuing time

Latency

Efficient operations

Distribution optimization

Communication network optimization

Environmental load

Exhaust gas/CO2

Power consumption

SafetyCorrect delivery of goods
Few traffic accidents

Few communication failures
High level of security

services has come under the spotlight, so environmental load and safety have also become of concern.
In this industry, environmental load means low power
consumption and safety means few network failures
and a high level of security.
Among the five viewpoints listed in Table 1, theInnovative Optical and Wireless Network (IOWN)
and All-Photonics Network (APN) under researchand development at NTT aim for services that take
into account the three points of large capacity, lowdelay, and low environmental load that appeal most to
customers [1]. The first step in adding the viewpointof “safety = security” to IOWN/APN is the secure
optical transport network proposed in this article.
1.2 Necessity of an optical transport network
Many people have come to appreciate how theirlives have become more convenient thanks to theproliferation of mobile phones and smartphones andthe expansion of the large-capacity and low-latency
fifth-generation mobile communications system
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(5G). Large capacity and low latency are also desirable features in communication and transmission
services targeting corporate customers. Customer
needs have come to focus on datacenter interconnect
services envisioning the need for datacenter disasterrecovery as well as on uncompressed video transmission services for remote production to enable simultaneous and parallel work between a video production site in the field and an editing site. Transmitting
such large-capacity data with low latency in real timeto the extent possible requires the application of optical transport [2]. This article introduces our efforts in
adding security to optical transport.
2. Current technologies
2.1 Internet standards
To add security to communication and transmission
services, we can expect the application of current
technologies used on the Internet to be effective andto mature in terms of evaluating security the longer
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IKE

IKE
Internet

SA(D)

SA(D)

ESP
/AH

ESP
/AH

Fig. 2. IPsec architecture.

they stay in use.
On the Internet, Secure Sockets Layer/Transport
Layer Security (SSL/TLS) and Security Architecture
for Internet Protocol (IPsec) are typical protocols
used for configuring safe communication paths(secure channels). SSL/TLS is a standard protocol for
configuring a secure channel between a web serverand client. IPsec is a standard protocol for configuring secure channels between sites such as between acompany’s main office and its branch offices. It is atechnology used in virtual private network services.
The secure optical transport network introduced inthis article is a communication and transmission service operating between sites.

tography, which uses a problem that is difficult tosolve mathematically as a basis for ensuring security.
For example, the Rivest-Shamir-Adleman (RSA)
cryptosystem uses the fact that factoring the productof two large prime numbers takes an extremely longamount of time as a basis for security. However, if agenuine quantum computer having error resilience
could be achieved, factoring the product of two large
prime numbers could be performed in a relatively
short time. If so, the RSA cryptosystem could nolonger be called secure. To solve this problem, we
have been researching and developing a key-exchange
scheme that cannot be broken by a quantum computer.

2.2 IPsec
IPsec for configuring a secure channel betweensites is specified by the Internet Engineering Task
Force (IETF), an organization that formulates defacto Internet standards. The IPsec specifications areorganized into architecture, encryption, authentication, and key exchange [3].
IPsec’s architecture features the following mechanisms: Internet key exchange (IKE) that exchanges
keys, encapsulated security payload (ESP) that performs encryption and authentication, authentication
header (AH) that performs authentication, and security association database (SAD) that conveys the keys
agreed upon in IKE via ESP or AH (Fig. 2). “Authentication” includes message authentication and entity
authentication, which test the validity of a message
delivered from a communication destination and thatof the communication destination, respectively.
Next, we discuss how this IPsec configuration
might change in a secure optical transport network.

3.2 Quantum key distribution
Quantum key distribution (QKD) is a mechanism
for distributing keys by quantum physics. It sharesinformation on a secret key via quantum states on aquantum channel that can transmit quantum states.
The most outstanding feature of QKD is the ability todetect eavesdropping by a third party when sharing
the secret key. This originates in a property unique toquantum mechanics that measuring a quantum statechanges the state. If a third party is attempting toeavesdrop, that is, to carry out measurements while
two parties are sending and receiving a quantum
state, the sent quantum state and received quantum
state will differ. Consequently, if the two parties
should then check with each other on their sent andreceived states and find that they differ, they would be
able to detect that a third party is eavesdropping. Performing this process of sending/receiving quantum
states and checking for eavesdropping repeatedly
increases accuracy and eventually enables the twoparties to share a secret key.

3. Issues and proposals (I): Possibility ofadvances in quantum computers
3.1 Possibility of advances in quantum computers
Current communications on the Internet and othernetworks use key exchange based on public-key crypNTT Technical Review

Vol. 20 No. 1 Jan. 2022

3.3 P
 ost-quantum cryptography-based key distribution
Post-quantum cryptography (PQC) is a public-keycryptography and key-distribution mechanism inwhich problems that are mathematically difficult to34

Feature Articles

2
b1

1

b2

0
shortest vectors
−1
−2
−4

−2

0

2

4

Two-dimensional lattice vectors (blue points) generated by basis
vectors {b_1, b_2} = {(3, 1), (4, 0)}. The shortest vectors in this lattice
are (1, -1) and (-1, 1). The shortest vector problem—a major lattice
problem—consists of finding the shortest vectors when given basis
vectors {b_1, b_2}.

Fig. 3. Example of a lattice problem difficult for quantum computers.

solve provide a basis for security. In particular,
problems that are assumed to be difficult even for aquantum computer to solve are used as grounds forsecurity. In lattice-based cryptography, for example,
it is assumed that finding the lattice points closest to
the origin in a given set of lattice points is a difficult
problem to solve even for a quantum computer,thereby providing a basis for security.
At NTT, research and development in this area iscentered about NTRU, a type of PQC lattice-based
cryptography incorporated in technology developedby a team including NTT (Fig. 3).
We generically refer to QKD and PQC-based key
distribution (PQKD) as xKD.
4. Issues and proposals (II): Countermeasuresagainst new attackers in architecture design
4.1 C ountermeasures against attackers in a zerotrust network
Designs that envision attackers in a zero trust network, which, as the name indicates, is a closed network that cannot be trusted [4] have become widespread. In this architecture design, it is necessary toassume attackers on all types of networks including
telecommunications carrier networks and intra-site
networks. In a telecommunications carrier network, it
is assumed that an attacker will be intercepting communications by physically connecting to optical fiber,
while in an intra-site network, it is assumed that an
NTT Technical Review

Vol. 20 No. 1 Jan. 2022

attacker intercepting communications has accessrights in that network.
We first consider an attacker attempting to intercept
communications by physically connecting to opticalfiber in a telecommunications carrier network. A
defense can be mounted through hop-by-hop encryption such as OTNsec, a protocol that protects Layer 1(physical layer), and MACsec, a protocol that protects Layer 2 (data link layer). Implementing encryption functions in lower layers in this manner should
enable the addition of security without hindering the
low-latency feature of IOWN/APN.
Next, to defend against an attacker who is attempting to intercept communications within an intra-site
network while having access rights in that network,architecture design for inter-site communications
typified by IPsec must be reviewed from the bottom
up. In the secure optical transport network, key
exchange equivalent to IPsec/IKE described above
will correspond to xKD equipment, and encryption
equivalent to ESP/AH in IPsec will correspond to an
optical transponder or white-box switch. Given thetrend toward a disaggregated architecture describedlater, it must be assumed that separate devices will
perform key exchange and transmission and that the
key exchange and encryption functions that were
integrated in IPsec will take on a separated configuration(Figs. 4, 5, and 6). As a result, key information corresponding to SA(D) in IPsec will circulate in a network
external to the device, which means that new measures
35Feature Articles

IKE

IKE
Internet

SA(D)
ESP
/AH

IPsec
router

SA(D)
ESP
/AH

IPsec
routerFig. 4. Ordinary IPsec equipment configuration.

IKE

IKE
IKE equipment

IKE equipment

Intra-site network

Internet

Intra-site network
SA(D)

SA(D)
ESP
router

ESP
/AH

ESP
/AH

ESP
routerFig. 5. Configuration with IPsec equipment separated.

Optical fiber
direct

QKD

Intra-site network
PQKD

Intra-site network
Internet or
NTT network

PQKD equipment

SA(D)
WBS

PQKD
PQKD equipment

Intra-site network

WBS

QKD
QKD equipment

QKD equipment

Intra-site network

NTT network(APN, closed)

SA(D)
WBS

WBS

WBS: white-box switch

Fig. 6. Configuration with equipment of secure optical transport network separated.

must be studied for protecting communications on
any type of network assuming a zero trust network.
Specifically, it will be necessary to design a secure
method for key distribution from xKD equipment to
the optical transponder and a secure method forequipment authentication between xKD equipment
and the optical transponder. For details on these studies, the reader is asked to consult a previously published paper [5].

NTT Technical Review

Vol. 20 No. 1 Jan. 2022

4.2 N
 ecessity of architecture and equipment thatcan be tested from the outside
In a zero trust network, the ability to test the reliability of architecture, protocol, equipment, etc. fromthe outside is required. The ability to make updates
separately to architecture, protocol, equipment, etc. isalso required as a fundamental security measure in
anticipation of some type of danger. For architecture
design, protocol design, and equipment selection
described in this article, we adopted formal verification
36

Feature Articles

Videotransmission
controlfunction

Switching
controlfunctionxKD client
function

Opticaltransmission
controlfunction

Softwarefunction group

Network OS (Linux-based)
x86 architecture

VideoPIU

White-box switch

SwitchASIC

Encryptionfunction

SDI video signal

ASIC: application-specific integrated circuit
DSP: digital signal processor

Coherent
DSP

Hardwarefunction group

Optical transmission

OS: operating system
PIU: plug-in unit

Fig. 7. Disaggregated architecture of white-box switch.

and the white-box switch as technologies for testing
reliability from the outside and making updates separately.
4.3 Formal verification
At the time of protocol design including cryptography, there is a need for testing that can mathematically guarantee security as in maintaining the confidentiality of secret information within a protocol andensuring the integrity of messages. In this regard,
formal verification technology has been used for testing the safety of protocols such as SSL/TLS and
IPsec that serve as transport layers and for testing thesafety of authentication protocol on the 5G standard.
Formal verification is a technology that describes a
system and the properties that the system must satisfy
in a formal language and that tests whether the systemis satisfying those properties on the basis of logicalreasoning. In formal verification, there are many
components that can be automated by computer, so
this technology excels in testing results from the outside including checking for reproducibility and in
adaptively retesting in the face of protocol updates.
For the secure optical transport network introduced inthis article, we designed an IPsec-based protocol thatcombines xKD equipment with an optical transponder and tested its security using the ProVerif formal
verification tool [6].
4.4 White-box switch
Transmission equipment for optical-transport purposes had been provided in a form that integrated
NTT Technical Review

Vol. 20 No. 1 Jan. 2022

optical modules and various functions. In contrast,
there is also equipment that adopts technology thatenables flexible configuration changes, the additionof new functions, cost reductions, etc. by separating
the various functions of the transmission equipment
and controlling them by standardized interfaces in adisaggregated architecture. This equipment is calleda white-box switch or white-box transponder. In ourcurrent research, we have taken a white-box switch
and added an xKD client function for obtaining an
encryption key from xKD equipment in the software
function group in order to set the key and control theencryption function of the hardware function group(Fig. 7). We also added a function for directly inputting an SDI (serial digital interface) signal (video
signal) and showed that uncompressed 8K60P video
in excess of 40 Gbit/s could be securely transmittedwith ultra-low latency using this function. Therefore,
we have demonstrated the feasibility of secure opticaltransport linking xKD equipment and optical transponders.
5. Toward the future
In this article, we introduced a secure optical transport network as an initiative to add security functions
to IOWN/APN now being researched and developedat NTT. We also introduced key issues and proposals
in relation to this initiative. We consider our efforts to
be one step in our ongoing plan to contribute to theprovision of safe and secure technologies and services.
37

Feature Articles

References
[1]
[2]

[3]

Website of NTT R&D, IOWN, https://www.rd.ntt/e/iown/
M. Tomizawa, A. Kaneko, and S. Kimura, “Device Technology
Development for Beyond 100G Optical Transport Network,” NTT
Technical Review, Vol. 14, No. 9, 2016.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=
ntr201609fa1.html
IETF, “Security Architecture for the Internet Protocol,” RFC 4301,
https://datatracker.ietf.org/doc/rfc4301/
IETF, “Internet Key Exchange Protocol Version 2 (IKEv2),” RFC
7296, https://datatracker.ietf.org/doc/rfc7296/

Tetsuya Okuda

Research Engineer, NTT Social Informatics
Laboratories.
He received a B.S. and M.S. from the University of Tokyo in 2009 and 2011. Since 2011, hehas been engaged in research & engineering on
security protocol at NTT. He is a member ofInformation Processing Society of Japan (IPSJ).
He received the IPSJ/Computer Security Symposium Student Paper Award in 2019.

Koji Chida

Senior Research Engineer, Supervisor, NTT
Social Informatics Laboratories.
He received a B.S., M.S., and Dr.Eng. fromWaseda University, Tokyo, in 1998, 2000, and2006. Since 2000, he has been engaged inresearch on cryptography and privacy-enhancing
technologies at NTT. He is a member of theInstitute of Electronics, Information and Communication Engineers (IEICE) and IPSJ. He
received the IPSJ Best Paper Award in 2012.

[4]
[5]

[6]

IETF, “IP Encapsulating Security Payload (ESP),” RFC 4303, https://
datatracker.ietf.org/doc/rfc4303/
IETF, “IP Security (IPsec) and Internet Key Exchange (IKE) Document Roadmap,” RFC 6071, https://datatracker.ietf.org/doc/rfc6071/
S. Rose, O. Borchert, S. Mitchell, and S. Connelly, “Zero Trust Architecture,” NIST SP 800-207, Aug. 2020.
S. Maeda, M. Nakabayashi, and T. Okuda, “Architecture Design and
Security Evaluation with Formal Verification for Secure Optical
Transport Network,” 95th Conference of the Special Interest Group on
Computer Security (IPSJ-CSEC), Nov. 2021.
B. Blanchet, “Automatic Verification of Security Protocols in the
Symbolic Model: The Verifier ProVerif,” Foundations of Security
Analysis and Design VII, pp. 54–87, Springer, 2013.

Sakae Chikara

Senior Research Engineer, Information Security Technology Research Project, NTT Social
Informatics Laboratories.
He received a B.E. and M.E. in electrical andelectronic engineering, system of electronic from
Tokyo Institute of Technology in 1988 and 1990.
He joined NTT Telecommunication Networks
Laboratory in 1990 and studied network architecture, network management systems, and distributed computing systems. He also joined the
projects of ITS (intelligent transport systems),
development of cryptographic systems, andinformation security systems. His current interests are secure network systems, especiallyquantum computing systems, post quantum
computing systems, and fiber optical network
systems. He is a member of IEICE.

Tsunekazu Saito

Senior Research Engineer, NTT Social Informatics Laboratories.
He received a B.S. and M.S. from Waseda
University, Tokyo, in 2006 and 2008 and Ph.D. inmathematics from Kyushu University, Fukuoka,
in 2011. Since 2011, he has been engaged inresearch on elliptic curve cryptography and postquantum cryptography at NTT.

Daisuke Shirai

Senior Research Engineer, Supervisor, Frontier
Communication Laboratory, NTT Network Innovation Laboratories.
He received a B.E. in electronic engineering,
M.E. in computer science, and Ph.D. in media
design from Keio University, Kanagawa, in 1999,
2001, and 2014. He pioneered the world’s first
4K JPEG 2000 codec system, which enables low
latency 4K60p video transmission on a Gigabit
network. He has applied his expertise acrossmultiple domains through his study of practicalapplications in digital audio and video broadcasting technology, image coding, information theory, networking, human-computer interaction, andsoftware architecture. His current research topics
include remote video production network, ultralow latency visual communication and its security over optical transport networks.

NTT Technical Review

Vol. 20 No. 1 Jan. 2022

Misato Nakabayashi

Information Security Technology Research
Project, NTT Social Informatics Laboratories.
She received an M.Sc. from Tohoku University, Miyagi, in 2019 and joined NTT the same
year. Her current research interest is in formal
verification.

38

Feature Articles

Kazuki Yamamura

Information Security Technology Research
Project, NTT Social Informatics Laboratories.
He received an M.S. from Japan Advanced
Institute of Science and Technology (JAIST),
Ishikawa, in 2021. Since 2021, he has been
engaged in research on cryptography at NTT.

Yuri Tanaka

NTT Social Informatics Laboratories.
She received a B.E. and M.E. from Keio University, Kanagawa, in 2019 and 2021. Sincejoining NTT Secure Platform Laboratories in
2020, she has been engaged in research on quantum security and computing. She is a member of
the Physical Society of Japan.

NTT Technical Review

Vol. 20 No. 1 Jan. 2022

Katsuyuki Natsukawa

Executive Research Engineer, Supervisor,
NTT Social Informatics Laboratories.
He received an M.E. from Nara Institute of
Science and Technology in 1996. He joined NTT
the same year and is currently conducting R&D
on data protection technologies centered on cryptography.

Koichi Takasugi

Executive Research Engineer, Director, Headof Frontier Communication Laboratory, NTT
Network Innovation Laboratories.
He received a B.E. in computer science from
Tokyo Institute of Technology, M.E. from JAIST,
and Ph.D. in engineering from Waseda University, Tokyo, in 1995, 1998, and 2004. He wasinvolved in the design and standardization of the
Next Generation Network architecture. He has
implemented and installed super high-density
Wi-Fi systems in several football stadiums. He
was also active in the artificial intelligence field,
such as diagnosing diabetes by machine learning.
He is currently leading research on the networkarchitecture and protocols in optical and wirelesstransport networks.

39

Feature Articles: Research and Development ofSecurity in the IOWN Era

Cryptographic Circuit Technology
Consisting of Optical Logic Gates
Junko Takahashi, Koji Chida, Kimihiro Yamakoshi,
Shota Kita, and Akihiko Shinya
Abstract

With the progress in nanophotonics, miniature optical devices have been fabricated and the researchand development of optical logic gates has become active. We are researching cryptographic circuits
consisting of optical logic gates for use in data encryption and authentication in optical computing andoptical information communications on the All-Photonics Network, a key element of the Innovative
Optical and Wireless Network. In this article, we introduce methods of implementing cryptographic
circuits using optical logic gates for the Advanced Encryption Standard, which is one of the de facto
standard algorithms.
Keywords: All-Photonics Network, optical logic gate, cryptographic circuit

1. Optical computational operations on the
All-Photonics Network
information-processing platform
Targeting the All-Photonics Network (APN) information-processing platform, a key element of theInnovative Optical and Wireless Network (IOWN),
we aim to achieve low-power, high-quality, largecapacity, and low-latency information processing by
introducing optical technology from the communications network and communications platform up toterminal devices. While data processing on conventional network equipment and computational operations on terminal devices had been executed on electronic circuits, the use of optical technology in such
equipment and devices on the APN information-processing platform should improve processing andoperation performance. Optical circuits consisting of
optical logic gates to enable logical operations constitute one example of optical technology. It has beenshown, for example, that optical circuits can be used
for the computational operations required by learningalgorithms in the field of deep learning and that lowlatency and low-power operations can be achieved[1].

NTT Technical Review

Vol. 20 No. 1 Jan. 2022

2. Optical cryptographic circuit technology
On the APN information-processing platform, optical circuits will be used to achieve various types ofdedicated hardware to improve computing performance. Therefore, optical circuits will also be used to
implement dedicated cryptographic hardware
required for ensuring the safety of this platform. It isalso desirable for the circuits to be designed to suppress delay and power consumption so that cryptographic operations will not result in overall performance bottleneck. Taking this into account, we havebeen researching optical cryptographic circuits thatcan execute encryption and authentication operations
by optical signals. In this section, we introduce methods for implementing the Advanced Encryption Standard (AES) by optical circuits.
2.1 AES encryption scheme
AES is a block cipher with a 128-bit block length.
Key length may be selected from 128, 192, or 256 bits[2]. Here, 128 bits of intermediate values called a“state” are represented by a 4 × 4 matrix with eachelement consisting of 8 bits. Repeated application ofa round function—the basic structure of encryption—
to the state outputs the ciphertext. The round function
40

Feature Articles

Voltage ON (electrical signal “1”)Voltage ON/OFF

Optical coupler

Input light

Output light

Optical coupler

Phase
shifter

Voltage OFF (electrical signal “0”)Input light
Output light(a) MZI switch(b) Switch operation

Fig. 1. MZI switch and its operation.

consists of SubBytes, which is a nonlinear operation,
ShiftRows and MixColumns, which are linear operations, and AddRoundKey, which combines the state
and key. This section focuses on SubBytes and MixColumns as the main operations of AES and introduces methods for achieving these operations by
optical circuits.
2.2 Implementing SubBytes by optical logic gates
The SubBytes operation converts each byte toanother byte on the basis of a substitution box (S-box)
table determined from specifications. The S-box table
is an 8-bit input/output nonlinear conversion. Given a
set of 8 bits as input, the operation references thetable to obtain an 8-bit output value. For example, theS-box output for an input value of 0xf0 would be
0x8c (input/output values are expressed in hexadecimal numbers).
This type of conversion based on a table can be
implemented using a Mach-Zehnder interferometer
optical switch (MZI switch), which is a type of optical logic gate. As shown in Fig. 1(a), an MZI switch
consists of optical couplers and a phase shifter.
Applying a voltage to the path embedded in the phaseshifter can change the refractive index of the opticalwaveguide, thus changing the phase difference
between the two paths. This enables the MZI switch
to operate as a switch that changes the optical pathway. In Fig. 1(b), for example, when inputting lightinto the upper path and applying a voltage to the pathembedded in the phase shifter (corresponding to elecNTT Technical Review

Vol. 20 No. 1 Jan. 2022

trical signal “1”), the optical signal travels straightahead resulting in output from the upper path. However, when not applying a voltage (corresponding toelectrical signal “0”), the optical signal crosses overto the lower path resulting in output from that path.
We devised a method for implementing table conversion that outputs a 1-bit optical signal against 8
input bits. This is accomplished by interconnecting a
number of MZI switches in accordance with the number of input bits in table conversion and switchingpaths (Fig. 2). In Fig. 2, the method prepares 256 (=28) optical signals branched from a single opticalsource in which each optical signal is set to “light on”(corresponding to an optical signal of bit “1”) or“light off” (corresponding to an optical signal of bit“0”). The method then passes light through the MZIswitches while selecting paths in accordance with the
8-bit input (x1, x2, …, x8) and finally selects and outputs one optical signal. This method achieves table
conversion that outputs a 1-bit optical signal against
an 8-bit input using MZI switches.
Interconnecting multiple MZI switches, as
described above, and appropriately setting the 256
optical signals makes it possible to configure an
S-box table. Input to the S-box table is set as MZIinput (electrical signals) and output of the S-box table
is set as an optical signal. For example, if the leastsignificant bit of each of the 256 values of the S-box
table is set as an optical signal, then the least significant bit of the S-box table output with respect to the
8-bit input (x1, x2, …, x8) can be obtained. In the same41

Feature Articles

Input 8 bits (electrical signals)
MZI switch
X8

X7

X6

X5

X4

X3

X2

X1

1
0
1
1
0

Output 1 bit (optical signal)
Selects and outputs one
optical signal from multiple
optical signals“1”

Optical signals(256 (= 28))0
10Fig. 2. Method of implementing table conversion using MZI switches.

OutputState

Fixed matrix

(a)

(b)

Y1

02

03

01

01

X1

Y2

01

02

03

01

X2

Y3

01

01

02

03

X3

Y4

03

01

01

02

X4

Y1 = {02} • X1  {03} • X2  X3  X4 …(1)Legend:: Exclusive OR (XOR)•: Multiplication

Fig. 3. Configuration of MixColumns in AES.

manner, if the nth bit (n = 1, …, 7) of each of the 256
values of the S-box table output is set as an opticalsignal, the nth bit of the S-box table output withrespect to the 8-bit input can be obtained.
To obtain 8 bits of S-box table output, the above
processing can be repeated 8 times by time divisionmultiplexing or 8 instances of the circuit in Fig. 2 canbe implemented in parallel. For optical signals, it isalso possible to calculate 8 bits of S-box table output
using only one instance of the circuit in Fig. 2 bymultiplexing eight wavelengths and deriving the nth
bit of the S-box table for each wavelength.
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2.3 Implementing MixColumns by optical logicgates
As shown in Fig. 3(a), the MixColumns operation
is defined as the multiplication of a fixed matrix andthe state (where X and Y indicate 8-bit values). On
calculating this matrix equation, each 8-bit output canbe expressed using Eq. (1) shown in Fig. 3(b) (onlyY1 is shown in the figure). Furthermore, in carryingout these multiplications, Eq. (1) can be expressed asfive 5-bit exclusive OR (XOR) operations (an XOR
operation with 5 input bits and 1 output bit) and three
7-bit XOR operations (an XOR operation with 7
42

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Input optical signal A

Junction point
Output optical signal

Input optical signal B
Y-gateOpticalsignalCase

Input optical signal A

Input optical signal B

Output opticalsignalOutputbit value

(1)

0

(2)

1

(3)

1

(4)

0

Fig. 4. XOR operation using a Y-gate.

input bits and 1 output bit) [2]. To give an example,
we present a method for configuring a 7-bit XOR
operation by optical logic gates. A 5-bit XOR operation can be configured in the same manner.
A Y-gate is an optical device that can execute an
XOR operation [3]. A Y-gate superposes two input
optical signals at a junction point where they meet.
An XOR operation or OR operation can be achieved
using the property that an optical signal is a “wave”
having amplitude and phase, which results in operations approximately 300 times faster than those withelectrical logic gates [3].
The principle of an XOR operation by a Y-gate isshown in Fig. 4. This Y-gate inputs two optical signals (input optical signal A and input optical signal B)of equivalent amplitude having a phase difference of180°. In Fig. 4, “—” indicates a state in which theamplitude of the input optical signal is 0, that is, astate in which there is no input optical signal. These
two optical signals are input into the Y-gate and themagnitude of the output optical signal is determined.
In case (4) in Fig. 4, for example, the two input optical signals have equivalent amplitude but a phasedifference of 180° with the result that the signals
cancel each other out, making the amplitude of theoutput signal 0. Therefore, if we assign bit “0” to thestate in which the amplitude is 0 and bit “1” to thestate in which the magnitude of the amplitude isessentially the same as that of the input optical signal,an XOR logical operation can be executed, as shown
NTT Technical Review

Vol. 20 No. 1 Jan. 2022

by the bit values of the output optical signal in the
figure. In other words, an XOR operation can beachieved using a Y-gate by limiting the two input
optical signals to a phase difference of 180°.
However, while executing a 7-bit XOR operation
would involve the connecting of multiple Y-gates,
taking the results of XOR operations as the input of
the next XOR operation means that the phase difference of the two input optical signals of each Y-gatewould not necessarily be 180°. (For example, when
executing a 4-bit XOR operation (a⊕b⊕c⊕d), theresult of the XOR operation between a and b and thatbetween c and d could both be the output of case (2),and those results would then be input to another XOR
operation.) There is therefore a need for an operationthat can change the phase difference of the two input
optical signals to each Y-gate depending on operation
results. Such an operation, however, would increase
delay and power consumption.
To eliminate this need for converting phase during
operations, we devised a method that operates on the
input to a Y-gate as optical signals having the same
phase and corrects the output result by threshold processing at the end of the operations. This method is
outlined in Fig. 5. It consists of Y-gate superposition
and threshold processing within an optical detector.
Y-gate superposition adds up optical-signal amplitudes using a total of 7 Y-gates (since there are 7 input
signals, the amplitude of the 8th input is taken to be“0” (light off). Threshold processing, however, uses
43

Feature Articles

x1

Y-gate

Z1

x2

W1
Z2

x3
Input
light

Output light

Optical detector:
amplitude detection +threshold processing

Operation result(electrical signal)
y

x4
Z3

x5

W2

x6

y=1

Z4

x7

…

0
Light
Case

x1

x2

x3

Z1

Z2

W2

Output
light

y=1
y=0

1
y=1
2

128

Fig. 5. Method for implementing a 7-bit-input/1-bit-output XOR operation.

the fact that the greater the number of optical signals
with non-zero amplitudes from among the input optical signals (x1, x2, x3, x4, x5, x6, x7), the larger theamplitude of the output optical signal. It detects themagnitude of this amplitude to determine the output
bit. On detecting no output signal (light off) or an
amplitude that is an even multiple (2, 4, or 6 times aslarge) of the amplitude of the input signals, the output
result is determined to be bit “0”, and on detecting anamplitude that is an odd multiple (1, 3, 5, or 7 times
as large) of the amplitude of the input signals, theoutput result is determined to be bit “1”. This method
enables XOR operations without having to convert
the phase of input optical signals at every Y-gate
operation. It also enables the processing of Y-gate
output to be decreased from 7 times (the number of
Y-gate outputs) to 1 time (only at the time of threshold processing).
If we let the 7-bit XOR and 5-bit XOR operations
calculated from Eq. (1) in Fig. 3(b) correspond to theoperation method shown in Fig. 5, one bit of Y1 canbe calculated. As with the SubBytes implementations, the calculation of Y1 (8 bits) can be implemented by either of three methods: time division multiplexing, using multiple operation circuits, or multiNTT Technical Review

Vol. 20 No. 1 Jan. 2022

plexing wavelengths in one operation circuit.
3. Future developments
We devised methods for implementing AES
encryption circuits using optical logic gates. Goingforward, ensuring safety on the APN informationprocessing platform will require an optical security
accelerator that implements security technologies by
optical circuits for logical operations, authentication,etc. through a variety of encryption schemes. This
type of accelerator is considered a constituent of photonic disaggregated computing [4], a type of architecture supporting the APN information-processing
platform shown in Fig. 6. The central processing unit,
memory, and other types of devices had been confined to servers, but photonic disaggregated computing is a new architecture that can be treated as computers on a rack or a datacenter scale by connecting
and distributing those devices over a high-speed
optical network. An optical security accelerator willlead to a safe photonic disaggregated computing platform and the provision of safe smart services on that
platform. To achieve a low-latency and low-power
optical security accelerator, we will continue our
44

Feature Articles

Smart sports

Smart mobility

Smart city

Smart agriculture

Photonic disaggregated computing platform
Optical security accelerator
Source: N. Shibutani, “NTT’s Growth Strategy from the Perspective ofCTO,” NTT IR DAY 2020 (2020).

Fig. 6. APN information-processing platform equipped with optical security accelerators.

research on new schemes for implementing encryption and authentication processes by taking advantage of optical characteristics. Therefore, we wish tocontribute to the deployment of a safe IOWN.
References[1]

J. Peng, Y. Alkabani, S. Sun, V. J. Sorger, and T. El-Ghazawi,“DNNARA: A Deep Neural Network Accelerator using Residue,”Arithmetic and Integrated, ICPP 20: 49th International Conference on

NTT Technical Review

Vol. 20 No. 1 Jan. 2022

[2]
[3]
[4]

Parallel Processing - ICPP, No. 61, pp. 1–11, (2020).
National Institute of Standards and Technology (NIST), “Announcing
the ADVANCED ENCRYPTION STANDARD (AES),” Federal
Information Processing Standards Publication 197, 2001.
S. Kita, K. Nozaki, K. Takata, A. Shinya, and M. Notomi, “Ultrashort
Low-loss Ψ Gates for Linear Optical Logic on Si Photonics Platform,”
Commun. Phys., Vol. 3, Article number: 33, pp. 1–8, 2020.
A. Okada, S. Kihara, and Y. Okazaki, “Disaggregated Computing, theBasis of IOWN,” NTT Technical Review, Vol. 19, No. 7, pp. 52–57,
July 2021.
h t t p s : / / n t t - r ev i ew. j p / a r c h ive / n t t t e c h n i c a l . p h p ? c o n t e n t s =ntr202107fa7.html

45

Feature Articles

Junko Takahashi

Senior Researcher, Information Security Technology Research Project, NTT Social Informatics Laboratories.
She received a B.S. and M.S. in physics fromWaseda University, Tokyo, in 2004 and 2006, andPh.D. in engineering from the University ofElectro-Communications, Tokyo, in 2012. She
joined NTT Information Sharing Platform Laboratories in 2006. She has studied hardware security such as side-channel analysis and automotive
security and has been studying security of opticalcircuits. She is a member of the Institute of Electronics, Information and Communication Engineers (IEICE) and Information Processing Society of Japan (IPSJ). She has been a member oftechnical committee on hardware security in the
IEICE and special interest group on systemarchitecture in the IPSJ. She was awarded the2008 Symposium on Cryptography and Information Security (SCIS) paper prize, and her paper in
Journal of Information Processing Vol. 25 wasselected as a specially selected paper from the
IPSJ in 2017. She also received best paper
awards from international conferences such as
the International Conference on Information andCommunications Security (ICICS) 2020 andInternational Workshop on Security (IWSEC)
2020.

Koji Chida

Senior Research Engineer, Supervisor, Information Security Technology Research Project,
NTT Social Informatics Laboratories.
He received a B.S., M.S., and Dr.Eng. fromWaseda University, Tokyo, in 1998, 2000, and2006. Since 2000, he has been engaged inresearch on cryptography and privacy-enhancing
technologies at NTT. He is a member of IEICE
and IPSJ. He received the IPSJ Best Paper Awardin 2012.

Shota Kita

Senior Researcher, Photonic Nanostructure
Research Group of NTT Basic Research Laboratories and NTT Nanophotonics Center.
He received a B.E., M.E., and Ph.D. in engineering from Yokohama National University in
2007, 2009, and 2012. He was a postdoc
researcher in Loncar’s group at Harvard University, USA, for 3 years. He returned to Japan andjoined Notomi’s group at NTT Basic ResearchLaboratories, where he is investigating nanophotonic devices and circuits. His interests are insilicon photonic-based nanofabrication andpackaging technologies. He received the Poster
Presentation Award at the International NanoOptoelectronics Workshop (iNOW) 2009 andYoung Scientist Presentation Award from theJapan Society of Applied Physics (JSAP) in
2010. He is a member of JSAP, IEICE, and Optical Society (OSA).

Akihiko ShinyaGroup Leader, Senior Research Scientist,
Supervisor, Photonic Nanostructure ResearchGroup of NTT Basic Research Laboratories and
NTT Nanophotonics Center.
He received a B.E., M.E., and Ph.D. in electrical engineering from Tokushima University in
1994, 1996, and 1999. In 1999, he joined NTT
Basic Research Laboratories, where he has been
engaged in R&D of photonic crystal devices. He
is a member of JSAP and the Laser Society ofJapan.

Kimihiro Yamakoshi

Senior Research Engineer, Information Security Technology Research Project, NTT Social
Informatics Laboratories.
He received a B.E. in physics from Waseda
University, Tokyo, in 1988 and M.E. in physics
from Tokyo Institute of Technology in 1990. He
joined NTT in 1990 and engaged in research anddevelopment (R&D) of LSI (large-scale integrated circuit) design and high-speed network
switching systems. In 2004, he moved to NTT
Cyber Communications Laboratory Group,
where he researched IC-card security technology
including measures against side-channel attacks.
In 2007, he moved to NTT Microsystem Integration Laboratories and engaged in R&D of lowpower wireless ubiquitous terminals. He is currently investigating an information security
technology for IOWN.

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46

Feature Articles: Research and Development ofSecurity in the IOWN Era

Trusted Data Space for Creating
Value from Data in a Chain Reaction
MannerTomoaki Washio, Hiroki Itoh, Koki Mitani,
Gembu Morohashi, Kenji Umakoshi, Tetsuya Okuda,
Kazuyuki Takaya, Kei Ohmura, and Gen Takahashi
Abstract

The Smart World holds the possibility of maximizing the value of data throughout society by enabling
diverse organizations to bring each other data for analysis and create data for new purposes in a chain
reaction manner beyond the walls of companies and industries. In reality, however, the use of data amongorganizations goes no further than the provision of limited data to limited parties, which prevents a value
chain from being achieved. This article introduces a new mechanism for data sharing called “trusted data
space” as an initiative to solve this problem and describes key technologies for making it a reality.
Keywords: security, data sharing and utilization, data space

1. Smart World enabling data sharing
across industries
There has been much activity in the research anddevelopment of technology for not only reproducing
real-world systems such as manufacturing lines andchemical plants in cyberspace to analyze and predict
system operations but also for data sharing and analysis beyond individual organizations, business fields,
and industries.
In a smart city, for example, a massive amount of
output from sensors, video cameras, etc. installed inphysical space can be converted to data so that the
movements of people and things can be analyzed incyberspace in a cross-sectoral fashion. The results ofthis analysis could then be used as a basis for directing the behavior of people and things in the city, thatis, in the physical space. The Smart World that fuses
physical space and cyberspace in such an advancedmanner is fast approaching.
In the Smart World, data will be continuously generated from a variety of individuals and companies on
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a global scale at a level of quality and volume notseen before. There will therefore be a need for amechanism that can effectively use this massive
amount of diverse data. In particular, there is a needfor a data marketplace in which everyone can bringeach other data for analysis and generate data for new
purposes in a chain reaction manner beyond the wallsof companies and industries. This would have theeffect of uncovering value from each other’s data andmaximizing the value of data throughout society. Thismechanism is called “trusted data space” (hereafter,
data space).
Both providers and users participate in a data space.
The data in a data space, while placed under the management of the providers, can be used virtually in themanner of one massive data lake and searchedthrough freely. The providers present terms of datause (period of use, allowed processing, secondary use
conditions, etc.), while the users can use the data
within the allowed range after agreeing with thoseterms. This type of mechanism enables data collected
for a certain purpose to be used for a new purpose,47

Feature Articles

Trusted data space
Data sharing/utilization

Cross-sector
analysis/
prediction

Cyberspace

Domain linking
Domaindata

Domaindata

Domaindata

Domaindata

Domaindata

Domaindata

Domaindata

Domaindata

Feedback

Feedback
Transportation

Healthcare

Buildings

EnergyPhysical space

Housing

Distribution
logistics

Factories

Disaster/crime
prevention

Fig. 1. Smart World and trusted data space.

which points to the possibility of generating data withnew value from existing data in a chain reaction manner. For example, marketing data collected throughthe cooperation of amusement facilities, transportation operators, and eating and drinking establishments for making user recommendations on personal
behavior on a certain day could also be used by local
governments for various purposes such as disasterand crime prevention, promoting the health of its
residents, and urban development. In short, things
that could not be achieved by a particular business
entity alone would become possible (Fig. 1).
1.1 Issues with cross-organizational use of data
Despite heightened expectations for such a society,the social adoption of data sharing and analysis technology remains at the level of local value discovery.
Data collected by an organization is generally used
only for the purpose for which the data were collectedby the collecting company, while the use of data
among organizations stops at the provision of limited
data to limited parties, preventing the creation of avalue chain. We call this the “data sharing wall.”Overcoming the data sharing wall requires technology for resolving three types of issues: issues in discovering an appropriate data provider and optimaldata, issues in forming an agreement on data use, andissues in sharing and using data on the basis of thatagreement (Table 1).
By providing technology for resolving these issues,
we should be able to achieve a form of data sharingthat creates new value in a chain reaction manner
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while also maximizing the value of data throughout
society.
2. Trends in data sharing throughout the world
In Europe, data sharing is being revitalized with afocus on the manufacturing industry. Typical of thismovement is the Gaia-X [1] project that aims toestablish a data-sharing infrastructure for Europe.
The Gaia-X vision of supporting data sharing and use
on a European scale was announced on October 29,
2019 by the German and French governments. Thiswas followed by the founding of the Gaia-X AISBL
non-profit organization for achieving this vision in
January 2021. The plan is to construct an infrastructure that can provide a technical mechanism forensuring interoperability with diverse cloud services
while controlling data access based on rules andagreements and protecting data sovereignty *. In
Japan, the Data Society Alliance was founded on
April 1, 2021 in the wake of this movement with theaim of constructing a platform called DATA-EX [2]to facilitate data linking across diverse fields. A number of projects have been established as data sharing
initiatives using Gaia-X with the aim of constructing
data-sharing infrastructures composed of companies
in a trustworthy relationship such as a supply chain.
In Germany, for example, there is Mobility Data
Space for achieving Mobility as a Service (MaaS) and*Data sovereignty: The right of a data provider to determine therange of data disclosure, usage applications, etc.

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Table 1. Issues with cross-organizational data sharing.
Issues in discovering appropriate
data providers and optimal data

• Prevent data giving/receiving among undesirable parties• Enable data users to discover data applicable to their conditions

Issues in forming an agreement

Form an agreement between the data provider and data user on data-processing
conditions and process the data on the basis of those conditions

Issues in sharing and using data on
the basis of the agreement formed

Enable the data possessed by a provider to be processed and provided to data
users without disclosing the data and processing method to the other party

Catena-X
Germany: Automobile
supply chain

Smart
Connected Supplier Network
The Netherlands: Supply chains forsmall/medium-sized businesses

iShareThe Netherlands:
Data sharing

Mobility Data Space
Germany: Transportation

Japan data space

Fig. 2. Data sharing platform beyond industry walls.

Catena-X for achieving an automobile manufacturing
supply chain, while in The Netherlands, there is the
Smart Connected Supplier Network (SCSN) forsmall/medium-sized businesses in the manufacturingindustry. Catena-X and SCSN plan to build data sharing infrastructures on a scale of 1000 and 3000 companies, respectively, by 2022.
The construction of data-sharing infrastructures
across industries has already begun. However, thisprocess is still at the stage of setting up rules centeredabout Gaia-X; as a result, data sharing has been limited to companies that are already in a trustworthy
relationship. In addition, major issues are expected toarise from here on in terms of providing security toprotect data from cyber attacks and providing protection of data sovereignty that enables data sharing
while protecting the rights of data providers. The
questions to be answered are what technologies
should be implemented to achieve these goals andhow should such a system be constructed as a social
infrastructure (Fig. 2).
3. Technology for configuring a data space
The following three mechanisms must be considered to resolve the issues described in Section 1.
(1)	Mechanism for discovering data, applications,
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and business partners that can be trusted:
Catalog data/applications and business partners and visualize information on their reliability to gauge their appropriateness. Matchup with business partners that can be trusted
on the basis of this visualized information.
(2)	Mechanism for forming an agreement on dataprocessing conditions: Form an agreement
between the data provider and data user on
data-processing conditions, disclosure conditions, and processing methods on the basis of
cataloged information. Determine whether acertain type of data processing can proceed
according to the content of that agreement.
(3)	Mechanism for processing data based on anagreement: The data provider manages thedata on its own and virtually shares and integrates the data only when necessary. The data
user executes various types of analysis andprocessing deemed necessary while keeping
secret not only the data but the data-processing methods as well.
Current data processing executes risk managementon the basis of contracts such as non-disclosureagreements (NDAs) and operation management policies, but there is a need for corroboration based on technology, as in mechanism (3). To execute transactions
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Feature Articles

with unknown parties with which no business relationship has been established and create value in achain reaction manner, there is a need for forming anagreement on data-processing conditions, as in mechanism (2). Finally, there is also a need for discovering
partners, data, and applications that can be trusted, as
in mechanism (1).
We introduce a data-processing mechanism basedon an agreement centered about a data space. Thismechanism gathers and virtually integrates data dispersed among organizations and individuals in an
encrypted state through the use of a virtual data lake
and processes that data while they are encrypted byusing either of two methods: data sandbox or securecomputation. We also introduce our forward-looking
work on an agreement-forming mechanism for dataprocessing conditions.
3.1 Virtual data lake
When sharing one’s data with another party, only
the minimum required amount of data must be provided, and information protection and management
must be executed according to data usage conditions
established beforehand. A virtual data lake isachieved through technology that virtually integrates
data under different management entities scatteredover a wide area while maintaining the governance ofeach management entity and that transfers only aminimum amount of data on the basis of the requirements of the data user. On top of this, a virtual data
lake includes mechanisms for quickly informing thedata user that data generation has begun and forallowing the data user to begin using a portion of thatdata before data generation is fully completed. This
makes it possible to use even a large amount of dataat an early stage as needed and accelerate data sharing.
For example, a company that is generating data
could simultaneously generate and update data management information (metadata such as a data catalog
and control policies) and notify the platform of such.
The platform, in turn, could appropriately control the
sharing of that data by informing approved users of
the existence of that data and transmit to them that
portion of the data deemed necessary on the basis ofdata management information. In addition, users
would be able to find desirable data with good efficiency by referring to a virtually integrated list of data
and begin using those data at an early stage. Thesemechanisms enable safe and convenient use of data
beyond individual organizations.

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3.2 Data sandbox technology
Data sandbox technology brings together an organization that possesses data but no analytical technology and that has no desire to share that data withanother company and an organization that possesses
analytics technology but has no desire to share thattechnology. Therefore, analysis results can beobtained without these organizations having to sharedata and analytics technology with each other.
If a data owner and analytics technology ownerwere to reach an agreement on the use of a data sandbox, a dedicated data sandbox that includes data andanalytics technology could then be created on thebasis of that agreement. A data sandbox blocks communications with the outside and encrypts internal
communications, storage, and memory so that eventhe data sandbox provider cannot decrypt that content. In short, data can be analyzed without anyone
including the data owner, analytics technology
owner, and data sandbox provider accessing decrypted data or analytics technology.
The data sandbox saves the results of analysis in alocation that can be viewed by the data owner and/or
analytics technology owner on the basis of the agreement reached between those two parties. First, thecase in which the data owner may view the results ofanalysis means that the data owner can access analysis results without having to share data with anotherparty and that the analytics technology owner can becompensated for the use of its data analysis technology by the other party without having to share algorithms with another party, all through the use of a data
sandbox. Next, the case in which the analytics technology owner may view the results of analysis meansthat the data owner can be compensated for the use ofits data for analysis by the other party without having
to share data with another party and that the analytics
technology owner can access analysis results using
another party’s data that it does not possess without
having to share analytics technology with anotherparty, all through the use of a data sandbox.
3.3 Secure computation
Secure computation is an advanced encryption
technology that can process data while they are
encrypted without returning to the original data evenonce. In 2019, NTT developed secure computation
deep learning to provide security and privacy measures for data used in artificial intelligence (AI). This
technology executes deep-learning training and prediction while keeping the target data encrypted without returning to the original data even once. Since the50Feature Articles

conventional technology had performance issues, thistechnology became an alternative using processingthat was even simpler than that of ordinary (unencrypted) deep learning training and prediction. NTT’s
secure computation deep learning uses world-classsecure computation-processing performance andreproduces the training process using standard optimized processing executed in deep learning as aworld’s first by secure computation.
In other words, all the steps required for data usage
in deep learning, that is, (1) data provision, (2) data
storage, (3) training, and (4) prediction, can be executed in an encrypted state. Since data are always
kept in an encrypted state without returning to their
original form even once, this technology enables
users and organizations to provide data with peace ofmind compared with conventional technology. Thisshould lead to an increase in the amount and types ofdata that can be used for training. It is exactly thisexpansion of data that should enable AI to achieveeven more accurate and advanced analysis.

pare data conditions and requirements of data usage
between the provider and user then form an agreement.
It has been common for a provider and user toexpress provision conditions and usage conditions,
respectively, in the form of policies, which would
then be checked manually by each other to form anagreement. In the future, however, we can consider anapproach in which the content of a user request fordata usage is compared with those policies at the timeof that request to automatically determine whether
the agreement is being satisfied. If differences exist
between requirements and conditions, the ability todynamically adjust those requirements and conditions between the provider and user would enable
more flexible agreement formation. This kind of
approach must also be targeted for future study topromote the use of data among companies and organizations.

3.4 Agreement-forming mechanism
In the use of data, there are two conditions underwhich the provider approves of data usage andrequirements that the user demands of that data. The
content of those conditions and requirements differ
depending on the provider and user. The provider
may specify as conditions under which parties are
permitted to use the data, the purpose of use, therange of use, the period of use, etc. The user, on theother hand, may specify as requirements the target
data, purpose of use, desired processing, etc.
To enable data usage in a form that both sides agree
upon, there is a need for a mechanism that can com-

The creation of a data space should accelerate thesharing of data beyond corporate and industry walls,
which has been difficult, and enable data sharing thatcreates new value in a chain reaction manner. To
make the data space a reality, we plan to research anddevelop key technologies while accelerating the testing of those technologies with partners.

Tomoaki Washio

Senior Research Engineer, Social Information
Sharing Research Project, NTT Social Informatics Laboratories.
He received a B.E. and M.E. in systems andinformation engineering from Hokkaido University in 2000 and 2002. Since joining NTT in
2002, he has been engaged in research and development (R&D) of authentication systems andsecure data sharing technologies.

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4. Toward the future

References[1][2]

Gaia-X, https://www.gaia-x.eu/
DATA-EX, https://data-society-alliance.org/about/visionmission/#top

Hiroki Itoh

Senior Research Engineer, Social Innovation
Research Project, NTT Social Informatics Laboratories.
He received a B.S. from Tokyo University of
Science in 2002, M.E. from Tokyo Institute ofTechnology in 2004, and M.S. in management oftechnology from Tokyo University of Science in2009. He is engaged in leading practical application of research outcomes from NTT Social
Informatics Laboratories.

51

Feature Articles

Koki Mitani

Senior Research Engineer, NTT Social Informatics Laboratories.
He received a B.E. in information and computer science and M.Sc. in engineering in sciencefor open and environmental systems from Keio
University, Kanagawa, in 2003 and 2005. In 2005
he joined NTT. From 2011 to 2015, he was a
product manager of global network services in
NTT Europe Ltd. and NTT Communications
Corporation. He returned to NTT in 2015, where
he currently leads open and collaborative innovation for building global infrastructure for data
sharing across businesses at NTT Social Informatics Laboratories.

Gembu Morohashi

Senior Research Engineer, Social Information
Sharing Research Project, NTT Social Informatics Laboratories.
He received a B.S., M.S., and Ph.D. from the
University of Electro-Communications, Tokyo,
in 2001, 2003 and 2009. He began working at
NTT in 2003, and his main research interests are
cryptography and information security.

Kenji Umakoshi

Senior Research Engineer, Social Information
Sharing Research Project, NTT Social Informatics Laboratories.
He received an M.E. from Waseda University,
Tokyo, in 2009. He joined NTT in 2009 and has
been researching and developing in areas such asubiquitous/Internet of Things computing, smart
room/factory, and data sharing platform. He also
worked as a product manager of a cloud service
in NTT Communications Corporation from 2014
to 2016.

Kazuyuki Takaya

Senior Research Engineer, Supervisor of Data
Sharing Infrastructure Project, NTT Software
Innovation Center.
He received an M.E. from Waseda University,
Tokyo, and joined NTT in 2000. He is engaged in
R&D of technologies and platforms for data
sharing.

Kei Ohmura

Senior Research Engineer, Data Sharing Infrastructure Project, NTT Software Innovation
Center.
He received an M.E. from Waseda University,
Tokyo, in 2009. Since joining NTT the same
year, he has been engaged in developing platforms for cloud, Internet of Things, and AI
leveraging open source software.

Gen Takahashi

Senior Research Engineer, Social Information
Sharing Research Project, NTT Social Informatics Laboratories.
He received a Master of Media and Governance from Keio University, Tokyo, in 2005 andjoined NTT in 2006. His research interests
include information security and cryptographic
engineering.

Tetsuya Okuda

Research Engineer, NTT Social Informatics
Laboratories.
He received a B.S. and M.S. from the University of Tokyo in 2009 and 2011. Since 2011, hehas been engaged in R&D on security protocol atNTT. He is a member of the Information Processing Society of Japan (IPSJ) and received the
IPSJ/Computer Security Symposium Student
Paper Award in 2019.

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52

Feature Articles: Olympic and Paralympic Games Tokyo 2020
and NTT R&D—Technologies that Colored Tokyo 2020 Games

Initiatives toward a New Way ofExperiencing and Supporting theTorch Relay
Shingo Kinoshita
Keywords: Olympic and Paralympic Games, Torch Relay, ultra-realistic communication technology
Kirari!

1. Tokyo 2020 Olympic Torch Relay
The Tokyo 2020 Olympic Torch Relay, whichstarted in Fukushima Prefecture on March 25, 2021,
was supported by 10,515 torchbearers over 121 days
through all 47 prefectures in Japan. The purpose of
the Torch Relay is to embody the Olympic ideals ofpeace, unity, and fraternity by connecting the entire
host country with the torch, which is the symbol of
the Olympic Games, and build momentum for theupcoming Games throughout the country.
NTT believes in the purpose of the Torch Relay andinitiated various support activities to help spread thislight of hope throughout Japan. We were involved infour activities: (i) supporting the torchbearers, (ii)supporting celebration events, (iii) supporting
expanded versions of the celebration events, and (iv)
hosting regional torch-relay events.
(i)	The first activity (torchbearer support)
involved recruiting and recommending torchbearers and providing various types of support
for the selected torchbearers and cheering
them on during the relay run.
(ii)	The second activity (celebration events),
which was held at the points where the torchbearers finished each day, involved cheeringon the torchbearers from a stage and holding
exhibitions such as a commemorative photography of a Torch Relay torch.
(iii)	T he third activity (expanded celebration
events) involved expanded versions of thesecond activity and large-scale events such aslive performances and exhibitions. We origiNTT Technical Review

Vol. 20 No. 1 Jan. 2022

nally planned to hold such events with anaudience of 5000 people in Osaka on April 13
and in Yokohama on June 30.
(iv)	The fourth activity (NTT event) involved designating business sites as the Torch Relay
route and holding events through whichneighbors, students, employees working onsite, and others could experience the Torch
Relay together. NTT research and development (R&D) laboratories organized one such
event at the NTT Yokosuka R&D Center,
which invited elementary and high-school
students from around the neighborhood.
Due to the spread of novel coronavirus (COVID19), the Torch Relay was postponed for one year.
After the postponement, it was still affected by the
pandemic in various ways. At the beginning of theTorch Relay, many torchbearers ran on public roads;
however, as the pandemic worsened, more and more
local governments decided to take the Torch Relay off
public roads, eleven prefectures took it off publicroads altogether and nine prefectures took it off certain public roads. Accordingly, most of the celebration events were restricted or even cancelled. The
expanded celebration event scheduled to be held inOsaka was streamed online instead of being attended
on site by the general public. The expanded celebration event scheduled to be held in Yokohama was also
streamed online and closed to the general public, andonly torchbearers and their families and friends wereallowed to watch on site. A number of regional torchrelay events—as well as events organized by NTT—
were also cancelled.
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Feature Articles

Fig. 1. Virtual torch kiss experience with Kei Nishikori using Kirari!.

Unfortunately, the festive momentum that was initially expected did not fully develop; regardless, NTT
continued its support because it felt the need to use
the power of communication to protect communication between people and spread the light of hopethroughout Japan.
2. A new form of experiencing and supporting
the Torch Relay by NTT R&D
NTT R&D has been researching and developing
communication technologies and experimentally
applying them to various fields to explore new formsof entertainment and art that connect people andenable amplification and sharing of emotions throughcommunication. We have been engaged in ultra-realistic stage production and live transmission of kabuki,
music concerts, fashion shows, sports, and otherevents by using our ultra-realistic communication
technology called Kirari!, spatial-image production
based on moving display bots using robot- and videocommunication control technology, and other art
exhibitions.
For the Tokyo 2020 Olympic Torch Relay, we used
these communication technologies and expertise tohelp make the Torch Relay more exciting. Using thelatest communication technologies, such as Kirari!
and the communication control technology called“Swarm,” we could support the above-mentioned
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events.
3. Commemorative photo of the Torch
Relay torch
At the celebration and the expanded celebration
events, we hosted a booth at which visitors could takecommemorative photos of the Torch Relay torch byusing communication technology. The best user
experience for visitors was to actually hold the torchin their hands, appreciate its beauty and weight, andfeel as if they were torchbearers. We further enhanced
that experience by applying communication technology in the following exhibits.
The first was the Virtual Torch Kiss, Torch Relay
Commemorative Photo Corner: Kirari! Version. In
this experience, the participant was able to share a“virtual torch kiss” with the professional tennis
player Kei Nishikori displayed as a holographic
image (Fig. 1).
The second was the Torch Relay Commemorative
Photo Corner: Optical Illusion Version. In this experience, projecting light triggered optical illusions thatcreated a mysterious “trick space” in which the still
pictures on panels appeared to move.
The third was the Torch Relay Commemorative
Photo Corner: Kabuki Version. This was an interactive-experience exhibit that combined NTT’s communication technologies. When participants held a54

Feature Articles

Fig. 2. Spatial production to cheer on the torchbearers via display bots.

kabuki mask in front of their faces for a few seconds,
their faces appeared on a monitor in kabuki makeup
and they could have a commemorative photo taken
while holding up a torch.
4. Spatial production to support torchbearers
Communication technology was used to coordinate
countless moving displays (display bots) and create aspace from which to cheer on the torchbearers while
the road surface was being decorated with images(Fig. 2). The magical expressions created by the multiple display bots by approaching or moving awayfrom each other, displaying images individually or asa group, and so on gave the feeling that they were aswarm of living creatures. This spatial production
was the result of joint research by NTT and Ars Electronica, a world-renowned media art research institute.
5. Stage production for celebrating theTorch Relay
Kirari! was used for a stage production called“GENERATIONS from EXILE TRIBE” in the
expanded celebration events held in Osaka and Yokohama. We attempted to overcome and improve thecircumstances that made it difficult to bring people
together due to the COVID-19 pandemic through the
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power of communication.
The first part of this production was “remote collaboration” (Fig. 3). It had become difficult for artists
to get together due to the COVID-19 pandemic. Artists from different locations tried to create a group
dance in tune with the song “Choo Choo TRAIN” by
EXILE. Images of artists dancing separately were
instantly cropped by Kirari! to create a composite
image that gave the impression that the artists were
dancing together in the same place.
The second part of the production was “remote live
viewing” (Fig. 4). This viewing experience createdthe impression of the artist being teleported in frontof the viewer even though the viewer could not go to
the live venue due to the pandemic.
The third part of the production was “remote faninteraction” (Fig. 5). Due to the pandemic, it had
become difficult for artists to interact with their fans.
Therefore, we created an experience that made thefans feel like they were standing next to the artist
while sharing the same space.
6. Regional torch-relay events
We had initially planned to invite local elementary
school students to the NTT Yokosuka R&D Center toparticipate in the torch-relay event. As a new meansof cheering during the pandemic, each student madea device for “paper-cup communication” that would
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Fig. 3. Stage production using Kirari! (remote collaboration).

Fig. 4. Stage production using Kirari! (remote live viewing).

let them cheer while preventing droplets spraying
from their mouths when they shouted (Fig. 6). This
event was cancelled because of the increase in
COVID-19 cases; nevertheless, to give the students(who were looking forward to the event) memories of
the Torch Relay, we went to the school and held a
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cheering event using paper cups, holding a torchcommemorative photo shoot by the students, andpresenting a technical lecture by researchers, all ofwhich the students enjoyed.

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Fig. 5. Stage production using Kirari! (remote fan interaction).

Fig. 6. Cheering on the torchbearers by using paper-cup communication devices made by the students.

NTT is an Olympic and Paralympic Games Tokyo
2020 Gold Partner (Telecommunication Services).

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57

Feature Articles

Shingo Kinoshita

Vice President, Head of NTT Human Informatics Laboratories.
He received a B.E. from Osaka University in1991 and M.Sc. with Distinction in technology
management from University College London,
UK, in 2007. He joined NTT in 1991 and was asenior manager of the R&D planning section of
the NTT holding company from 2012 to 2015.
He is currently a visiting professor at the Art Science Department, Osaka University of Arts, andvisiting executive researcher at Dentsu Lab
Tokyo. He has served as a member of the Japan
Science and Technology Agency (JST) JSTMirai Program Steering Committee, member ofthe All Japan Confederation of Creativity (ACC)TOKYO CREATIVITY AWARDS 2021 Judging
Committee, and member of the Broadband Wireless Forum Steering Committee. He has been
engaged in R&D of a media-processing technology, user interface/user experience, communication protocols, information security, machinelearning, service design, and technology management. Until recently, he had been in charge ofNTT’s Tokyo2020 initiatives, including sportswatching video technology, inclusive design forsocial issues, and promoting the use of ICT in
kabuki, entertainment, and media arts such as live
music.
He has been in his current position since 2021,
where he manages R&D on information andcommunication processing of humans based onhuman-centered principles.

NTT Technical Review

Vol. 20 No. 1 Jan. 2022

58

Feature Articles: Olympic and Paralympic Games Tokyo 2020
and NTT R&D—Technologies that Colored Tokyo 2020 GamesTorch Relay Commemorative
Photography × Ultra-realistic
Communication Technology Kirari!
Yoshiyuki Mihara, Masami Nagata, Keisuke Hasegawa,Taiji Nakamura, Junji Watanabe, Tatsuya Matsui,
Hideaki Iwamoto, and Shingo Kinoshita
Keywords: Olympic and Paralympic Games, Torch Relay, ultra-realistic communication technology
Kirari!

1. Overview
To foster the momentum of the Olympic GamesTokyo 2020, we wanted as many people as possible
to experience the Olympic Torch Relay. We therefore
created three experiential exhibits that enabled participants to take commemorative photos with a torch
as a personal experience of the Olympic Torch Relay.
The first exhibit was the Virtual Torch Kiss, Torch
Relay Commemorative Photo Corner: Kirari! Version, where participants could carry an actual torchand virtually experience a torch kiss using the Kirari!
ultra-realistic communication technology. Kirari!,
which conventionally needs to be set up in a laboratory and include large devices, was packaged into atruck, making it possible to hold the exhibit anywherearound the country. The second exhibit was the Torch
Relay Commemorative Photo Corner: Optical Illusion Version. By projecting a special light that elicits
phantasmagoric optical illusion onto a still image, wecreated the mysterious effect of making a supposedly
unmoving image of a flame appear to move. Unlike
shooting in front of a regular panel, it was possible toprovide a more dynamic experience despite using still
images. The third exhibit was the Torch Relay Commemorative Photo Corner: Kabuki Version. This
exhibit combined kabuki, which has a long history inJapan, and the Olympic Torch Relay, which connected the regions of Japan, by enabling participants
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to take a commemorative photo with a torch while
having kabuki makeup virtually applied to their faces.
2. Torch Relay Commemorative Photo Corner:
Kirari! Version
We modified a truck that enabled participants to doa virtual torch kiss with the professional tennis player
Kei Nishikori, who was holographically projectedusing Kirari! inside the truck (Fig. 1). The holographic display was based on a two-dimensional (2D) aerial image display [1]. We set up the display on thefloor of the truck and mounted a transparent screen at
a 45-degree angle from the display. The image of Kei
Nishikori shown on the display was reflected andtransmitted to the transparent screen, making it
appear as if he were standing on the stage.
Setting up the stage for this purpose usuallyrequires time for installing truss parts and setting thetransparent screen diagonally. For this celebration
event, since we had to move and install the transparent screen on the truck every day, we implemented astructure that made it easy to store and install thetransparent screen. Thus, we were able to complete
the stage setup, which would usually take a day, in
only about two hours. Because also we had to travel
throughout the country for 121 days, we needed todisplay the exhibit in a bright environment during theday, depending on the actual venue and the time of59

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Fig. 1. Kirari! truck exterior view.

Fig. 2. Torch Relay Commemorative Photo Corner: Kirari! Version experience.

the event. Therefore, we used a light-emitting diode(LED) panel instead of a projector to improve thebrightness of the original image and enhance outdoor
visibility. We installed these pieces of equipment on
the loading deck of a 10-ton truck.
2.1 Flow of experience
Participants first climbed onto the stage on thetruck’s loading deck from the rear entrance of thevehicle and received a torch from the staff. We also
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installed a lift to enable wheelchair users to experience the exhibit.
Once the participant bearing the torch was in theproper position, a holographic image of Kei Nishikori appeared on the stage in such a way that the virtual Kei Nishikori and real-life participant appear to
be standing side-by-side (Fig. 2). We prepared two
patterns for displaying the holographic image of Kei
Nishikori: one where he was standing up and one
where he was kneeling. This made it possible for60

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Fig. 3. Visually impaired person trying the virtual torch kiss experience.

participants to make a torch kiss regardless of theirheight.
Since participants could not see Kei Nishikori
directly on the transparent screen, we prepared aseparate monitor through which the participants
could view the movement of Kei Nishikori’s torch as
they moved their torch toward his torch and do a virtual torch kiss. The torch carried by the participant
was equipped with an infrared sensor to detect its
position. As the participant’s torch approached Kei
Nishikori’s, its tip lit up with an image of the Olympic
flame.
The experience was captured using a camera
installed off stage, and the video was instantly
uploaded to an Internet server. We provided a means
for issuing a 2D code of the video’s URL (uniform
resource locator) to the participant after the experience so that they could immediately view the recorded video on their smartphone and post it on social
networking services (SNS).
2.2 Results
The novel coronavirus (COVID-19) continued tospread during the Olympic Torch Relay period, andmany municipalities canceled local torch relay celebration events, so the number of exhibitions was lessthan originally planned. We were able to hold thetorch commemorative photo corner using the Kirari!
truck at 34 venues in 25 prefectures, enabling a totalof 4498 people to experience the exhibit. Many peoNTT Technical Review

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ple were surprised at the realness of the life-size
holographic image of Kei Nishikori appearing on
stage, with many participants saying that they wereable to gain a realistic experience of being an Olympic torchbearer.
To improve the realness of the Torch Relay experience, we added a function to simulate the tactile
sensation of the fire being lit. This allowed people
with visual impairments to also enjoy the experience(Fig. 3). Since the torch kiss experience with Kei
Nishikori’s holographic image was visual based,visually impaired individuals had no way of knowing
when and how it was done. Therefore, by adding afunction that vibrated the torch simultaneously withthe torch kiss, we were able to deliver a haptic experience for the passing of the flame from Kei Nishikori’s
torch to the participant’s.
This was done by attaching a small vibration
device, which can be switched on and off by an external infrared signal, to the torch, and having a staff
member turn the vibration on and off in accordancewith the timing of the torch kiss for visually impaired
individuals. We also designed the vibration to make iteasier for visually impaired individuals to sense
flames. This experience was provided only at one
venue (Yokohama, June 30, 2021). A visually
impaired person who experienced it commented that
“Although the vibration was weak immediately after
being lit, it gradually became stronger as I raised thetorch above me, so I was impressed by the effort put
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Fig. 4. Torch Relay Commemorative Photo Corner: Optical Illusion Version experience.

into making it possible to feel even the changing
intensity of the fire.”
3. Torch Relay Commemorative Photo Corner:
Optical Illusion Version
In this exhibit, a special light was projected onto apanel showing an image of Kei Nishikori bearing atorch to trigger the illusion that the flames on thepanel and the flurry of cherry blossoms in the background are moving (Fig. 4). Position matching wasimportant for this exhibit because light was appliedon the feature points on the panel. To accurately carryout alignment at each venue, we accurately projected
the light to a specific location on the panel by linking
the projector with the camera. This made it possible
for the local staff to easily set up the exhibit.
A total of 5616 people in 3373 groups experienced
this exhibit. All participants were surprised at the
movement of still images that were not supposed tomove.
4. Torch Relay Commemorative Photo Corner:
Kabuki Version
NTT began its initiatives to create new experiencesby combining traditional culture with informationand communication technology (ICT) in 2016. As
part of these initiatives, we have been focusing on
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kumadori, the distinctive kabuki style of makeup, andcreated the unusual experience of having your chosen
kumadori mask virtually adhere to your face using
ICT. Packaging this experience exhibit in a container,
we have traveled to Fukushima and Kumamoto prefectures to provide a fun experience through ICT.
Building on these initiatives, we provided the Torch
Relay Commemorative Photo Corner: Kabuki Version as an experience with the theme of “connecting,”as exemplified by the Olympic Torch Relay that connected the regions (Fig. 5).
4.1 Flow of experience
First, participants chose their preferred mask fromamong the many painted with kumadori makeup(Fig. 6). We also projected the same special light usedin the optical illusion version to make it appear thatthe kumadori masks hanging on the wall were casually changing their expressions. Once the participant
stood in front of the monitor and placed their chosenmask on their face, the system automatically recognized the kumadori mask and overlaid it on the faceof the participant. The kumadori mask had augmented reality (AR) features, i.e., it followed the person’s
facial expressions and movements in all directions on
the monitor in real time while the mask remained
attached to the person’s face. The background in themonitor was also rendered to match the selected
kumadori mask. We also prepared a background62

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Fig. 5. Torch Relay Commemorative Photo Corner: Kabuki Version booth.

Fig. 6. Selection of kumadori mask.

specifically inspired by the Olympic Torch Relay(Fig. 7). With their chosen mask attached to theirfaces, participants could pose any way they wanted
while carrying the torch. Going to the next room,
participants then found their faces being projected
onto a gigantic 1.2-meter-high, three-dimensional
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(3D) face, to give them an element of surprise(Fig. 8). Photos of the experience were later posted
on SNS and made available for download.
4.2 Results
This experience was intended to be offered at the63

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Fig. 7. Torch Relay Commemorative Photo Corner: Kabuki Version experience.

Fig. 8. A gigantic 3D face with a height of 1.2 m.

Olympic Torch Relay expanded celebration events at
two locations, namely, the Expo ’70 Commemorative
Park in Osaka and the Yokohama Red Brick Warehouse Square in Yokohama. However, due to the
spread of COVID-19, it was only held at the Yokohama Red Brick Warehouse Square. A total of 82
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people, including Olympic torchbearers and otherpeople involved, experienced the exhibit. Participants
laughed once they saw their chosen kumadori masks
attached to their faces upon holding the masks up,
and many got into character as kabuki actors while
taking commemorative photos with the torch in hand.
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5. Summary

Acknowledgments

Due to the spread of COVID-19, the number ofpeople who experienced the exhibits was less thanplanned. Nevertheless, we were able to deliver surprises and smiles to the participants at the venues
where we could provide the experiences. We believethat these interactions with the advanced technologies of our laboratories, which are not normallyaccessible to the public, enabled many people toexperience firsthand NTT’s innovativeness.
Going forward, we will continue to work on creating new experiences using ICT and connect people
with each other.

We would like to express our gratitude to the members of the Tokyo Organising Committee of the
Olympic and Paralympic Games and the representatives of the local governments who were involved in
the operations. We also would like to thank the members who handled the operation of the Kirari! truck at
the celebration venues.
NTT is an Olympic and Paralympic Games Tokyo
2020 Gold Partner (Telecommunication Services).
Reference[1]

Yoshiyuki Mihara

Senior Research Engineer, NTT Human Informatics Laboratories.
He received a B.Sc. and M.Sc. from Tokyo
Institute of Technology in 2004 and 2006. Healso received a Ph.D. from Kyoto University in2017. Since joining NTT in 2006, he has been
engaged in research and development (R&D) ofa home network management service. The home
network management protocols he designed havebeen standardized by Universal Plug and Play
(UPnP) Forum, International Telecommunication Union Telecommunication Sector (ITU-T),
and Japan’s Telecommunication Technology
Committee (TTC). He is currently promoting the
key protocols with a view to launching a home
network management service.

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Vol. 20 No. 1 Jan. 2022

S. Uchida, E. Ashikaga, M. Imoto, M. Wagatsuma, and K. Hidaka,“Concept of Immersive Telepresence Technology ‘Kirari!’,” Proc. of
the Media Computing Conference 2015, p. 39, 2015 (in Japanese).

Masami Nagata

Manager, NTT 2020 Public Relations Strategic
Business Development Division.
She joined NTT DOCOMO in 2002 and has
been engaged in marketing. She is currently
responsible for asset activation of the Tokyo 2020
Olympic Torch Relay as the Presenting Partner.

65

Feature Articles

Keisuke Hasegawa

Engineer, NTT Human Informatics Laboratories.
He received a B.E. and M.E. in informatics
from Kyoto University in 2012 and 2014. He
joined NTT WEST in 2014 and engaged in themaintenance of network facilities. Since joining
NTT Service Evolution Laboratories in 2016, hehas been engaged in research of media processing for the ultra-realistic communication technology Kirari!. He is a member of the Institute of
Image Information and Television Engineers(ITE).

Taiji Nakamura

Senior Research Engineer, 2020 Epoch-Making Project, NTT Human Informatics Laboratories.
He joined NTT DATA Communications Systems (now NTT DATA) in 1991. He has over 20
years’ experience in information systems planning and development in the national public sector.

Junji Watanabe

Senior Distinguished Research Scientist, NTT
Communication Science Laboratories.
He received a Ph.D. in information science andtechnology from the University of Tokyo in
2005. His research is focused on cognitive science and haptic communication devices withapplied perception. His academic work has been
published in scientific journals in the field of
psychology and interface technologies. He has
also presented his work at technology showcases
and art festivals such as SIGGRAPH and Ars
Electronica. His current research interest is how
technologies are designed to achieve the wellbeing of society.

NTT Technical Review

Vol. 20 No. 1 Jan. 2022

Tatsuya Matsui

Senior Research Engineer, NTT Information
Network Laboratory Group.
He received a B.Sc. and M.Sc. from Tokyo
Institute of Technology in 1993 and 1995. Sincejoining NTT in 1995, he has been engaged in
R&D of the cyber security, digital library, MICE
(meetings, incentives, conventions, exhibitions)application, interactive exhibition “Henshin
Kabuki.” He is currently working to improve theworking style of researchers at NTT labs.

Hideaki Iwamoto

Research Engineer, NTT Human Informatics
Laboratories.
He received a B.E. and M.E. in informationengineering from Kyushu Institute of Technology, Fukuoka, in 1991 and 1993. He joined NTT
Information and Communication Systems Laboratories the same year and engaged in R&D on
information retrieval and natural language communication. He is currently researching anddeveloping innovative user interface/user experience design and its showcasing.

Shingo Kinoshita

Vice President, Head of NTT Human Informatics Laboratories.
He received a B.E. from Osaka University in1991 and M.Sc. with Distinction in technology
management from University College London,
UK, in 2007. He joined NTT in 1991 and was asenior manager of the R&D planning section of
the NTT holding company from 2012 to 2015.
He is currently a visiting professor at the Art Science Department, Osaka University of Arts, andvisiting executive researcher at Dentsu Lab
Tokyo. He has served as a member of the Japan
Science and Technology Agency (JST) JSTMirai Program Steering Committee, member ofthe All Japan Confederation of Creativity (ACC)TOKYO CREATIVITY AWARDS 2021 Judging
Committee, and member of the Broadband Wireless Forum Steering Committee. He has been
engaged in R&D of a media-processing technology, user interface/user experience, communication protocols, information security, machinelearning, service design, and technology management. Until recently, he had been in charge ofNTT’s Tokyo2020 initiatives, including sportswatching video technology, inclusive design forsocial issues, and promoting the use of ICT in
kabuki, entertainment, and media arts such as live
music.
He has been in his current position since 2021,
where he manages R&D on information andcommunication processing of humans based onhuman-centered principles.

66

Feature Articles: Olympic and Paralympic Games Tokyo 2020
and NTT R&D—Technologies that Colored Tokyo 2020 Games

Direction for Supporting
Torchbearers × Swarm
Communication Control Technology
Masafumi Suzuki, Hiroshi Chigira, Hitoshi Yamaguchi,
Takuya Indou, and Shingo Kinoshita
Abstract

In connection with the Tokyo 2020 Olympic Torch Relay, NTT held NTT Presents Tokyo 2020 Olympic Torch Relay Celebration events in Yokohama and Osaka and presented a torchbearer-support program that welcomes torchbearers exchanging torch kisses using spatial-expression technology withrobots. In this article, we introduce the control technologies used for the display bots that enabled thetorchbearer-support program.
Keywords: Olympic Torch Relay, supporting torchbearers, spatial expression using robots

1. Overview
NTT is working to create new experiences by combining art and technology, and one of the results ofour research in this area is “Art of Swarms,” a spatialexpression technology using display bots. Spatial
expression refers to the creation of an organicallychanging visual space through the coordinatedabove-ground movements of a swarm of robots
equipped with multiple displays. Unlike projection
through the entire floor surface, display bots, whichhave physical mass, move as a swarm to create avisual space that enables an unconventional and tangible visual experience.
NTT introduced the concept of spatial expression at
the 2018 NTT R&D Forum. Since then, we have
expanded the scale and examined the theatricaleffects of using display bots, including through demonstrations at the world’s largest art festival in Linz,
Austria in 2018 and exhibits at the Sports Viewing
Re-Imagined Exhibition in July 2019. At the Sports
Viewing Re-Imagined Exhibition, we presented acollaboration of a swarm of more than 30 display botswith prominent artists Akiko Nakayama [1] and Ei
Wada [2]. We also used a swarm of display bots for
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sports expression, which received high praise frommany people who watched the exhibit.
Using the knowledge gained from these demonstration experiments, we applied Art of Swarms to theTokyo 2020 Olympic Torch Relay. We wanted many
people to have a more dramatic experience of theTorch Relay and enable them to witness the possibilities of the fusion of NTT’s communication technologies with art. We directed a festival to welcome
the torchbearers arriving at the venue during the NTT
Presents Tokyo 2020 Olympic Torch Relay Celebration events (Figs. 1 and 2).
1.1 N
 TT Presents Tokyo 2020 Olympic Torch
Relay Celebration•	Osaka: April 13, 2021, in front of the Tower of
the Sun Plaza at the Expo ’70 CommemorativePark•	Yokohama: June 30, 2021, at the Red Brick
Warehouse Event Square
We originally planned for many local people towatch these two events. However, due to the spread of
the novel coronavirus (COVID-19), onsite viewing
through general admission was canceled; thus, we
presented the event online.
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Fig. 1. Torch kiss scene at the Osaka event.

Fig. 2. Torch kiss scene at the Yokohama event.

We collaborated with Ars Electronica, a worldclass media art research institute, to create dramatic
scenes for the stage presentation. The original plan
was for members of Ars Electronica to come to Japanto take part in local operations with members of NTT.
However, they could not travel due to COVID-19, so
instead they provided support online from Austria.

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2. System configuration and technologies used
Display bots are robots that move on the groundand equipped with hexagonal displays (Fig. 3). They
are composed of a display component at the top anda driving function component at the bottom, each
operating independently. This configuration enables
the robots to move in any direction while keeping thedisplay surface in a fixed direction, thereby increasing
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Fig. 3. Display bots.

DOCOMO IoT high-precision GNSS positional information service

Acquisition of RTK-GNSS
correction information(4G LTE communications)

Roles of display bots
(2.4 GHz Laird communications)
Scenario
Scenario-content allocation, etc.
(2.4/5.2-GHz Wi-Fi communications)
Editing system

Control system

Display bots

Fig. 4. Overview of system configuration.

the breadth of the spatial-image expression. In addition to the display, the top part includes devices forcommunicating, positioning, and controlling the
movement of the display bot. The bottom part
includes the driving mechanism and battery.
Figure 4 shows an overview of the entire system,
including the display bots. The editing system is used
for generating scenarios in which movements of multiple display bots and video-content assignments areprogrammed on the basis of the desired final image
expression for the entire space. The control systemthen delivers and executes the specific scenarios andvideo content to the display bots. This enables display
bots to move organically as a swarm.
The position of each display bot must be measured
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accurately to enable coordinated movements while
they move close to each other at a distance of around10 centimeters. We had used motion capture with
infrared cameras and reflective markers for positioning during previous demonstration experiments since
they were conducted indoors. The same method,
however, could not be applied since the torch relay
event was going to be held outdoors. Although Global Positioning System (GPS) is commonly used foroutdoor environments, the normal positioning accuracy of GPS exceeds a few meters, making it impossible to apply it as is. We therefore adopted a highprecision positioning system called real-time kinematic global navigation satellite system (RTKGNSS). However, RTK-GNSS had not been widely
69Feature Articles

used, and using it for simultaneous control of 60
robots had never been attempted. RTK-GNSS enableshigh accuracy (error of a few centimeters) even outdoors by using correction information generated inreal time from observation data at different locations
called base stations in addition to the positional information obtained from regular GPS antennas. For thisproject, we applied NTT DOCOMO’s “DOCOMO
IoT high-precision GNSS positional information service” [3] to RTK-GNSS, a first-of-its kind initiative.
Using RTK-GNSS enables accurate location information to be obtained, but it does not enable measurement of the exact direction. If the exact direction
could not be determined, the direction of each display
bot’s display would be different from one other, andthe entire image would be become corrupt. We therefore installed two antennas diagonally on the display
bot and obtained the direction information using thedifferential information from the two antennas.
We used proprietary standard Laird communications (2.4 GHz) and Wi-Fi communications (2.4/5.2
GHz) for communication between the display botsand control system and fourth-generation (4G) LongTerm Evolution (LTE) communications via mobilerouters for communication with the DOCOMO IoT
high-precision GNSS positional information service.
Before the display bots start moving, the scenarios
are communicated simultaneously to each bot via
radio signals from the control system upon the operator’s command. Each display bot then begins to movein accordance with the transmitted scenarios. The
bots move in accordance with the programmed scenario, but they can also be controlled in real time by
the operator, such as to stop display bots simultaneously or decrease their speed, since they always operate in concert with the control system.
3. Testing
Testing with 100 display bots requires a space thatis large enough to store, charge, and operate them andthat is relatively free from obstructions to enable
reception of the satellite signals for RTK-GNSS. We
therefore conducted tests at the NTT Tsukuba R&D
Center (Tsukuba City, Ibaraki Prefecture), whichmeets these requirements. After the decision to postpone the Tokyo 2020 Games, at the time of test
resumption, the plan was to hold the event in collaboration with members from Ars Electronica. However,
COVID-19 infections did not subside as we had
expected, increasing the likelihood that they could
not come on the day of the event. We therefore
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promptly changed our policies as follows (Figs. 5 and 6).
•	Control and preparations for actual event andtests at Tsukuba was carried out by only Japanese members mainly from NTT.
•	Ars Electronica members did not come to Japanbut supported the operations online.
As a result, NTT members had to deal with many
unfamiliar tasks, such as handling hardware issues,troubleshooting and analyzing problems, and othertasks that were originally supposed to be handled bymembers of Ars Electronica. Many hours were therefore spent on remote correspondence with members
in Austria. Due to the time difference with Austria,
there were many time constraints; thus, it was necessary to efficiently carry out testing, problem analysis,
and response.
4. Live performance
We held the first live event in front of the Tower of
the Sun Plaza at the Expo ’70 Commemorative Parkon April 13, 2021. The final torch kiss with the last
torchbearer of the day would have been welcomed
through a spatial-expression show by a swarm of display bots, with the Tower of the Sun, the symbol of
the Expo ’70 Commemorative Park, in the background.
Around April 7, when we traveled to Osaka for the
preparations, the number of new COVID-19 infections in Osaka Prefecture began to increase sharply,
and the declaration of the third state of emergency
became imminent. Eventually, on April 7, anannouncement was made that the Torch Relay along
public roads would be canceled and held at the Expo
’70 Commemorative Park. Although we were able to
avoid having the event on April 13 canceled, it washeld with no spectators. In addition, the Osaka prefectural government requested us to avoid presenting
in front of the Tower of the Sun, which was illuminated in red after sunset during the state of emergency. To comply with this request, we needed to start theevent before sunset. However, since the display bots
create the magical spatial expression by moving as aswarm of images in the dark, holding the event before
sunset meant that the presentation would lose muchof its charm. Also, given that many display-bot hardware failures had occurred since we arrived in Osakaand that GPS reception in the field was poor andpositioning failed during preliminary rehearsals, tobe safe, we decided to carry out the live performancein Osaka with 48 display bots in a stationary state.
During the day of the event, while it was raining70

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Fig. 5. Remote collaboration with members of Ars Electronica.

heavily, the stationary display bots welcomed thetorchbearers and rendered a coordinated display oflights along with the torch kiss.
After the completion of the Osaka event, we were
faced with two major issues to be resolved in preparation for the Yokohama event scheduled on June 30.
The first issue was the repair of the broken display
bots. More than half of the bots had some sort ofproblem, so we needed to quickly carry out troubleshooting and repair to ensure that as many display
bots as possible were operational before the next
event. For the repair of the display bots, we determined which ones had to be returned to Austria for
repair and which ones could be repaired in Japan.
Considering all possible factors, including the number of units necessary for the entire production, number of days required for repair, and number of days
required for testing, we created a repair plan andchanged it in accordance with the daily situation. As
a result, we were able to secure 48 operational display
bots before the live event.
The second issue was the stabilization of their positioning. The location of GPS satellites on the day ofthe event and the surrounding environment had asignificant impact on positioning. Even if we conducted prior testing in the same location and obtained
good results, there was no assurance that we could
obtain the same results during the actual event. We
therefore used two methods to increase the reliabilityof positioning.
The first was improving the antenna-installation
method. From our experience in Osaka, we found thatraising the position of the antenna could lead to more
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Fig. 6. Testing at NTT Tsukuba R&D Center.

stable positioning. However, installing the antennas
too high leads to many issues, such as difficulty infixing the antenna in place or an unsightly appearance, so it was necessary to find a height that balances functionality with aesthetics. After various
tests, we determined that the optimum height wasaround 15 cm from the surface of the display. The
second was achieving failsafe positioning. We needed
to ensure that positioning would continue even if the
RTK-GNSS positioning fails. To achieve this, weused an odometer to estimate the position and direction using the amount of rotation, etc. of the wheel ofthe display bots.
The second event was held at Yokohama Red Brick
Warehouse on June 30, 2021. Due to the COVID-19
situation, like in Osaka, onsite viewing through general admission was canceled, and the event was conducted exclusively through online streaming. Fromrehearsals to the live performance, the display bots
did not fail, and their positioning was stable andalmost never failed. In the area between Buildings
No. 1 and No. 2 of the Red Brick Warehouse, thedisplay-bot program showcased a magical display oflights through coordinated movements of 48 display
bots as the last torch kiss of the day was exchanged
and the final torchbearer was sent off to ignite thecauldron (Fig. 7).
5. Summary
Onsite viewing through general admission was canceled for both the Osaka and Yokohama events, preventing the general public from experiencing the71Feature Articles

Fig. 7. Direction support for the Torch Relay in Yokohama.

display-bot presentation in person. Nevertheless, weconsider it a major achievement to have enabledmany people to enjoy via online streaming the presentation of lights and movements by the swarm ofdisplay bots around the torchbearers and for the show
to be featured in various media events, including the
opening ceremony presentation, as an iconic scene of
the Tokyo 2020 Olympic Torch Relay.
Going forward, we will continue to study further
possibilities of the fusion of art and technology.

sincere gratitude to the people of Osaka and Kanagawa Prefectures for supporting the events, members ofDentsu and Dentsu Live, members of Ars Electronica, and many others who were involved in the preliminary rehearsals, tests, as well as during the live
performance.
NTT is an Olympic and Paralympic Games Tokyo
2020 Gold Partner (Telecommunication Services).
References

Acknowledgments
The implementation of the display-bot torchbearersupport program was made possible with the cooperation of many people. We would like to express our

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[1]
[2]
[3]

Akiko Nakayama, http://akiko.co.jp/akikoweb/
Ei Wada, https://eiwada.com
DOCOMO IoT high-precision GNSS positional information
service (in Japanese), https://www.nttdocomo.co.jp/biz/service/
highprecision_gnss_positioning/72

Feature Articles

Masafumi Suzuki

Research Engineer, NTT Human Informatics
Laboratories.
He received an M.E. in engineering from Ritsu­
meikan University, Kyoto, in 2011. After joining
NTT in 2011, he engaged in research on cloudservices using carrier network functions. He
developed a number of proof-of-concept systems
at NTT Service Integration Laboratories, NTT
Cyber Solution Laboratories, and NTT Service
Evolution Laboratories. In 2015, he joined the2020 Epoch-Making Project. He has been
involved in the development of systems to promote NTT’s cutting-edge technology for the
Tokyo 2020 Games.

Hiroshi Chigira

Senior Research Engineer, NTT Human Informatics Laboratories.
He received a B.E. and M.E. in engineeringfrom Waseda University, Tokyo, in 2007 and2009, and joined NTT in 2009. Since then he has
been engaged in research on human-computerinteraction and developed vital sensing hardware
at NTT Cyber Solution Laboratories and NTT
Service Evolution Laboratories. In 2016, hejoined the 2020 Epoch-Making Project, where hehas been engaged in several creative research
projects combining NTT’s cutting-edge technologies, design, and art to celebrate Tokyo 2020
Games.

Hitoshi Yamaguchi

Senior Research Engineer, NTT Human Informatics Laboratories.
He received a B.E. in physics from Keio University, Kanagawa, and M.E. in applied physics
from Tokyo Institute of Technology in 1997 and
1999, and joined NTT in 1999. Since then he has
been engaged in the development of network
node systems at NTT Network Service Systems
Laboratories, and the development of smartphone applications at NTT DOCOMO.

NTT Technical Review

Vol. 20 No. 1 Jan. 2022

Takuya Indou

Senior Research Engineer, Supervisor, NTT
Human Informatics Laboratories.
He received a B.S. in physics from Kyoto University in 1993. In the same year, he joined NTT.
His research interests include media processing
and human-computer interaction. He is a member of the Information Processing Society ofJapan (IPSJ), and the Association for Computing
Machinery (ACM).

Shingo Kinoshita

Vice President, Head of NTT Human Informatics Laboratories.
He received a B.E. from Osaka University in1991 and M.Sc. with Distinction in technology
management from University College London,
UK, in 2007. He joined NTT in 1991 and was asenior manager of the R&D planning section of
the NTT holding company from 2012 to 2015.
He is currently a visiting professor at the Art Science Department, Osaka University of Arts, andvisiting executive researcher at Dentsu Lab
Tokyo. He has served as a member of the Japan
Science and Technology Agency (JST) JSTMirai Program Steering Committee, member ofthe All Japan Confederation of Creativity (ACC)TOKYO CREATIVITY AWARDS 2021 Judging
Committee, and member of the Broadband Wireless Forum Steering Committee. He has been
engaged in R&D of a media-processing technology, user interface/user experience, communication protocols, information security, machinelearning, service design, and technology management. Until recently, he had been in charge ofNTT’s Tokyo2020 initiatives, including sportswatching video technology, inclusive design forsocial issues, and promoting the use of ICT in
kabuki, entertainment, and media arts such as live
music.
He has been in his current position since 2021,
where he manages R&D on information andcommunication processing of humans based onhuman-centered principles.

73

Feature Articles: Olympic and Paralympic Games Tokyo 2020
and NTT R&D—Technologies that Colored Tokyo 2020 Games

Stage Production for Celebration of
Torch Relay × Ultra-realistic
Communication Technology Kirari!
Taiji Nakamura, Keisuke Hasegawa, Yoshiyuki Mihara,
Takashi Miyatake, and Shingo Kinoshita
Keywords: ultra-realistic communication technology Kirari!, Torch Relay, live performance

1. Overview
The Tokyo 2020 Olympic Torch Relay, whichstarted in Fukushima Prefecture on March 25, 2021,
was carried by 10,515 runners over 121 days throughall 47 prefectures in Japan. The Torch Relay usually
involves the torchbearers running on public roads anda celebration event at the final point of the relay at theend of each day. At the celebration event, the final
torchbearer of the day lights the Olympic flame in its
cauldron, local residents and sponsors perform songs
and dances on stage, and people can have their photos
taken with an Olympic torch at the Olympic Torch
Relay Commemorative Photo Corner and enjoy otherexhibits to add to the excitement of the Torch Relay.
As an extended version of the celebration event,“NTT Presents Tokyo 2020 Olympic Torch Relay
Celebration - CONNECTING WITH HOPE” wasstaged by NTT in Osaka on April 13 and in Yokohama
on June 30. In addition to the torch being carried by
the final torchbearer of the day, GENERATIONS
from EXILE TRIBE performed live, junior-highschool students, EXILE ÜSA, and EXILE TETSUYA
performed “Rising Sun -2020-,” and calligraphy artist
Soun Takeda performed using calligraphy. Initially,
we planned to invite a general audience of about 5000
people; however, due to the spread of the novel coronavirus (COVID-19), general audience viewing at
both venues were canceled and switched to online
streaming instead.
NTT research and development (R&D) laboratories
have been conducting demonstration experiments of
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ultra-realistic live broadcasts and stage productionsof kabuki, live music, fashion shows, sports events,and other events by using our ultra-realistic communication technology Kirari! (Fig. 1).
On the basis of the results of those demonstration
experiments, for the live performance by GENERATIONS from EXILE TRIBE in the extended celebration event, we created three new stage productions byusing Kirari!, i.e., “remote performance,” “remote
viewing,” and “remote fan collaboration.”
2. Details of stage productions
2.1 Remote performance
During the COVID-19 pandemic, it has become
increasingly difficult for artists to get together, especially if they are far apart. The purpose of the remoteperformance in such an environment is to harness thepower of communication to create an experience thatmakes remote artists feel as if they are performing inthe same place. For this remote-performance stage
production, we created a group dance in tune with thesong “Choo Choo TRAIN” by artists in remote locations.
Normally, artists at distant venues would collaborate with each other; however, in this case, to simulate
the experience, we used two locations on the stage as
remote locations and a transparent screen above thestage as a virtual shared space. As shown in Fig. 2,
points (1) and (2) on the stage are the remote locations, and the transparent screen (3) is a shared space
above those locations. The images of the artists dancing
74

Feature Articles

U.S. professional baseball league(ultra-wide-video live viewing)

Table tennis (real table-tennis table
and holographic players)

Kabuki (1 real performer and 3 holographic
video performers performing together)Live music (holographic transmission
from Tokyo in Japan to Austin in USA)

Fig. 1. Demonstration experiments using Kirari!.

(3) Transparent screen

CONNECTING WITH HOPE
(1)

(2)

Stage

Fig. 2. Stage production.

at points (1) or (2) were transferred to the transparent
screen. At that time, the background images were cut
out by Kirari! and only each artist’s image was transmitted. The images projected on the transparent
screen appeared to be three-dimensional, and thatappearance created an experience in which the viewer
feels that the artists are actually dancing there. Fiveartists dance in turn, so, each time, the number of artists on the transparent screen increased (Fig. 3(a));
finally, when all artists have finished dancing, theimages of the five artists merged into one as if they
were dancing in circular motions at the same location(Fig. 3(b)). It is also possible to extract and transmit
the images of all the artists dancing at the same timein real time.

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2.2 Remote viewing
During the pandemic, it has also become difficult
for fans to attend live-music concerts, especially forfans in provincial areas wanting to go to concerts in
big cities. The purpose of this remote viewing was toharness the power of communication in such an environment to create an experience through which theartist appears to be performing right in front of you.
Our challenge was to transmit the video of the artists on the main stage to another remote stage with thefans present. Normally, we would have streamed theimages to a remote site far away; however, for the
purpose of simulating the experience, as shown in
Fig. 4, we transmitted the data to a Kirari! truck set
up at a remote location in Yokohama. The Kirari!
truck housed a transparent screen similar to the one
75Feature Articles(a) Remote performance (performer in lower right is the real image,and the performers in center stage are virtual images)(b) Remote performanceFig. 3. Group dance in tune with the song “Choo Choo TRAIN” via Kirari!.

CONNECTING WITH HOPE

Main stage

Kirari! truck

Fig. 4. Configuration of remote viewing.

forming the main stage and, as shown in Fig. 5, theartists transferred by Kirari! were displayed on thescreen in a holographic manner to create an experience in which the artists appear to have come to perform right in front of the fans.
2.3 Remote fan collaboration
It has been difficult for fans and artists to interact
with each other during the pandemic. Even if the fanscould go to a venue, the experience of shaking handswith a celebrity like before has become impossible.
The purpose of remote fan collaboration was to harness the power of communication in such an environment to create an experience in which the artist
appears to come and perform with the fans.
We faced two challenges for this production. One
was to transfer the artist on the main stage and theother was to transfer the fans at the venue next to theartist on the stage. For the first challenge, the imagesof the artist on the stage were extracted using Kirari!
and superimposed next to the images of the fans displayed on a monitor on the stage. As shown in Fig. 6,
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this process gave the fans in the audience the virtual
feeling of being next to the artist. For the other challenge, the images of the artist extracted using Kirari!
were transferred to the remotely located Kirari! truck
in a manner that created the feeling that the artist had
been transferred next to the fans in the truck.
3. Technology
We now explain one of the technologies that makeup Kirari!, “real-time extraction of objects with arbitrary background” technology [1]. This technology
can extract a specific object from a video without theneed to use a green background. NTT developed“KIRIE” [2] in 2018, which systemizes object extraction using this technology, and used it for the abovedescribed stage productions.
With KIRIE, the object is extracted by switching
between two methods: one using only backgroundsubtraction and the other combining background subtraction and machine learning. With backgroundsubtraction, an image without an object is acquired in76Feature Articles

Fig. 5. Appearance of remote viewing.

(a) The performers are transferred next to the fans in the audienceso they can all dance together(b) The performer interacts with fans on the Kirari! truck

Fig. 6. Appearance of remote fan collaboration.

advance as a background, and the area in which theobject is to appear is identified by taking the difference between the background and image being captured.
Using machine learning, in addition to the abovementioned background image, multiple images
showing the object and background at the same time
are taken. By learning the combination of background color and color of the object to be extracted astraining data, it is possible to determine what area
corresponds to the object.
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The method that only uses background subtraction
has the advantage of not requiring prior training;
however, it is not easy to extract objects in colors
close to the background color. Another disadvantage
is that if the background changes even slightly, theextraction accuracy will decrease. In contrast, themethod of combining background subtraction andmachine learning has advantages such as being able
to extract images even when the colors of the background and object are similar and being able to handlechanges in the background. However, it requires prior
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Feature Articles

training.
For the above-mentioned stage productions, when
the performers could participate in the rehearsal the
day before and the color of the costume they would
wear on the day was decided, we aimed for moreaccurate object extraction by using the method of
combining background subtraction and machinelearning. When the performers could not attend therehearsal on the previous day, however, we used themethod that only uses background subtraction to
extract the objects.
4. Results
The extended versions of the Torch Relay celebration, which were streamed online, were viewed bymany people, with 100,000 views on YouTube Livewith a maximum of 12,000 simultaneous connections. We also received a large amount of positive
feedback on social networking sites, where over 90%of the responses were positive.
Using the above-mentioned technologies for the
remote-performance, remote-viewing, and remotefan-collaboration productions, we could extract
objects with high accuracy.
Even under the condition that the color of the background tends to change, such as when it was raining
during the previous day’s rehearsal but sunny on thenext day’s rehearsal, we could extract the object by
combining background subtraction and machinelearning with an accuracy acceptable for viewing. In
some cases, the arrangement of the production suddenly changed on the day, and performers different
from those targeted in the previous day’s rehearsal
became the extraction target; nevertheless, the method using only background subtraction still produced
generally acceptable extraction results. The average
processing delay of KIRIE was 166 ms, which indicates that we achieved real-time object extraction
with low latency and high accuracy.

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5. Concluding remarks
For the extended celebration events of the Tokyo
2020 Olympic Torch Relay, we conducted three stage
productions, remote performance, remote viewing,
and remote fan collaboration using Kirari!. Although
the public viewing was cancelled due to the spread of
COVID-19, we could still demonstrate to tens of
thousands of viewers the possibility of new remoteentertainment during the pandemic through online
streaming and received positive feedback from the
majority of those viewers. Taking the above-describedchallenges as a first step, NTT R&D will continue toresearch and develop technologies toward the creation of a new form of live entertainment suitable forthe “new normal” era.
Acknowledgments
We thank the Tokyo Organising Committee of the
Olympic and Paralympic Games, Osaka Prefecture,
Suita City, Kanagawa Prefecture, Yokohama City,and our partner companies for their cooperation inpromoting this project. We also thank GENERATIONS from EXILE TRIBE and all the performers
who graced the stage of the extended celebration.
NTT is an Olympic and Paralympic Games Tokyo
2020 Gold Partner (Telecommunication Services).
References
[1]

[2]

H. Kakinuma, J. Nagao, H. Miyashita, Y. Tonomura, H. Nagata, and
K. Hidaka, “Real-time Extraction of Objects from Any Background
Using Machine Learning,” NTT Technical Review, Vol. 16, No. 12,
pp. 12–18, 2018.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=
ntr201812fa2.html
J. Nagao, H. Miyashita, T. Sano, K. Hasegawa, and T. Isaka, “Kirari!
for Arena: Real-time Remote Reproduction of 4-directional Views
with Depth Perception,” Journal of the Imaging Society of Japan, Vol.
58, No. 3, pp. 306–315, 2019 (in Japanese).

78

Feature Articles

Taiji Nakamura

Senior Research Engineer, 2020 Epoch-Making Project, NTT Human Informatics Laboratories.
He joined NTT DATA Communications Systems (now NTT DATA) in 1991. He has over 20
years’ experience in information systems planning and development in the national public sector.

Keisuke Hasegawa

Engineer, NTT Human Informatics Laboratories.
He received a B.E. and M.E. in informatics
from Kyoto University in 2012 and 2014. He
joined NTT WEST in 2014 and engaged in themaintenance of network facilities. Since joining
NTT Service Evolution Laboratories in 2016, hehas been engaged in research of media processing for the ultra-realistic communication technology Kirari!. He is a member of the Institute of
Image Information and Television Engineers(ITE).

Yoshiyuki Mihara

Senior Research Engineer, NTT Human Informatics Laboratories.
He received a B.Sc. and M.Sc. from Tokyo
Institute of Technology in 2004 and 2006. Healso received a Ph.D. from Kyoto University in2017. Since joining NTT in 2006, he has been
engaged in R&D of a home network management service. The home network management
protocols he designed have been standardized by
Universal Plug and Play (UPnP) Forum, International Telecommunication Union Telecommunication Sector (ITU-T), and Japan’s Telecommunication Technology Committee (TTC). He iscurrently promoting the key protocols with aview to launching a home network management
service.

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Vol. 20 No. 1 Jan. 2022

Takashi Miyatake

Senior Research Engineer, Supervisor, NTT
Human Informatics Laboratories.
He received an M.E. in engineering from Kobe
University in 1995. In the same year, he joined
NTT and engaged in research on image processing and human interface. He also worked as asystem engineer at NTT Communications andother companies. He is currently engaged inresearch on the ultra-realistic communication
technology Kirari!.

Shingo Kinoshita

Vice President, Head of NTT Human Informatics Laboratories.
He received a B.E. from Osaka University in1991 and M.Sc. with Distinction in technology
management from University College London,
UK, in 2007. He joined NTT in 1991 and was asenior manager of the R&D planning section of
the NTT holding company from 2012 to 2015.
He is currently a visiting professor at the Art Science Department, Osaka University of Arts, andvisiting executive researcher at Dentsu Lab
Tokyo. He has served as a member of the Japan
Science and Technology Agency (JST) JSTMirai Program Steering Committee, member ofthe All Japan Confederation of Creativity (ACC)TOKYO CREATIVITY AWARDS 2021 Judging
Committee, and member of the Broadband Wireless Forum Steering Committee. He has been
engaged in R&D of a media-processing technology, user interface/user experience, communication protocols, information security, machinelearning, service design, and technology management. Until recently, he had been in charge ofNTT’s Tokyo2020 initiatives, including sportswatching video technology, inclusive design forsocial issues, and promoting the use of ICT in
kabuki, entertainment, and media arts such as live
music.
He has been in his current position since 2021,
where he manages R&D on information andcommunication processing of humans based onhuman-centered principles.

79Feature Articles: Olympic and Paralympic Games Tokyo 2020
and NTT R&D—Technologies that Colored Tokyo 2020 GamesTorch Relay Regional Event ×
Voice-recognition Communication
Technology
Yusuke Ichikawa and Yuki Yoshida
Abstract

To celebrate the Tokyo 2020 Olympic Torch Relay, NTT held a hands-on event that enabled children
from local elementary schools to cheer on the Torch Relay. During this event, we created a new cheeringexperience by developing a cheering-production system together with the elementary-school students
that visualizes the cheers of the children as text using voice-recognition communication technology andsends the text cheers to the runners. This article introduces the event and cheering-production system.
Keywords: Torch Relay, voice-recognition communication technology, experience design

1. Overview
The NTT Yokosuka R&D Center was selected as
one stop on the route of the Tokyo 2020 Olympic
Torch Relay, which traveled the length and breadth ofJapan. An event to welcome the torch to the center
was managed by NTT. NTT research and development (R&D) laboratories recruited a wide range ofstaff from across several laboratories to plan andorganize the event. A total of 18 people from 9 laboratories worked together as a study team to organize
the event. The team decided to welcome the torch to
the NTT Yokosuka R&D Center by inviting local
residents to participate—with whom we have hadmany exchanges in the past.
The concept of the Tokyo 2020 Olympic Torch
Relay was “Hope Lights Our Way.” Established in1972 in Yokosuka, Japan, the NTT Yokosuka R&D
Center has long been involved in exchanges withlocal residents through technology. Combining thisbackground with the concept of the Torch Relay, we
decided on the theme of “Connecting ages, connecting communities, and connecting technologies” forthe event.
In accordance with that theme, we selected seniorresearchers as initial torchbearers who would pass thetorch to young researchers who would in turn pass it
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to local students. In addition, elementary-school students from nearby schools (Awata and Iwato Elementary Schools in Yokosuka City) were invited as spectators to cheer on the Torch Relay. The entire Torch
Relay, including the spectators, was designed to connect ages and communities. Students from Kanagawa
Prefectural Yokosuka High School, which had beeninteracting with the NTT Yokosuka R&D Center
through programs such as “Super Science HighSchool,” were also selected as local student torchbearers.
On the basis of the theme of connecting communities and technologies, this event aimed to provide an
opportunity for elementary-school students to experience the communication technology of the NTT
Yokosuka R&D Center through cheering. The aim of
the event was to provide a new experience of cheering
for the Torch Relay. We developed a cheering-production system using voice-recognition communication technology that enables the cheers of elementary-school students to be visualized and transmitted tothe torchbearers. To expose the students to suchtechnology, we introduced a paper-cup microphonethat they could make themselves using commerciallyavailable paper cups, magnets, and coils and use as an
input device for the cheering-production system.
Before the event, we asked the students to make their
80Feature Articles

Fig. 1. The cheering-experience event at Iwato Elementary School.

own paper-cup microphones. By making the microphones themselves, the students had a chance to learn
the principles of communication by which sound istransmitted by a magnet and coil.
In March 2020, in the midst of these preparations,
it was decided to postpone the Torch Relay and the
Olympic and Paralympic Games for one year due tothe spread of the novel coronavirus (COVID-19).
Nevertheless, members of the study team organizing
the event continued to prepare to welcome the torch
to the NTT Yokosuka R&D Center. In March 2021,
the Torch Relay started as scheduled; however, two
weeks before our event, due to continuing spread of
COVID-19 infections, the Kanagawa prefectural government decided to take the Torch Relay off publicroads in the prefecture. Consequently, the Torch
Relay event at the NTT Yokosuka R&D Center wascancelled. Although it was decided to cancel theevent, all the members of the study team had one goalin mind, to create memories for the elementaryschool students who had participated in making theirpaper-cup microphones. With that goal in mind, we
worked together and immediately started planning analternative event. Since we could not hold a grouptype event at the NTT Yokosuka R&D Center, we
decided to take the cheering-production system to the
Awata and Iwato elementary schools and hold a similar Torch Relay cheering-experience event on thosepremises. The paper-cup microphones, which was an
idea of the members of the study team, has the advantages of not only preventing oral droplets fromspreading but also amplifying voices without theneed for shouting. From that viewpoint, we were conNTT Technical Review

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vinced that we could hold the event safely even in the
midst of the pandemic. When we consulted with theelementary schools about our plan, they readily
agreed to hold the event in the gymnasium at Awata
Elementary School and in the audiovisual room at
Iwato Elementary School. The participants were sixth
graders. The event was simultaneously held at bothschools on June 29, which was the date the Torch
Relay was originally scheduled to be held (Fig. 1).
The total number of participants was 107, including
61 from Awata Elementary School and 46 from Iwato
Elementary School.
2. Cheering-production system
The cheering-production system visualized thevoices of the students through paper-cup microphones by using voice-recognition communication
technology. The configuration of the system is shownin Fig. 2. To obtain the sound of a student’s voice,each student’s paper-cup microphone was connected
to his/her smartphone. The voice collected by the
paper-cup microphone was sent to the voice-recognition communication network through the smartphone((1) in Fig. 2). Through the voice-recognition communication network, the speech content was converted into characters and output during the communication. The speech content output from the voicerecognition communication network was displayedon a projector at the event venue that can also be seenby the torchbearers ((2) in Fig. 2). We improved therecognition accuracy by limiting the recognition to
two specific cheering words, “ganbare!” (“Go for81

Feature Articles

Set up in elementary schools

Voice-recognition communication network(1)

Smartphone

Voice-recognition
server

Paper-cup microphone
Wireless accesspoint (AP)(Approximately 120 units)Internet

Projector
Speaker

Cheeringproduction
display system(2)

Cheering-wordcount-up server

Camera(capturing
runners)

Fig. 2. Overview of cheering-production-system configuration.

it!”, “Come on”, etc.) and “faito!” (lit. “fight!”). The
number of times each cheering word was uttered was
also counted, and from the results of the counting, theimage projected by the projector at the venue and thecheers collected with the paper-cup microphones andoutput to the loudspeakers were visualized and transmitted to the torchbearers (Fig. 3).
3. Technology
3.1 Voice-recognition communication technology
The signal-to-noise ratio of the speech collectedwith paper-cup microphones is low, and the frequency of the band required for speech drops. Therefore,
the failure to recognize phonemes (sound units suchas the vowels /a/, /i/, /u/, /e/, and /o/) posed a challenge to implementing the cheering-production system. Therefore, we developed a learning model andtuned it to the characteristics of a paper-cup microphone. For this event, it was important to recognize
the specified cheering word without omission. Therefore, we were able to improve the cheering experience by limiting the number of words to be recognized and tuning the model by prioritizing reproduction rate (sensitivity) over relevance rate (accuracy).
We asked the elementary-school students to maketheir own paper-cup microphones for transmitting
their cheers to the voice-recognition communication
network. The creation of the paper-cup microphones
was part of the technology-education program thatwas implemented in the children’s science class held
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at the NTT Yokosuka R&D Center Open House in2012.
For this cheering-experience event, all students had
to complete their paper-cup microphones within thetime allotted by the school, i.e., two periods of 120
minutes. With that allocated time in mind, the studyteam members repeated trials, identified steps thatwould take time, and devised ways such as omitting
work steps requiring scissors and prepared an allyou-need kit. All the students completed their microphones within the allocated time. A scene from theday of the event is shown in Fig. 4.
On the day of the event, the procedure was as follows. On completing their paper-cup microphones,
each student, in order of finishing, connected themicrophone to their smartphone and recorded their
voice on the smartphone. Their recorded voices werethen played back from the speaker, and the operationof the cheering-production system was checked. The
students were able to enjoy learning about the mechanism of voice communication, for example, when
their voice was actually played back from the speaker, we heard them exclaim “Ooh!” and “Aah!”
4. Results
During the cheering-experience event, teachers
from the school ran with torches around classrooms
and gymnasiums, and when each torch-bearing
teacher reached the next teacher, they conducted asimulated “torch kiss” by touching the tips of their82

Feature Articles

Fig. 3. E xample of displayed cheering words and number of times the words were uttered (The center of the screen is acomposite display of an actual runner’s image.).

Fig. 4. A snapshot of a student making a paper-cup microphone.

torches. The simulated Torch Relay lasted about 15
minutes, during which the students continued cheering while desperately trying to keep their voices
down to prevent droplet infection. Although thecheers were not loud, they were amplified by the
paper-cup microphones and became louder, and thetwo cheering words were counted about 9000 times
and displayed while the torchbearers were running.
After the event, all of the participating students wrote
their impressions (in a completely free format) withcomments such as, “I was so happy when I could
make a sound with the paper-cup microphone,” “I
could speak with a normal voice even though myvoice came from a microphone,” and “It was amazing
to cheer with the paper-cup microphone just like witha real microphone.” We were amazed to see that the
NTT Technical Review

Vol. 20 No. 1 Jan. 2022

cheering experience was not only fun but also led to
an interest in technology. We heard the students’interest in the fundamentals of technology with comments such as “I want to know why it is the way it is.”This event was evaluated as having value in termsof not only regional exchange but also education. The
school principals said, “I think it was good for learning that various communication technologies arebeing researched at local facilities” (Principal
Kaneko, Awata Elementary School) and “It was verysignificant in regard to career education to be exposed
to NTT’s research and technology” (Principal Haraguchi, Iwato Elementary School).

83

Feature Articles

5. Concluding remarks

Acknowledgments

The planned regional event of the Torch Relay inthe form of inviting elementary-school students to the
NTT Yokosuka R&D Center was not possible. However, from making paper-cup microphones to actual
cheering, the elementary-school students actively
experienced a simulated relay, and we believe that wewere able to reach our goal set out in our original
theme of “Connecting ages, connecting communities,
and connecting technologies.” We believe that the
exposure to the Torch Relay helped build momentum
for the Tokyo 2020 Games. To be a research institutethat continues to develop together with the community, we will continue to connect with the local community through technology.

We thank the teachers and students of Awata Elementary School and Iwato Elementary School in
Yokosuka City for understanding the value of thisevent and participating in it. We also thank the
Kanagawa Prefectural Sports Bureau, Yokosuka City
Policy Promotion Department, Kanagawa Prefectural
Police Security Department, and Kanagawa Prefectural Yokosuka High School for their cooperation in
the preparation of the Torch Relay.

Yusuke Ichikawa

Senior Research Engineer, Cyber-World Laboratory, NTT Human Informatics Laboratories.
He received a B.E. and M.E. in measurement
engineering from Keio University, Kanagawa, in
1995 and 1997, and Ph.D. in informatics from
Shizuoka University in 2020. He joined NTT
Multimedia Network Laboratories in 1997. Since
1998, he has been researching and developing
recommendation systems. He is a senior memberof the Information Processing Society of Japan(IPSJ) and received the 2005 and 2019 IPSJ
Yamashita SIG Research Award.

NTT Technical Review

Vol. 20 No. 1 Jan. 2022

NTT is an Olympic and Paralympic Games Tokyo
2020 Gold Partner (Telecommunication Services).

Yuki Yoshida

Research Engineer, NTT Human Informatics
Laboratories.
She received a B.Sc. and M.Sc. from the University of Tsukuba. She joined NTT and engaged
in R&D of human interface. In 2019, she joined
the 2020 Epoch-Making Project, where she has
been engaged in service promotion to celebrate
the Tokyo 2020 Games.

84

Feature Articles: Olympic and Paralympic Games Tokyo 2020
and NTT R&D—Technologies that Supported Tokyo 2020 Games

High-efficiency Wi-Fi Technologies
Toshiro Nakahira, Motoharu Sasaki,
Masayoshi Nabeshima, Tomoaki Ogawa,Takatsune Moriyama, Ken Hiraga, Kento Yoshizawa,and Ikutaro Ogushi
Abstract

NTT undertook the technical development and implementation of high-efficiency Wi-Fi technologies
to provide spectators and related personnel a stress-free wireless communications environment at theJapan National Stadium and other venues of the Olympic and Paralympic Games Tokyo 2020. These
technologies are expected to lead to new sports-viewing styles using the network of a venue and a varietyof new services using a flexible network at events such as meetings, incentives, conferences, and exhibitions (commonly referred to as MICE).
Keywords: high-efficiency Wi-Fi, wireless resource control technology, wireless quality visualization
technology

1. Introduction
Everyone’s lifestyle has been changing along withthe widespread use of smartphones and social networking services (SNSs), and the way in which people participate in events such as when attending
sports matches or live concerts has likewise beenchanging. For example, it has become common forspectators at a venue to take photos or video of an
exciting scene using their cameras or smartphones
and immediately post such images simultaneously on
SNSs or upload them to a cloud environment. In asimilar manner, it was envisioned that many spectators at venues of the Olympic and Paralympic GamesTokyo 2020 would be simultaneously using the networks of these venues.
The Japan National Stadium, the main venue of theTokyo 2020 Games, required a stress-free communications environment for spectators appropriately
linked to a variety of systems to become a world-classstadium as the new hub for sports in Japan. To thisend, specialists having high technical competence
through extensive experience in constructing Internet
Protocol (IP) networks, Wi-Fi* systems, etc. wererecruited from NTT Group companies to set up an
NTT Technical Review

Vol. 20 No. 1 Jan. 2022

information-and-communication-technology environment on a world-class level. These specialists
used their diverse experience and expertise in constructing and operating Wi-Fi systems at large-scalestadiums to achieve an optimal arrangement of accesspoints (APs) tailored to the construction and shape of
the Japan National Stadium. This arrangement featured an AP for every 70 seats and provided coverageof areas where people would tend to gather such asconcourses, vendor stalls, and ticket counters. The
end result was a total of approximately 1300 APs,making for a high-density, world-class Wi-Fi system.
To achieve such a high-density configuration, optimalchannel settings to avoid radio-wave interference andtuning performed at the final stage of construction
were important. Therefore, it was decided to use thehigh-efficiency Wi-Fi technologies being developed
by NTT laboratories to create a stable and highquality Wi-Fi environment. This provided smoothconnections to the Internet enabling everyone in thestadium to share their feelings or impressions on
SNSs or elsewhere.

*“Wi-Fi” is a registered trademark of Wi-Fi Alliance.

85

Feature Articles(a) AP wireless control: Dynamic control of AP operating frequency band (920 MHz,
2.4 GHz, 5 GHz) and wireless parameters(b) Terminal connection control: Dynamic control of terminal wireless-connection
destination from the AP side between multiple APs and frequencies

Control engine

Wireless LAN
controller(a) AP wireless control

Wireless LAN AP
IEEE 802.11ax

IEEE 802.11ah

IEEE 802.11ac(b) Terminal
connection
control
IEEE: Institute of Electrical and Electronics Engineers
LAN: local area network

Fig. 1. Wireless resource control technology.

2. Introduction to high-efficiency
Wi-Fi technologies
The following introduces high-efficiency Wi-Fi
technologies for achieving a stable and high-quality
Wi-Fi environment.
2.1 Wireless resource control technology
The wireless resource control technology derives
an optimal combination of Wi-Fi parameters such as
the operating frequency channel, bandwidth, andtransmission power of each AP depending on theradio-interference conditions among multiple APs(Fig. 1) [1]. It derives, in particular, an optimal channel combination that avoids interference between
APs through iterative optimization processing using a
genetic algorithm. Carrying out this processing
dynamically enables the parameters of each AP to becontrolled in accordance with changes in the environment.
2.2 Wireless quality visualization technology
The wireless quality visualization technology estimates the degree of congestion under peripheral wireless conditions by listening to and analyzing control
signals radiated in an area through the use of monitoring devices (boxes) installed at locations near APs or
NTT Technical Review

Vol. 20 No. 1 Jan. 2022

users (terminals) [2]. This technology makes it possible to estimate the positions of transmitting/receiving terminals, issue alerts in the event of a sudden
increase in traffic, and provide an operator with uservicinity information needed to clarify the cause of
network instability (Fig. 2).
3. Demonstrations at venues
The opening event for the new Japan National Stadium was held in December 2019 immediately after
completion of the structure. Filled to capacity with
64,000 spectators, the stadium hosted a program that
included relay races by famous athletes and live performances by popular artists. During these activities,
there were moments when images and video taken byspectators were simultaneously posted to SNSs or
emailed throughout the world. Through this event, it
was shown that 64,000 spectators could simultaneously make SNS postings without problems as anextension of their everyday life and that the communications infrastructure of the Japan National Stadium could provide stable and high-quality connections.
This opening event provided an ideal opportunity todetermine changes in the wireless environment andshifts in traffic for an actual high-density gathering of86

Feature Articles

Uses boxes that can easily capture Wi-Fi environment
information and quality information by simply placing
them at certain locations.

Technology features:
Captures radio signals at multiple boxes

Extracts required information andconverts to quality information
Extract

Consolidate/convertHow to use:
FLOOR
MAP
1F

ON!

Network
Connecting to the
network enables realtime remote monitoring

Quality information for each installation
location• Each channel’s utilization rate
• Retry rate (amount of overflow)
Can simultaneously consolidate one’s APs
and peripheral APs of other companies

Fig. 2. Wireless quality visualization technology.

spectators. With the wireless quality visualization
technology, the analysis of wireless-environment
data that were collected widely and continuously
confirmed that traffic could be accommodated without problem during peak traffic occurrences evenfrom the viewpoint of data communications (Fig. 3).
Analysis based on data collected using this technology clarified the effects of human-body shielding
with respect to receiving radio waves in an environment closely packed with spectators (Fig. 4). It has
been reported that the shielding and attenuation ofradio waves by human bodies in a crowd of spectatorsin an environment such as the Japan National Stadium can affect wireless communications, but the magnitude of that effect has not been quantitatively clarified. These analysis results provided beneficial datafor detailed designs of Wi-Fi parameters using thewireless resource control technology.
This opening event was the first large-scale event in
the world to use the 5.2-GHz band, which had notbeen approved for outdoor use prior to the event.
Japan, however, was a prime promoter of worldwide
system revisions with respect to this band andachieved a revision of radio regulations allowing its
outdoor use in November 2019 just in time for the
opening event. As a result of this achievement, NTT
received the 31st Radio Achievement Award of the
NTT Technical Review

Vol. 20 No. 1 Jan. 2022

Minister of Internal Affairs and Communications
from the Association of Radio Industries and Businesses.
With a view to the Olympic and Paralympic GamesTokyo 2020, there was a need for dividing channels
into those for spectator use and those for management
use at the same stadium. The aim was to ensure astable level of communications quality for people
related to the Tokyo 2020 Games and actual sports
events even during the occurrence of large volumes oftraffic generated by as many as 60,000 spectators.
From the analysis results of the opening event, a test
calculation of traffic volumes was conducted beforehand, and it was found that insufficient capacity
would occur at an event on the scale of the Olympic
Games if the number of available channels was limited [3] (Fig. 5). NTT’s high-efficiency Wi-Fi technologies can dynamically derive an optimal combination of Wi-Fi parameters even with such a limited
number of resources. The effectiveness of thesetechnologies was recognized, and it was decided toprovide them at the Japan National Stadium. Unfortunately, it was decided to hold the Tokyo 2020
Games without spectators, so Wi-Fi for spectators
was switched off and these technologies were notused at the Japan National Stadium. However, they
were used in the free Wi-Fi environment at the Tokyo
87

Feature Articles

A

ed

m
ssu

l

cel

A

A

S1

225

Collection
terminal

AP

A
A

S3-1

Collection
terminal

Collection
terminal
BLK
224

NTT is currently measuring

Channel-utilization rate

Channel-utilization rate

S3-1

Fig. 3. C ollection of wireless-environment information at opening event of Japan National Stadium using wireless quality
visualization technology.

No people

Crowded (seated)

−60

400

RSSI (dB)

Number of samples

Start

−65
−70
−75
−80
−85
14 : 00

Doors openEnd
16 : 00

18 : 00
Time

20 : 00

22 : 00

Unoccupied (14:00–16:00)
Crowded (19:00–21:00)

350
300
250
200

Center value drops
Dispersion increases

150
100
50
0
−85

−80

−75 −70
RSSI (dB)

−65

−60

RSSI: received signal strength indicator

Fig. 4. Example of loss in receiving radio waves due to human-body shielding in a crowd of people.

Big Sight Aomi Exhibition Halls that became theshowcase venue for sponsors of the Tokyo 2020
Games. It contributed to the provision of a stress-freewireless environment at this location.
4. Toward the future
At NTT, we have been researching and developing
high-efficiency Wi-Fi technologies to optimize the
network within a venue and provide stable throughNTT Technical Review

Vol. 20 No. 1 Jan. 2022

put with an eye to creating new viewing styles andnew types of events. For example, these technologies
will enable the flexible allocation of communication
resources in accordance with network demand perunit area and the provision of flexible networks that
can improve throughput at particular locations suchas premium seating and press galleries.
These wireless technologies have been given thegroup name Cradio® [4], which we will continue toresearch and develop toward the implementation of88

Feature Articles

Maximum traffic amount at
opening event: 100%

Maximum traffic amount (%)

120

109.0%

100
80

59% insufficient
capacity

60
41.3%

40
20
0
All channels areavailable for use

Number of available
channels are limited

Fig. 5. Example of calculating throughput when available channels are limited.

the Innovative Optical and Wireless Network (IOWN)
vision promoted by NTT.

[2]

NTT is an Olympic and Paralympic Games Tokyo
2020 Gold Partner (Telecommunication Services).

[3]

References

[4]

[1]

NTT Access Network Service Systems Laboratories, “Technology for
Efficiently Providing Optimal Wireless LANs,” ANSL R&D Times,
Vol. 116, Aug. 2020 (in Japanese), https://www.rd.ntt/as/times/116/04/
top.html

NTT Technical Review

Vol. 20 No. 1 Jan. 2022

NTT Access Network Service Systems Laboratories, “Developmentof Wireless Communication Environment Information Platform,”
ANSL R&D Times, Vol. 111, Dec. 2019 (in Japanese), https://www.
rd.ntt/as/times/111/02/top.html
M. Sasaki, T. Nakahira, K. Wakao, and T. Moriyama, “Human Blockage Loss Characteristics of 5 GHz Wi-Fi Band in a Crowded Stadium,” IEEE Antennas and Wireless Propagation Letters, Vol. 20, No. 6,
pp. 988–992, June 2021. doi: 10.1109/ LAWP.2021.3069004
M. Sasaki, T. Nakahira, T. Moriyama, T. Ogawa, Y. Asai, and Y. Takatori, “Multi-radio Proactive Control Technology (Cradio®): A Natural
Communication Environment where Users Do Not Need to Be Awareof the Wireless Network,” NTT Technical Review, Vol. 19, No. 8, pp.
37–45, Aug. 2021.
h t t p s : / / n t t - r ev i ew. j p / a r c h ive / n t t t e c h n i c a l . p h p ? c o n t e n t s =ntr202108ra1.html

89Feature Articles

Toshiro Nakahira

Research Engineer, Wireless Access Systems
Project, NTT Access Network Service Systems
Laboratories.
He received a Bachelor of Maritime Safety
from Japan Coast Guard Academy in 2009 and
M.I. in informatics from Kyoto University in2012. In 2012, he joined NTT Network Innovation Laboratories. He is now working at NTT
Access Network Service Systems Laboratories.
He received the Best Research Award of the
fourth basic course workshop of the Institute ofElectronics, Information and Communication
Engineers (IEICE) Communication Quality in2017 and the Young Engineer Award from IEICE
in 2019. His recent research interests include
natural area design and dynamic control techniques using multiple wireless access. He is amember of IEICE.

Motoharu Sasaki

Senior Research Engineer, Wireless Access
Systems Project, NTT Access Network Service
Systems Laboratories.
He received a B.E. in engineering and an M.E.
and Ph.D. in information science and electricalengineering from Kyushu University, Fukuoka,
in 2007, 2009, and 2015. In 2009, he joined NTT
Access Network Service Systems Laboratories.
He has been engaged in research on propagation
modeling for various wireless communication
systems; propagation modeling of interference
between mobile terminals for spectrum sharing
wireless access systems, propagation modelingin very high-frequency bands for emergency
wireless systems, and propagation modeling inhigh frequency bands for 5G. He received theYoung Researcher’s Award and the Best Paper
Award from IEICE in 2013 and 2014, respectively. He received the Best Paper Award at theInternational Symposium on Antennas andPropagation (ISAP) in 2016 and the Young Engineer Award from the Institute of Electrical andElectronics Engineers (IEEE) Antennas andPropagation Society Japan chapter in 2016. Healso received the Young Researcher Award andthe Excellent Paper Award from IEICE TechnicalCommittee on Antennas and Propagation in 2012
and 2018, respectively. He is a member of IEEE.

Tomoaki Ogawa

Senior Research Engineer, Supervisor, NTT
Access Network Service Systems Laboratories.
He received a B.E. and M.E. from Keio University, Kanagawa, in 1996 and 1998. He joined
NTT Wireless System Laboratories in 1998,
where he has been engaged in the research anddevelopment of indoor location systems. His
recent interest focuses on development of 6G
wireless network technologies. He is a memberof IEICE.

Takatsune Moriyama

Senior Research Engineer, Supervisor, NTT
Access Network Service Systems Laboratories.
He received a B.E. and M.E. from MuroranInstitute of Technology, Hokkaido, in 1991 and1993. He joined NTT in 1993. From 1999 to June
2019, he worked at NTT Communications,where he was in charge of network service development and operation for corporate customers.
He has been in his current position since July
2019.

Ken Hiraga

Senior Research Engineer, NTT Network Innovation Laboratories.
He received a B.E., M.E., and Ph.D. in electronics and information engineering from Hokkaido University in 2003, 2005, and 2013. Since
2005, he has been engaged in research and standardization on high-speed wireless systems at
NTT. From 2018 to 2021, he was with NTT
Broadband Platform Inc., where he designed
radio coverage areas of commercial wireless
local area networks. He is a member of IEEE and
IEICE.

Kento Yoshizawa

Masayoshi Nabeshima

Research Engineer, Wireless Access Systems
Project, NTT Access Network Service Systems
Laboratories.
He received a B.E. and M.E. in electrical communication engineering from Waseda University,
Tokyo, in 1992 and 1994. He joined NTT in
1994. His research interests include traffic analytics and visualization for wireless networks.

Engineer, NTT Broadband Platform, Inc.
He received a B.E. and M.E. from Yokohama
National University, Kanagawa, in 2014 and2016. He joined NTT Network Innovation Laboratories in 2016. His research interests are highreliable radio access system, large-capacity
wireless backhaul, and overlapping and powersaving technique for low power wide area radio
systems. Since 2021, he has been affiliated withthe wireless technology department in NTT
Broadband Platform and engaged in the quality
control of radio and development for radio accessnetwork system.

Ikutaro Ogushi

Senior Manager, NTT Broadband Platform,Inc.
He received a B.E. and M.E. in electrical engineering from Osaka University in 2000 and 2002.
In 2002, he joined NTT Access Network Service
Systems Laboratories. His research interests
include research and development of an opticalfiber line testing system for submarine cables andoptical fiber distribution system for use in central
offices. He is a member of IEICE. He has been in
his current position since July 2019.

NTT Technical Review

Vol. 20 No. 1 Jan. 2022

90

Feature Articles: Olympic and Paralympic Games Tokyo 2020
and NTT R&D—Technologies that Supported Tokyo 2020 Games

Network Security
Takashi Mishina, Akiko Matsuhashi, Takemi Nisase,and Hidehiro Shito
Abstract

Events that attract worldwide attention, such as the Olympic and Paralympic Games and international
exhibitions, have become easy targets for cyber attacks, and it is no longer rare to hear of reports of damage from such attacks. The Olympic and Paralympic Games Tokyo 2020 was held in 2021 after a oneyear delay due to the novel coronavirus (COVID-19), and NTT, as a Gold Partner (Telecommunications
Services), had the responsibility of managing the network infrastructure supporting the Tokyo 2020
Games, thus dealing with the threat of cyber attacks. This article describes how NTT-CERT (NTT Computer Security Incident Response and Readiness Coordination Team) of NTT Social Informatics Laboratories faced cyber attacks as the representative computer security incident response team of the NTT
Group.
Keywords: information security, cyber attack, CSIRT

1. Olympic and Paralympic Games andcyber attacks
The Olympic and Paralympic Games is an international event with a long history. It attracts worldwide
attention, therefore, it can become a target of many
parties with a variety of malicious intentions. The
event can be misused as a site for advancing political
agendas, swindling money, or generating a loss ofconfidence in the host nation by inducing failure. The
modus operandi of attackers having such malicious
intentions have begun to spread to cyberspace beyond
physical activities. In past Olympic and Paralympic
Games, a variety of attacks having the potential of
impacting their operations and management havebeen confirmed. These include disruptive acts caused
by denial-of-service (DoS) and distributed denial-ofservice (DDoS) attacks, the breaching of systems
belonging to organizations related to the Games, andtargeted attacks toward malware infections. To obtain
results at a single international event, attackers havebeen watching for opportunities and refining theirtechniques. Organizations related to the Olympic andParalympic Games must therefore implement extensive and reliable systems to protect the Games fromsuch advanced attacks. As a Gold Partner (TelecomNTT Technical Review

Vol. 20 No. 1 Jan. 2022

munications Services) of the Olympic and Paralympic Games Tokyo 2020, NTT had the important
responsibility of managing the network infrastructure
supporting the Tokyo 2020 Games, thus having todeal with the threat of cyber attacks. This article
introduces the activities of NTT-CERT (NTT Computer Security Incident Response and Readiness
Coordination Team) of NTT Social Informatics Laboratories at the Olympic and Paralympic GamesTokyo 2020.
2. NTT-CERT activities at Olympic andParalympic Games Tokyo 2020
NTT-CERT, a research group operating within
NTT Social Informatics Laboratories, acts as the representative computer security incident response team
(CSIRT) of the NTT Group (Fig. 1). NTT-CERT
activities, which do not include the operation ofequipment, have two major objectives: (i) collectinformation and share that information seamlessly
with NTT Group companies to prevent cyber attacks
from occurring, and (ii) provide support to minimize
the damage caused by actual incidents and prevent
their reoccurrence. NTT-CERT also feeds back theknowledge gained from such activities to research91

Feature Articles

Commercial
intelligence

Surface/dark
web information

Large-scale events,
analysis reports,
vulnerability
information

Document-sharing
sites, SNSs,
communities, newssites, etc.

Hacktivists, nations, crime syndicates, thrill seekers
DoS attack,site tampering,etc.

External organizations
JPCERT/CC
NCFTA, etc.

Analysis, evaluation

NTT-CERTOSINT

Threatintelligenceplatforms

System hijacking,information theft,
etc.

NTT Group companies

Information provision,
incident response support

CSIRT organization

Ransomware,scam site

In-house expansion of
security-related
information
Handling and determining
vulnerability information
Information sharing and status
reporting in collaboration within-house organizations
Integration of anddetermining in-houseincidents

Feedback toresearch activities

NTT-CERT main activities(1) Information collection & analysis(2) Incident response support(3) Technology surveys, productevaluation/education

JPCERT/CC: Japan Computer Emergency Response Team Coordination Center
NCFTA: National Cyber-Forensics and Training Alliance
SNSs: social networking services

Fig. 1. Role of NTT-CERT.

activities and promotes research toward moreadvanced and robust security technologies.
As described above, the NTT Group had the
responsibility of creating and maintaining a safe andsecure network infrastructure in support of the Tokyo
2020 Games. Therefore, it was essential that NTTCERT functions be enhanced to protect the NTT
Group and network infrastructure from a diverse
array of attackers from around the world. As an organization related to the Tokyo 2020 Games, we drafteda policy of preventing the possibility of a cyber attack
before it occurs, and if an incident should occur, of
minimizing any damage and impact on the Tokyo
2020 Games. We focused our efforts on enhancing
our information collection and analysis functions.
Since NTT-CERT possesses no network facilities
that it directly operates, the target of its informationcollection is mainly external open source intelligence(OSINT). However, collecting such a large volume ofrandomly arranged OSINT information would benearly impossible no matter how many people areassigned to the task. We decided to prioritize the typeof threat analysis to be conducted for the Tokyo 2020
Games and the information that should be collected.
We analyzed cyber attacks that would seem likely tooccur at the Tokyo 2020 Games by analyzing threats
from the following four viewpoints: 1) What kind of
attacker or organization using 2) what type of attack
technique and having 3) what purpose would mount
NTT Technical Review

Vol. 20 No. 1 Jan. 2022

an attack on 4) what attack target? On the basis ofthese four viewpoints, it became possible to organize
information in terms of what attack target should beprioritized and protected by NTT-CERT and what
information on attack techniques should be prioritized and detected, and on the whole, to classify withgood efficiency the information that should be prioritized and collected. It was first necessary to list andanalyze as many cyber attacks as possible that could
occur at the Tokyo 2020 Games.
With this in mind, we began by collecting information on cyber attacks that occurred in the past. Ranging from the Olympic Games London 2012, during
which full-fledged cyber attacks occurred, to the
Olympic Winter Games PyeongChang 2018, during
which targeted attacks were confirmed, we analyzed
both Japanese and overseas news articles on past
Olympic Games, reports issued by security vendors,
etc. To obtain a comprehensive understanding of
attacks that should be expected, we broadened oursurvey range to attacks that targeted personnel related
to the Olympic Games and spectators and prepared alist of damages that occurred and damages that could
be assumed. To carry out the threat analysis describedabove, we classified these data into “attacker,” “purpose,” “technique,” and “target.”
After using that list to determine “attacker,” “purpose,” and “technique” for which an attack could be
detected from outside sources, NTT-CERT prioritized92

Feature Articles

Threat reports
and news
related to past
Olympic Games

NTT-CERT knowledge,
expertise

Threat list andimportance ranking

Analysis of threats to
the NTT Group
1. Attacker
2. Purpose
3. Technique
4. Target

Information sources
usable by NTT-CERT,
analysis information
Monitoring prioritization,
extraction ofpriority targets

Combination ofmonitoring targets
and survey
techniques

Recent attack
trends, damage
reports

Fig. 2. Analysis toward enhanced monitoring.

the information that should be collected from theviewpoint of “target.” Specifically, attacks for which
the NTT Group would be the direct attack target wereset as top priority followed by attacks on personnel
related to the Tokyo 2020 Games that could have an
impact on the NTT Group and attacks on spectatorsin that order. “Technique” and “purpose” were prioritized on the basis of what NTT-CERT could detectfrom OSINT information. For example, while thethreat level of a targeted mail attack targeting the
NTT Group was high, it would be difficult to directly
detect the receiving of such mail at NTT-CERT, so
devoting resources there would be inefficient. We
therefore studied how the NTT Group could be protected from such threats on the basis of informationthat could be detected from the outside. We considered, for example, detecting phishing sites having
domains similar to those of NTT that might act as an
inducement, determining whether stolen information
is being sold on the dark web, and checking for the
existence of hacktivists (persons engaged in hacking
activities to advance their social or political agendas)
who warn of politically oriented attacks. In short, weinvestigated a variety of attacks that could be detectedfrom NTT-CERT’s position (Fig. 2).
After prioritizing the information that should becollected, the next step was to enhance the range andvolume of information collection. Until recently,
NTT-CERT’s main target of information collection
had been the surface web as well as dark web information from intelligence vendors with survey languages being Japanese and English. However, as
described above, it was considered insufficient todetect as much information as possible on information for sale on the dark web or on hacktivists’ agendas, so we used machine translation to add two survey
NTT Technical Review

Vol. 20 No. 1 Jan. 2022

languages for which there were many past cases.
Dark web surveys developed by NTT-CERT werealso launched. Though we had been conducting surveys of domains similar to those of the NTT Group,
we decided to simultaneously conduct surveys of
domains similar to those of the Olympic and Paralympic Games Tokyo 2020 that were predicted toincrease while the Tokyo 2020 Games were being
held (including the preparatory period) and collected
information on phishing sites in detected domains.
These activities can be regarded as surveys that introduced new tools and applied accumulated knowledge
as functional enhancements making use of research
results in the automation of CSIRT functions.
No matter how much a single company’s functions
can be enhanced through such efforts, there is a limit
to how much information a company can collect.
Therefore, NTT-CERT proactively shared information in collaboration with a variety of communities
that it had thus far fostered. It participated, for example, in the Japan Cybersecurity Information Sharing
Platform (JISP), an information-sharing tool of the
National Center of Incident Readiness and Strategy
for Cybersecurity (NISC), and the information sharing platform for the Olympic and Paralympic GamesTokyo 2020 set up by the ICT Information Sharing
and Analysis Center (ICT-ISAC). These activities
created a state in which NTT-CERT could accessunreleased or original information. Collaboration
with NTT Security’s Global Threat Intelligence Center also created a state of detailed information sharing
from overseas sites with respect to cyber attacks on
the Tokyo 2020 Games. This information obtained
through such external collaborations was distributed
to NTT Group companies along with additional surveys
and analysis results from NTT-CERT. These efforts
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Table 1. Monitoring results: Information sources and examples of detection results.
Information source

Information source details

Examples of detection results

Public organizations

JPCERT/CC, IPA, etc.

Vulnerability information, general attack information, etc.

SNSs

Twitter, blogs, message board

Posts encouraging attacks on Tokyo 2020 Games personnel,
information on discovered phishing sites, etc.

News sites

Newspaper companies, broadcast stations,information technology-related news sites

News on fake sites posing as deliverers of Tokyo 2020 Games
videos, news on cyber attacks on past Olympic Games-relatedorganizations, articles on malware pretending to be Tokyo 2020
Games-related, etc.

Dark web

Hacker forums, black-market trading sites, etc.

Information on credential selling/buying thought to be Tokyo 2020
Games-related.

Fake site information Domain abuse, Google search results, etc.
Other

Information on new domains that can be mistaken as Tokyo 2020
Games-related (some of which are confirmed to be phishing sites)

Manually prepared reports, vendor reports, etc. Analysis information on assumed attackers, malware, etc.

could be seen as boosting the role of NTT-CERT as a
hub between external organizations and the NTT
Group.
To prepare for the discovery of information on vulnerabilities that could impact the network infrastructure and operating systems, NTT-CERT strengthened
its vulnerability-information collection system aswell as its test system for cases in which attack code
came to be released.
Preparations for the activities described above weremade right up to the beginning of the Tokyo 2020
Games, and cyber exercises were finally held within
the NTT Group in anticipation of attacks. In these
exercises, NTT-CERT was in charge of creating
attack scenarios in which information on attacks presumed to have occurred or actually detected was to beshared within the NTT Group. Each company was tocheck their contact system and response procedure
for any problems and confirm whether appropriate
measures could be taken. Thus, the NTT Group
worked together in its preparations for the opening of
the Olympic and Paralympic Games Tokyo 2020.
3. Results of activities for the Olympic andParalympic Games Tokyo 2020
As a result of the functional enhancements taken
for the Tokyo 2020 Games, NTT-CERT collected andanalyzed information from a variety of sources andpassed on information for review to each company in
the NTT Group (Table 1). In this information forreview, NTT-CERT shared detection details that if
ignored could allow an attack to gain a foothold, e.g.,
warnings of attacks due to growing geopolitical tensions in Southeast Asia and information on the buying and selling of credential information thought to
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be related to the Tokyo 2020 Games, although nosmall-scale DDoS attacks or damage actuallyoccurred. By repeatedly providing information in thismanner, we were able to prevent major damage frombeing done and provide each company in the NTT
Group with a feeling of security. It was reported after
the Tokyo 2020 Games that Japan’s National Police
Agency had declared that “No Acts of Terrorism or
Cyber Attacks Occurred during the Olympic andParalympic Games” [1], which agreed with ourdetection results.
4. Comparison with past Olympic GamesThe largest difference between the Tokyo 2020
Games and past Olympic Games is that most of thevenues held events with no spectators due to the novel
coronavirus (COVID-19) pandemic. It was probably
for this reason that no sites selling fake tickets or
cyber attacks on the venue admission system as seenin past Olympic Games were observed, and sites selling fake goods were likewise hardly seen. While
DDoS attacks carried out by hacktivists as in past
Olympic Games are regarded to be dangerous, there
has recently been a drop in the frequency of suchattacks that push a political agenda. There were also
very few organizations in Japan that were greatly
opposed to the Tokyo 2020 Games. We consider that
this is why no DDoS attacks of this kind occurred.
In summary, the enhancing of NTT-CERT functions and nurturing of collaborations enabled thedetection of information not previously available and,while small in scale, the sharing of information on anumber of attacks that had the potential of gaining afoothold. The network infrastructure supporting theTokyo 2020 Games suffered no incidents due to cyber
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Feature Articles

attacks and the closing ceremony was reached without problem. We feel that all of these results testify tothe significance of our activities in protecting theTokyo 2020 Games.
5. Future outlook
We consider that the threat analysis we conducted
for the first time on cyber attacks against the Tokyo
2020 Games was effective. We feel that this threat
analysis, which included related parties on the outside while considering the impact on the NTT Groupand our ability to detect information and threats notpreviously detectable, should enable us to conduct
flexible surveys on future large-scale events that the
NTT Group will participate in as a provider of a network infrastructure. As an effort to strengthen NTTCERT functions, we expanded our survey range by

Takashi Mishina

increasing our survey languages and dark-web surveys, analyzing the actors involved in attacks, etc.
Now that the Tokyo 2020 Games are over, we shouldbe able to collect information of even higher quality
by applying these achievements to our survey range
in normal situations. Once this knowledge becomes
formalized, it is our intention to distribute it to NTT
Group companies to help improve the security of theentire NTT Group.
NTT is an Olympic and Paralympic Games Tokyo
2020 Gold Partner (Telecommunication Services).
Reference[1]

The Sankei Shimbun news, Sept. 9, 2021 (in Japanese).
https://www.sankei.com/article/20210909KOK2GCDO3JK2LPIBAJOBHBRW6Y/

Takemi Nisase

Research Engineer, Social Innovation Research
Project, NTT Social Informatics Laboratories.
He joined NTT EAST in 2011 and engaged in
network design, network operation, and systemconstruction. He is currently with NTT Social
Informatics Laboratories, where he is in chargeof research and development (R&D) of information-leakage detection using intelligence services.

Vice Director, Social Innovation Research
Project, NTT Social Informatics Laboratories.
He joined NTT in 1987 and engaged in the
R&D of an asynchronous transfer mode network
service, OCN service, Next Generation Network
service, etc. He joined NTT Security Platform
Laboratories, where he was in charge of handlingsecurity incidents. He is currently with NTT
Social Informatics Laboratories, where he is incharge of security incident response support andresearch on risk-analysis techniques.

Akiko Matsuhashi

Hidehiro Shito

Senior Research Engineer, Social Innovation
Research Project, NTT Social Informatics Laboratories.
She joined NTT Communications in 2003 andengaged in the maintenance of web servers. In
2016, she joined NTT Security Platform Laboratories, where she was in charge of handlingsecurity incidents. She was also a member of theTokyo Organising Committee of the Olympic
and Paralympic Games from 2019 to 2021. She
is currently with NTT Social Informatics Laboratories and engaged in NTT-CERT activities.

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Vol. 20 No. 1 Jan. 2022

Director, Social Innovation Research Project,
NTT Social Informatics Laboratories.
He received a B.E. and M.E. in mechanical andsystem engineering from Yamanashi University
in 1994 and 1996. He joined NTT in 1997. Afterseveral years of experience in R&D, operation,and construction of communications infrastructure, he began his career as a member of CSIRTs
at NTT EAST and NTT DATA. He joined NTT
laboratories in 2018, and his current position is adirector of NTT-CERT, the representative CSIRTof the NTT Group.

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Global Standardization Activities

Report on ITU-T SG2
Standardization of
Telecommunication Numbering
Koji Isshiki
Abstract

The Working Party (WP) 1 of the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) Study Group 2 has been engaged in the allocation and management of international telecommunication numbering, naming, addressing, and identification resources. Due to therecent migration to Internet Protocol networks and the rapid development and globalization of Internetof-Things services and over-the-top services, the issues have been diversified. Since the problems offraud by spoofing by telecommunication number misuse have increased, it has become an urgent topic
for discussion. In the WP2, they discuss the issues concerning network management.
This article mainly reports on the telecommunication numbering and identifications studied in WP1,
subjected by the World Telecommunication Standardization Assembly Resolutions.
Keywords: telecommunication numbering, IoT numbering, number spoofing

1. WTSA Resolutions on telecommunication
numbering and identification
World Telecommunication Standardization Assembly (WTSA) is the primary meeting of the International Telecommunication Union Telecommunication Standardization Sector ( ITU-T), and its output,
WTSA Resolutions, give direction of the activities of
ITU-T. Resolution 2 defines the responsibilities andobligations of each Study Group (SG) and the other
Resolutions are materialized further and mapped tothe studies in each SG. The following are the WTSA
Resolutions relevant to telecommunication numbering and identifications discussed in SG2 Working
Party (WP) 1 [1].
Extraction of WTSA Resolutions relevant to telecommunication numbering and identifications•	Resolution 20: Procedures for allocation andmanagement of international telecommunication
numbering, naming, addressing, and identification resources•	Resolution 29: Alternative calling procedures on
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international telecommunication networks•	Resolution 49: ENUM*•	Resolution 60: Responding to the challenges
concerning the evolution of the identification/
numbering system and its convergence with
Internet Protocol (IP)-based systems/networks•	Resolution 61: Countering and combating misappropriation and misuse of international telecommunication numbering resources•	Resolution 64: IP address allocation and facilitating the transition to and deployment of IPv6
•	Resolution 65: Calling party number delivery,
calling line identification, and origin identification information•	Resolution 70: Telecommunication/informationand communication technology accessibility for
persons with disabilities•	Resolution 88: International mobile roaming•	Resolution 91: Enhancing access to an electronic
repository of information on numbering plans*

ENUM: E.164 Number Mapping; the framework of mapping ofIP address and telecommunication number.

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Global Standardization Activities

WTSA Resolutions (numbering-related issues) [1]

SG2 Work Items (numbering-related issues)(1) IoT numbering
Resolution 20 - Procedures for allocation and

IoT numbering recommendation (E.IoT-NNAI), IoT & roaming, eCall callback(2) IMSI

management of international telecommunication
numbering, naming, addressing and identification
resources

E.118 revision for the issuer identification number, extraterrestrial usage, IMS
expansion, E.212 Annex H

Resolution 29 - Alternative calling procedures
on international telecommunication networks

E.nphs & number allocation for the service

Resolution 49 - ENUM
Resolution 60 - Responding to the challengesof the evolution of the identification/numberingsystem and its convergence with IP-based
systems/networks
Resolution 61 - Countering and combating
misappropriation and misuse of international
telecommunication numbering resources

Resolution 64 - Internet protocol address
allocation and facilitating the transition to anddeployment of IPv6
Resolution 65 - Calling party number
delivery, calling line identification and origin
identification
Resolution 70 - Telecommunication/
information and communication technology
accessibility for persons with disabilities

Resolution 88 - International mobile roaming
Resolution 91 - Enhancing access to anelectronic repository of information on numberingplans published by the ITU Telecommunication
Standardization Sector

Resolution 98 - Enhancing thestandardization of Internet of things and smart
cities and communities for global development(3) Global number for humanitarian services(4) Optimization of number usage
E.157, TR.spoofing, calling line identity (CLI) authorization procedure,
E.156, 888 misuse, E.ACP (alternative calling procedure), unacceptable traffic,
TR.OTT number, TR.MMWF(5) Maintenance of existing ITU-T E-series numberingrelated Recommendations
Revision of E.169.1: Int’l freephone, revision of E.164, requirement forallocation of global numbering resources(6) Efficient procedure of international numbers
Reconsideration of the global numbering allocation process, allocation of global
resources of machine to machine (M2M)(7) Number portability
Revision of E.164 Supplement 2, connecting carrier switching, regulation of
M2M/IoT number portability(8) Interworking
E.370, Service control between 2 countries (E.112)(9) ENUM
E.ENUMINF, E.A-ENUM, E.A-N/GoC(10) National numbering
TR.G4Dir, issues of national numbering, national numbering plan, emergency
call number, TR.eenm(11) (12) INR, WTSA20
INR revenue, report and proposal for WTSA next period(13) IPv6
IP addressing, IP migration, IPv6 address prefix for E.164(14) Disaster recovery
FG-AI4NDM (Artificial Intelligence for Natural Disaster Management)(15) Coordination with regional organization
Shared information from the European Conference of Postal and
Telecommunications Administrations (CEPT)/Electronic Communications
Committee (ECC)

Fig. 1. Mapping of SG2 studies and WTSA Resolutions.

published by the ITU-T•	Resolution 98: Enhancing the standardization ofInternet of Things (IoT) and smart cities andcommunities for global development
2. Issues under study in SG2 WP1Issues with telecommunication numbers and identifications under study in ITU-T SG2 WP1 are diversifying and categorized into items (1) to (15) listed in
the next subsection. Figure 1 shows the subdivisionof these individual issues and their relation to the
WTSA Resolutions. The issues concerning (1) the
allocation of international numbers for IoT and (4)the status of optimizing the use of numbers that are
actively discussed are introduced in Section 3. Section 4 presents a list of the recommendations, includNTT Technical Review

Vol. 20 No. 1 Jan. 2022

ing some drafts, based on the studies of the issues.
Categorization of the studies in SG2(1) Allocation of IoT international numbers, (2)Allocation of international mobile subscriber identity(IMSI) for mobile subscriber identification, (3)Global number for humanitarian services, (4) Optimization of number usage, (5) Maintenance of existing ITU-T E-series numbering-related Recommendations, (6) Efficient procedure of international numbers, (7) Number portability, (8) International interworking, (9) ENUM, (10) Issues with national numbering, (11) Revenue from International Numbering
Resources (INR), (12) Input to WTSA20, (13) IPv6,(14) Disaster recovery, (15) Coordination with
regional organization.

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Global Standardization Activities

Retailer A

Country
1

Operator A
CLI=
Country 1

Kingston
LockKingston
LockKingston
Lock
2GB Kingston
Lock
2GB Kingston
Lock
2GB
2GB
2GB

Operator B

CLI=
Country 2

Retailer B

Country 2

Note: Example of falsification of international call charges
The calling number (CLI): Country 1 is replaced with Country 2 by SIM box etc. between theorigination country (Country 1) and termination country (Country 2).

Fig. 2. Example of number spoofing during an international call (referred from TR.spoofing).

3. Active issues
Even though the issues are diversifying due to therecent migration to IP networks and the rapid development and globalization of IoT and over-the-top(OTT) services, the items actively discussed most forstandardization are the studies on the proper use of
telecommunication numbers. The issues with IoT
numbering have also been high priority for discussion. The status of the two studies are introduced on
the basis of the results from the 9th meeting held fromMay 31 to June 11, 2021.
3.1 Optimization of number usage
The items being actively discussed most for standardization are the studies on the proper use of telecommunication numbers.
3.1.1 Approval of the revised recommendation(E.157): International calling party number
delivery
Since the background has enhanced to include theservices on the Internet and OTT, which are beyond
the current basis of public switched telephone networks and public land mobile networks, the discussion regarding the revised E.157: International calling party number delivery in the meeting has diversified due to the opinions regarding scope, level ofdetails, degree of obligation, etc. The editor of the UK
then elaborated to coordinate the group and brought
the solution with agreement to edit the recommendaNTT Technical Review

Vol. 20 No. 1 Jan. 2022

tion, i.e., removing the section of preventing individual cases of spoofing to the separate technical reportbased on the general principles.
3.1.2 Consent of TR.spoofing
As mentioned in 3.1.1, countering spoofing is a
new item separated from E.157 describing the methods of preventing individual cases of spoofing. It
covers the mechanism of number spoofing caused by
SIM (subscriber identification module) boxes etc.,
internationally carried out by OTT operators, andSTIR/SHAKEN (Secure Telephony Identity Revisited/Signature-based Handling of Asserted Information Using Tokens), which is being introduced in the
United States as a countermeasure against number
spoofing, including comparison with blockchain
technology etc. Figure 2 shows an example of number spoofing in international communications.
3.1.3 Discussion on creation of technical reporton Wangiri
Sudan proposed a new Work Item to create a technical report on methodologies to mitigate Wangiri fraud(i.e., a callback scam). The proposal was approved tocreate a new Work Item of TR.MMWF (methodologies to mitigate Wangiri fraud). Interactive voice
response facility, using artificial intelligence technology, number blocking, and sharing of blacklists arebeing introduced for the technological method tomitigate Wangiri and number administration.
3.1.4 Discussion on OTTAs a fraudulent case associated with the use of98

Global Standardization Activities

Geographic number

Allocation

Structure

ITU to National Regulatory

Country code + national number(Ex. Japan81+ national number)CountryA

Network
structure& routing
image

Country
B• For temporary internationalroaming• Permanent use in othercountries is out of scope(extra-terrestrial use)

Non-geographic number

Directly from ITU to service providers
1. International network number(ex. 883 (international network number) +subscriber number)
2. International service number
The direction to apply for IoT numbering(ex. 878 (UPT number) + subscriber number)
1. International network number
Connection with a network through countries
CountryA

Country
B

CountryX

2. International service number
Connection by going through networks of countries
CountryCountryCountry
A
X
B

Fig. 3. International numbers for IoT services.

E.164 numbers for OTT services that are deployed on
the Internet, the UAE proposed to start studying
countermeasures for cases in which mobile numbers
and fixed numbers are used to authenticate andlaunch apps such as WhatsApp. It was agreed to contact the OTT application provider through the ITU
Telecommunication Standardization Bureau (TSB)
regarding this issue. In addition, the United States
proposed to encourage WhatsApp to participate in
future discussions on this matter.
3.2 S
 tandardization of allocation of IoT international numbers
3.2.1 Background of studies on IoT numbering
recommendation: E.IoT-NNAI (naming
numbering addressing and identifiers)
This issue started with the UK editor as one of the
major issues for this study period for the study toassign appropriate international numbers in responseto the rapid increase in global IoT services.
Initially, the eCall service, which is standardizing
emergency calls within Europe, is specified as a use
case, and it was decided to be used as part of the international service number (E.164-number for global
services) applied to universal personal telecommunication (UPT) services. It is regarded that the 878
number allocated for the global mobility services as
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Vol. 20 No. 1 Jan. 2022

UPT services will be appropriate usage for IoT since
the usage of the number is currently still low. However, the roaming of the existing national mobile
number (E.164-number for geographic areas) andinternational network numbers (E.164-number for
networks), such as 883, have been applied for currently deployed eCall and other various global IoT
services, while the studies of IoT numbers continue.
Such difference in number usage also needs discussion. Figure 3 illustrates the IoT international numbers.
3.2.2 Draft recommendation of E.IoT-NNAI at
the 9th meeting
At the 9th meeting, the following contributions were
input, and the discussion will continue on the basis of
the draft reflecting the inputs.
•	NTT proposed Annex-A in the draft recommendation describing the number portability of IoT
services. The proposal was agreed, and the studies of carrier switching of service providers will
start with this draft for the next meeting.
•	Malta proposed to include that the IoT number
878 should not be used for existing voice andshort messaging services in the E.IoT-NNAI
Recommendation, and it was decided to proceedwith further studies.
•	Russia proposed a list of issues such as definition
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Global Standardization Activities

Table 1. ITU-T SG2 Recommendations and relevant WTSA Resolutions.
Recommendation
numberRelevant WTSA
Resolutions

Recommendation title

E.112

Arrangements to be made for controlling the telephone services between two countries

E.118

The international telecommunications charge card

E.157

International calling party number delivery

E.164.1

Criteria and procedures for the reservation, assignment, and reclamation of E.164 country
codes and associated identification codes

Resolution 20

E.370

Service principles when public circuit-switched international telecommunication networks
interwork with IP-based networks

Resolution 60

TR.disabSpecification of an international numbering resource for use in the provisioning of services for
persons with disabilities and persons with specific needs

Resolution 70

E.nphsApplication of E.164 numbering plan for humanitarian services

E.dit

Deemed impermissible traffic

Resolution 29, 61, 65

Resolution 70
Resolution 29, 61, 65

E.IOT-NNAI

IoT naming numbering addressing and identifiers

E.164 Sup.2

Number portability

TR.EENM

Guidelines for effective and efficient national numbering resources administration

TR.Spoofing

Countering spoofing

TR.MMWF

Methodologies to mitigate Wangiri fraud

TR.OTTnum

Current use of E.164 numbers as identifiers for OTTs

E.ACP

Resolution 60
Resolution 60, 98

Resolution 60, 98
Resolution 20
Resolution 91
Resolution 29, 61, 65
Resolution 61
Resolution 61, 65

Alternative calling procedures

Resolution 29

Differentiating between ENUM and infrastructure ENUM

Resolution 49

TR ERIN

Guidance for the Director TSB as stated in Resolution 91 (Hammamet 2016) “Enhancing
access to an electronic repository of information on numbering plans published by the ITU
Telecommunication Standardization Sector”

Resolution 91

TR.INCCBS

Implementation of network colour codes in the border sites

Resolution 61

TR.DOTT

Definitions for telecom and telecom interconnection

Resolution 60

E.A-ENUM

Principles and procedures for the administration of E.164 country codes for registration into thedomain name system

Resolution 49

E.A-N/GoC

Administrative procedures for ENUM for E.164 country codes and associated identification
codes (ICs) for networks and group identification codes (GICs) for groups of countries

Resolution 49

E.ENUMINF

of terms, regulation of each field of IoT numberings, number portability, and global/domesticrole of number management, and it was decided
to proceed with further examination.
4. Recommendation of the output of the studies
Table 1 lists the recommendations that will be theoutput of the examination of various issues introduced in Section 2. The WTSA Resolutions associated with each recommendation are also listed.

services and changes in network formats, the roles ofnumbers and identifiers are changing, and SG2 has avariety of activities from short-term issues that
require immediate response to medium- to long-term
issues. While observing these trends, we will continue to engage actively in activities such as standardization activities related to numbers and identifiers withdiscussions at the TTC (Telecommunication Technology Committee) Numbering Planning Expert Committee in Japan.
Reference

5. Conclusion[1]

WTSA Resolutions of ITU-T, https://www.itu.int/pub/T-RES

Along with the development of telecommunication

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Global Standardization Activities

Koji Isshiki

Professional Staff, Network Innovation Business Headquarters, NTT Advanced Technology
Corporation.
He joined NTT Advanced Technology Corporation in 2001 after he had engaged in the
research and development of voice and dataswitching systems at research section, businesssection, and international business section inNTT. Since then he has been engaged in theinvestigation and standardization of telecommunication numbers and related technologies byattending ITU-T SG2, Internet Engineering Task
Force, European Telecommunications Standards
Institute (ETSI), Third Generation Partnership
Project (3GPP), and CEPT ECC Working Group
Numbering and Networks, and by visiting number NRAs (national regulatory authorities) in the
US and European countries every year.

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101

External Awards
EuroUSEC 2021 Best Paper Award
Winners: Tenga Matsuura, Waseda University; Ayako A. Hasegawa,
Mitsuaki Akiyama, NTT Social Informatics Laboratories; TatsuyaMori, Waseda University/NICT/RIKEN AIP
Date: October 11, 2021
Organization: The European Symposium on Usable Security(EuroUSEC)
For “Careless Participants Are Essential for Our Phishing Study:
Understanding the Impact of Screening Methods.”
Published as: T. Matsuura, A. A. Hasegawa, M. Akiyama, and T.
Mori, “Careless Participants Are Essential for Our Phishing Study:
Understanding the Impact of Screening Methods,” EuroUSEC 2021,
Oct. 2021.
Outstanding Reviewer Award (Top 10%)Winner: Shiro Kumano, NTT Communication Science Laboratories
Date: October 27, 2021
Organization: The 23rd ACM International Conference on Multimodal Interaction (ICMI 2021)
CSS2021 Best Paper Award
Winners: Kazuki Nomoto, Waseda University; Mitsuaki Akiyama,
NTT Social Informatics Laboratories; Masashi Eto, Ministry ofInternal Affairs and Communications; Atsuo Inomata, Osaka University; Tatsuya Mori, Waseda University/NICT
Date: October 28, 2021
Organization: Information Processing Society of Japan (IPSJ)
For “Understanding the Risks of Re-identification Attack on theContact Tracing Frameworks and Its Countermeasures.”
Published as: K. Nomoto, M. Akiyama, M. Eto, A. Inomata, and T.
Mori, “Understanding the Risks of Re-identification Attack on theContact Tracing Frameworks and Its Countermeasures,” Computer
Security Symposium (CSS) 2021, Oct. 2021.
CSS2021 Outstanding Paper Award / MWS2021 Outstanding Paper Award
Winners: Toshinori Usui, NTT Social Informatics Laboratories/

Institute of Industrial Science, The University of Tokyo; Tomonori
Ikuse, Yuhei Kawakoya, Makoto Iwamura, NTT Social Informatics
Laboratories; Kanta Matsuura, Institute of Industrial Science, The
University of Tokyo
Date: October 28, 2021
Organization: IPSJ
For “Automatically Appending Execution Stall/Stop Prevention to
Vanilla Script Engines.”
Published as: T. Usui, T. Ikuse, Y. Kawakoya, M. Iwamura, and K.
Matsuura, “Automatically Appending Execution Stall/Stop Prevention to Vanilla Script Engines,” CSS2021, Oct. 2021.
CSS2021 Encouragement Award
Winners: Shu Aakabane, Kanagawa Institute of Technology; Yuhei
Kawakoya, Makoto Iwamura, NTT Social Informatics Laboratories;
Takeshi Okamoto, Kanagawa Institute of Technology
Date: October 28, 2021
Organization: IPSJ
For “Identifying Library Function Names Based on Function
Dependencies and Linking Ordering in IoT Malware.”Published as: S. Aakabane, Y. Kawakoya, M. Iwamura, and T. Okamoto, “Identifying Library Function Names Based on Function
Dependencies and Linking Ordering in IoT Malware,” CSS2021,
Oct. 2021.
CSS2021 Encouragement Award
Winners: Toshiki Shibahara, Takayuki Miura, Masanobu Kii, Atsunori Ichikawa, NTT Social Informatics Laboratories
Date: October 28, 2021
Organization: IPSJ
For “Privacy Risk of Differentially Private Bayesian Neural Network.”
Published as: T. Shibahara, T. Miura, M. Kii, and A. Ichikawa, “Privacy Risk of Differentially Private Bayesian Neural Network,”
CSS2021, Oct. 2021.

Papers Published in Technical Journals andConference Proceedings
Computational Self-testing for Entangled Magic States
A. Mizutani, Y. Takeuchi, R. Hiromasa, Y. Aikawa, and S. TaniarXiv:2111.02700, November 2021.

NTT Technical Review

Vol. 20 No. 1 Jan. 2022

In the seminal paper [Metger and Vidick, Quantum ’21], they
proposed a computational self-testing protocol for Bell states in asingle quantum device. Their protocol relies on the fact that the target

102

Papers Published in Technical Journals and Conference Proceedings

states are stabilizer states, and hence it is highly non-trivial to reveal
whether the other class of quantum states, non-stabilizer states, canbe self-tested within their framework. Among non-stabilizer states,
magic states are indispensable resources for universal quantum computation. In this letter, we show that a magic state for the CCZ gate
can be self-tested while that for the T gate cannot. Our result is appli-

NTT Technical Review

Vol. 20 No. 1 Jan. 2022

cable to a proof of quantumness, where we can classically verify
whether a quantum device generates a quantum state having non-zero
magic.

103