International Mutual Recognition: A Description of Trust Services in US,

UK, EU and JP and the Testbed “Hakoniwa”

Satoshi Kai

, Takao Kondo

, Naghmeh Karimi

, Konstantinos Mersinas

, Marc Sel

, Roberto Yus

and Satoru Tezuka

Keio University, Tezuka-Laboratory, 5322 Endo, Fujisawa, Kanagawa, 252-0882 Japan

University of Maryland, Baltimore County, U.S.A.

Royal Holloway, University of London, Department of Information Security, U.K.

Keywords:

Mutual Recognition, Digital Trust, Signatures, Tampering, Impersonation, Testbed.

Abstract:

With the proliferation of digital transactions, trust is becoming increasingly important, as exempliﬁed by the

World Economic Forum’s Data Free Flow with Trust. Digital signatures are utilized to establish trust to prevent

spooﬁng and unauthorized modiﬁcation of transmitted digital data. However, the extent of trust is limited by

jurisdictions, trusted lists and bridge certiﬁcate authorities, and does not have international coverage. For this

reason, mutual recognition is needed, i.e. trust relationships established across countries. Establishing mutual

recognition is complex and time-demanding due to the legislations, systems, and technologies involved. In

parallel, electronic signatures consist of complex systems and structures and, thus, focusing on the technical

requirements and solutions can enhance mutual recognition processes. The purpose of our approach is to

develop a testbed that can verify technical aspects of mutual recognition. This paper describes the concept of

the testbed “Hakoniwa” which includes analyzing the requirements, simulating and testing mutual recognition

trust services across US, UK, EU and JP.

1 INTRODUCTION

The Internet of Things (IoT) is generating, collecting,

and storing large amounts of digital data as more

and more information from the real world can be

collected in cyberspace. The IoT enables us to collect

more information and reproduce real-world situation

in cyberspace in greater detail. This will enable

us to understand complex causes, predict future

phenomena and consider optimal countermeasures

and plans, which were more difﬁcult to achieve

before.

On the other hand, digital data has become

an object of interest to malicious actors, and it

has been subject to the threat of tampering and

spooﬁng. Especially when business applications

become highly dependent on digital data, tampering

or impersonation of digital data can lead to signiﬁcant

business damages. A typical example includes

business email fraud.

Under these circumstances, different countries

and organizations are designing measures to protect

international digital commerce. For instance, Japan

proposed the concept of Data Free Flow with Trust

(DFFT) (Digital Agency, 2019) in 2019. DFFT aims

to promote the free ﬂow of data internationally, where

data useful for business and social issues can freely

come and go without regard to national borders, while

ensuring trust in privacy, security, and intellectual

property.

However, in order for data to be transferred

freely without national borders obstacles, it is

increasingly necessary to conduct research that

includes different perspectives, including legal,

technological and societal ones. The authors

are conducting research on international mutual

recognition in three groups under the international

research framework INCS-CoE (INCS-CoE, 2022)

project.

• Technical group;

• Human group;

• Ontologies group.

In this paper we present the work of the technical

group which develops a testbed for international

mutual recognition with the aim of promoting

research in this ﬁeld. In the following sections, we

describe the basic concept of the testbed and the

selected use cases under consideration.

764

Kai, S., Kondo, T., Karimi, N., Mersinas, K., Sel, M., Yus, R. and Tezuka, S.

International Mutual Recognition: A Description of Trust Services in US, UK, EU and JP and the Testbed â

AIJHakoniwaâ

DOI: 10.5220/0012124200003555

In Proceedings of the 20th International Conference on Security and Cryptography (SECRYPT 2023), pages 764-771

ISBN: 978-989-758-666-8; ISSN: 2184-7711

 2023 by SCITEPRESS – Science and Technology Publications, Lda. Under CC license (CC BY-NC-ND 4.0)

2 OVERVIEW OF EACH

COUNTRY’S TRUST SERVICES

Countries have developed an infrastructure called

trust services for the creation, veriﬁcation, and

validation of electronic signatures, electronic seals

or time stamps, and their associated certiﬁcates

(EUR-Lex, 2014), as a mechanism to prevent digital

data from being tampered with or spoofed. This

chapter describes the status of trust services in each

country as shown in Table 1.

Table 1: Country comparison of trust services.

Items EU UK US JP

Legal eIDAS

eIDAS

FICAM

program

Electronic

Signature

Act

Trust service

representation

Trusted List Bridge

2.1 European Union

In 1999, a Directive of the European Parliament on a

Community framework for electronic signatures was

enacted. According to this Directive, an electronic

signature is considered equivalent to a handwritten

signature. The eIDAS Regulation (EUR-Lex, 2014)

is a groundbreaking direct law that ensures a certain

level of trust in the data in circulation to allow

for secure electronic transactions across different

countries within the EU. The eIDAS Regulation has

been enforced since 2016 and it gives legal effect to

trust services.

Article 3 of the regulation provides a deﬁnition of

trust services which shows digital signature, e-seal

and timestamp etc. Furthermore, it is stated that

each trust service “shall not be denied legal effect or

admissibility as evidence in legal proceedings solely

because it is in electronic form” (EUR-Lex, 2014).

The regulation speciﬁes that a National

Supervisory Body (Supervisory Body) is to

be established in each EU member state and a

Conformity Assessment Body is to be designated

to assess the conformity of Qualiﬁed Trust Service

Providers.

It stipulates that a Trusted List (TL) of qualiﬁed

trust service providers and services be compiled for

each member state, managed and published in a

uniform format, and that the information in the list

be machine-readable with an electronic signature or

e-seal. It also stipulates that the EU will make these

national lists publicly available.

As of November 2022, there are 222 qualiﬁed

trust service providers. A list of these Qualiﬁed

Trust Services is published in each of the EU

Member States in a machine-readable format called a

Trusted List (TL). In addition, a List of Trusted Lists

(LoTL) (eIDAS, 2022) links all Trusted Lists of the

EU member states.

2.2 United Kingdom

The UK eIDAS Regulation (ICO, 2022a) provides the

legal framework for the use of electronic trust services

offered within the UK and identiﬁes equivalent

services offered in the EU. Electronic trust services

can be used in a number of ways to provide

security for electronic documents, communications

and transactions, e.g. to help ensure that documents

sent electronically have not been altered in any way

and that the sender can be easily authenticated.

Electronic trust services allow for such security

properties to be applied and then validated and thus

help ensure conﬁdence in the electronic transfer of

information.

While being a member of EU, UK’s trust services

were listed on the UK TL (ICO, 2022b), which is

linked from the EU LoTL. After leaving the EU, UK

maintains its own UK TL according to UK eIDAS

2.3 United States

The United States (US) consider threats on its digital

information and communications infrastructure

as a signiﬁcant security challenge. In order

for the federal government to address these

threats, the security control measures necessary

to prevent and detect unauthorized access to federal

information technology networks, systems, and

data are critical. The Federal Identity, Credential,

and Access Management (FICAM) (FICAM, 2022)

initiative is a means for addressing the nation’s

cybersecurity needs. FICAM’s recommendations

include increasing the authentication strength of

individuals and devices, using privacy-enhancing

technologies, and expanding the availability of

identity management capabilities to address cyber

threats.

If the functions of Identity, Credential, and

Access Management (ICAM) for each agency run

independently, users are forced to deal with multiple

incompatible credential, authentication, and access

control functions. In addition, each ICAM function

has a separate administrative interface used for

registration and authorization management, which

would result in redundancy and inefﬁciency if left to

https://tl.ico.org.uk/uktrustedlist/UKTL.xml

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each agency. Therefore, when establishing functions

for use across federal applications, users needed to

re-establish credentials by providing identity proof

in each system across the federal government. For

that reason, the Federal PKI Trust Architecture (GSA,

2022)] was developed and consists of the Federal

Bridge Certiﬁcation Authority (FBCA) and the

Federal Common Policy Certiﬁcation Authority

(FCPCA).

2.4 Japan

The Electronic Signature Act of 2001 (Ministry of

Justice, 2022) establishes a legal foundation for

electronic signatures that is of equal validity to

handwritten signatures and seals. The Act states the

presumption that an electromagnetic record (e.g., an

electronic document) is authentic when it is signed

by a certain electronic signature of the person in

question.

The structure of the Japanese Certiﬁcation

Authorities is based on the Government Bridge

CA (GPKI, 2022) as its core, which is interconnected

with the GPKI (Government PKI), the LGPKI (Local

Government PKI), the Commercial Registration CA,

and the JPKI (Japanese PKI). In addition, private

accredited certiﬁcation authorities (JIPDEC, 2022)

are connected to the Government Bridge CA under

the Electronic Signature Act.

3 BASIC CONCEPT

There exist trust services which work in one country

or one region, but trust services amongst countries or

regions can be challenging. One solution for global

trust services is having a centralized trust service

as shown in Figure 1(a). Although there are some

example of centralized trust services (Adobe, 2023),

such a solution has signiﬁcant political, technical

and ethical considerations. Another solution is a

mechanism called mutual recognition according to

which what is recognized as a trustworthy entity

in one country or region is also recognized as

trustworthy in another country or region. In this

fashion, trust services are connected to each other in

a decentralized manner as shown in Figure 1(b).

Without mutual recognition, trust services need

to conform to the norms of the country or region

where they are accepted. On the other hand, if

mutual recognition is in place, then a country’s own

national customs become trust for other countries and

regions. Especially since digital trade is becoming

commonplace, if following a country’s or region’s

trust services style becomes a trustworthy entity

for another country or region, the cost-effectiveness

of trust veriﬁcation can be improved. Such

cost-effectiveness can be achieved by the following

means:

• Scope increase for trust service veriﬁcation, via

mutual recognition;

• Equal footing with one’s own country or region.

Figure 1: Centralized versus Decentralized Trust Services

(adapted and modiﬁed from (Baran, P. , 1964)).

Focusing on mutual recognition, we identify two

practical models for connecting domains of trust: one

based on the Trusted Lists and the other based on the

Bridge (or Bridge CA) type, as shown in Figure 2.

Both these models require, for the sake of simplicity,

one Bridge CA or TL which cross-certiﬁes each CA

in its domain (e.g. in one country) in a connected

certiﬁcation fashion. Then, there is cross-certiﬁcation

of the corresponding entities (Bridge CAs or TLs)

across countries via mutual recognition. We do

not consider certiﬁcation hierarchies here, as having

a single Root CA at international level is more

challenging than establishing the pair-wise mutual

recognition. We also do not consider certiﬁcate chains

since, at governmental, country level, a connected

certiﬁcation model reduces the complexity of the

veriﬁcation process. In verifying certiﬁcates issued

by the trust service, path ﬁnding, path veriﬁcation,

and equal footing are common to both types. For

this purpose, it is necessary for a country or region

to support both the Trusted List type and the Bridge

type. In this study, we proceeded under the

assumption that Japan supports both types.

4 MUTUAL RECOGNITION

TESTBED “HAKONIWA”

Mutual recognition takes time to be established

because of the variety of laws, systems, and

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Figure 2: Two types of mutual recognition.

technologies involved. On the other hand, since

digital signatures consist of complex systems,

exploring possible technical solutions can enhance

mutual recognition processes. A trust service

infrastructure based on international mutual

recognition is built at Keio University so that it

can be easily accessible. This section describes the

testbed requirements for mutual recognition.

Figure 3: Overall picture of testbed.

4.1 Trust Service Veriﬁcation in Each

Country or Region

The testbed enables us to simulate the veriﬁcation of

trust services in each country and region. All trust

services include servers for signature and certiﬁcate

veriﬁcation, as shown in Table 2.

Table 2: “Hakoniwa” trust service design.

Items EU UK US JP

Trusted List

representation

EU LoTL

MS TL

UK TL N/A

(New)

JP TL

Bridge

representation

N/A N/A FBCA

(New)

JBCA

• The EU trust service infrastructure includes EU

LoTL and MS TL.

• The UK trust service infrastructure includes the

UK TL.

• The US trust service infrastructure is equipped

with the FBCA (Federal Bridge CA).

• The JP trust service infrastructure includes a

tentative JP TL and JBCA hypothetically.

4.2 Trust Service Veriﬁcation According

to Mutual Recognition

The testbed enables to simulate technical part of

mutual recognition between countries.

• Tentative mutual recognition between Trusted

Lists.

• Tentative mutual recognition of Bridge CAs.

Mutual recognition between the Trusted List type and

the Bridge type will be achieved through Japan by

having Japan support both types of representation.

4.3 Provides an Easy-to-Use API from

the Application

The testbed enables us to verify both the signature

and certiﬁcate issued by the trust service. For the

purposes of usability, the testbed provides two types

of interfaces:

• A Web interface for direct human operation; and

• REST API for machine-readable.

REST API is for IoT devices that supports

communication between web applications. In most

cases, JSON is used over HTTP for data transfer.

5 TESTBED “HAKONIWA” BASIC

DESIGN

The trust service infrastructure was conﬁgured

as virtual machines and virtual networks. This

section provides an overview of these. The trust

service infrastructure in each country will enable the

veriﬁcation of Qualiﬁed Services for each country.

5.1 Countries’ Network and Server

Designs

The virtual network for “Hakoniwa” is shown in

Figure 4. The virtual network was conﬁgured by

dividing it into segments that simulated the networks

of different countries. From the management

network, each country’s network can be accessed.

The networks in each country are also mutually

accessible.

International Mutual Recognition: A Description of Trust Services in US, UK, EU and JP and the Testbed â

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Figure 4: Virtual network conﬁguration.

Figure 5 shows the server conﬁguration within

the JP network. The server conﬁguration consists of

(a) certiﬁcate issuing, (b) signature generation, and

One feature of the Japanese network is hypothetically

that it is equipped with both Trusted List type

veriﬁcation and Bridge type veriﬁcation. This server

conﬁguration enables path ﬁnding, path veriﬁcation,

and equal footing for both types.

Figure 5: JP server conﬁguration.

The server conﬁguration of the EU network is

shown in Figure 6. As in the Japanese case, it consists

of (a) certiﬁcate issuing, (b) signature generation, and

One additional feature is that the Trusted List type

consists of two levels, i.e., a Trusted List for EU

member states and a List of Trusted Lists for the EU

as a whole.

Figure 6: EU server conﬁguration.

The server structure of the US network is shown

in Figure 7 and it consists of (a) certiﬁcate issuing,

(b) signature generation, and (c) signature veriﬁcation

and certiﬁcate validation, as in JP (Figure 5) and the

EU (Figure 6). One feature of US is that bridge CAs

are multi-tiered.

Figure 7: US server conﬁguration.

5.2 Mutual Recognition Between

Countries

This section describes the logical connection between

Trusted Lists and Bridges, respectively, in order to

technically realize mutual recognition. This mutual

recognition allows veriﬁcation across countries,

unlike trust services that are conﬁned in each country.

5.2.1 Trusted List Type

In our approach, it is assumed that JP TL and EU

LoTL are equivalent and mutually recognized by JP

and EU LoTL for path construction, path veriﬁcation

and equal footing. Their relationship is shown in

Figure 8. The JP TL points to the EU LoTL by URI

(Uniform Resource Identiﬁer) and includes a public

key certiﬁcate to verify the digital signature of the EU

LoTL. Conversely, the EU LoTL includes a public

key certiﬁcate to verify the digital signature of the JP

TL, along with a URI to point to the JP TL.

As shown by the real line, when signing in the EU

and verifying in JP, the path is traced from the JP TL

to the EU LoTL and then to the MS TL. Conversely,

as shown by the dotted line, in the case of signing in

JP and verifying in the EU, the path starts from the

EU LoTL and ends at the JP TL.

The information for equal footing is shared

between LoTL and JP TL in the same sense of

qualiﬁcation. LoTL speciﬁes JP TL’s qualiﬁed

digital signature (a digital signature that conforming

to hypothetical Japanese law), e-seal (an electronic

signature that authenticates that the document was

issued by a legal entity), and time stamp as

EU-equivalent qualiﬁed services, respectively, while

JP TL does the same. and EU’s qualiﬁed

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Figure 8: Trusted list type mutual recognition.

digital signature, e-seal, and timestamp are each

designated as a qualiﬁed service equivalent to JP.

The information for this equal footing i.e. equivalent

meaning of each trust services, is outside the scope

of this study, although it is important to highlight

that there are legal challenges for mutual recognition,

beyond the technical ones.

The speciﬁcation of such equivalent meaning is

addressed by the ontology team. Two approaches

are followed. The ﬁrst approach consists in the

creation of a new ontology by integration of existing

relevant ontologies. The second approach makes

use of enterprise data created and made public

under controlled conditions to add instance data to

a knowledge graph. The trustworthiness evaluation

policy is extended to make use of this additional

information during evaluation. The enterprise data

from GLEIF

is used as instance data. The T E

(Trustworthy Ecosystem) ontology proposed by Sel

(Sel and Mitchell, 2021) is used to build the

knowledge graph. Querying the graph allows a trustor

to interpret information about a potential trustee

according to a trustworthiness policy with semantics

that are formally speciﬁed in OWL Description Logic.

5.2.2 Bridge Type

Japan already has a government Bridge CA, but

its purpose is to verify LGPKI and JPKI, not a

Bridge CA to connect to other countries. Since the

FBCA is originally intended for Bridge certiﬁcation

with legacy CAs and CAs in other countries, it was

assumed that existing FBCAs would be connected

to the JBCA. A diagram of the relationship between

Bridge CAs is shown in Figure 9.

Information for equal footing is shared in the

JBCA and FBCA mutual authentication certiﬁcates.

In certiﬁcates issued by the JBCA to the FBCA,

the certiﬁcate policies deﬁned in the CP/CPS of the

FBCA will be mapped to the JP’s certiﬁcate policies.

Publicly published daily, available at https://data.

world/gleif

Figure 9: Bridge type mutual recognition.

For certiﬁcates issued by the FBCA to the JBCA, the

certiﬁcate policy deﬁned in the CP/CPS of the JBCA

will be mapped to the US certiﬁcate policy. These

mappings are expressed as correspondence between

the OIDs of the certiﬁcate policies.

5.3 Digital Signature and Veriﬁcation

Flow

The ﬂow of signature creation in EU and signature

veriﬁcation in JP is shown in Figure 10. In the

ﬁgure, the upper part in white is the application and

the lower part in blue shading is the trust service

infrastructure.

(a) The EU client generates a key pair, and the

EU trust service grants a certiﬁcate to the public key.

(b) The EU client signs the document with its

own private key. The client passes the three sets

(document, signature, and public key certiﬁcate) to JP.

client veriﬁes the signature and the certiﬁcate using

the trust service infrastructure. Those results are

output as a veriﬁcation report.

Figure 10: Veriﬁcation ﬂow when EU entity is as

subscriber; JP as relying party.

The ﬂow of signature generation by JP and

signature veriﬁcation by EU is shown in Figure 11.

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Veriﬁcation is the reverse process to the explanation

shown in Figure 10, from EU to JP.

Figure 11: Veriﬁcation ﬂow when JP entity is as subscriber,

EU entity as relying party.

In both cases, the common point is that the relying

party veriﬁes the signatures created in other countries

using its own trust service infrastructure and the

relationship this infrastructure established with the

other trust service infrastructure.

6 FUTURE RESEARCH AND USE

CASE

A use case to demonstrate mutual recognition

considering invoices across countries is work in

progress, as shown in Figure 12.

Figure 12: Sample showcase of invoicing.

The scenario is as follows: a supplier in country

A sends goods or services to another country X, and

issues an invoice. The sender in country A signs the

invoice with his/her private key and sends the three

variables (invoice, signature value, and public key

certiﬁcate, these are all included in XML Advanced

Electronic Signature, XAdES format) to another

country X. In another country X, the recipient veriﬁes

the above 3-variable set with its own trust service

infrastructure. At this point, the mutual recognition

mechanism (path ﬁnding, path veriﬁcation and equal

footing) veriﬁes the validity of the certiﬁcate of one

country A. In country X, after the veriﬁcation of the

invoice validity, the amount of goods is be paid.

Indicatively, from the standpoint of Japan, the

Bridge CA method can be utilized, but Trusted Lists

are not an available option yet. Table 3 depicts the

envisioned items to be veriﬁed.

Table 3: Veriﬁcation item for trusted list type.

No. Item Description

1 Veriﬁcation

of List of

Trusted Lists

Verify the authenticity and integrity of the

List of Trusted Lists (XML).

2 Veriﬁcation

of Trusted

Lists for each

country

Verify the authenticity and completeness of

the Trusted List (XML). Do this for the

number of countries included in the List of

Trusted Lists.

3 Retrieval of

listed trust

services that

match the

certiﬁcate

Use the Trusted List to obtain information

on trust services that match the certiﬁcate

at a speciﬁc date and time.

4 Determination

of Qualiﬁed

Certiﬁcates

The Trusted List is used to determine

which type of qualiﬁed certiﬁcate

matches at a particular date and time.

Type of qualiﬁed certiﬁcate is one of

qualiﬁed digital certiﬁcate, qualiﬁed

e-seal, qualiﬁed website authentication

certiﬁcate

5 Determination

of Qualiﬁed

Signature/e-Seal

Generating

Device

(QCSD)

Using the Trusted List, determine that the

private key corresponding to a qualifying

certiﬁcate is present in the QCSD at a

particular date and time.

6 Determination

of Qualiﬁed

Time Stamp

Use the Trusted List to determine that the

timestamp token was a qualiﬁed timestamp

at the time it was generated.

Future research tasks include:

• The creation of the aforementioned use case;

• An analysis of the requirements for consistency of

trust services components for equal footing, and

• The mapping of these requirements against legal

interpretations.

7 CONCLUSION

There is a mutual recognition mechanism for trust

services which are recognized as qualiﬁed in one

country to be also recognized as qualiﬁed in another.

It will take a considerable amount of time for mutual

recognition to become operational. In this study, we

present a testbed to try out mutual recognition from

a technical perspective. The testbed simulates the

trust service infrastructure of the EU, UK, US, and

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Japan, and examines both the Trusted List and Bridge

CAs methods of mutual recognition across countries

to be tested. Future research involves the expansion of

these methods into semantic representations to allow

for the internalisation of trust services.

ACKNOWLEDGEMENTS

This research was partially supported by grants from

the International Cyber Security Center of Excellence

(INCS-CoE). We would also like to thank Prof Niki

Panteli, from Royal Holloway, University of London,

for her support and contribution.

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APPENDIX

Abbreviations

CA Certiﬁcation Authority

CP Certiﬁcate Policy

CPS Certiﬁcation Practices Statement

CRL Certiﬁcate Revocation List

CSP Certiﬁcation Service Provider

DSS Digital Signature Service

EC European Commission

EU European Union

EUMS European Union Member States

FBCA Federal Bridge CA

GPKI Government PKI

JBCA Japanese Bridge CA

JP Japan

JPKI Japanese PKI

LGPKI Local Government PKI

LOTL List Of Trusted Lists

MS Member State

OCSP Online Certiﬁcate Status Protocol

PKC Public Key Certiﬁcate

PKI Public Key Infrastructure

OID Object Identiﬁer

QC Qualiﬁed Certiﬁcate

QSCD Qualiﬁed Signature/e-Seal

Creation Device

TL Trusted List

TSA Time-Stamping Authority

TSL Trust-service Status list

TSP Trust Service Provider

TST Time-Stamp Token

XAdES XML Advanced Electronic

Signature

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