ISO/TR 23644:2023

TECHNICAL ISO/TR
REPORT 23644
First edition
2023-05
Blockchain and distributed ledger
technologies (DLTs) — Overview of
trust anchors for DLT-based identity
management
Reference number
© ISO 2023
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 1
5 Types of trust anchors . 2
5.1 Overview . 2
5.2 Legal trust anchors . 3
5.3 Data trust anchors . 4
5.4 Cryptographic trust anchors . 5
5.5 Cybersecurity trust anchors . 5
5.6 Social trust anchors . 6
6 Existing trust anchors for DLT-based identity management . 7
6.1 Overview . 7
6.2 Cryptographic trust anchors in public key infrastructures . 8
6.3 Cryptographic trust anchors — Federated PKI . 10
6.4 Social trust anchor architectures .12
6.5 Cryptographic trust anchors — Autonomic identifiers .13
6.6 Data trust anchors in eID regulations – eIDAS Regulation .13
6.7 Data trust anchors in non-PKI-based SSI solutions using DIDs . 16
6.8 Data trust anchors in non-PKI-based, non-DID partial SSI solutions using ZKP . 18
7 Using trust anchors .19
7.1 Representing multiple dimensions of risk . 19
7.2 Chains of trust . 21
7.2.1 General . 21
7.2.2 Legal trust anchors . 21
7.2.3 Data trust anchors . 21
7.2.4 Cryptographic trust anchors . 21
7.3 Use of trust anchors in applications . 22
Bibliography .23
iii
Foreword
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This document was prepared by Technical Committee ISO/TC 307, Blockchain and distributed ledger
technologies, in collaboration with Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 27, Information security, cybersecurity and privacy protection.
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iv
Introduction
In recent years, new decentralized digital identity management systems have emerged, some of
them based in distributed ledger technologies (DLTs) providing support functions. As explained in
ISO/TR 23249, these include associating identifiers with public keys, supporting the attestation of
credentials, enabling credentials revocation, defining common credential templates or implementing
trust anchors.
DLT systems provide and rely on different types of trust anchors for DLT-based identity management,
each being important in terms of some dimension of policy, technology, data, security, assurance, etc.
Each trust anchor presents opportunities and risks to a DLT-based identity management system, and the
DLT-based identity management system actors need guidance and standards to develop an appropriate
operating model and risk mitigation strategy.
However, the DLT-based identity management system actors have also to take into account risks,
including those shared with other organizations in chains of trust, and to have a governance model
that is suitable for distributed and decentralized ecosystems formed by multiple actors. The DLT-
based identity management system actors have to consider technological change and new types of
technology with new risks that can address, create or result in opportunities and threats. The overall
effectiveness of the DLT-based identity management system is critically dependent on the quality of the
data it holds and shares; this is a high priority in DLT-based identity management system governance
and operational models.
This document provides an overview of trust anchors for DLT-based identity management systems.
v
TECHNICAL REPORT ISO/TR 23644:2023(E)
Blockchain and distributed ledger technologies (DLTs) —
Overview of trust anchors for DLT-based identity
management
1 Scope
This document describes concepts and considerations on the use of trust anchors for systems leveraging
blockchain and distributed ledger technologies (DLTs) for identity management, i.e. the mechanism by
which one or more entities can create, be given, modify, use and revoke a set of identity attributes.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 22739:2020, Blockchain and distributed ledger technologies — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 22739:2020 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Abbreviated terms
AML anti-money laundering
BIP bitcoin improvement proposal
CA certification authority
CAB Certification Authority Browser (CA/Browser)
DID decentralized identifier
DKMI decentralized key management infrastructure
DKMS decentralized key management system
DLT distributed ledger technology
eIDAS electronic identification, authentication and trust services
ETSI European Telecommunication Standards Institute
EU European Union
ID identity
IDP identity provider
IETF Internet Engineering Task Force
IoT internet of things
IP internet protocol
KERI key event receipt infrastructure
KYC know your customer
LoA level of assurance
LoIP level of identity proofing
MPC multi-party computation
OID object identifier
PDP policy decision point
PKI public key infrastructure
RFC request for comments
RP relying party
SED self-encrypting drive
SSI self-sovereign identity
ToIP trust over IP
TPM trusted platform module
UID unique identifier
VC verifiable credential
ZKP zero knowledge proof
ZVE zero knowledge proof verification engine
5 Types of trust anchors
5.1 Overview
Identity management is defined in ISO/IEC 24760-1:2019, 3.4.1, as the “processes and policies involved
in managing the lifecycle and value, type and optional metadata of attributes in identities known in a
particular domain”. ISO/IEC 24760-1:2019, 3.1.2, defines identity as a “set of attributes related to an
entity”, and ISO/IEC 24760-1:2019, 3.1.3, defines an attribute as a “characteristic or property of an
entity”. Parties involved in identity management, such as relying parties (RPs), typically have trust
relationships among them based in various features, which can be collectively designated as trust
anchors.
There is no single definition of a trust anchor because it can mean different things to different people.
NOTE Some authors identify different types of trust anchors, including government trust anchors (i.e. see
Reference [38]).
However, for the purposes of this document, the following five different types of trust anchor are
described that exist
...