Attest402

Cryptographically signed and timestamped evidence of a public web or API response. Agent-native, paid per call via x402 — 0.20 USDC on Base. No accounts, no API keys.

An agent submits a public HTTPS URL → Attest402 fetches it securely, hashes body/headers/redirects, signs the canonical record with Ed25519, anchors it with an independent RFC-3161 timestamp and returns a portable evidence package that verifies fully offline.

The evidence confirms the integrity of the captured data and Attest402's observation at the stated time. It does not certify the truth, legality or authorship of the captured content.

Quickstart (local)

pip install -r requirements.txt
cp .env.example .env                  # defaults: dev mode, Base Sepolia
uvicorn app.main:app --reload
# → http://localhost:8000 (landing page, /openapi.json, /llms.txt)

Disable the paywall for local experiments with X402_ENABLED=false.

API

Endpoint	Method	Price	Function
/v1/attest	POST	0.20 USDC	Create an evidence package
/v1/verify	POST	free	Verify attestation (+ optional body)
/v1/verify/{id}	GET	free	Attestation metadata (90 d retention)
/v1/evidence/{id}	GET	free	Download evidence package (24 h retention)
/.well-known/attest-keys.json	GET	free	Ed25519 public keys (old keys permanent)
/.well-known/x402.json	GET	free	x402 discovery manifest
/llms.txt	GET	free	Agent-readable description
/health	GET	free	Healthcheck

Architecture

app/
  main.py       FastAPI app, routes, retention loop
  payments.py   x402 middleware (exact/USDC/Base) + Bazaar discovery extension
  fetcher.py    SSRF-hardened fetcher (DNS-pinned, 2 MB cap, 3 redirects, 10 s)
  ssrf.py       URL/DNS/IP policy (blocks private, loopback, metadata, rebinding)
  attest.py     Pipeline: fetch → canonical record → sign → RFC-3161 → package
  canonical.py  Deterministic canonical JSON + SHA-256
  signing.py    Ed25519 key management (secret-store only, rotation-aware)
  tsa.py        RFC-3161 client (freetsa + DigiCert fallback)
  evidence.py   Evidence zip builder (offline-verifiable)
  verify.py     Verification logic (shared with /v1/verify)
mcp_server/     MCP server: attest_web_response / verify_attestation / get_attestation
scripts/        generate_keys.py · verify_offline.py (30-line standalone verifier)
docs/           DEPLOY.md · GO-LIVE-CHECKLIST.md · LISTINGS.md
listings/       Ready-to-submit listing materials (Bazaar, ecosystem PR, MCP registries)

Payments (x402)

• Scheme exact, USDC, price $0.20, network Base Sepolia by default
• X402_USE_MAINNET=true flips to Base mainnet (feature flag, no code change)
• Settlement only after a successful capture — failed fetches are never charged
• Idempotency-Key header dedupes retried jobs
• Bazaar discovery metadata is declared on the paid route → automatic listing in the x402 Bazaar after the first CDP-facilitator settlement on mainnet

Verify an evidence package offline

python scripts/verify_offline.py attest_xxx-evidence.zip

Only needs cryptography. Checks canonical-record hash, Ed25519 signature, body/headers/redirect hashes and the RFC-3161 token hash — no network access.

Tests

python -m pytest tests/ -q     # 45 tests: SSRF policy, canonical determinism,
                               # sign/verify roundtrips, API flow, idempotency

Deploy

See docs/DEPLOY.md (Railway + Render, incl. mainnet switch and key rotation) and docs/GO-LIVE-CHECKLIST.md. Get listed: docs/LISTINGS.md.