README.md

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Learn about Decentralized Trust Chains (DTCs) on cheqd.	title description tableOfContents outline pagination visible true visible true visible true visible true visible true

Decentralized Trust Chains (DTCs)

Introduction​

Verifiable Credentials (VCs) are most commonly issued by legal entities to assert facts such as identity, qualifications, or authorisation. Their core purpose is to provide the Relying Party — the entity verifying the credential — with a Level of Assurance (LoA) that the claims within the credential are legitimate.

However, in practice, it’s often difficult for relying parties to determine whether a legal entity issuing a credential is authentic, or a fraudulent impersonation. There is no built-in mechanism in most credential ecosystems for verifying whether a DID-based issuer is recognised, authorised, or trustworthy.

{% hint style="info" %} Note: This lack of trusted issuer infrastructure is a critical blocker for many digital credential ecosystems — and a common reason why solutions stall before reaching production. {% endhint %}

To fully establish trust, relying parties must be able to:

• Identify who issued a credential
• Understand whether the issuer was authorised to issue it
• Trace who accredited the issuer, and under what governance framework

Introducing Decentralized Trust Chains (DTCs)

To solve this challenge, cheqd introduces a verifiable trust infrastructure called Decentralized Trust Chains (DTCs) — a model that complements and extends approaches like the EBSI Trust Chain Framework.

DTCs allow participants to create hierarchical chains of trust, where:

• A Root Trusted Accreditation Organisation (rTAO) defines the governance model
• Verifiable Accreditations delegate authority to other legal entities (e.g., TAOs, Trusted Issuers)
• Verifiable Credentials are issued by accredited issuers, with embedded metadata that references the trust chain

Together, these components form a decentralized trust registry for each ecosystem.

Publicly Verifiable, Policy-Governed Trust

cheqd’s DTC model introduces both permissions and policies:

• Permissions define what an entity is allowed to do (e.g. issue or accredit)
• Policies define who granted that permission, under what framework, and with what legal or operational requirements.

This infrastructure is made publicly resolvable by publishing all authorisations and accreditations as DID-Linked Resources on the cheqd ledger. This means:

• 🧩 Trust relationships are machine-verifiable
• 🔍 Verifiers do not need prior knowledge of each entity
• 🛠️ Resolution follows W3C standards like DID-Core, DID Resolution and DID-Linked Resources.

The result: A scalable, cryptographically verifiable way to determine whether an issuer — and the credential they issue — can be trusted.

Glossary​

There are many terms used within this guide, and as such, familiarise yourself or refer back to the concepts within the glossary below:

Abbreviation	Term	Description
-	Accreditation Policy	A machine-readable policy embedded in a Verifiable Accreditation that defines the scope, conditions, and governance under which an entity is authorised to accredit others or issue Verifiable Credentials.
-	Attestation Policy	A machine-readable policy embedded in a Verifiable Credential that links the credential to the issuer’s accreditation and root authorisation, enabling verifiers to validate that the issuer was authorised to make the attestation.
DID	Decentralized Identifier	Legal entity identifier for Trust Registry, cannot be natural person in context of Trust Infrastructure
GA	Governance Authority	The legal entity or consortia responsible for writing the Governance Framework. In many instances the Governance Authority is also a Root TAO
GF	Governance Framework	A policy document outlining the purpose, roles, scopes and permissions for a given ecosystem using the Trust Infrastructure.
Root TAO (rTAO)	Root Trusted Accreditation Organization	A Root Trusted Accreditation Organisation (rTAO) is the top-level authority in a Decentralized Trust Chain responsible for defining the governance framework and issuing the Root Authorisation that anchors all downstream accreditations and attestations within the trust ecosystem.
TAO	Trusted Accreditation Organization	A Trusted Accreditation Organisation (TAO) is an entity accredited by a Root Trusted Accreditation Organisation (rTAO) or another TAO to govern a segment of the trust chain by issuing accreditations to other entities or authorising the issuance of Verifiable Credentials within a defined scope.
-	Trust Chain	Hierarchy of Verifiable Accreditations. Multiple Trust Chains may comprise a Trust Registry.
TI	Trusted Issuer	A Trusted Issuer is an entity accredited within a Decentralized Trust Chain to issue domain-specific Verifiable Credentials, operating under the scope and governance defined by an upstream accreditation and the overarching trust framework.
-	Trust Infrastructure	The overall set of technical and governance components to establish end-to-end trust.
-	Verifiable Accreditation	A Verifiable Accreditation is a Verifiable Credential that delegates authority from one entity to another, specifying the types of credentials they are permitted to issue or the roles they are authorised to perform within a defined trust framework.
-	Verifiable Trust Model	Permissions with policies to either accredit, or to attest

Establishing a Trust Hierarchy

Decentralized Trust Chains are based on the concept of a hierarchical trust model, conceptually similar to traditional Public Key Infrastructure (PKI). At the top sits a Root of Trust, from which trust is delegated through a verifiable chain of credentials.

In this model, each participant is identified by a Decentralized Identifier (DID) and may be granted permission — via a Verifiable Accreditation — to accredit others or issue credentials themselves.

How the Hierarchy Works

Trust is delegated top-down through Verifiable Accreditations:

Role	Description
Root TAO (rTAO)	Issues Root Authorisations and initial Accreditations to other TAOs. Sets the governance baseline.
Trusted Accreditation Organisation (TAO)	Can accredit other TAOs or Trusted Issuers. Acts as an intermediary layer in larger ecosystems.
Trusted Issuer (TI)	Issues Verifiable Credentials to users/entities, based on permissions received from an upstream TAO.

The following diagram show how a Root TAO accredits two TAOs lower in the hierarchy:

Each role is cryptographically linked through issued Verifiable Credentials, creating a machine-verifiable trust path.

Verifiable Credentials & Policy Enforcement

• Credentials are issued with a termsOfUse section that references an Attestation Policy, linking them back to the issuer’s accreditation and the root of trust.
• Digital Wallets or agents can present these credentials for verification.
• Verifiers can then resolve and validate the entire trust chain — from the issuer to the rTAO — using DID resolution and optional DNS anchoring.

Trust Infrastructure Roles and their Permissions

As shown in the diagram above, legal entities can play the following roles:

• In a Decentralized Trust Chain, each legal entity assumes a defined role with clearly scoped permissions. While a single DID may represent multiple roles in simple ecosystems, every complete trust chain should include these three functional roles:

  • Root Trusted Accreditation Organisation (rTAO)
  • Trusted Accreditation Organisation (TAO)
  • Trusted Issuer (TI)

  Only the Trusted Issuer (TI) is permitted to issue domain-specific Verifiable Credentials (VCs).

Root Trusted Accreditation Organisation (rTAO)

The rTAO is the root of governance in a trust chain. It establishes the ecosystem’s rules and authorises who can issue or accredit within it.

Capabilities:

• Issue a Root Authorisation that defines the Trust Framework
• Self-accredit for governance or issuance
• Accredit TAOs and TIs to delegate responsibility
• Revoke accreditations from any participant in the trust chain

Credential Type:

• VerifiableAuthorisationForTrustChain

Policy Type:

• TrustFrameworkPolicy (included in termsOfUse)

Root Authorisations	Learn how Root TAOs can set the governance baseline, including the governance framework for the trust chain through Root Authorisations.	root-authorisations.md
RTAO -> TAO	Learn about how Root TAOs can accredit other TAOs in the trust ecosystem with permissions and Trust Framework Policies.	rtao-to-tao.md

Trusted Accreditation Organisation (TAO)​

A TAO manages a delegated segment of the trust chain under the rTAO. It may further accredit entities or take on the role of issuer if permitted.

Capabilities:

• Accredit itself to issue VCs
• Accredit other TAOs or Trusted Issuers
• Revoke accreditations issued within its scope

Credential Type:

• VerifiableAccreditationToAccredit

Policy Type:

• AccreditationPolicy (included in termsOfUse)

TAO -> SubTAO	Learn about how TAOs can accredit other SubTAOs in the trust ecosystem with permissions and Accreditation Policies.	tao-to-subtao.md
TAO - TI	Learn about how TAOs can accredit Trusted Issuers to issue credentials within the trust ecosystem, using permissions and Accreditation Policies.	tao-to-ti.md

Trusted Issuer (TI)​

A Trusted Issuer is an entity that issues domain-specific Verifiable Credentials under the conditions granted by its accreditation.

Capabilities:

• Issue Verifiable Credentials to users or organisations
• Only within the types, schemas, and jurisdictions defined in their accreditation

Credential Type:

• VerifiableAccreditationToAttest

Policy Type:

• AccreditationPolicy (accreditation) +
  AttestationPolicy (included in the issued credential’s termsOfUse)

Referencing Trust Registry within a Verifiable Credential	Learn how a Trusted Issuer can reference a Trust Registry in an issued credential, enabling a relying party to traverse the Trust Chain.	referencing-in-credential.md

Policies Overview​

Policies define the rules, permissions, and governance bindings for each layer of the trust chain. They are embedded into credentials via the termsOfUse field and fall into three types:

Policy Type	Used In	Purpose
TrustFrameworkPolicy	Root Authorisation	Defines the root governance model
AccreditationPolicy	Verifiable Accreditation	Constrains and describes the scope of authority
AttestationPolicy	Verifiable Credential	Links the credential back to the issuer’s accreditation and trust framework

How Policies are Linked

• Root Authorisation includes a TrustFrameworkPolicy
• Each Accreditation must reference:
  • A parent AccreditationPolicy, or
  • The original TrustFrameworkPolicy
• Each Credential (Attestation) must reference:
  • The AttestationPolicy pointing back to the issuer’s accreditation

Diagram showing different policy relationships in the trust chain

This layered policy model enables verifiers to traverse and validate the entire trust chain — from a single credential back to a rTAO (optionally anchored in DNS) — while ensuring that all participants adhere to consistent governance and operational standards.

Trust Types in Decentralized Trust Chains

Trust Chains are constructed from three verifiable building blocks:

1. Authorisations

• Define the rules of the ecosystem
• Issued by the rTAO as a VerifiableAuthorisationForTrustChain
• Reference the root governance framework

2. Accreditations

• Grant permission to accredit or issue
• Are always domain-specific and non-transferable
• Must include an AccreditationPolicy in termsOfUse
• Allow entities to govern or issue only within the authorised scope

3. Credentials (Attestations)

• Assert facts (identity, qualifications, rights)
• Must include an AttestationPolicy that:
  • Links back to the issuer's accreditation
  • Establishes a trust path to the root authority
• Issuable only by accredited Trusted Issuers

In Summary:

Element	Purpose
Authorisations	Define the governance and policy rules at the root of the trust chain
Accreditations	Delegate trust authority for accreditation or credential issuance
Credentials (Attestations)	Assert verifiable facts within the scope of a governed trust framework

Get Started

Get started

Use cheqd Studio APIs to define, issue, and publish trust registry entries:

• Create and manage Root Authorisations, Accreditations, and Attestations
• Resolve trust chains in real time using standard DID resolution
• Anchor trust registries on-chain while keeping business logic off-chain

For verification, use TRAIN to validate the trust registry to determine whether an issuer DID is accredited, and what they are accredited for — by traversing the full trust chain to its root.

Set up Trust Chain	Design and build a trust chain for establishing a trust hierarchy in your ecosystem.	set-up	cheqd_logo_card.jpg
Get started with TRAIN	Deploy TRAIN and start validating trust chains with DNS-anchored roots and cryptographic accreditations.	train	fraunhofer.png