TRAIL Protocol — did:trail DID Method

Trust Registry for AI Identity Layer

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What is TRAIL?

TRAIL (Trust Registry for AI Identity Layer) is an open cryptographic trust protocol for AI systems and autonomous agents operating in B2B commerce environments.

As AI agents increasingly act on behalf of organizations — negotiating contracts, providing advice, executing decisions — there is no infrastructure to answer the fundamental question: "Can I trust this AI system?"

TRAIL solves this by providing:

• Decentralized Identifiers (did:trail) for AI systems and the organizations behind them
• Verifiable Credentials attesting to AI identity, policy, and behavior standards
• Revocation mechanisms that create real economic consequences for misuse
• 3-Tier Trust Model — from local self-signed verification to fully audited registry credentials
• Support for organizational EU AI Act compliance alignment (Articles 13, 14, 26, 49, 52)

TRAIL is not a blockchain. It builds on established web infrastructure (W3C DID Core 1.0, VC 2.0, Ed25519) — the same standards that underpin Europe's eIDAS 2.0 digital identity infrastructure.

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Quick Start

# Install
npm install @trailprotocol/core

# Generate an Ed25519 keypair
npx @trailprotocol/core keygen

# Create a self-signed DID (works offline, no registry needed)
npx @trailprotocol/core did create --mode self

# Resolve a self-signed DID
npx @trailprotocol/core did resolve did:trail:self:z6MkhaXgBZDvotDkL5257faiztiGiC2QtKLGpbnnEGta2doK

Programmatic Usage

import {
  generateKeyPair,
  createSelfDid,
  createOrgDid,
  TrailResolver,
  createSelfSignedCredential,
  verifyCredential,
} from '@trailprotocol/core';

// Generate keys
const keys = generateKeyPair();

// Create DIDs
const selfDid = createSelfDid(keys.publicKeyMultibase);
const orgDid = createOrgDid('ACME Corporation', keys.publicKeyMultibase);

// Resolve (self-mode works offline)
const resolver = new TrailResolver();
const result = await resolver.resolve(selfDid);
console.log(result.didDocument);

// Create and verify a credential
const vc = createSelfSignedCredential(selfDid, orgDid, { role: 'operator' }, keys.privateKeyBytes);
const verification = verifyCredential(vc, keys.publicKeyBytes);
console.log(verification.valid); // true

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DID Examples

did:trail:org:acme-corp-a7f3b2c1e9d04f5a
did:trail:agent:sales-assistant-e4d8f1a9b3c57d2e
did:trail:self:z6MkhaXgBZDvotDkL5257faiztiGiC2QtKLGpbnnEGta2doK

A did:trail DID uniquely identifies either:

• An organization (org) operating AI systems — with content-addressable hash suffix
• A specific AI agent (agent) operated by a registered organization — with hash suffix
• A self-signed identity (self) for local verification — using the public key as identifier

Trust Tiers

Tier	Mode	Verification	Use Case
0	self	Cryptographic proof only	Development, testing, early adoption
1	org/agent	Registry + KYB verification	Production B2B
2	org/agent	Registry + KYB + independent audit	Regulated industries

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Repository Structure

trail-did-method/
├── README.md                    <- This file
├── LICENSE                      <- CC BY 4.0 (spec) + MIT (code)
├── CONTRIBUTING.md              <- How to contribute
├── spec/
│   └── did-method-trail-v1.md  <- Complete DID Method Specification (v1.1.0-draft)
├── packages/
│   └── trail-core/            <- @trailprotocol/core — reference implementation
│       ├── src/               <- TypeScript source (zero runtime dependencies)
│       ├── bin/               <- CLI tool
│       └── test/              <- End-to-end tests
├── methods/
│   └── trail.json             <- W3C DID Registry submission file
├── examples/
│   ├── org-did-document.json  <- Example org DID Document
│   ├── agent-did-document.json <- Example agent DID Document
│   └── self-did-document.json <- Example self-signed DID Document
└── .github/
    └── ISSUE_TEMPLATE/        <- Issue templates

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Specification

The full did:trail DID Method Specification v1.1.0-draft is available in spec/did-method-trail-v1.md.

Key sections:

• DID Method Syntax — including content-addressable hash suffixes
• DID Document Structure
• CRUD Operations — with DID-based authentication
• Trust Extensions — 3-Tier Trust Model, transparent Trust Score
• Security Considerations — including Key Recovery
• Governance — dispute resolution, registry operator requirements

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W3C Registry Submission

The methods/trail.json file in this repository is submitted for inclusion in the W3C DID Extensions.

Status: PR #669 submitted

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Design Principles

1. Open Protocol — The protocol itself is free and open. Trust comes from transparency.
2. Standards-based — Built on W3C DID Core 1.0, VC 2.0, Ed25519 — no proprietary dependencies.
3. Vendor-neutral — Registry infrastructure supports federation; no single operator lock-in.
4. Regulation-ready — Designed to support organizational EU AI Act (2027) and eIDAS 2.0 compliance.
5. Graduated trust — Start with did:trail:self: (Tier 0) without any registry. Graduate to full registration when ready.

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Prior Art & Related Work

Standard	Relationship
W3C DID Core 1.0	Foundation — did:trail IS a DID method
W3C VC 2.0	TRAIL issues VCs conforming to this standard
OpenID4VC (OID4VC)	Complementary — OID4VC handles credential exchange; TRAIL provides trust layer
eIDAS 2.0 / EUDIW	Future integration target — TRAIL credentials can be embedded in EUDIW-compatible wallets
EU AI Act (2024/1689)	Regulatory driver — TRAIL supports compliance with Art. 13, 14, 26, 49, 52

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Roadmap

• v1.0 — Specification draft
• v1.0 — W3C DID Registry submission (PR #669)
• v1.1 — Reference implementation (@trailprotocol/core) with CLI
• v1.1 — Specification v1.1.0-draft (9 critical improvements)
• v1.2 — TRAIL Registry alpha (Early Adopter Program)
• v2.0 — Production registry + independent security audit
• v2.1 — Universal Resolver driver
• v3.0 — EUDIW integration + B2C extension

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Contribute

We welcome contributions, questions, and challenges. If you find a flaw in the specification — that's exactly what we want to know.

• Open an issue for specification questions, security concerns, or improvement suggestions
• Join the discussion at the W3C Credentials Community Group: public-credentials@w3.org
• Contact the author: christian.hommrich@gmail.com

See CONTRIBUTING.md for guidelines.

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Author

Christian Hommrich TRAIL Protocol Initiative https://trailprotocol.org

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License

• Specification (all .md files in spec/): Creative Commons Attribution 4.0 International (CC BY 4.0)
• Reference implementations (all code in packages/): MIT License

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First committed: 2026-03-01 — establishing Prior Art for the did:trail namespace and TRAIL Protocol concept. Spec v1.1.0-draft: 2026-03-04 — addressing 9 critical improvements based on expert review.