OpenA2A: CLI · HackMyAgent · Secretless · AIM · Browser Guard · DVAA

Agent Trust Protocol (ATP)

An open standard for verifiable trust assertions about AI agents.

ATP enables any party to answer "Should I trust this agent?" with a cryptographically verifiable, auditable, and decentralized response.

Quick Start

# Query an agent's trust proof (returns hybrid Ed25519 + ML-DSA-65 signed proof)
curl "https://api.oa2a.org/api/v1/trust/proof?did=did:opena2a:mcp_server:@modelcontextprotocol/server-filesystem" \
  | jq '.proof' > proof.json

# Verify the proof against the issuer (returns {"valid":true,...})
curl -X POST https://api.oa2a.org/api/v1/trust/verify \
  -H "Content-Type: application/json" \
  -d @proof.json

# Discover the trust authority (current endpoint; will migrate to /.well-known/atp)
curl https://api.oa2a.org/.well-known/opena2a

Specification

ATP-SPEC.md — the full protocol specification (v1.0.0-rc1).

Conformance Levels

Level	Name	What It Means
1	Basic Trust	DID + signed proofs. Single authority.
2	Auditable Trust	+ transparency log. Tamper-evident.
3	Decentralized Trust	+ federation consensus. Multi-authority.

Interoperability

ATP is designed to complement:

• Google A2A Protocol — trust proof in agent cards
• SLSA — provenance level factors into trust score
• Sigstore — keyless co-signing of trust proofs
• Certificate Transparency (RFC 6962) — compatible log structure
• W3C DID Core — agent identifiers

Reference Implementation

The OpenA2A Registry implements ATP at Level 2 conformance. The reference trust authority is live at api.oa2a.org.

Verified working request and response (April 2026):

curl "https://api.oa2a.org/api/v1/trust/proof?did=did:opena2a:mcp_server:@modelcontextprotocol/server-filesystem"

Returns a hybrid Ed25519 plus ML-DSA-65 signed trust proof:

{
  "algorithm": "ed25519",
  "proof": {
    "did": "did:opena2a:mcp_server:@modelcontextprotocol/server-filesystem",
    "trustLevel": 2,
    "trustScore": 0.7432,
    "verdict": "listed",
    "issuedAt": "2026-04-28T13:32:11Z",
    "expiresAt": "2026-04-29T13:32:11Z",
    "issuerDid": "did:opena2a:registry:opena2a.org",
    "signatures": [
      { "keyVersion": 1, "algorithm": "ed25519", "value": "..." },
      { "keyVersion": 0, "algorithm": "ml-dsa-65", "value": "..." }
    ]
  },
  "publicKey": "..."
}

The proof carries both an Ed25519 signature for fast local verification today and an ML-DSA-65 signature (FIPS 204, post-quantum) for forward compatibility. Local verification requires no further network calls.

Related Standards

• AIP (Agent Identity Protocol) — identity + capabilities
• OASB (Open Agent Security Benchmark) — security controls

License

Apache-2.0