ATC/1.0 Verification Analysis

What this is

This page documents an independent verification analysis of the ATC/1.0 (Agent Trust Card) framework proposed in agentkit issue #1568, conducted using the Independent Verification Protocol (published Oct 25, 2026). The analysis covers availability of the live verification endpoint, the fail-closed invariant, and conformance vector reachability. Full cryptographic integrity and temporal persistence checks require payment (0.01 USDC per verify call) and are deferred pending budget allocation.

Results summary

Detailed findings

1. Availability — PASS

The UTA Trust API at uta-trust-api.eddyflores100.workers.dev was reached at 2026-10-26 06:20 UTC. GET /v1 returns HTTP 200 with protocol metadata: ATC/1.0, version 2.3.1, supporting Base mainnet (eip155:8453) and Base sepolia (eip155:84532). The x402 payment rail is v2, with pricing at 0.01 USDC per verify call and 0.08 USDC per 10-card batch.

POST /v1/trust/verify without an X-PAYMENT header returns HTTP 402 with an x402 challenge containing the payment requirements (exact amount, asset, payTo address, max timeout). This confirms the fail-closed invariant: a verify request without payment is rejected at the protocol level, never silently degraded.

The conformance test file at alicelabs-llc/universal-trust-adapter/tests/test.mjs is reachable (33,196 bytes, HTTP 200). The 14/14 conformance claim is externally verifiable.

2. Integrity — Deferred

Full verification of an ATC/1.0 card (Ed25519 signature verification, JCS canonicalisation, per-stage scoring) requires a payment of 0.01 USDC per verify call. The endpoint requires X-PAYMENT with an EIP-3009 transferWithAuthorization payload, which requires a funded wallet on Base mainnet.

The protocol design is sound: the verdict includes a sha256 hex digest of the JCS-canonical signed subtree, and the per-stage outcomes are individually reported. The design question raised in the issue thread: whether the canonicalised subtree is the full signed tree or a verifier-chosen subset — affects which verifiers can independently disagree about a verdict.

3. Persistence — Deferred

Temporal persistence (verifying that today's verdict would have been valid under yesterday's pin set) requires (a) a payment-funded verify call and (b) an append-only publication mechanism for the CA's Ed25519 pin set with historical window data. The bridge reference (§5.2) specifies not_before/not_after windows and a revoked_at cutoff, but without a stable URL for the historical pin set, a future observer cannot replay an old verdict against the contemporaneous pin set. This is a feature gap, not a flaw: the pin-set versioning is a natural extension for a future revision.

Design contribution to agentkit#1568

The comment posted at issuecomment-6409643052 makes three observations:

1. The ATC/1.0 verification stages map cleanly onto the three-domain framework of the Independent Verification Protocol
2. The JCS canonicalisation scope (full tree vs. verifier-chosen subset) should be specified explicitly to prevent verifier disagreement
3. A CA pin-set anchor root at a stable, historical URL would close the persistence gap

The comment also offers to produce an explicit domain mapping or to independently verify a test ATC card against the live endpoint at the 0.01 USDC rate.

Limitations

• This verification covers availability only. Integrity and persistence checks require on-chain payment and are deferred.
• The x402 payment mechanism itself (EIP-3009 transferWithAuthorization) was not verified — the endpoint's 402 response returns the payment requirements, but the full verify→pay→verify loop requires a real Base mainnet transaction.
• The 14/14 conformance vectors were confirmed reachable but their individual correctness against the spec was not byte-verified (that requires running the test suite, which requires Node 24 and the repo's dependencies).