3. Focused Research (2)IIJ’s eSIM Initiatives

3.1 What is an eSIM?

using RSP. They were developed because a mechanism foreSIM has become an oft-heard keyword ever since the iPhone

installing profiles over a network was required for SIMs used

XS was announced in September 2018. Here, we provide

in embedded applications.

a technical explanation of eSIM and go over IIJ’s initiatives
in this area.

Some embedded applications employ SIM chips that are
soldered directly to the circuit board instead of the more

Traditional SIM cards consist of the following and are pro-common card-type SIMs. The following advantages of SIM

duced in tamper-resistant packages.

chips explain why.

• Subscription Data for the mobile service• Targeted at industrial equipment and thus offer high• Applets for valued-added services

durability• Secure storage for the subscription data and applets• A processor that performs authentication, encryption key generation, etc.

• Soldered to the board and thus resilient to the loosening of connections caused by vibration• Soldered to the board during manufacturing, thus
obviating the SIM insertion process

Of particular note, authentication and encryption keys them-• Small size enables device miniaturization

selves cannot be read off of the SIM.
To take advantage of these benefits, IIJ added SIM chips toWith eSIM, on the other hand, these elements are split into

its full MVNO SIM lineup in February 2019.

two parts: the profile, which contains the data and applets,
and the eSIM card, which contains the storage and pro-

Although SIM chips offer such advantages, it is virtually im-

cessor. In addition, the profile can be installed on the eSIM

possible to change the SIM once it has been embedded into

card from a dedicated server over a network. The speci-

the device during the manufacturing process. This means

fication was developed by GSMA*1. The mechanism forthat the SIM’s mobile line needs to be determined at manu-

installing a profile via a network is called RSP (Remote SIM

facture, which raises the following problems.

Provisioning). RSP itself is also used with traditional SIMs asa means of remotely changing data on the SIM using OTA(Over-the-Air) technology. As a full MVNO, IIJ also uses
OTA to write phone numbers to some SIMs when activating
the lines.

• Inability to standardize inventory of products for different export destinations• An active phone line needs to be used to check operating status at the time of manufacture• Mobile line cannot be switched even if the location

The term eSIM stands for embedded subscriber identifier
module, or embedded SIM. At present, it mostly refers toSIMs to which profiles can be installed over a network*1

where the product is used changes• Mobile line cannot be switched to, e.g., reduce communication costs

Short for the GSM Association, an industry group that represents mobile operators. Formed in 1995 to promote the spread of the GSM 2G standard. It is the largest
group in the industry, encompassing over 1,000 companies across 220 countries, including around 800 mobile operators. Also known as the organizer of Mobile
World Congress (MWC), the world’s largest exhibition for the mobile industry, held every February.

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3. Focused Research (2)While the use of SIM cards solves these problems, there

The ISD-R*2 is a direct interface between the inside andare on-site work costs associated with swapping out cards.

the outside of an eSIM and is what manages the eSIM.
Operations like downloading a profile, installing a down-

So eSIMs were developed to solve the above problems. The

loaded profile, and switching to or deleting an installed

profile can be installed after manufacture, eliminating the

profile are all performed via the ISD-R.

need for a mobile line contract to be set up when the SIM isembedded. Because profiles can be installed remotely, there

The ISD-P*3 is the equivalent of a traditional SIM card and isare no on-site costs associated with exchanging SIMs.

created for each installed profile. Profiles downloaded fromservers are formatted so as to describe the procedure for

3.2 How eSIM Works

creating the ISD-P. The profile is interpreted during instal-

3.2.1 eSIM Internal Structure

lation to create the ISD-P. Once the ISD-P to be used for

Figure 1 depicts the internal structure of an eSIM. Among

communications is activated, the eSIM looks like a normal

the elements shown, ISD-R, ISD-P, and ECASD are what

SIM from the device’s perspective.

characterize eSIMs.

Figure 1: Internal Structure of an eSIM

*2

ISD-R: Issuer Security Domain Root

*3

ISD-P: Issuer Security Domain Profile© Internet Initiative Japan Inc.

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The ECASD*4 stores the keys used in protecting the data

To obtain a GSMA signature, suppliers need to obtain SAS

when downloading a profile. A stored key is used for au-

accreditation for each of their eSIM production sites andthentication between the server and the eSIM card. A stored

profile storing server sites. Because of the high cost of

key is also used to decrypt the downloaded profiles, which

SAS accreditation, accredited eSIM production and server

are encrypted by the server.

sites are limited in number. In most cases, operators do nothave their own servers but instead use the services of SAS-The data protection keys stored in the ECASD are signed

accredited suppliers.

using Public Key Infrastructure, and a similarly signed key
is stored on the server side. To ensure SIM security, GSMA

As of June 2019, there are broadly two specifications forsigns these keys as the root certificate authority, and keys

eSIMs that support the remote intallation of profiles in thissigned by other certificate authorities are treated as invalid.

manner.

Figure 2: The M2M Model Interface*4

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ECASD: eUICC Controlling Authority Security Domain© Internet Initiative Japan Inc.

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3. Focused Research (2)■ The M2M model

The eSIM card communicates with the SM-SR server di-

Under this standard developed for M2M devices, eSIMs arerectly, and only SMS and packets are transferred on thecontrolled remotely. It is aimed at embedded devices, thedevice in which the eSIM card is embedded. The device

original purpose of eSIMs.

itself does not need much in the way of functionality; anordinary modem of recent incarnation is generally fine.

■ The Consumer model

The specification is geared to environments where only

Under this standard developed for end user-managed

limited functionality can be implemented, like embedded

devices, eSIMs are controlled via the device. The spec-

devices.

ification improves on parts of the M2M model that are
difficult to deal with when it comes to end user-managed

Since the SM-SR server controls the eSIM card in the M2M

devices.

model, the eSIM card only communicates with a specific
SM-SR server. Since they are set up to only communicate

3.2.2 The M2M Modelwith a specific SM-SR server, the platform operator that

The M2M model was the first eSIM specification developed.

manages the SM-SR server also supplies the physical eSIM

Since it is aimed at IoT devices, it allows profiles to be in-card. And since all profiles are installed via the SM-SR server,

stalled, switched, and deleted remotely. Figure 2 shows thethe platform operator that manages the SM-SR server also

elements of the M2M model. The main ones are as follows.

obtains the profiles to be installed. Hence, profile choices
depend on the platform operator.

• eSIM card
• Device with an embedded eSIM card

Communication between the eSIM card and SM-SR server• SM-SR*5 server for secure routing to the eSIM card

uses the IP protocol, but SMS is first used to trigger eSIM

• SM-DP

access by the SM-SR server. A mobile line is needed to send

*6

server to provide profiles

SMS messages, so eSIM cards that use the M2M model
In the M2M model, control of the eSIM card revolves aroundhave a factory-installed profile called the bootstrap. Since

the SM-SR server. An SMS is sent from the SM-SR server

all eSIM operations are performed remotely, bootstrappingto the eSIM card, a secure route between the SM-SR server

requires connectivity in all countries, so one challenge isand the eSIM card is opened, and the following operations

how to obtain this profile. Also, bootstrapping is unneces-are performed.

sary in cases where profiles do not need to be switched.
There is no need to replace profiles in products used only in• Profile download and installation

the domestic market, so traditional SIM chips are generally• Profile switchingfine in this case.

• Profile deletion*5

SM-SR: Subscription Manager - Secure Routing*6

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3.2.3 The Consumer Modelcalled the LPA manages profiles on the device. Another ad-

The Consumer model specification was developed following

dition is the SM-DS server, which is not present in the M2M

the M2M model. It is aimed at end user-operated devices,model. And because the SM-DP server has been modified

such as smartphones, and enables all eSIM operations to be

to meet requirements for consumer devices, it is called theperformed on the device. Figure 3 shows the elements of

SM-DP+ in this model.

the Consumer model. The main ones are as follows.
The LPA, added in the Consumer model, provides an inter• eSIM card

face to enable end users to do the following on the device.

• Device with an embedded eSIM card
• LPA*7 for managing the eSIM card on the device• SM-DP+ server, which provides the profile• SM-DS*8 server, which searches for profiles provided to the eSIM

• Enter the address of the SM-DP+ server where theprofile is stored and the profile identifier• Download profiles and install them on the eSIM chip
• Switch profiles• Delete unnecessary profiles

Unlike the M2M model, there is no SM-SR server for managing eSIM card profiles remotely. Instead, an application

Figure 3: The Consumer Model Interface

24*7

LPA: Local Profile Assistant*8

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3. Focused Research (2)Two implementations for the LPA are defined: LPAd, where

3.3 Moves by Major Vendors

the LPA runs in the device, and LPAe, where it runs in the

3.3.1 AppleeSIM card. When device vendors develop Consumer modelApple was an early mover in this space, providing eS-

eSIM devices, they need to choose whether to use an eSIM

IM-like functionality in the form of its Apple SIM. Details

that supports LPAe or to implement LPAd on the device.

of Apple SIM are not public, but it is thought to employ an

Because LPAe compatible eSIMs are not yet widespread,M2M-model eSIM. Yet it is very much a custom service;device vendors need to implement LPAd, so this is one hur-for example, because end users each enter into their own

dle to clear when developing Consumer model devices atphone line contracts, it incorporates a mechanism for acti-

present.

vating mobile services via the device. Although Apple only
provides the platform, the strength of its brand has seen it

With this model, everything is done on the device by the

successfully obtain profiles from mobile operators in many

LPA, so SMS is not needed the way it was in the SMS

countries.

model. And since profiles can also be downloaded via WiFi, there is no need for something like the M2M model’s

A feature of the Apple SIM is that it offers users worldwide

bootstrap profile. Because no extra mobile contracts are re-connectivity in a single SIM card. That said, only data plans,quired, LPA is also implemented and the Consumer model

not voice call contracts, are available with an Apple SIM.

adopted for IoT devices in some cases. On the other hand,

Possibly this comes down to voice contracts requiring morein the interests of end user convenience, some eSIMs arein the way of identity checks than data contracts and the

supplied with a mobile line profile installed so as to enable

varying regulations from country to country making it diffi-

the downloading of profiles.

cult to provide a solution within a single platform.

To install a profile, the following must be passed into theApple has continued to use the Apple SIM for the iPad but

LPA: the SM-DP+ server address and a Matching ID to iden-

adopted a standard consumer-model eSIM for the iPhone

tify the profile to be installed. A string called an activation

XS, released in 2018, probably because it was not possible

code (like the one below) is used to do this.

to uncouple the iPhone, which is a phone after all, fromvoice contracts. Given that the Apple SIM is still used on

1$SM-DP-PLUS.EXAMPLE.COM$MY-MATCHING-ID-0123456789

non-voice devices like iPads released after the eSIM-compatible iPhone XS, it would seem that Apple has only given

The string consists of the version number (currently fixed atup on voice contracts being provided via the Apple SIM. The“1”), SM-DP+ server address, and Matching ID, delimited

reasoning behind the decision was probably that adopting

by a “$” character. Entering these strings by hand is diffi-

a standard eSIM would mean that mobile operators create

cult, so they are usually converted to a QR code and readthe platform, making it possible to meet the voice contract

into the device (Figure 4).

regulations.
With the Apple SIM, the contracts went through Apple,
which made it difficult for an MVNO like IIJ to offer services. With the consumer-model eSIM on the iPhone XS
and later models, there are no limitations on the profiles
installed, so IIJ’s full MVNO profile fits the bill. Users of theiPhone XS/XR are one major target of the IIJ eSIM services.
3.3.2 Microsoft
Microsoft included a standard LPA in Windows 10 version
1703, probably because it believes that eSIMs will be usefulin realizing its Always-Connected PC concept. The inclusionof an LPA service in the OS obviates the need for device

Figure 4: An Activation Code in QR Code Form

vendors to implement their own LPA, meaning it is now© Internet Initiative Japan Inc.

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easy for vendors to make eSIM-compatible devices so long

the world. Yet while it is limited to US residents, it does pro-as they obtain eSIM cards and compatible modem modules.

vide voice services, unlike with the Apple SIM. Google was

So we can expect this simplification of device manufactur-

probably able to achieve this because it provides the service

ing to help fuel the spread of eSIM-equipped devices ahead.

as an MVNO and because it zeroed in on US-resident users,

One sign of this is that Microsoft itself has released eS-

so that it only had to deal with the US regulations relating toIM-equipped Surface Pros.

end-user voice services.

Microsoft also provides an app called Mobile Plans that lets

3.3.4 Similar Services

users sign up for mobile plans via their device, like with the

While not the same as eSIM, some vendors are selling pro-Apple SIM. In Japan as of June 2019, profiles can be pur-files based on proprietary specifications, mainly in Greaterchased from KDDI, GigSky World Mobile Data, and Ubigi.

China. They provide a proprietary SIM along with an OTA
service for installing profiles on the SIM, allowing end

On another front, at Microsoft Ignite 2018, held at end-No-

users to download and use profiles from mobile operators

vember 2018 in the US, Microsoft revealed plans to integrate

in a wide range of countries. Outbound travelers are the

eSIM support into enterprise MDM*9. Enterprise customers

end-user target group, and the objective is to provide lessneed device management for their PCs, and bringing theexpensive connectivity on the road than roaming services.

management of mobile subscriptions into the MDM fold will

An example of this type of service in Japan is the Henn nagive enterprise device managers control over the eSIM pro-

SIM series sold by H.I.S. Mobile.

files used in their devices as well.
With the appearance of eSIM-equipped devices like the3.3.3 Google

iPhone XS, though, these services also seem to be transi-

Google seems to be lagging Apple and Microsoft when ittioning away from proprietary specifications to open eSIM

comes to eSIM support. Although it defined APIs related toplatforms.

eSIM in Android Pie, the OS itself does not have LPA functionality, so each vendor needs to implement an LPA app.

3.4 IIJ’s Initiatives

Google itself does offer eSIM-compatible, LPA-equipped de-

As a full MVNO operator, IIJ can provide its own profiles forvices like the Pixel 2, Pixel 3 and Pixel 3a. But as of thisinstallation on eSIMs. We have already launched an eSIM

writing in June 2019, the devices sold in the Japanese mar-service providing our full MVNO profiles as one of our full

ket are equipped with NFC*10 instead of eSIM support, so it

MVNO service sales channels.

looks like Japanese users are unable to use an eSIM withthese Google offerings.

As discussed, eSIMs come in two forms: the M2M modeland the Consumer model. IIJ has started targeting the26

Google has launched its own eSIM-based MVNO service

Consumer model first with its eSIM services. The reason

called Google Fi, providing connectivity around the world.

for this is that because IIJ’s own profiles only provide con-

While the range of supported Android devices is limited, thenectivity in Japan, we believe the Consumer model is more

iPhone is also supported. Given that the service is available

suitable for our full MVNO services than the M2M model,

for devices Google itself does not manage, like the iPhone,which is geared to overseas deployment. Additionally,

one can infer that it uses consumer-model, rather thanit can be difficult to ensure connectivity outside of theM2M-model, profiles. However, the service is only available

Japanese market with full MVNO profiles, and they cannot

to US residents; access does not extend to end users aroundbe used to bootstrap.

*9

MDM: Mobile Device Management*10

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3. Focused Research (2)Last year, we carried out PoC testing based on the Consumer

3.5 eSIM Use Cases and Future Trends

model as part of our efforts to get eSIM services off theWhat does the future have in store for eSIM usage?

ground. In the PoC, we installed the our full MVNO profile ina Microsoft Surface Pro LTE Advanced and accessed to the

The big difference between eSIMs and traditional SIMs is theInternet with the profile successfully. We are also testing theelimination of the physical SIM. Eliminating the physical card

operation of other target devices and building up our knowl-and handling profiles as electronic data obviates SIM cardedge base. One thing we learned is that compatibility issuesdelivery costs (not only money but distance and time). Therebetween profiles and eSIM cards can arise. As described

is a tendency to focus on price when it comes to costs, butearlier, eSIM card profiles have a specific format. A tem-with eSIMs, there is no need to travel to a store or wait forplate notation is defined to simplify the profile descriptors,

a SIM to be delivered. This means end users can purchase

but we discovered that certain patterns result in installation

profiles anytime, wherever they need them. Long-term con-errors with certain eSIM cards. We also discovered installa-

tracts may not play to this benefit, but it makes purchasingtion problems triggered by the absence of certain optional

prepaid contracts easier, especially for travelers looking toparameters in the profiles. Unlike the M2M model, which

temporarily make use of services at their destination. Plus,

assumes control over the eSIM card, the Consumer model

there is no need to swap out physical SIM cards, the advan-

targets a wide range of eSIM cards, so building this sort oftages of which include mitigating the risk of loss. And withknowhow is crucial to providing services under this model.

DSDS*11 devices like the iPhone XS, the main voice contract
SIM card can go in the SIM slot while prepaid data SIMs can

On July 18, 2019, we commercially launched our eSIM

be purchased as and when needed. But within the context

Plan (beta version). Unlike eSIM services offered in Japanof the Japanese market, fully adopting eSIMs and the high(Docomo’s dtab, KDDI’s prepaid plans for Windows), ourdegree of mobility they afford consumers would not be di-service is broadly available and not restricted to a particular

rectly beneficial to the mobile operators. So it is difficult to

subset of devices. Building our own SM-DP+ server is notsee eSIMs gaining traction unless device makers take themuch of an option since it would require SAS accreditation

lead in offering SIM-free devices. By making eSIM services

from the GSMA, so we will use other companies’ services

available as soon as possible, IIJ hopes to set the stage forlike other mobile operators do.

device makers to roll out eSIM-compatible devices.

Daisuke Maruyama
MVNO Service Development Section, Technology Development Department, MVNO Division
Mr. Maruyama joined IIJ in 2018. He is working on the development of service infrastructure for full MVNO services. Most recently, he has
been developing eSIM service infrastructure of the type discussed in this volume.

*11

DSDS: Dual SIM Dual Standby© Internet Initiative Japan Inc.

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