INSTITUTE of INFORMATION SECURITY
Graduate School of Information Security
Master’s Thesis

Attack and Countermeasure for GPS-based Ship
Navigation Systems

Student ID 5505504
Saneyuki Senda

Supervisor Kuniyasu Suzaki

February 2024

i

Abstract
Navigation systems such as AIS and ECDIS are indispensable for ship operations, andmany of them rely heavily on satellite systems such as GPS to obtain the location information.
On the other hand, several maritime cases have reported attacks on GPS, and the vulnerability of GPS has been revealed. However, cybersecurity measures for ships, including
navigation systems, have been very slow and many maritime organizations are exploring
various countermeasures, but most of them are focused on conventional cyber-attack countermeasures and few are speciﬁc to ships.
This paper ﬁrst investigates the relationship between GPS and GPS-based navigation
systems in order to present the importance of GPS signals to ships. Next, the probabilityof radio frequency attacks such as jamming and spooﬁng against GPS-based navigation
systems and security measures are investigated. We also examine the impact of GPS
attacks on navigation systems and vessels, and the ship-speciﬁc countermeasures for opensea and near-sea vessels, and propose a response chart showing the procedures for applying
GPS and existing navigation systems as a GPS-independent method. Then, the similarity
between the navigator’s response to a GPS spooﬁng attack and the proposed method is
veriﬁed using a ship-handling simulator device to identify new problems and to derivecountermeasures necessary for future ship operations.

iii

Contents

Chapter 1

Introduction

1

1.1

Research Background . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

1.2

Research Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . .

4

1.3

Research Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5

1.4

Structure of this paper . . . . . . . . . . . . . . . . . . . . . . . . . .

5Technical Background

6

Technical background in Shiphandling . . . . . . . . . . . . . . . . .

6

2.1.1 AIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6

2.1.2 Marine Radar . . . . . . . . . . . . . . . . . . . . . . . . . .

7

2.1.3 ECDIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8Chapter 2
2.1

2.2

Chapter 3
3.1

Chapter 4

Background of Navigation technical. . . . . . . . . . . . . . . . . .

10

2.2.1 Inertial Navigation . . . . . . . . . . . . . . . . . . . . . . .

102.2.2 Terrestrial Navigation . . . . . . . . . . . . . . . . . . . . .

11

2.2.3 Celestial Navigation . . . . . . . . . . . . . . . . . . . . . .

11

2.2.4 Radio Navigation . . . . . . . . . . . . . . . . . . . . . . . .

16

2.2.5 GNSS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

19

2.2.6 Galileo . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

20

2.2.7 GLONASS . . . . . . . . . . . . . . . . . . . . . . . . . . .

20

2.2.8 Beidou. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

20

2.2.9 NavIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

21

2.2.10 QZSS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

21

What is GPS?

23

GPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

23

3.1.1 GPS Overview . . . . . . . . . . . . . . . . . . . . . . . . .

23

3.1.2 GPS Signal . . . . . . . . . . . . . . . . . . . . . . . . . . .

26

3.1.3 GPS receiver conﬁguration . . . . . . . . . . . . . . . . . .

29

Related Research

30

iv

Contents

4.1

GPS Vulnerability . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.1.1 GPS jamming

4.2

4.3
Chapter 5
5.1

30. . . . . . . . . . . . . . . . . . . . . . . . .

30

4.1.2 GPS Spooﬁng . . . . . . . . . . . . . . . . . . . . . . . . . .

33

4.1.3 GPS Meaconing . . . . . . . . . . . . . . . . . . . . . . . .

33

Security countermeasures for GPS . . . . . . . . . . . . . . . . . . .

34

4.2.1 Protection by signal processing . . . . . . . . . . . . . . . .

35

4.2.2 Protection by Authentication . . . . . . . . . . . . . . . . .

37

4.2.3 Protection by Sensor Fusion . . . . . . . . . . . . . . . . . .

37

4.2.4 Protection by Antenna . . . . . . . . . . . . . . . . . . . . .

37

Challenges with existing security countermeasures . . . . . . . . . .

38

Proposed Method

40

Organize navigation systems・Maneuvering・Navigation techniques .

40

5.1.1 Comparison of positioning performance by navigation method 40
5.2
Chapter 6
6.1

6.2

6.3

Chapter 7
References

5.1.2 Organize Categories . . . . . . . . . . . . . . . . . . . . . .

41

Response Chart to GPS Attack (Proposed Flow) . . . . . . . . . . .

43

Evaluation

47

Attack Feasibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

47

6.1.1 Execution cost and eﬀort . . . . . . . . . . . . . . . . . . .

47

6.1.2 Required cost of simulator . . . . . . . . . . . . . . . . . . .

47

6.1.3 Required Cost of Meaconing . . . . . . . . . . . . . . . . .

48

Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

48

6.2.1 Environmental for Experiment . . . . . . . . . . . . . . . .

48

6.2.2 Experimental Scenario . . . . . . . . . . . . . . . . . . . . .

52

Experimental Results and Discussion . . . . . . . . . . . . . . . . . .

57

6.3.1 Vessel Trajectory Results . . . . . . . . . . . . . . . . . . .

57

6.3.2 Questionnaire Survey Results . . . . . . . . . . . . . . . . .

57

Summary and Future Issues

63
67

v

List of Figures

2.1

Conﬁguration of the navigation system . . . . . . . . . . . . . . . . . . .

9

2.2

Navigation systems (AIS, Marine radar, ECDIS) . . . . . . . . . . . . . .

9

2.3

Position acquisition by cross bearing . . . . . . . . . . . . . . . . . . . .

12

2.4

Cocked Hat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12

2.5

The entire process of sky surveying in celestial navigation . . . . . . . .

13

2.6

Acquisition of position by hyperbolic curve . . . . . . . . . . . . . . . . .

17

2.7

Loran Chain Signal and Ideal Pulse . . . . . . . . . . . . . . . . . . . . .

18

2.8

Example of Loran C International Cooperation Chain . . . . . . . . . . .

18

3.1

GPS operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

25

3.2

GPS satellite constellation coverage . . . . . . . . . . . . . . . . . . . . .

26

3.3

Example of GPS signal generation . . . . . . . . . . . . . . . . . . . . . .

27

3.4

Signals from GPS satellites . . . . . . . . . . . . . . . . . . . . . . . . . .

28

4.1

GPS jammer unit installed in Flamborough Head, England . . . . . . . .

31

4.2

GPS jammer unit coverage area . . . . . . . . . . . . . . . . . . . . . . .

32

4.3

GNSS jamming experiment in the north of Daru Peninsula . . . . . . . .

32

4.4

GPS spooﬁng situation . . . . . . . . . . . . . . . . . . . . . . . . . . . .

34

4.5

GPS spoofed receiver status . . . . . . . . . . . . . . . . . . . . . . . . .

35

4.6

2-antenna based spooﬁng detection of typical signal arrival shapes . . . .

38

5.1

Navigation Systems and Maneuvering (Navigation) Categories (Layered)

42

5.2

(A) Flow of handling GPS jamming/spooﬁng (GPS unavailability) . . .

44

5.3

(B) Flow of handling GPS jamming/spooﬁng (Area of ocean you are navigating) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

44

5.4

(C) Flow of handling GPS jamming/spooﬁng (Weather Conditions) . . .

45

5.5

(D) Flow of handling GPS jamming/spooﬁng (Visibility Conditions) . .

45

5.6

Flow of actions to be taken by navigators in response to GPS jamming/spooﬁng . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

46

vi

List of Figures

6.1

Experiments (test subjects) on a shiphandling simulator . . . . . . . . .

6.2

Conﬁguration of Shiphandling Simulator【Marine Radar (Left)，ECDIS

49(Light) 】 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

50

6.3

Conﬁguration of Shiphandling Simulator【Steering System】 . . . . . . .

51

6.4

Conﬁguration of Shiphandling Simulator【International VHF Radio Telephone System】 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

51

6.5

Experiment Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

53

6.6

Sea area of experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . .

54

6.7

Navigational status of other vessels . . . . . . . . . . . . . . . . . . . . .

54

6.8

GPS spooﬁng . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

56

6.9

Ship’s wake (Voyage track: red dotted line)

59. . . . . . . . . . . . . . . .

vii

List of Tables

1.1

Cyber Incidents Aﬀecting Ships ( 2010〜2024 ) . . . . . . . . . . . . . .

3

2.1

Comparison of each radio navigation system . . . . . . . . . . . . . . . .

16

2.2

Example of Loran C International Cooperation Chain . . . . . . . . . . .

19

2.3

Types of GNSS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

22

3.1

GPS signal (frequency band & PRN code) . . . . . . . . . . . . . . . . .

28

5.1

Comparison of positioning performance by navigation method (Absolute
Position)

5.2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

41

Comparison of positioning performance by navigation method (Relative
Position). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

41

6.1

Experiment Simulator Conﬁguration . . . . . . . . . . . . . . . . . . . .

49

6.2

Questionnaire items for subjects . . . . . . . . . . . . . . . . . . . . . . .

50

6.3

Subject’s background and other information . . . . . . . . . . . . . . . .

55

6.4

Results of post-experiment questionnaire to subjects . . . . . . . . . . .

60

6.4

Results of post-experiment questionnaire to subjects . . . . . . . . . . .

61

6.4

Results of post-experiment questionnaire to subjects . . . . . . . . . . .

62

1

Chapter 1

Introduction
1.1 Research BackgroundIn the maritime industry, with the development of maritime broadband communications such as satellite lines and ICT (Information and Communication Technology), there
are concerns about various risks such as cyber attacks that violate ship navigation safety
and economic damage. Ships are experiencing technological developments such as thewidespread use of navigational instruments such as Automatic Ship Identiﬁcation Systems(AIS) and Electronic Chart Information Display Systems (ECDIS), and rapid advances insensors, IoT, AI, and big data processing. Large ships are being operated with fewer crew
members than ever before, and the supply and demand for crew members is becomingtighter. In order to reduce the workload and improve eﬃciency, countries are developing
and implementing autonomous ship technology. In Japan, the Ministry of Land, Infrastructure, Transport and Tourism has indicated that it plans to aim for the realizationof autonomous ships in stages. Traditionally, each piece of equipment and system on aship was independent, but as satellite links have become faster, some systems have beencombined, making it possible to communicate data with land.
The maritime industry is a relatively small-scale industry; for example, there are approximately 98,000 commercial ships with propulsion of over 100 gross tonnage operatinginternationally[1]. This limits the industry’s ability to conduct systematic analysis andlearn from others, making it diﬃcult to improving cybersecurity measures. A ship is acomplex ”sailing village” equipped with a variety of ICT. The range is wide-ranging, fromoﬃce systems to life support systems, engine automation, and navigation systems. Ships
typically have a lifespan of 25 to 35 years, and software upgrades occur at diﬀerent timeintervals for each piece of equipment. In other words, most ships have a mix of general IT(Information Technology) and OT (Operation Technology) equipment, which is complex
and extremely diﬃcult to maintain. Ships are subject to international regulation, but that
regulation tends to focus on minimum technical requirements to ensure economic fairness,

2

Chapter 1

Introduction

making it a highly competitive and highly cost-sensitive market. Many stakeholders in themaritime industry do not give cybersecurity the priority it needs. Compared to generalcybersecurity incidents, very little information has been made public about cybersecurity
incidents in the maritime industry. This is said to be because there is no incentive to disclose information in the maritime industry. It is also said that this is due to reporting bias
by the industry itself. Even so, the number of cases that are too big to hide is increasing
as they tend to pose a threat to cybersecurity these days. Also, the number of incidents
related to year and attack location does not have statistical signiﬁcance to reveal a clear
trend. Therefore, it is necessary to make a qualitative interpretation of the results. [2].
Over the past 14 years (2010-2024), the two main types of cyber incidents that aﬀected
ships were ”Radio Wave Jamming” and ”Malware infections” (particularly ransomware)(Table 1.1).
There have been several incidents in which shipboard IT systems have been attacked bymalware, but the attack vectors are often accidental rather than targeted. Typical attack
vectors are email attachments and links, which often render the ship’s servers and clientsunusable. Since all data is erased, the forensic evidence left behind is limited, making
investigation diﬃcult. OT systems are usually isolated from other systems, so they are
rarely exposed. Nevertheless, instances of incidents against OT systems have occurred,
and the consequences have been severe. Examples of attacks are system intrusions via
infected USB memory sticks or computers that are unintentionally connected to the wrong
network.Examples of systems targeted by attacks include ECDIS and propulsion control
systems, and appear to occur during chart updates and system updates.
There are several examples of attacks on the communications systems of onshore andoﬀshore facilities. While the impact on shipboard communications is less severe, there
are many diﬀerent and necessary communication systems on board that remain potential
victims. These incidents show that hacking and ransomware tend to result in loss ofavailability
Vessels’ position information is mainly obtained using GPS (Global Positioning System)
signals. Since the GPS signal is used by ships for navigation purposes, attacks on the GPS
signal are often related to ”jamming” or ”spooﬁng”. This type of threat usually tends tomanifest itself in geopolitically disputed areas such as the Black Sea.
Systems used for ship operations are increasingly integrating IT and OT. OT in ships
are devices related to mechanical or electrical subsystems that automate shipboard operations, reducing costs and crew members’ hazardous work. IT on ships, on the other
hand, provides support for ship navigation planning, navigation control, and monitoring.Commercial vessels that sail internationally, such as large passenger ships and tankers,
are subject to multilateral conventions that require them to be equipped with a varietyof electronic devices [7]. The International Maritime Organization (IMO) has been pro-1.1 Research Background3

Table. 1.1: Cyber Incidents Aﬀecting Ships ( 2010 〜 2024 年 )[2]Year

AttackSummary

2016

Radio Wave Jamming

In South Korea, 280 ships had problems with their navigation systems and had to return to port. North Korea isbelieved to be the cause, but evidence is scarce [3].

2017Radio Wave Jamming

In the Black Sea near Novorossiysk, the position data of atleast 20 vessels indicated positions about 32 km away fromtheir actual positions. These observations appear to be due
to GPS spooﬁng [3][4].

2018〜2019

Radio Wave Jamming

Several GPS disturbances were observed in northern Norway
over a period of about two years. Some impact, but fortunately serious damage was avoided [1].

2019Radio Wave Jamming

Ships exposed to GPS spooﬁng in the Black Sea. Although
the ships were at sea, location information from the ships’
navigation systems indicated that many ships were on land.
This phenomenon reportedly occurred four times in threedays, with the maximum occurrence time being approximately 30 minutes[2].

2019

MalwareOn a large ship bound for New York, the ship’s control system and network were infected with malware, limiting functionality [5].

2019

MalwareThe management server of a tanker near the port of Naantali
in Finland was infected with ransomware, and its backup
data was also erased. Remote Desktop Protocol (RDP), USB
devices, and email attachments have been identiﬁed as attack
vectors. [2].

2019

MalwareTwo vessels owned by the same owner were infected withthe ransomware ”Hermes 2.1” via a Word ﬁle attached to an
email. Multiple workstations on the management network
were aﬀected[2].

2020

MalwareThe ship’s server and multiple client PCs on a ship dockednear Tynemouth, UK, were infected with the ransomware”Ryuk”. All data was encrypted and the system became
unusable. Restored the system by complete reinstallation[2].

2020

MalwareRansomware Sodinokibi infected the management systemsof three American-ﬂagged ships[2].

2023〜2024

Radio Wave Jamming

At least six cases of GPS jamming and spooﬁng, believed to
be by Russia, have occurred targeting Northern Europe andthe Baltic Sea countries. [6].

Chapter 1

4

Introduction

moting e-Navigation [8] and other regulations and initiatives that have led to a signiﬁcantdigitization of shipboard systems, in which multiple systems are intricately integrated.
The Integrated Navigation System (INS) is at the core of this digitization. By collecting
information from various navigation systems and integrating their functions, the INS assists navigators and contributes to an improved overall situational awareness of the vessel[9].
On the other hand, the art of navigation is one of the basic skills for navigators, alongwith the art of shiphandling. Astronomical navigation used to be the cornerstone ofship and aircraft navigation, but it has been largely replaced by radio navigation. Radio navigation technology has evolved to include ground-based systems such as Loran,satellite-based systems such as GPS, and mixed systems such as Diﬀerential Global Positioning Systems (DGPS), which compensate for GPS positioning.. DGPS in Japan will
be discontinued in 2019 due to the expected improvement of GPS accuracy and the startof operation of correction systems such as QZSS (MICHIBIKI) [10].
On top of that, ships stipulated by SOLAS (The International Convention for the Safetyof Life at Sea) are equipped with ship-speciﬁc systems such as ECDIS and other navigation
systems that are mandatory to be installed to support crews.
And after 2021, IMO mandates that the Safety Management System (SMS) of shipowners and operators of all ships, based on the International Safety Management Code (ISM
Code) in SOLAS, must include cyber risk analysis and methods to protect ships andship systems from cyber-attacks [11]. The IACS (International Association of Classiﬁcation Societies) has issued a set of minimum requirements for ship cyber resilience. E26(Cyber Resilience of Ships) [12] applying the NIST cybersecurity Framework as the minimum requirements for cyber resilience of ships and E27 (Cyber Resilience of Systems andEquipment on Ships) [13] applying IEC62443 as the uniform rules for cyber resilience of
onboard systems and equipment. The two URs (Uniﬁed Requirements) will be applied toships contracted for construction after July 2024. However, not many security measuresagainst radio interference are described.
And since it is becoming more and more diﬃcult to secure a crew these days, plans areunderway to realize an automated vessel with independent decision-making and operating
functions to further reduce the workload of vessel operation.

1.2 Research Objectives
The research objectives of this paper are to investigate the vulnerabilities of GPS andnavigation systems, attacks on GPS and their impact, and current security measures forprotection, and to propose a GPS-independent method and verify its similarity in order
to identify issues for security measures for new navigation systems.

1.3 Research Results

5

1.3 Research Results
The contributions of this study include the following.
• The impact of GPS attacks on navigation systems and vessels, and the organizationof ship-speciﬁc countermeasures for open seas and near-shore waters• Proposed response chart showing procedures for applying GPS and existing navigation systems• Veriﬁcation of similarity between GPS spooﬁng attacks and response charts using
ship-handling simulator equipment at ”National Institute of Technology, Hiroshima
College”, and veriﬁcation of new problem extraction
This paper was presented at the ”Computer Security Symposium 2023” [14] of the Information Processing Society of Japan and the ”Symposium on Cryptography and Information Security 2024” [15] of the Institute of Electronics, Information and Communication
Engineers.

1.4 Structure of this paper
This paper is organized as follows.
Chapter 2 describes existing navigational systems and support systems that are essential
for navigating a ship, as well as existing navigational system maneuvering techniques thatare tools for the operator (navigator) to obtain ship’s position information. Chapter 3
describes the basic technical features of GPS. In Chapter 4, we describe the characteristics
of attacks on GPS, mainly in the form of radio jamming, and discuss related research on
countermeasures. In Chapter 5, we propose a response chart showing the procedures to be
applied to existing navigation systems in case of GPS attacks. In Chapter 6, the response
to GPS spooﬁng attacks is veriﬁed using a ship-handling simulation system to conﬁrm thesimilarity of the proposed response chart. Finally, Chapter 7 summarizes this researchand discusses issues to be solved in the future.

6

Chapter 2

Technical Background
This chapter describes the technical background of ship operation and navigation. Ships
are equipped with navigation systems to assist in ship operation. The navigation system
consists of several pieces of equipment.

2.1 Technical background in Shiphandling
Shiphandling techniques include the following.
• AIS (Automatic Identiﬁcation System)• Marine Radar• ECDIS (Electronic Chart Display and Information System)

2.1.1 AISAIS (Automatic Identiﬁcation System) is a system that transmits and receives information between ships or between ships and land using VHF radios to support safe andeﬃcient ship navigation and to improve ship traﬃc operations. All passenger ships, shipsof 300 gross tons or more engaged in international voyages, and ships of 500 gross tons ormore not engaged in international voyages are required to be equipped with this system.
The system exchanges static information such as the ship’s name, identiﬁcation code, andtype of ship; dynamic information such as the ship’s position, course, speed, and navigation status; and navigation information such as destination and estimated time of arrival.
The dynamic information is displayed on the plotter screen of the ship radar or ECDIS
by displaying the target symbol and vector representing the vessel, so that the speed andcourse of the vessel and the speed and course of other vessels can be easily grasped [16] ．
AIS also has the same vulnerabilities as GPS[17][18] .

2.1 Technical background in Shiphandling7

2.1.2 Marine Radar
RADAR (RAdio Detection And Ranging) is a system that uses radio waves to detectsurrounding objects. The entire RADAR system depends on a variety of devices, but if
we consider only the two main ones, the antenna unit and the display conﬁguration, or
PPI (Plan Position Indicator), the antenna rotates 360 degrees around a vertical axis,
radiates radio waves, and receives the reﬂected waves from the target The antenna rotates
360 degrees around the vertical axis, radiates radio waves, and receives reﬂected waves
from the target.
Marine radar onboard ships detects images of other vessels, route markers, and landfalls,
and forms a crew’s situational awareness based on the azimuth and distance of the images,
as well as their time-varying information, and plays an important role in determining ship
encounter situations and avoidance maneuvers (avoiding collisions and boarding), and inmeasuring positions [19]. Until the advent of ECDIS and AIS, radar has been used as a
vessel’s second set of eyes. ARPA (Automatic Radar Plotting Aid) enables Marine radar
to automatically detect the tracks of other vessels [20].
Integration between shipboard radar systems and INS components is supported bynavigation networks, two standard network protocols ”NMEA 0183” and ”ASTERIX
CAT-240” [21]. The former allows interconnection between all devices and the latterallows video data transmission between shipboard radar antennas and displays. Twotypes of frequencies are used for shipboard radar: X-band (9 GHz band) and S-band (3GHz band). On the other hand, S-band radar requires a larger antenna than X-bandradar, but it can maintain its object detection capability even under the inﬂuence of fog,
rain, and sea surface reﬂection. When two radars are installed, such as on a large ship,
one X-band and one S-band radar are generally installed.
Diﬀerent manufacturers have diﬀerent speciﬁcations for shipboard radar antennas, including rotational speed and resolution related to bearing and range. Rotational speed
speciﬁes the speed at which the motor rotates the antenna. Azimuth resolution (angularresolution) determines the ability to separate nearby targets from targets at the same
distance. Range resolution determines the ability to separate two targets in the same
direction but at slightly diﬀerent distances.
The antenna geometry is a slotted antenna with a narrow horizontal beamwidth and alarge vertical beamwidth to allow for object detection even when the ship is moving. The
horizontal beamwidth is generally 1 to 2 degrees and the vertical beamwidth is generally
20 to 30 degrees, depending on the antenna size and frequency. Horizontal polarization isused to reduce the eﬀect of sea surface reﬂections.

8

Chapter 2

Technical Background2.1.3 ECDISECDIS (Electronic Chart Display and Information System) [22] aggregates data fromvarious sensor devices, including shipboard radar and GPS, with ENC (Electronic Navigational Chart) as the lowest layer. The ENC (Electronic Navigational Chart) is thebottom layer of the ECDIS, which aggregates data from various sensor devices, including
Marine radar and GPS.
It is mandatory for SOLAS vessels to have it on board, and if two units are installed
on a vessel, the vessel is exempted from carrying paper charts.
ECDIS has been shown to be critically vulnerable to weaknesses due to backup conﬁguration (deployment), underlying operating system updates and secure setup, and in
addition, has been determined to have a high risk level of cyber threat[23][24].
Fig. 2.1 and Fig. 2.2 show the conﬁguration of AIS, shipboard radar, and ECDIS,
which are the navigation systems used in this study. The NMEA 0183 standard wasestablished by the National Marine Electronics Association as a communication standard
for GPS receivers and navigation systems. The NMEA 0183 standard was speciﬁed andmanaged by the National Marine Electronics Association as a communication standard for
GPS receivers and navigation systems, and was internationally standardized as IEC611621 and IEC61162-2. 7-bit ASCII asynchronous serial communication is used, and deviceson the data transmission and reception sides are respectively a talker and a listener. Data
is sent from a single talker to a single or multiple listeners.
ENCs, which are charts displayed in ECDIS, are displayed by SENC (System ENC),
which is a standard for each ENC dataset by S-57, in order to have an eﬃcient data
structure that allows quick display of data. SENC is converted to the ECDIS internal
machine language format. The SENC format is diﬀerent for each ECDIS manufacturer.
The functional requirements for ECDIS are as follows.
• All SENC information can be displayed.
• Select and highlight safety isobaths and safety depths.
• Can update ENCs and have a way to verify that they are loaded correctly into the
SENC.
• When displaying radar and radar plotter (RP) information in ECDIS, charts,
radar images, and RP information must match in scale, orientation, and projection
method.
• ECDIS is equipped with a true azimuth display.
In addition, updating ENC data, which is essential for ECDIS, is done manually via
USB memory or external storage media such as DVDs when data is downloaded via the2.1 Technical background in Shiphandling

9Internet or by e-mail, etc. Therefore, there is an inherent risk of infection by malware,
etc. between air gaps.

Fig. 2.1: Conﬁguration of the navigation system

Fig. 2.2: Navigation systems (AIS, Marine radar, ECDIS)

10

Chapter 2

Technical Background

2.2 Background of Navigation technicalThe line segments drawn on the Earth’s surface during vessel movement include thefollowing line segments.
• A line of sight: A line segment drawn when a ship is sailing on a constant coursewith constant angles of intersection with meridians at various locations.
• Great Circle: A line segment connecting two points on the surface of a sphere withthe shortest distance between them, used when crossing an ocean.
When the true calf line (true north-south line) is used as a reference, the intersection
between it and the ship’s wake is called the ”True Course,” and the intersection between
the bow and stern lines (bow-stern line) is called the ”Apparent Course. The intersectionof the true bearing with the great circle passing through the surveyor and the object
marker is called ”True Bearing”, and the intersection of the north-south line of the compass
with the great circle passing through the surveyor and the object marker is called thecompass bearing.
Ship navigation is a method of guiding a vessel from one point to another. The routea ship travels does not have a clear path like a road traveled by a car.In addition, ships
cannot follow the route accurately due to external forces such as wind and waves, and will
deviate from the route. Therefore, in order to guide a vessel to the desired point, it must
periodically determine its exact position and correct its course and speed.
There are four main types of ship navigation: inertial navigation, geographic navigation, astronomical navigation, and radio navigation. The ﬁrst navigation method developed was geographic navigation, which uses landmarks such as well-known landmarks aslandmarks. Astronomical navigation, which uses celestial objects to navigate the open
seas, was developed later.Inertial navigation is used to obtain a ship’s course.

2.2.1 Inertial Navigation
Navigation systems have evolved over a long period of time based on a multitude oftechnological developments. INS (Inertial Navigation Systems) is the most importantsystem of inertial navigation that indicates a ship’s course.
The mechanism of the inertial navigation system uses an accelerometer and a gyroscope IMU (Inertial Measurement Unit) to measure acceleration and direction to obtain
the heading that the bow of the ship is facing. Then, by integrating them, it is possible to obtain the speed and distance. By entering the starting position, the current
position can be calculated relative to the distance and direction traveled. Therefore, in2.2 Background of Navigation technical11

order to calculate the relative position of one’s vessel, the starting point and heading are
indispensable.
Inertial navigation systems do not rely on external radio signals, so they are less susceptible to weather and interference. However, because they calculate the relative positionof the ship by integrating the measurements from the sensors, the accuracy of the system deteriorates over long periods of time and long distances as gyro-compass errors andintegration errors accumulate.

2.2.2 Terrestrial Navigation
Terrestrial navigation is a method of guiding a vessel to a target point while conﬁrming
its position (ship’s position) by using prominent landmarks (mountain peaks, headlands,
lighthouses, and other landmarks) marked on nautical charts. Since the ship is locatedin two-dimensional space on the earth’s surface, it is necessary to determine two or moreelements of the relationship between the location of the marker and the ship, such asazimuth, distance, and emphasis (two markers appear to overlap in the same direction),in order to determine the position of the ship[25].
Terrestrial navigation involves a wide variety of individual navigation methods for deriving ship positions. Among these, the most commonly used method to obtain accurate
ship’s position while navigating along the coast is called cross bearing. In cross bearing,
multiple beacons (two or more) are selected, their azimuths are measured, and the ship’s
position is determined by the intersection of the line of position (LOP) that is the line
segment of each beacon (図 Fig. 2.3). However, in the case of measuring the bearingsof three object beacons, if the measurement errors overlap, the lines of position from thethree object beacons do not intersect at a single point and an error triangle (Cocked Hat)
is generated (図 Fig. 2.4). In order to minimize the error triangle as much as possible,
it is necessary to pay attention to the intersection angle of the lines of position, select a
prominent object whose position is accurate and whose distance is close, and measure theazimuth as soon as possible starting from the object whose azimuth changes quickly.

2.2.3 Celestial Navigation
Celestial navigation is a method of guiding a ship to a target point while checking
its position using celestial objects[26]. In celestial navigation, two spheres are used forconvenience: the real ”Earth” and a virtual sphere called the ”Celestial Sphere. The
celestial sphere is assumed to be the surface of the celestial sphere with the earth at its
center and inﬁnite radius, and the positions of celestial objects on the celestial sphere areconsidered ﬁxed. Since the earth rotates the center of the celestial sphere, the position

12

Chapter 2

Technical BackgroundFig. 2.3: Position acquisition by cross bearing[25]Fig. 2.4: Cocked Hat[25]of the sun on the celestial sphere is apparently shifted, and the shifted path is called theecliptic. The two points where the ecliptic and the celestial equator intersect are called”Vernal Equinox” and ”Autumnal Equinox”, respectively. The position of a celestial bodyon the celestial sphere is expressed in terms of its declination (angle from the equator)
and right ascension (angle from the vernal equinox). The location of the celestial body to
be observed from a ship at the time of observation can be expressed in terms of the local
hour angle, which is the diﬀerence between the latitude on the earth and the celestial
equatorial latitude. The time that has elapsed since the vernal equinox passed the local
meridian (longitude time) is Sidereal Time, and the time we usually use is Mean Solar
Time (equatorial time), which is based on the hypothetical sun (mean sun) that moves at
a constant speed along the equator.
The relationship between the Right Ascension of Mean Sun and the equatorial longitudeof each celestial body can be obtained from ”The Nautical Almanac Japanese and UK
edition (The Nautical Almanac Japanese edition is no longer available[27])”. If the normal
time at the time of observation is known, the position of the celestial body on the earth
at that time (equatorial latitude and local time angle) can be determined. Since the only
thing that can be observed in relation to a celestial body and a ship is the azimuth and2.2 Background of Navigation technical13

altitude of the celestial body, it is necessary to obtain the true altitude by correcting theobserved altitude. On the other hand, the altitude of a celestial body can be calculated(Calculated Altitude) based on the estimated position (Dead Reckoning Position), andsince the observed position is diﬀerent from the estimated position, the diﬀerence inlatitude and longitude between the observed position and the estimated position can beobtained from two or more celestial bodies by observation, drawing and The diﬀerencein latitude and longitude between the observed and estimated positions can be obtained
from two or more celestial objects by drawing and calculating from observations.
The ﬂow of the celestial survey on a vessel is as shown below, and consists of threephases: ”Preparation,” ”Altitude measurement,” and ”Position determination[26](Fig.
2.5).

Fig. 2.5: The entire process of sky surveying in celestial navigation[26](1)Preparation
1. Coordinated Universal Time grasp
In order to determine the calculated altitude of a celestial object, the positionof the object is required. The positions of celestial objects are listed in The
Nautical Almanac. In order to retrieve the position of a celestial object fromThe Nautical Almanac based on Coordinated Universal Time (UTC), the worldtime at the time of the celestial survey must be known. In order to keep
track of world time, ships need high-precision shipboard reference clocks suchas chronometers. However, it is necessary to keep track of any errors (e.g.,

14

Chapter 2

Technical Backgroundchronometer errors) that may occur in the clocks.
2. Understanding sextant instrumental diﬀerences
Sextant instrumental error (Index Error) aﬀects the altitude calculation andmust be understood.
3. Onboard time management
The horizon must be visible to determine the altitude of a celestial body using
a sextant. The time of day, sunset or twilight, when the horizon is visible,
should be taken into account when selecting the observation period.
4. Star Search
It is necessary to identify the objects to be observed. As mentioned above, theSun, stars, planets, and the Moon are candidates. However, the objects to beobserved are those that are within the range of 90° from the zenith to the true
horizontal at the time of the observation. In addition, the magnitude of theobject and the degree of refraction of the light rays must be comprehensively
taken into consideration while taking into account the crossing angle between
the lines of position.
5. Preliminary calculations of ”Calculated Altitude” and ”Azimuth
Once the ”time of observation” and the ”estimated position” are determinedfrom 1 to 4 above, the ”azimuth” and ”calculated altitude” of each object canbe determined in advance. When observing, it is important to conﬁrm on whichside of the ship the object you have searched for is visible, taking into accountthe ”azimuth” and the ”ship’s course”.
(2)

Altitude measurement
1. Measurement of various quantities required for ”Advanced Revision
Atmospheric conditions (atmospheric pressure, air and sea temperatures) must
be observed in order to better revise the measured altitude (altitude revision).
Since eye level is also a necessary factor for altitude revision, it is essential to
conﬁrm the eye height on the deck to be observed.
2. Altitude measurement
Record the sextant altitude and Coordinated Universal Time (UTC) when the
sextant telescope is aligned with the celestial body and the horizon.
3. Understanding the amount of movement during an observation
At twilight, the sextant altitudes and UTCs are obtained for each of the multiple
sources. Since the vessel is moving slightly, ﬁne adjustment is required for eachposition line. The course and speed of the vessel at the time of observation
should also be conﬁrmed.

2.2 Background of Navigation technical

(3)

15

Determination of position
1. Recalculation of calculation altitude
The estimated position and the position of the celestial object are determinedagain from the onboard time and UTC when the altitude was measured, andthe calculated altitude and azimuth are recalculated based on these. The calculated altitude calculated in advance deviates from the actual time of themeasurement. The larger the time deviation, the larger the estimated position
deviation, and thus the larger the correction diﬀerence. As the correction difference increases, an intersection of position lines appears at a distance fromthe estimated position. The greater the distance between the intersection andthe guessed position, the greater the eﬀect of the error in linear approximation.
Recalculation is performed to avoid this.
2. Alteration of altitude
The sextant altitude is the sextant reading when the altitude is measured. The
instrumental error (I.E.) is added or subtracted to obtain the observed altitude.
Various altitude corrections are added to this value to obtain the true altitude.
3. Determination of position
Subtract the calculated altitude from the true altitude to obtain the corrected
diﬀerence. From the corrected diﬀerence and azimuth, the line of position is
identiﬁed, and latitude and longitude are determined as the true position by
drawing or calculation.

The unique measurement methods used in astronomical navigation make it extremely
diﬃcult to automate. In order to replace human vision (visual observation), automatedvessels can use images captured by cameras to identify objects through machine learning.
The feasibility of automating astronomical navigation has already been veriﬁed by simulations using a hybrid system of deep learning and convolutional neural networks to train
a composite image of celestial objects combined with the time the image was taken [28].

16

Chapter 2

Technical Background2.2.4 Radio Navigation
Radio navigation, also called hyperbolic navigation, determines a line of position as oneof a group of hyperbolas whose focal point is a ﬁxed point if the distance diﬀerence fromthe ﬁxed point is known, and the ship’s position is determined as the intersection of sucha line of position with other lines.
The following two methods are used to measure the diﬀerence in distance.
(1)

Using pulsed waves, the diﬀerence in arrival time of radio waves from two transmitting stations is measured by utilizing the constant speed of radio waves (Lorannavigation system [29]) ．

(2)

Continuous waves are used to measure the phase diﬀerence between the radio waves
from two transmitting stations (Decca navigation system [30], Omega navigation
system [31]).

These transmitting stations are located on the ground, but can be considered satellite
navigation if they are located in space. The performance of each system is shown in
Table. 2.1.
However, these transmitting stations have already been decommissioned and are nolonger available [32].
Table. 2.1: Comparison of each radio navigation system

System NameRadio Wave

Loran navigation system

A:MF(1,750 〜 1,950kHz)[29]

C:(100kHz)

Decca navigator system[30]
Omega navigation system[31]

Positioning Accuracy(Approx.)
Several hundred m

LF(70 〜 130kHz)

100 m

HLF(10.2 〜 13.6kHz)

1,000 〜 2,000 m

The newest system in radio navigation is the LOLAN navigation system (LOng RAnge
Navigation system). The LOLAN system is a navigation system that operates at 100 kHz.
It was developed during World War II and played an important role in the navigation ofships at sea [29].
Initially, the system was operated as Loran A, and Loran C was developed and operated

2.2 Background of Navigation technical17

as a later model. Later, a system called eLoran (Enhanced Long-Range Navigation) was
studied, but has not been adopted due to the current GPS operational status. The Loransystem uses the diﬀerence in arrival time of frequency signals from each radio station
to obtain a position. Loran stations transmit (broadcast) pulse signals in groups called
chains, each chain covering a speciﬁc area. Each chain consists of a main station (M) andseveral secondary stations (W, X, Y, Z). The secondary stations have eight pulses, the main
station has nine, and the last pulse is used to identify the main station. The pulses in eachchain are broadcast repeatedly at ﬁxed time intervals called Group Repetition Intervals(GRI). The repetition interval of each GRI is designed to be diﬀerent to eliminate crossrate interference. The station pulse interval is 1,000 µsec, with the last pulse of the main
station 2,000 µsec away from the eighth pulse. For example, the West Coast chain is GRI
9940, whose pulses are transmitted every 0.0994 sec. The Loran stations are synchronized,
and the timing of station transmissions is controlled by the system area monitor [33]. Fig.
2.7 shows a diagram of the Loran chain signal and an ideal pulse [33]. Loran C enabledthe Loran system to acquire positions by forming a chain of coordinated radio stations
through international cooperation among the countries operating the system (Fig. 2.8，
Table. 2.2) [34] .

Fig. 2.6: Acquisition of position by hyperbolic curve [33]

18

Chapter 2

Technical BackgroundFig. 2.7: Loran Chain Signal and Ideal Pulse [33](a) Northwest Paciﬁc Ocean Chain(b) Korean Chain(c) Russia Chain(d) China North Sea・China East Sea・China South Sea
ChainFig. 2.8: Example of Loran C International Cooperation Chain[34]2.2 Background of Navigation technical19

Table. 2.2: Example of Loran C International Cooperation Chain [34]Chain Name

Station Name

Master & Slave

Transmission Power

Northwest PaciﬁcNiijima(Japan)

Master(M)1000kW

Ocean Chain

Tokatibuto(Japan)

Slave(Y)

1000kW

GRI:8930

Gesashi(Japan)

slave(W)

1000kW

Pohang(Republic of Korea)

Slave(Z)

150kW

Russia Chain

Alexandrovsk(Russia)

Master(M)

700kW

GRI:7950

Petropavlovsk(Russia)

Slave(W)

700kW

Okhotsk(Russia)

Slave(Z)10kW

Ussuriisk(Russia)

Slave(X)

700kW

Tokatibuto(Japan)

Slave(Y)600kW

Korean Chain

Pohang(Republic of Korea)

Master(M)150kW

GRI:9930

Niijima(Japan)

Slave(Y)

1000kW

Gesashi(Japan)

Slave(Z)600kW

Kwangju(Republic of Korea)

Slave(W)50kW

China North Sea

Rongcheng(China)

Master(M)1200kW

Chain

Helong(China)

Slave(W)

1200kW

GRI:7430

Xuancheng(China)

Slave(W)

1200kW

China East Sea

Xuancheng(China)

Master(M)1200kW

Chain

Rongcheng(China)

Slave(Y)1200kW

GRI:8390

Raoping(China)

Slave(X)

1200kW

China South Sea

Hexina(China)

Master(M)1200kW

Chain

Chongzuo(China)

Slave(Y)1200kW

GRI:6780

Raoping(China)

Slave(X)

1200kW

2.2.5 GNSS
Each country has developed a GNSS (Global Navigation Satellite System) system as
an alternative to GPS for radio navigation. The types of systems are listed in Table.
2.3. Each system operates in a diﬀerent frequency band to avoid signal collisions withother systems. However, in order to use GNSS, it is necessary to have a receiver that iscompatible with the frequency of each positioning satellite’s signal or that can convert thesignal and receive it.
GNSS is a group of satellites that transmit time and position from orbit, and several
satellite networks exist. There are several satellite networks:

20

Chapter 2

Technical Background

1. GPS (originally known as Navstar GPS)
2. Galileo (European Union)
3. GLONASS (Russia)
4. BeiDou (China)
5. NavIC (India)
6. QZSS (Japan)
The performance of GNSS makes it a potential target for many attackers. In addition,
the low power of many GNSS signals makes them a serious technical weakness, as they
are often subject to interference from natural solar ﬂares, the Earth’s ionosphere, otherradio frequencies, and spectral congestion.

2.2.6 Galileo
Galileo[35] was developed in 1998 by the European Union (EU) to ensure full compatibility with the GPS system by providing an independent satellite positioning system forcivilian use around the world. The SOL (Safety Of Life) service includes an authentication service to ensure that the received satellite signal is truly transmitted by Galileo.
In addition, the SOL service includes integrity monitoring and notiﬁcation, which alerts
the user if the safe use of SOL signals cannot be guaranteed according to the speciﬁcations. 28 satellite constellations and a global ground control segment are used to ensureinteroperability between the two systems. Measures are in place to ensure interoperability
between the two systems.

2.2.7 GLONASSGLONASS [36] is a Russian satellite positioning system that corresponds to GPS. It
consists of a constellation of satellites in mid-Earth orbit, ground control segments, anduser equipment. The constellation consists of 24 satellites in orbit. The signals are G1(1602.00 MHz), L2 (1246.00 MHz), and L3 (1204.704 MHz). The feature of this systemis that the frequencies are assigned in such a way that they do not interfere with other
GNSS frequency bands.

2.2.8 Beidou
Beidou (BeiDou Navigation Satellite System) is China’s own satellite positioning system[37]. The constellation has 52 satellites in orbit, the most of any satellite positioning
system. There are ﬁve satellite signal frequencies: B1I (1561.098 MHz), B1C (1575.42
MHz), B2a (1176.45 MHz), B2b (1207.14 MHz), and B3I (1268.52 MHz), with B1C and2.2 Background of Navigation technical21

B2a complementing GPS L1 and L2.

2.2.9 NavIC
NavIC (Navigation Indian Constellation) is a GPS-compatible satellite positioning system that covers a limited area in and around India (including the Indian Ocean) [38]. The
constellation of eight satellites is operated in two frequency bands: L5 (1176.45 MHz),
which is the same as GPS, and S (2492.08 MHz), which is a stand-alone frequency band.
It is a satellite system that can be operated only in the vicinity of India, which is a very
diﬃcult environment for normal use as an alternative to GPS.

2.2.10 QZSSQZSS (Quasi-Zenith Satellite System), also called MICHIBIKI (Quasi-Zenith Satellite
System), is a Japanese satellite positioning system [39]. QZSS can be called the Japaneseversion of GPS because it is designed to complement GPS ﬁrst and foremost and covers all
GPS frequencies. The satellites are in quasi-zenith and geostationary orbits of about 200
to 1,000 km and 36,000 km, respectively, and as of 2024, four satellites are in operation.
Three of the four satellites cover the Asia-Oceania region. Currently, MICHIBIKI iscomplementing GPS and Galileo, but it is expected that a system of seven satellites will
eventually be established, and that MICHIBIKI alone will be able to provide continuous
positioning because more than four satellites will always be in the sky over Japan.
In addition, as a countermeasure against spooﬁng in satellite positioning services, a”Signal Authentication Function” that adds authentication information (digital signature)
to navigation messages has been added and is scheduled to be operational from FY2024
[40].

22

Chapter 2

Technical Background

Table. 2.3: Types of GNSS
System Name
Developing
Countries

Galileo[35]

GLONASS[36]Beidou[37]NavIC[38]QZSS[39]

EU

Russia

China

India

Japan

28

24

52

8

4

24,000 (3)200 - 1,000

NumberofSatellites
Approx.
Altitude23,00019,10021,800250 (5)36,000E1(1575.42)

G1(1602.00)

B1I(1561.098)

L5(1176.45)

L1(1575.42)

E5(1176.45)

L2(1246.00)

B1C(1575.42)

S(2492.08)

L2(1227.60)

E6(1278.75)

L3(1204.704)

B2a(1176.45)

L5(1176.45)

B2b(1207.14)

L6(1278.75)(km)Frequency(MHz)

B3I(1268.52)

23

Chapter 3

What is GPS?
3.1 GPSGPS is the ﬁrst familiar satellite positioning system using satellites (positioning satellites) owned by the U.S. government and operated by the U.S. Air Force [9].

3.1.1 GPS Overview
To use GPS for positioning, we use four positioning satellites to obtain position information (x, y, z). Calculate the distance between yourself and each of the four satellites
to obtain four distances. The point where the four distances intersect is mathematicallydetermined to be your position.
Assume a number of GPS satellite transmitters Si orbiting at a known position LS ∈R3 , each equipped with a synchronous clock with no clock. The exact time is oﬀset totS and the navigation signal si (t) is transmitted (broadcast). The signal in that casepropagates at speed c.
GPS receiver V using an omni-directional antenna at coordinates L ∈ R3 receives thetransmitted signal. It receives all signals that are within range:g(L, t) =

∑
i

(
Ai si

|LS − L|t− ic)+ n(L, ts )(3.1)

where Ai is the attenuation the signal undergoes between LS and L, |LSi − L| is the
Euclidean distance between LSi and L, and n(L, t) is the noise.
Due to the characteristics of the GPS signal si (t), the receiver can separate each termof this sum and extract the relative spread-sign phase, satellite ID, data content, etc. byusing a spread-sign replica. Then, given the data and relative phase oﬀset, the receiver
can estimate the distance by identifying the time delay |LSi − L|/c for each satellite.

24

Chapter 3

What is GPS?

Then, given three known distances di and a known GPS transmitter position LSi , thethree equations 3.2 can be uniquely formulated for L. except when all three Si are locatedon the line.

di = |LSi − L|

(3.2)

Since the GPS receiver V is not bi-directionally clock-synchronized, having a clock oﬀset(t = tS + δ) yields the equation 3.3 from the equation 3.1.

S

g(L, t ) =

∑
i

(
Ai si

)
di
t−
− δ + n(L, tS )
c

(3.3)

On the other hand, given a pseudorange Ri , the GPS receiver can infer the equation
3.3 from the delay di /c − δ.
Ri = di + c・δ

(3.4)

The clock oﬀset δ can be solved for both L and δ by adding a fourth unknown scalarvalue, so that the resulting equation 3.4 can be solved for both L and δ if pseudo-distancemeasurements for at least four GPS transmitters Si are available. The resulting equation
can be solved for both L and 3.4 to obtain both the exact position and time, without theneed for an exact clock.
Then, if LSi = (xSi , yiS , ziS ) , L = (x, y, z) , ∆ = c・δ then we can transform the expression
3.4 into the expression 3.5 [41][42].

(x − xSi )2 + (y − yiS )2 + (z − ziS )2 = (Ri − ∆)2 ∀Si(3.5)

Radio waves transmitted from a positioning satellite contain information on the time oftransmission, so the diﬀerence between the time of transmission and the time of arrival of
the radio wave at one’s location determines the time of propagation. Calculations showthat three pieces of distance information are enough to determine one’s position, but thereceiver’s clock contains only a small amount of ”error. However, because there is a slighterror in the receiver’s clock, there is a discrepancy in the position information among the3.1 GPS

25

Fig. 3.1: GPS operation (Ship assumption)[42]

three satellites. To compensate for this slight error, information from at least one moresatellite is required.
GPS positioning methods include ”Independent Positioning,” ”DGPS (Diﬀerential GPS
Positioning),” ”Relative Positioning,” ”RTK-GPS Positioning,” and ”Network RTK-GPS
Positioning.
There are two main types of positioning methods: single positioning and relative positioning. The single positioning method covers the entire world with an accuracy of about
10 m. The relative positioning method covers only the vicinity of a reference station, but
provides highly accurate positioning.
GPS can determine the latitude and longitude of the current position by receiving radio
waves from GPS satellites. For this purpose, there are about 31 GPS satellites orbiting
around six orbits at an altitude of about 20,000 km (about 24 satellites in operation), as
shown in Fig. 3.2. GPS satellites are constantly transmitting GPS signals to the earth’s
surface.
Because GPS uses radio waves, the receiver needs an antenna. The larger the antenna,
the better the positioning accuracy. As mentioned earlier, GPS cannot be used indoors
in tunnels and underground malls, where there are obstructions from satellites. Even
indoors, it is often diﬃcult to get a GPS signal, but high-sensitivity GPS receivers aredesigned to provide some position information.
To measure the distance between the satellite and the user and determine the position,
the GPS signal must have at least the following three characteristics.
1. Must be able to measure the distance from the propagation time of radio waves.
2. Must be able to measure the distance to more than 3-4 satellites simultaneously.

26

Chapter 3

What is GPS?

item The user must be able to calculate the position of a satellite from time to time.
To satisfy the above requirements, each of the following conditions must be met.
1. The user must be able to determine when the currently received GPS signal wastransmitted from a satellite.
2. The user must be able to receive GPS signals from each satellite without interference.
3. The information about the position of the satellite must be sent with the GPS
signal.
GPS constellation coverage extends far beyond the land-based Loran system describedabove [43].

Fig. 3.2: GPS satellite constellation coverage [43]3.1.2 GPS Signal
GPS [44] signals are produced by modulating the carrier wave with two codes called
PRN codes (Pseudo Random Noise Codes) and navigation messages. The PRN code isan irregular code that randomly generates ”0s” and ”1s” and repeats the same patternover a ﬁxed length. In the early days of operation, GPS satellites transmitted data in
two frequency bands, L1 (1575.2 MHz) and L2 (1227.6 MHz), with L1 being a ”C/A The
C/A code is used to identify GPS satellites and is used for coarse distance measurements,
while the P(Y) code is used to identify GPS satellites and is used for coarse distancemeasurements. L2 carries only the P(Y) code, which is classiﬁed as classiﬁed, but it ispossible to obtain a system that can receive the P(Y) code.
The PRN code has two characteristics. The ﬁrst is that the code consists of a ﬁxed
pattern, so the user can know where in the overall pattern the currently received signal

3.1 GPS

27

falls. As a result, if the transmitter deﬁnes the timing of code transmission, the user
can determine when the currently received signal was transmitted from the satellite. The
shorter the length per bit of the code, the more accurate it is, so the P(Y) code is moreaccurate than the C/A code. Another feature is that the signal power of the modulated
carrier is spread over a wide frequency band because the PRN code is a pseudo-random
number; in the case of the P(Y) code, the signal power is spread over a band of about
20 MHz, and in both cases the signal is buried in the noise. This is why many GPS
satellites do not interfere with each other even if they use the same frequency, and thesignal power from the other satellites is less than the noise. This type of communication
method is called spread spectrum communication, and is said to be excellent for multiplex
communication and concealment. In order for a receiver to receive a GPS signal from aparticular satellite, it is necessary to multiply the same PRN code again with the GPS
signal transmitted by that satellite and remove the eﬀect. As a result, the signal powerthat was spread over a wide bandwidth is returned to a very narrow bandwidth, allowing
the signal to be captured. This process is called inverse diﬀusion. Because back-diﬀusionof GPS signals from unobjected satellites also causes interference, PRN codes are chosen
to have the lowest possible cross-correlation (the correlation value between codes with
diﬀerent patterns).
Later, in the process of updating GPS, L1C ( L1 Civil ) signals were added to L1, L2C( L2 Civil ) signals to L2, L5 signals [45] to a frequency band called L5 (1,176.45 MHz),and military signals called M codes to L1 and L2 (Fig. 3.4，Table. 3.1)[46].

Fig. 3.3: Example of GPS signal generation [44]The DOP (Dilution of Precision) is a value that indicates the degree of degradation of
GPS positioning accuracy. The DOP value depends on the position of the GPS satellites,
and the more evenly distributed they are in the sky, the higher the accuracy.
The ﬁeld strength of the transmitted GPS signal is very small. It is transmitted atabout 30 to 50 W, and by the time it arrives at earth, it is 10−16 W. This is why it is so28

Chapter 3

What is GPS?

Fig. 3.4: Signals from GPS satellites (Old signal (upper row) & current signal (lowerrow)) [47]easy to achieve GPS jamming [47]. The ﬁeld strength of the transmitted GPS signal isvery low. This is why achieving GPS jamming is so easy. All that is needed is a signal of
the right frequency.
Table. 3.1: GPS signal (frequency band & PRN code)
L1

L2

L5

( 1575.42 MHz )( 1227.60 MHz )( 1176.45 MHz )C/A：Civil code

L2C：

Civil code

L1C：

Civil code

P(Y)

：

Military code

P(Y)

：

Military code

M：

Military code

M：

Military code

L5：

Civil code

3.1 GPS

29

3.1.3 GPS receiver conﬁguration
A GPS receiver receives all GPS signals transmitted by GPS satellites orbiting in the sky
and measures the distance between the GPS satellites. The GPS receiver can calculate its
own position if it can receive signals from at least three to four GPS satellites, dependingon the type of GPS receiver. If conditions are good, the receiver can determine thecurrent position with an accuracy of several meters, although this depends greatly on
the performance of the GPS receiver and the surrounding environment. The processing
circuitry of a GPS receiver is now on a chip and can be integrated into a cellular phone.
In addition to reverse diﬀusion of the PRN code and decoding of the navigation message,
the receiver also performs carrier wave phase tracking. The carrier phase represents theintegral of the Doppler shift between the satellite and the user, and is used to output
the delta range and the observed quantity called the carrier phase. The conﬁgurationof the receiver varies depending on how the hardware is assembled, but as a result ofrecent advances in semiconductor technology, most receivers use digital processing circuits
and control processors to perform the main processing, while the analog portion consists
only of an antenna and a circuit that down-converts the carrier wave to an intermediate
frequency. The digital processing consists of a delay-lock loop that performs inverse PRN
code diﬀusion, a costus loop that tracks the carrier phase, and a message decoding loopthat decodes the navigation message. In general, the order of processing is as follows: thedelay lock loop performs inverse diﬀusion, followed by the costus loop, which establishes
carrier phase synchronization and extracts the navigation message [47].

30

Chapter 4

Related Research
In this study, we present related research mainly in the navigation systems that may
be attacked by GPS and in the satellite line equipment that supports the communicationlines.

4.1 GPS Vulnerability
4.1.1 GPS jamming
GPS jamming, also known as masking, is an attack in which a signal is transmitted at thesame frequency as the target signal and with equal or greater power, making the receiver
unable to distinguish between the legitimate signal and the jamming signal. Jamming is
an attack that makes the receiver unable to distinguish between a legitimate signal and a
jamming signal, or makes the receiver unable to recognize a legitimate signal. Jamming
does not require advanced techniques, although it requires the collection of informationsuch as frequencies and output magnitudes in advance. As described in Section. 3.1.2,
attacks on GPS receivers need to be limited to the downlink, which is the communicationfrom GPS satellites to ground radio stations including ships, and since the output powerof GPS signals transmitted from satellites is very small, it is very easy to achieve attacks
on GPS. Depending on the distance, a signal of a few W is enough to achieve this. The
PPD (Personal Privacy Device) jammer, which is an attack tool, is inexpensive, costing
only a few tens of thousands of yen, and is readily available on the Internet [48].
The attack only aﬀects the receiver while it continues to transmit, so once the attack
is stopped, the legitimate signal can be received again, and it does not necessarily cause
permanent damage to the receiver.
However, in the event of an attack, it is possible to detect the direction of the attack,but it is diﬃcult to measure the distance. In the event of an anomaly in the navigation
system, it is very diﬃcult to determine whether the attack was intentional or an accidental

4.1 GPS Vulnerability

31

failure.
As a related study of GPS jamming for ships, GPS jamming experiments were conductedin actual sea areas [49]. The test was conducted by transmitting a known PRN code (C/Acode) over the entire 2 MHz bandwidth of L1 from a GPS jammer unit at 25 m above
the ground with a total power of about 2 dBW ( 〜 1.5 W) at low power (maximum
power 1.58 W). Dynamic and static tests were conducted over a period of three days bynavigating the attacked vessel in the surrounding waters, and the possible eﬀects of GPS
jamming on various factors of safe navigation were conﬁrmed (Fig. 4.1，Fig. 4.2).
Vessels subjected to GPS jamming attacks lost their GPS positioning capabilities and
ECDIS was particularly aﬀected, aﬀecting the safe navigation of ships at sea and in particular the ability of the crew to navigate safely. The safety and security of the crew
may be seriously aﬀected by the inability of the ship’s crew to recognize that they arebeing GPS jammed and by the loss of the opportunity to switch to an alternative navigation method. Alan’s [49] have identiﬁed a number of countermeasures to GPS jamming,
including the use of Roland Roland’s Roland Rockett (RRT), which is a GPS jamming
technique that can be used to detect and prevent GPS jamming. Alan’s proposed supplementing the Loran system as a countermeasure to GPS jamming. However, while many
vessels were equipped with Loran systems as a supplement to GPS at that time, they are
no longer feasible because the Loran system service has been discontinued or reduced inmany countries nowadays [32].

Fig. 4.1: GPS jammer unit installed in Flamborough Head, England [49]

Alan’s [49] also studied the impact of attacks by PPD jammer devices using the conventional method of GPS L1, as well as the impact of GNSS attacks in cooperation with
the German Aerospace Center (DLR: Deutsches Zentrum für Luftund Raumfahrt) and32

Chapter 4

Related Research

Fig. 4.2: GPS jammer unit coverage area [49]Fig. 4.3: GNSS jamming experiment in the north of Daru Peninsula [50]

the German Federal Network Agency for Electricity, Gas, Telecommunication, Post and
Railway (BNetzA), as well as Alan’s. The GNSS jamming testbed was prepared in coop-4.1 GPS Vulnerability

33

eration with the Federal Network Agency for Electricity, Gas, Telecommunication, Post
and Railway (BNetzA), as well as with Alan et al. (BNetzA), a GNSS jamming testbed
has been prepared and GNSS jamming experiments have been conducted in actual maritime environments. Daniel’s [50]. prepared three vessels (attack ship [A], damaged ship
[B], and alert ship [N]) in a test area located about 10 km north of the Dals peninsula in
the Baltic Sea, as shown in Fig. 4.3, for a period of 3 h (07:00 - 10:00 UTC on October22, 2015), where the attack ship was The test was conducted with the attacking vessel
anchored in the center of the experimental area, while the damaged vessel sailed at a
distance of 40 m to 4,000 m, at a maximum speed of 8 kts. The results of the experimentshow that even an attack with a PPD jammer device of relatively simple speciﬁcations
had an impact over a very large area. On the other hand, the results show that the GNSS
is not necessarily aﬀected when close to the source of the attack.

4.1.2 GPS Spooﬁng
GPS spooﬁng is the transmission of generated false signals to a target’s receiver toprovide deceptive information and confuse location information. A cybersecurity incident
involving GPS spooﬁng occurred in June 2017, when the navigation systems of approximately 20 vessels were guided to diﬀerent locations while sailing in the Black Sea, eventhough they were operating properly. It is believed that this was most likely due to interference with GPS signals caused by GPS spooﬁng by the Russian authorities [4]. In
addition, the GPS receiver of one of the vessels at that time is said to have conﬁrmed multiple GPS satellites showing approximately the same values of ﬁeld strength, suggesting
an attack from the same transmission output or the same location (Fig. 4.5)[51].
The attacked vessel was able to determine the presence or absence of a GPS spooﬁng
attack by using a VHF telephone to check for similar phenomena on other vessels sailingin the vicinity.

4.1.3 GPS Meaconing
GPS Meaconing is an attack that records a legitimate GPS signal, delays it for a certain
period of time, and then transmits it to a target receiver to confuse it. As in a man-inthe-middle attack, an RF recorder, which can receive, record, and play back any wirelesssignal, can be easily used as a meaconing device if it can play back the recorded GPS
signal by attaching an antenna to it for transmission. One possible countermeasure against
meaconing is to compare the GPS signal with a clock built into the GPS receiver, butthere is no uniﬁed standard for this function since it varies depending on the GPS receiver.
In addition, it is said that this is not an eﬀective countermeasure against meaconing by

34

Chapter 4

Related Research

Fig. 4.4: GPS spooﬁng situation [4]repeaters and those with only a very short delay even in playback [48].

4.2 Security countermeasures for GPS
The vulnerability of civilian GPS signals to spooﬁng attacks is discussed as a security
measure against attacks on GPS [44]. They also describe how GPS works and elaborate on
the structure of the GPS signal. warner’s [44] describe suggestions for detecting deception
signals to counter spooﬁng attacks, including monitoring GPS signal strength, monitoringsatellite identiﬁcation codes, checking time intervals, comparing time timings and using
an accelerometer to counter-checking using accelerometers, and so on. The proposals of
Warner’s are not demonstrated because no tests have been conducted to evaluate theperformance of each method. In addition, most of the proposed methods only monitor
signal characteristics.
In addition to the above, the following measures have been proposed.
1. Protection by Signal Processing
2. Protection by Authentication
3. Protection by Sensor Fusion
4. Protection by Antenna

4.2 Security countermeasures for GPS

35

Fig. 4.5: GPS spoofed receiver status [4]4.2.1 Protection by signal processing
There are spooﬁng detection techniques that can be implemented as signal processing
algorithms in standard GPS/GNSS receivers.
(1)

Signal distortion search(2)

Signal complex correlation function search(3)

Total acquisition search

The method in (1) searches for distortions or disruptions that occur during signal dragoﬀ. The simplest technique is to search for unreasonable sudden jumps in the received

36

Chapter 4

Related Researchcarrier amplitude Ai , beat carrier phase φi (t), or code phase τi (t). A sudden increase in
Ai or an unusual displacement of φi (t), or τi (t), is said to occur at the beginning of an
attack [52]. A search technique is to monitor the total received power of RPM (Received
Power Monitoring) on an absolute scale. What this technique requires is to look at allreceived Ai values and the Automatic Gain Control (AGC) settings of the receiver RF
front-end [53]. Then, the spoofer requires a signiﬁcant power advantage, As i ≫ Ai (for alli = 1, . , N ) is required, the total power may suddenly increase at the beginning of theattack. A sudden power spike may indicate an attack, especially if it increases by morethan 1 to 2 dB. However, it is vulnerable to overpower attacks, including Noise Floor
Spooﬁng [54].
The method in (2) is a detailed study of the complex correlation function when the receiver synthesizes the tracking loop discriminator. During the initial drag-oﬀ of a spooﬁng
attack, the autocorrelation function is distorted due to the mismatch between the truecode signal and the spoofed false code signal and carrier phase. To search for distortionsin the correlation function, even a typical GPS/GNSS receiver is considered capable ofcorrection [55]. The main requirement is to compute additional complex baseband correlations between the receiver’s signal replica and the received signal, and these correlations
are computed with a set of delay extensions along the code oﬀset axis.
However, searching for complex correlation functions has two drawbacks [52]. First,
natural multipath signals produce similar results. Therefore, the spooﬁng detector mustverify that the observed distortion cannot be proven as mere multipath before issuingan alarm. Second, detection performance is poor when the spoofer device signiﬁcantly
overpowers the true signal. The output of the spoofer equipment necessary to avoid
distortion is possible with the RPM detection scheme. Another issue is the transient
nature of the detection [52]. If an attack is not detected at drag-oﬀ, both methods (1)and (2) may miss the opportunity to detect the attack.
The method in (3) is to constantly attempt to reacquire all the signals tracked. For
each signal, a brute-force acquisition search is performed over the entire range of code
phase and carrier Doppler shift. However, brute-force acquisition searches impose a large
signal processing load on the receiver. Therefore, one reasonable approach is to search
for additional instances of the tracked signal sequentially, one signal at a time. If a
second version of the received signal is detected, the receiver is returned to the initialacquisition mode and all instances of all signals are searched again by brute force search.
The receiver then attempts to sort out the true signals from the spoofed signals and restore
the navigation function. However, this technique can be defeated by an overly powerfulspoofer device that intercepts the true signal and renders it undetectable during the research. For strong spoofer devices, the RPM scheme is considered eﬀective for detection[52].

4.2 Security countermeasures for GPS

37

4.2.2 Protection by Authentication
One of the countermeasures against spooﬁng is the authentication of positioning signals
transmitted by GPS satellites. This is done by using a public-key cryptosystem thatuses asymmetric key pairs for encryption and decryption to identify deception signals.
Although this method cannot be used for GPS signals whose speciﬁcations have alreadybeen published, it is being used in other satellite navigation systems [40]. Speciﬁcally, thepublic key used for decryption is made known to the user in advance (and installed in thereceiver), and if the signal can be decrypted correctly with this public key, it is guaranteed
to have been generated by an operator who possesses the private key corresponding to the
public key. However, it is diﬃcult to maintain the strength of the authentication because
the format of the information obtained as a result of decoding is known, the amount of
information is not large, and the key pair cannot be changed arbitrarily because it is a
one-way communication. On the other hand, encryption of positioning signals transmitted
by GPS satellites has also been considered [48] , but it is not considered necessary because
sensitive information is not included in the signals.

4.2.3 Protection by Sensor Fusion
If the physical movement status of the GPS receiver (antenna) is known, the presenceor absence of deception can be determined. For this purpose, it is useful to compare withposition sensors other than GPS [48]. Various sensors can be considered, but as mentioned
above, ships are equipped with many sensors, especially the IMU (gyrocompass), so it isconsidered easier to compare signals than in other types of vehicles.

4.2.4 Protection by Antenna
As a characteristic of spooﬁng and meaconing in past cases, the attacker is expected
to transmit from the vicinity of the ground. Therefore, although GPS receiving antennas
are omni-directional in nature, a countermeasure is to make them directional so that theyreceive only signals coming from the direction in which GPS satellites actually exist (Fig.
4.6). However, since parabolic antennas are commonly used for directional antennas andare large in size, array antennas using multiple antennas are being considered as the main
method of reception [48][56]．Since at least three types of antennas need to be arranged toachieve three-dimensional directivity, it is diﬃcult to adopt this method in mobile devices.
It is also impossible for an attacker to place an antenna at the same position as a GPS
satellite. Therefore, even if spooﬁng or meaconing is performed for a GPS receiver at a
speciﬁc location, the same eﬀect cannot be achieved for GPS receivers at distant locations.

38

Chapter 4

Related Research

In other words, it is not possible in principle to create a consistent deception signal fora wide geographic range of GPS receivers. It is proposed to use a network of many GPS
receivers [48]. The measurements obtained by the GPS receivers participating in the
network are compared and discrepancies are detected. Furthermore, it is also consideredthat GPS receivers exchange measurements and compare them with each other, which
would function as an autonomous deception detection method. However, the location of
the receivers for comparison may be diﬃcult because of the need for separate transmission
and reception.

Fig. 4.6: 2-antenna based spooﬁng detection of typical signal arrival shapes [52]4.3 Challenges with existing security countermeasures
As mentioned by Section 4.2, countermeasures against attacks on GPS have beenstudied in a wide range of areas, mainly detection, but have not been applied to existingnavigational systems. However, the application to existing navigational systems has notprogressed yet [57].
Because ship operations are subject to external environmental inﬂuences (e.g., wind,
waves, ship traﬃc, etc.), the availability and continuity of ship operations are extremely
important, and safe operations cannot be continued if they cannot be handled. Therefore,cybersecurity measures for OT equipment are highly necessary, but their application has
not progressed much. Therefore, it is necessary to study the incident response of operators(navigators) to cyber-attacks, and to promote a common understanding of information

4.3 Challenges with existing security countermeasures

39

security incidents with related parties based on these studies, otherwise, availability andcontinuity may be lost. In addition, as mentioned in Section 1.1, it is important tostudy this knowledge as automation and autonomization are progressing.

40

Chapter 5

Proposed Method
When a ship’s GPS is attacked by radio waves, it is very diﬃcult for existing navigation
systems to detect the presence or absence of the attack. In this chapter, we review
shiphandling and navigation techniques, as well as navigation systems related to them,in order to examine detection and response methods to GPS attacks on ships by radio
waves.
Based on the results, we derive the appropriate response ﬂow, and propose the appropriate action ﬂow to be taken by the crew (navigator or communicator) in case of an
attack.

5.1 Organize navigation systems・Maneuvering・Navigation
techniques
The positioning performance of the navigation methods used in navigation is compared,
and the navigation systems that serve as tools for navigators are organized and theirapplications are discussed. GNSS, including GPS, is originally one of the radio navigation
methods, but is treated as a separate method from radio navigation in order to separate
the methods to be selected.

5.1.1 Comparison of positioning performance by navigation method
In the navigation technique described in Section 2.2, the method that can obtain
position information as an absolute position by each navigation method is shown in Table
5.1. Radio navigation systems such as the Loran system are inferior to GNSS satellites,
including GPS, which can communicate data from the sky, because the system has notbeen updated. In addition, the coverage area is dependent on the country where theservice is provided, so it is also inferior in terms of application range. As mentioned in
Section 2.2.4, many countries have discontinued the service.

5.1 Organize navigation systems・Maneuvering・Navigation techniques

41

Table. 5.1: Comparison of positioning performance by navigation method (Absolute
Position)
Accuracy

Scope of Coverage(Approx.)(Approx.)

GNSS

1m

Unobstructed-Radio navigation

100 m

1,000 kmMany abolished

Terrestrial Navigation

185 m

60 km

Nautical charts(location dependent)

are required

Celestial Navigation

185 m

Visual range

Aﬀected by Weather

MethodRemarks

Table. 5.2 shows the methods that can be used to obtain position information as arelative position for each navigation method in the navigation techniques described in
Section 2.2. Visual observation is a visual measurement by the navigator, who is thecrew of the vessel, and the navigational decisions are made by selecting and comparing
the actual sea conditions, each system, and each navigation method.
Table. 5.2: Comparison of positioning performance by navigation method (Relative Position)

MethodAccuracy(Approx.)Scope of Coverage

Remarks

Inertial navigation

300 m

Unlimited

Situation dependent

Visual100 m

Only when visibility is good-

5.1.2 Organize Categories
Each system, shiphandling and navigation system is divided into four layers as shown in
Fig. 5.1. ”Layer 4” is the full speciﬁcation of each system, maneuvering and navigationfor vessel position acquisition, and the number of available systems and navigation options
decreases as one moves from ”Layer 4” to ”Layer 3” to ”Layer 2” to ”Layer 1”.

42

Chapter 5

Proposed Method

Fig. 5.1: Navigation Systems and Maneuvering (Navigation) Categories (Layered)5.2 Response Chart to GPS Attack (Proposed Flow)43

5.2 Response Chart to GPS Attack (Proposed Flow)
The navigator operating a vessel must navigate the vessel to a safe position by appropriately selecting the maneuvering and navigation techniques described in Chapter 2,
depending on the sea area and conditions in which the vessel is navigating. The navigatormust choose which maneuvering and navigation technique to apply based on the current
ship’s condition. However, the current state of the art is that which navigation techniqueand tool to use in the event of a GPS attack is still a matter of experience for each navigator, and has not yet been discussed. Therefore, this study proposes a ﬂow of measures
to be taken in the event of a GPS jamming/spooﬁng attack.
Assuming four ship situations from (A) 〜 (D), we propose the application of the ﬂows
shown in Fig. 5.2, Fig. 5.3, Fig. 5.4, Fig. 5.5. Then, we propose the application of
the ﬂow shown in Fig. 5.6 by synthesizing all of the ﬂows.
(A)

GPS unavailability
This is exactly the situation where an attack is made on GPS, and either thelocation information from GPS can’t be obtained, or the location information
has been falsiﬁed and does not indicate the correct location.

(B)

Area of ocean you are navigating (Outer Sea or Coastal Waters)(1) GPS attack in open sea (open sea with no land in sight)
The attack from land is likely to be by radio waves with high output power.
Attacks from the sea are likely to be made by ships and aircrafts sailing nearby.
The attacked vessel will lose its position and only know its direction ．
(2) GPS attack in near-shore (sea area near land, landmarks (lighthouses, etc.) visible)
Easy to execute attacks (low power is suﬃcient), regardless of whether they areat sea or on land. Tokyo Bay and other areas where vessels are crowded withships. When an attack succeeds, the inside of the bridge is in chaos, and a delay
in judgment can be fatal.
(C)

Weather Conditions
Vessels using celestial navigation cannot see the sun or planets if the weather in
the area they are navigating is anything other than ”clear”.

(D)

Visibility Conditions
Due to dense fog, heavy rain, etc., it is impossible to see the situation at sea fromthe ship’s bridge. Due to poor visibility, inertial navigation is applied to obtain

44

Chapter 5

Proposed Method

information on the vessel’s position, which is calculated and deduced from theheading in which the vessel is traveling.

Fig. 5.2: (A) Flow of handling GPS jamming/spooﬁng (GPS unavailability)

Fig. 5.3: (B) Flow of handling GPS jamming/spooﬁng (Area of ocean you are navigating)5.2 Response Chart to GPS Attack (Proposed Flow)

Fig. 5.4: (C) Flow of handling GPS jamming/spooﬁng (Weather Conditions)Fig. 5.5: (D) Flow of handling GPS jamming/spooﬁng (Visibility Conditions)

45

46

Chapter 5

Proposed Method

Fig. 5.6: Flow of actions to be taken by navigators in response to GPS jamming/spooﬁng

47

Chapter 6

Evaluation
We will conduct experiments and evaluate the similarity of the ﬂowchart shown in Fig.
5.6, conﬁrming the impact on ship operations and insecurity issues when assuming thata spooﬁng attack, which is considered to have the greatest impact on ships, occurs during
navigation using GPS radio waves.

6.1 Attack Feasibility
There have not been many evaluations of the feasibility of realizing jamming, spooﬁng,
and meaconing attacks in the ﬁeld. Attacks on the most common types of receivers, suchas cell phones and automobiles, are impractical due to the high degree of diﬃculty relative
to the return of beneﬁt to the attacker.
On the other hand, targets such as ships, airplanes, and power plants remain of higher
value.

6.1.1 Execution cost and eﬀort
The cost should be evaluated in terms of the practical costs associated with the simulation and the device according to the speciﬁcations of the GPS jammer and spoofer
devices described in Section 4.1, which depend on the speciﬁcations of the GPS jammer
and spoofer devices that will be used as attack tools and the type of attack targets to beconstructed. Much of this is so far only theoretical. However, simple GPS jammer devices
are available at low cost, in the order of tens of thousands of yen [48].

6.1.2 Required cost of simulator
Software to generate one or more GPS satellites is available from simulator manufacturers. There are two types: analog and digital [58]. Analog ones tend to be very expensive,
up to $ 500,000, because they require a separate transmitter to represent each satelliteChapter 6

48

Evaluation[58].

6.1.3 Required Cost of Meaconing
There are not too many references to building an instrument meaconner to realize
meaconing. However, it is expected to be relatively easy to build a meaconar based ona software-deﬁned radio (SDR), which sells for $ 2,300, and a wideband transceiver foran additional cost of $ 700. This could be combined with signals acquired from a GPS
antenna and played back after a delay [52]. However, introducing variable delays for
SCER (Security Code Estimation and Replay) and separating the various satellite signals
would require software development, and the ﬁnal cost would probably approach that ofan inexpensive full simulator.

6.2 Experiment6.2.1 Environmental for Experiment
Experiments were conducted to determine the impact of GPS spooﬁng on ship operations, to identify unsafe issues, and to clarify the similarity of the ﬂowchart shown in Fig.
5.6. In this study, a simulation of GPS spooﬁng was conducted using a ship-handlingsimulator device with the cooperation of ”National Institute of Technology, Hiroshima
College” *1 , and a simulation was conducted by a navigator with experience in ship operation. As shown in Fig. 6.1, the simulation was conducted with two people on duty:
the navigator on navigational duty and the helmsman who operates the steering system.
This is a typical duty system under typical traﬃc conditions in a typical sea area.
In this study, we constructed a GPS-spoofed scenario and investigated the eﬀects on thenavigation system through the behavior of the navigators, the trajectory of the voyage, anda questionnaire survey. In conducting the experiment, the subjects and the questionnaire
survey were conducted in accordance with the Ethics Code of the Japanese Psychological
Association.
The composition of the experimental environment is shown in Table. 6.1, and theitems of the questionnaire are shown in Table. 6.2.

*1 National

College of Technology in Osakikamijima-cho, Toyota-gun, Hiroshima, Japan. Department of Maritime Technology, Department of Electronic Control Engineering，Department
of Distribution and Information Engineering，Department of Maritime Systems Engineering：https://www.hiroshima-cmt.ac.jp/

6.2 Experiment49

Fig. 6.1: Experiments (test subjects) in the shiphandling simulator （Experimenter (before) & helmsman (after) )Table. 6.1: Experiment Simulator Conﬁguration
No.

Systems

Figure1Marine radar

Fig. 6.2

2

ECDIS

Fig. 6.2

3

Steering System

Fig. 6.3

4

VHF telephone system

Fig. 6.4

50

Chapter 6

Evaluation

Table. 6.2: Questionnaire items for subjects
No.

Questions

Q1

Were you able to react to or identify a GPS spooﬁng attack?

Q2

When were you able to react or identify the GPS spooﬁng attack?

Q3

How did you feel when you were able to react to or identify a GPS
spooﬁng attack?

Q4

Were you able to shift to GPS-independent navigation without
hesitation?

Q5

What is the destination of the navigation system after GPS isdisabled?

Q6

What is the destination of the navigation system after the GPS
was disabled?

Q7

Other special notes (free text)

Fig. 6.2: Conﬁguration of Shiphandling Simulator【Marine Radar (Left)，ECDIS (Light)】

6.2 Experiment51

Fig. 6.3: Conﬁguration of Shiphandling Simulator【Steering System】

Fig. 6.4: Conﬁguration of Shiphandling Simulator【International VHF Radio Telephone
System】

52

Chapter 6

Evaluation

6.2.2 Experimental Scenario
The scenario is based on a comprehensive review of past incidents against ships [2], thecost, eﬀort, and beneﬁt of the attack, and the impact of the attack, and the likelihoodof a direct attack on a ship is very low. Therefore, this experiment assumes a terrorist
attack on a ”military base” that exists to protect the lives and property of citizens, oran ”airport” that may cause great damage to lives and the economy. Therefore, the areaaround ”Port Island of Kobe” and ”Kobe Airport” were chosen because the environment
is very similar to past incidents against vessels. The Port of Kobe was selected as theexperimental sea area.
• Physical security and ”Terrorist attacks” on military installations, etc. (past casetrends)• Attacks on aircraft, drones, etc. ( high impact )• Attacks on vessels are low, but secondary damage is possible.
The time was set for a 12:00 start (daytime). The target vessel was a 1000 GT classgeneral cargo ship. The experimental area is shown in ﬁg: 6.6, where the antenna position
that causes GPS spooﬁng is assumed to be located on the embankment of Port Island,
and the spooﬁng range is deﬁned as the yellow zone.
The target vessel is assumed to operate in the direction of 220 degrees from the starting
point, then turn to 265 degrees, and continue straight for a while before terminating (Fig.
6.6). During this time, eight other vessels, including crossers, slow co-travellers, antitravellers, and ﬁshing boats, were assumed to be operating simultaneously in the traﬃcenvironment. ﬁg. 6.7 shows this situation. The simulator operator was assumed to beable to contact other vessels and the Vessel Traﬃc Advisory Service Center (VTASC) *2
via ”International VHF Telephone System”, and to organize VHF contacts and traﬃcarrangements. The scenario was aborted in the case of failure to comply with the various
laws and regulations.
GPS spooﬁng was designed to shift the GPS position by about 300 m in a 0 degrees(Northward) direction when the vessel entered the spooﬁng range, and to restore the GPS
position when the vessel left the range (First spooﬁng). The ship’s position was thenshifted signiﬁcantly by about 30,000 m in a 45 degree (Eastward) direction near the end
point (Second spooﬁng). GPS spooﬁng aﬀects the AIS data superimposed on the Marine*2 Established by the Japan Coast Guard at seven locations in Japan. It provides information necessary

for the safe operation of vessels and performs centralized navigation control in the shipping lanes
and congested waters designated by the Maritime Traﬃc Safety Law and the Port Regulations Law.
https://www.kaiho.mlit.go.jp/soshiki/koutsuu/toudai/center.html

6.2 Experiment53

radar.
For this scenario, it is recommended to navigate above the line between ”Kobe Oki
No.1 Light Buoy” and ”Kobe Oki No.2 Light Buoy” (this light buoy is designed to rectify
vessel traﬃc ﬂow), and the 300 m northward deviation would cause the vessel to navigate
more to the south than expected if it were to navigate while observing this line, resulting
in an unsafe position. This would result in an unsafe position, which could easily lead toa head-on collision. Therefore, as a criterion for evaluation in this simulation, we judged
whether the ship’s trajectory was above the line between ”Kobe Oki No.1 Light Buoy”
and ”Kobe Oki No.2 Light Buoy”.
The subjects of the experiment were mariners with a third-class maritime engineer’s
license (navigation) or higher and at least one year of experience on board a 1,000 GTclass ship. The classiﬁcation was based on whether they had ”experience in voyaging to
the experimental area” or ”experience on operational vessels,” as shown in Table. 6.3.
All ship operators are Japanese maritime engineers who were educated in Japan.

Fig. 6.5: Experiment Flow

54

Chapter 6

Evaluation

Fig. 6.6: Sea area of experimentFig. 6.7: Navigational status of other vessels

6.2 Experiment

Table. 6.3: Subject’s background and other information
Test subject

Experience in voyaging

Experienceto the experimental area

in operating vessels

A

Yes

More than 5 years

B

Yes

More than 5 years

B

Yes

More than 5 years

C

No

More than 5 years

D

Yes

More than 1 year
Less than 5 years

E

No

More than 1 year
Less than 5 years

F

No

Less than 1 year

G

No

Less than 1 year

55

56

Chapter 6

Evaluation

By the way, if there is an error in the GPS data format entering the navigation system,
the system itself such as AIS, ship radar, ECDIS, etc. will output an error alarm indicating
the GPS data error because normal GPS data is not input to the system. If the alarm isfor only one system, it is expected that only the system for which the alarm was issued will
fail. In other words, in the case of a GPS jamming attack, all systems will simultaneously
output error alerts because they cannot receive normal GPS data.
On the other hand, in the case of a GPS spooﬁng attack, no error alarm is output fromthe input navigational system because there is no abnormality in the GPS data format
since it is a falsiﬁcation of location information. Therefore, a GPS spooﬁng attack causes
a discrepancy between the ship’s own ship and radar image displayed in ECDIS and theelectronic nautical chart (ENC), as shown in Fig. 6.8, without an error alarm being
output. This is the ﬁrst indication that the ship’s navigator is aware of a possible GPS
spooﬁng attack.

Fig. 6.8: GPS spooﬁng

6.3 Experimental Results and Discussion

57

6.3 Experimental Results and Discussion
6.3.1 Vessel Trajectory Results
Fig. 6.9 shows the results of the ship’s trajectory using the ship-handling simulator.
Fig. 6.9 shows that all seven subjects were able to navigate above the line between”Kobe Oki No.1 Light Buoy” and ”Kobe Oki No.2 Light Buoy”. Therefore, it is clearthat they were navigating safely, and the proposed response chart is presumed to be
similar. However, in two cases, the ship terminated without any signiﬁcant change in thesituation before the end point, resulting in a northward-ﬂowing wake.

6.3.2 Questionnaire Survey Results
Next, the questionnaire shown in Table. 6.2 was administered to seven subjects after
the test. The results of the questionnaire are shown in Table. 6.4. According to Table.
6.2, six subjects responded that they were able to react and grasp the GPS spooﬁng attack,and one subject responded that he was unaware of the GPS spooﬁng attack. However,this result indicates that none of the subjects noticed that they had been spoofed after
the ﬁrst GPS spooﬁng attack, which shifted the GPS spooﬁng 300 m to the north, andthat they only became aware of the spooﬁng after the second attack. The subjects wereable to notice the spooﬁng by checking the ECDIS and the ship’s radar behavior after thevessel changed course.
The following two points can be inferred from the ship’s wake results and the questionnaire results.
1. GPS spooﬁng attacks, which provide ﬁne-grained changes, are less likely to aﬀect
experienced coastal navigators.
2. Navigators who tend to check ECDIS preferentially are more susceptible to GPS
spooﬁng attacks.
First, it can be inferred that an attack by a slight position change of about 300 m
in GPS spooﬁng may have little impact. This is because navigators who mainly haveexperience in coastal navigation mainly use geographic navigation (navigation using chartcross bearings) and radar navigation (navigation using shipboard radar) and do not pay
attention to the GPS position on ECDIS (electronic charts). Therefore, this inﬂuence isconsidered to be small. However, depending on the opposite viewpoint, it is highly likelythat they have already moved to ”Layer 1” and ”Layer 2” in the proposed response
chart (Fig. 5.6), and the proposed response chart can be implemented without any
discomfort as the behavior of navigators who usually navigate in Japan, especially those

58

Chapter 6

Evaluation

who are engaged in coastal navigation. It is assumed that the proposed response chart
can be implemented without any discomfort as the behavior of navigators who navigate
in Japan, especially in coastal navigation. It is also assumed that in waters where there
is a lot of traﬃc ﬂow, it is necessary to visually assess the sighting relationship of vessels,
and that the tendency to emphasize sighting was observed because safe navigation is notpossible without cross bearings using surrounding scenery and nautical charts.
On the other hand, there was one case in which a subject who was navigating while
keeping an eye on ECDIS made a mistake in recognizing his own position during GPS
spooﬁng, resulting in a signiﬁcant deviation from the planned navigation route and a panicked response later. This was presumably caused by the fact that the subjects tended
to trust ECDI, which can grasp a large amount of information, and to check it preferentially, unlike navigators who mainly have experience in coastal navigation, who tend toemphasize the aforementioned visual observation in vessel operation.
In the second GPS spooﬁng attack, which caused a large GPS displacement of 30,000
m to the east, some mariners noticed the anomaly and responded to it by checking the
instruction manuals and other documents. In addition, there were cases where navigators
reported ”navigation system anomalies” to the Maritime Traﬃc Center using an international VHF telephone system before entering waters covered by the Maritime Traﬃc
Safety Act, i.e., waters that require the use of an appropriate navigation system. Thisaction has precedents in past related studies, and it is assumed that it may be customary to do so [4][49]. In addition to the Maritime Traﬃc Center, the international VHF
telephone system may be used as a means of conﬁrmation with other vessels, and such
communications for fact-ﬁnding and reporting are likely to increase in areas where many
vessels are navigating. As a result, the radio frequencies for distress and emergency communications may be blocked, resulting in a temporary loss of communication between
vessels and between vessels and land. Because of this potential secondary damage, it isassumed that maritime traﬃc centers need to be aware of this possibility.

6.3 Experimental Results and Discussion

Fig. 6.9: Ship’s wake (Voyage track: red dotted line)

59

60

Chapter 6

Evaluation

Table. 6.4: Results of post-experiment questionnaire to subjects
No.

Questions

Summary

Results

Q1.

Were you able to react to or

Reaction or understanding was possi-

6

grasp the spooﬁng attack?

ble.
Response or could not be ascertained.

Q2.

When were you able to react or

I knew when I was blown wide open (thegrasp the spooﬁng attack?

second spoof), but I had no idea about

1

the exquisite spoof (the ﬁrst spoof).
I understood that my ship had disappeared, but I did not think it was an
attack.
I felt that the ship radar was behaving
strangely.
I didn’t see anything special about Marine Radar or ECDIS.
After changing the needle position, theship’s position was determined when
the ship checked the ECDIS screen to
determine its position.
Q3.

Q4.

How you feel when you are able

I felt fear.

0

to react to or grasp a GPS spoof-

I felt impatience.

3

ing attack.

I didn’t feel anything.

2

Other

2

Have you been able to transition

Migrated.

5

to GPS-independent operations

Could not migrate.

2

What is the transition destina-

Other GNSS

0tion for the navigation system

Radio Navigation

0

after GPS unavailability?

Terrestrial Navigation

2

Celestial Navigation0

Inertial Navigation

0

Visual Navigation

4

Other Method1

without hesitation?
Q5.

6.3 Experimental Results and Discussion

61

Table. 6.4: Results of post-experiment questionnaire to subjects
No.

Questions

Q6.

What is the transition destina-

Other GNSS

0tion for the navigation system

Radio Navigation

0

after GPS unavailability?

Terrestrial Navigation2(Answer any other voyage sys-

Celestial Navigation0

tems used other than those

Inertial Navigation0

in Q5.)

Visual Navigation

4

Other Method

1

Q7.

Other special remarks

Summary

Results

I noticed a problem with the ECDISand ship radar, but did not think
to take any particular action because
Kobe was a familiar place to me.
The Akashi Kaikyo Channel is a difﬁcult route, so our ﬁrst priority was
to keep the ship safe.

If I had had

the manpower, I would have solved the
problems that occurred in ECDIS. Usually, I navigate by comparing what I see
with my own eyes and the bearing to
the charts.
Before entering the Akashi Strait,
ECDIS and ship’s radar malfunctioned,
so we were not sure whether we could
continue to sail, so we contacted the Osaka Bay Marine Traﬃc Center via VHF
for conﬁrmation.
The vessel radar and ECDIS were reactivated.
In order to ﬁnd the cause of the error,
we searched for the operation manualsof the Marine Radar and ECDIS on thebridge. If the error was not resolved
after reading the manual, you called the
manufacturer to solve the problem.

62

Chapter 6

Evaluation

Table. 6.4: Results of post-experiment questionnaire to subjects
No.

Questions

Q7.

Other special remarks

Summary
I did not feel much of a sense of urgency
because I frequently changed course
settings based on the movements ofsurrounding vessels rather than being
aware of course lines.
In this case, we did not pay much attention to the ship’s position because we
had checked the charts before the experiment to make sure that there were
no obstacles or obstacles in the water.

Results

63

Chapter 7

Summary and Future Issues
This study proposes a response chart for the eﬀect of GPS spooﬁng on the navigation
system and the response after GPS spooﬁng, which are the most threatening factors in theoperation using electronic chart display systems (ECDIS/ECS). The purpose of this study
was to clarify the similarity of the response chart and the response after GPS spooﬁng
through an experiment using a navigation simulation for Japanese mariners educated inJapan.
The following ﬁndings were obtained from the results of this study.
• Japanese mariners with insuﬃcient knowledge of the threat of cyber-attacks wereable to shift to GPS-independent operations without hesitation and to continue
safe operations, even though they were unable to respond to or understand GPS
spooﬁng.
• On the other hand, Japanese mariners who were not able to grasp the response chart
and were dependent on ECDIS were found to be unable to grasp the situation andconducted unsafe operations.
• In the case of damage caused by GPS spooﬁng, the aﬀected vessels may increase thecommunication between the vessel and the marine traﬃc center using ”International
VHF Telephone System”, as well as between the vessel and the land.
These results conﬁrm the similarity of the response chart shown in Fig. 5.6. The
response chart is considered to be an important measure required of navigators for theoperation of vessels that will be increasingly automated in the future.
On the other hand, future issues in this study are mainly as follows.
• Handling of operators with little experience in navigating in near-shore waters• Time required to shift navigation timing• Incident response in case of anomalies in other sensors• Security measures for other GNSS

64

Chapter 7

Summary and Future Issues

The subjects of the experiment in this study are Japanese maritime engineers withvarying levels of experience navigating and operating vessels in the experimental area, so
the rules of the route and the sea area to be trained are mainly the waters surrounding
the Japanese archipelago. On the other hand, if foreign mariners with little experiencenavigating in Japan’s neighboring waters were subjected to this experiment, it is highly
likely that they would not be able to understand the situation as well as mariners who
relied on ECDIS, and thus would be more likely to operate unsafely.
Since the experiment in this study was conducted to verify the similarity of mariners’
behavior to the proposed response chart and GPS spooﬁng, the exact behavior of themariners was not veriﬁed. Therefore, we believe that by verifying the timing (time) of
the navigation transition, the time required, etc., it may be possible to derive detailed
countermeasures when subjected to radio interference, including jamming.
If a cyber-attack occurs that disables shipboard radar, which is a tool for applying geo
navigation, and gyro-compass, which is necessary for applying inertial navigation, as anindication that the subject has detected GPS spooﬁng, it is highly likely that the existing
system alone will not be suﬃcient to ensure safety. Therefore, it is necessary to consider
incident response in the event of an anomaly in sensors other than GPS.
As a future development of GNSS, the ”QZSS Signal Authentication Service” [40],”
which is scheduled to be provided from FY2024, will enable conﬁrmation that signals
received by GNSS receivers are true signals transmitted from positioning satellites, andthus it is expected that measures will be taken to prevent GPS spooﬁng in the AsiaOceania region only. This research is expected to be able to take countermeasures against
GPS spooﬁng in Asia and Oceania. Since this study mainly focused on GPS, it is necessary
to consider further assumptions including GNSS including QZSS in the future.
In addition to the navigation methods discussed in this study, there is a new navigation system, quantum navigation, which uses a quantum compass. Quantum compass is
said to be able to measure position without the use of GPS, combining the accuracy ofquantum technology with measurement technology such as gyrocompass, which provides
conventional ”self-position estimation [59]. Quantum navigation has been successfully
tested and implemented by the Royal Navy, which was the ﬁrst in the world to installa quantum navigation system on a submarine [60]. This success is attracting worldwide
attention as it represents an important step forward in naval technology and will havea positive impact on improving the navigability and operational eﬃciency of ships in avariety of maritime scenarios.

65

Acknowledgment
I would like to express my deepest gratitude to Professor Suzaki of the Graduate Schoolof Information Security for his great guidance throughout this research as my supervisor. I
am grateful to Professor Doi and Professor Fujimoto of the Graduate School of Information
Security for their advice and support as sub-reviewers in the preparation of this paper.
We also thank Associate Professor Kishi, and Mis. Sakamoto, Mis. Nomoto of National
Institute of Technology, Hiroshima College, and Mr. Hasegawa of LAC Co., Ltd. for theirgreat advice, experiments, and evaluations in conducting this research. Finally, we thankProf. Matsui., a visiting professor of the Graduate School of Information Security, for his
great advice and cooperation in the execution of this research. We would like to express
our gratitude to him.

67

References[1] NSM. 「risiko 2020」. https://nsm.no/getfile.php/131421-1587034764/NSM/
Hermans%20undermappe%20med%20bilder/NSM_Risiko_2020_web_0104.pdf, 2020.
(visited on Jan. 16, 2024).
[2] Per Håkon Meland, Karin Bernsmed, Egil Wille, Ørnulf Jan Rødseth, and Dag Atle
Nesheim. A retrospective analysis of maritime cyber security incidents. 2021.
[3] Anja Menzel and Lisa Otto. Connecting the dots: Implications of the intertwined
global challenges to maritime security. Global Challenges in Maritime Security: An
Introduction, pp. 229–243, 2020.
[4] Above Us Only Stars. Exposing GPS Spooﬁng in Russia and Syria. https://c4ads.org/wp-content/uploads/2022/05/AboveUsOnlyStars-Report.pdf, 2019.
(visited on Jan. 16, 2024).
[5] Robert Lemos. Coast guard warns shipping ﬁrms of maritime cyberattacks, 2019.
(visited on Jan. 16, 2024).
[6] Eric Tegle (Forbes JAPAN). 欧州で GPS 妨害が多発，航空機の運航に影響 発信源はロ
シアか. https://forbesjapan.com/articles/detail/68978, 2024.2.6. (visited on

Jan. 16, 2024).
[7] IMO. SOLAS―Consolidated Edition 2020. London, UK, 2020.
[8] IMO MSC. 1/Circ. 1595 e-Navigation Strategy Implementation Plan―Update 1.
London, UK, 2018.
[9] GPS: The Global Positioning System A global public service brought to you by the
U.S. government. https://www.gps.gov/. (visited on Jan. 16, 2024).
[10] 海上保安庁, ディファレンシャル GPS の廃止について. https://www.kaiho.mlit.go.
jp/10kanku/miyazaki/uminoanzen/kourohyoushiki/deta/dgpsnohaisi190301.
pdf, 2019. (visited on Jan. 16, 2024).
[11] IMO MSC. Resolution MSC.428(98) Maritime cyber risk management in Safety
Management Systems. London, UK, 2017.
[12] IACS. UR E26 ”Cyber Resilience of Ships.” IACS, 2022.
[13] IACS. UR E27 ”Cyber Resilience of On-board Systems and Equipment.” IACS, 2022.
[14] Saneyuki Senda and Kuniyasu Suzaki. Attack and Countermeasure for GPS-based

68

References

Ship Navigation Systems. Computer Security Symposium 2023 Collected Papers, pp.
1293–1300, 2023.
[15] Ayano Sakamoto, Rino Nomoto, Saneyuki Senda, TakumaTakuma Kishi, Kuniyasu
Suzaki, and Choichi Hasegawa. Basic study on the eﬀect s of ship GPS Spooﬁng
on navigation systems. Symposium on Cryptography and Information Security 2024
Collected Papers, 2024.
[16] 近藤信竹. AIS (自動識別通報装置). Techno marine 日本造船学会誌, Vol. 851, pp.
297–301, 2000.
[17] Marco Balduzzi, Alessandro Pasta, and Kyle Wilhoit. A security evaluation of ais
automated identiﬁcation system. In Proceedings of the 30th annual computer security
applications conference, pp. 436–445, 2014.
[18] Enricad Aﬄisio, Paolo Braca, Peter Willett. Malicious AIS spooﬁng and abnormal
stealth deviations: A comprehensive statistical framework for maritime anomaly detection. IEEE Transactions on Aerospace and Electronic Systems, Vol. 57, No. 4, pp.
2093–2108, 2021.
[19] Wu, Jianjun and Thorne-Large, James and Zhang, Pengfei. Safety ﬁrst: The riskof over-reliance on technology in navigation. Journal of Transportation Safety &Security, Vol. 14, No. 7, pp. 1220–1246, 2022.
[20] Alan G Bole, Alan D Wall, and Andy Norris. Radar and ARPA manual: radar, AI
and target tracking for marine radar users. Butterworth-Heinemann, 2013.
[21] International Electrotechnical Commission, et al. Maritime navigation and rediocommunication equipment and systems, track control systems, operational and performance requirements, methods of testing and required test results. IEC62065, pp.
64–72, 2002.
[22] Adam Weintrit. The electronic chart display and information system (ECDIS): an
operational handbook. CRC Press, 2009.
[23] Boris Svilicic, David Brčić, S Žuškin, and D Kalebić. Raising awareness on cybersecurity of ECDIS. TransNav: International Journal on Marine Navigation and
Safety of Sea Transportation, Vol. 13, No. 1, pp. 231–236, 2019.
[24] Mass Soldal Lund, Odd Sveinung Hareide, and Øyvind Jøsok. An attack on an
integrated navigation system. 2018.
[25] 松本吉春. 精説地文航法. 成山堂書店, 1997.
[26] 廣野康平. 天文航法の ABC: 天測の基本から観測・計算・測位の実際まで. 成山堂書店,
2020.
[27] 海上保安庁. 「天測暦」等の廃刊について. https://www1.kaiho.mlit.go.jp/KOHO/
announce.html. (visited on Jan. 16, 2024).
[28] Greg Tozzi. Toward Automated Celestial Navigation with Deep Learning. https://github.com/gregtozzi/deep_learning_celnav, 2020. (visited on Jan. 16, 2024).

69[29] United States. Coast Guard. Loran-C User Handbook. Department of Transportation,
Coast Guard, 1974.
[30] Walter Blanchard. The genesis of the Decca Navigator system. The Journal of
Navigation, Vol. 68, No. 2, pp. 219–237, 2015.
[31] J Kasper and C Hutchinson. The Omega navigation system–An overview. IEEE
Communications Society Magazine, Vol. 16, No. 3, pp. 23–35, 1978.
[32] 海上保安庁. 「慶佐次ロランＣ局の廃止について」. https://www.kaiho.mlit.go.jp/
info/kouhou/h26/k20140801/k140801-1.pdf. (visited on Jan. 16, 2024).
[33] Di Qiu, Dan Boneh, Sherman Lo, and Per Enge. Reliable location-based services
from radio navigation systems. Sensors, Vol. 10, No. 12, pp. 11369–11389, 2010.
[34] 海上保安庁. 「ロランＣ」. https://www.kaiho.mlit.go.jp/syoukai/soshiki/
toudai/lolanc/index.htm, 2014. (visited on Jan. 16, 2024).
[35] European GNSS Service Centre. What is Galileo. https://www.gsc-europa.eu/
galileo/what-is-galileo. (visited on Jan. 16, 2024).
[36] GLONASS. https://glonass-iac.ru/. (visited on Jan. 16, 2024).
[37] Beidou. http://www.beidou.gov.cn/. (visited on Jan. 16, 2024).
[38] NavIC. https://glonass-iac.ru/. (visited on Jan. 16, 2024).
[39] 内閣府宇宙開発戦略推進事務局. みちびきウェブサイト. https://qzss.go.jp/.
(visited on Jan. 16, 2024).
[40] 内閣府宇宙開発戦略推進事務局.「信号認証サービス」(みちびきウェブサイト). https://qzss.go.jp/overview/services/sv14_sas.html, 2023. (visited on Jan. 16, 2024).
[41] Nils Ole Tippenhauer, Christina Pöpper, Kasper Bonne Rasmussen, and Srdjan Capkun. On the requirements for successful GPS spooﬁng attacks. In Proceedings of the
18th ACM conference on Computer and communications security, pp. 75–86, 2011.
[42] Alan Bensky. Wireless positioning technologies and applications. Artech House, 2016.
[43] GPS.gov. GPS Standard Positioning Service (SPS) Performance Standard. https://www.gps.gov/technical/ps/2020-SPS-performance-standard.pdf, 2020. (visited on Jan. 16, 2024).
[44] Jon S Warner and Roger G Johnston. GPS spooﬁng countermeasures. Homeland
Security Journal, Vol. 25, No. 2, pp. 19–27, 2003.
[45] Stefan Erker, Steﬀen Thölert, Johann Furthner, and Michael Meurer. L5–the new
gps signal. Proceedings of IAIN, pp. 27–30, 2009.
[46] Brian C Barker, John W Betz, John E Clark, Jeﬀrey T Correia, James T Gillis,
Steven Lazar, Kaysi A Rehborn, and John R Straton. Overview of the GPS M codesignal. In Proceedings of the 2000 National Technical Meeting of the Institute ofNavigation, pp. 542–549, 2000.
[47] Elliott D Kaplan and Christopher Hegarty. Understanding GPS/GNSS: principles
and applications. Artech house, 2017.

70

References[48] Takeyasu Sakai. Security of GPS: Vulnerability and Countermeasures. IEICE Technical Report, Vol. 118, No. 193, pp. 1–6, 2018.
[49] Alan Grant, Paul Williams, Nick Ward, and Sally Basker. GPS jamming and theimpact on maritime navigation. The Journal of Navigation, Vol. 62, No. 2, pp. 173–
187, 2009.
[50] Daniel Medina, Christoph Lass, Emilio Pérez Marcos, Ralf Ziebold, Pau Closas, andJesús Garcı́a. On GNSS jamming threat from the maritime navigation perspective.
In 2019 22th International Conference on Information Fusion (FUSION), pp. 1–7.
IEEE, 2019.
[51] Dana, Goward. Mass GPS Spooﬁng Attack in Black Sea. https://www.maritimeexecutive.com/editorials/mass-gps-spoofing-attack-in-black-sea,

2021.

(visited on Jan. 16, 2024).
[52] Mark L Psiaki and Todd E Humphreys. Gnss spooﬁng and detection. Proceedings ofthe IEEE, Vol. 104, No. 6, pp. 1258–1270, 2016.
[53] Dennis M Akos. Who’s afraid of the spoofer? gps/gnss spooﬁng detection via automatic gain control (agc). NAVIGATION: Journal of the Institute of Navigation,
Vol. 59, No. 4, pp. 281–290, 2012.
[54] Ali Jafarnia-Jahromi, Ali Broumandan, John Nielsen, and Gérard Lachapelle. Predespreading authenticity veriﬁcation for gps l1 c/a signals. NAVIGATION: Journalof the Institute of Navigation, Vol. 61, No. 1, pp. 1–11, 2014.
[55] Esteban Garbin Manfredini, Beatrice Motella, and Fabio Dovis. Signal quality monitoring for discrimination between spooﬁng and environmental eﬀects, based on multidimensional ratio metric tests. In Proceedings of the 28th International Technical
Meeting of the Satellite Division of the Institute of Navigation (ION GNSS+ 2015),
pp. 3100–3106, 2015.
[56] Andriy Konovaltsev, Manuel Cuntz, Christian Haettich, and Michael Meurer. Autonomous spooﬁng detection and mitigation in a gnss receiver with an adaptive
antenna array. In Proceedings of the 26th International Technical Meeting of The
Satellite Division of the Institute of Navigation (ION GNSS+ 2013), pp. 2937–2948,
2013.
[57] 岸拓真, 濵崎淳, 清田耕司, 坂本彩乃. 船舶における OT 機器を伴うサイバーインシデント
へのレスポンスに関する教育プログラムの開発. 第 149 回講演会日本航海学会講演予稿集

11 巻 2 号, pp. 43–46, 2023.10.
[58] IIvan Petrovski and Takuji Ebinuma. Everything you always wanted to know about
GNSS simulators but were afraid to ask. Inside GNSS September (2010), pp. 48–58,
2010.
[59] Imperial College London. Imperial News「Quantum

compass

could allow naviga-

tion without relying on satellites」. https://www.imperial.ac.uk/news/188973/

71

quantum-compass-could-allow-navigation-without/, 2018. (visited on Jan. 16,2024).
[60] Imperial College London. Imperial News「Quantum sensor for a future navigation system tested aboard Royal Navy ship」. https://www.imperial.ac.uk/news/245114/
quantum-sensor-future-navigation-system-tested/, 2023. (visited on Jan. 16,2024).