Attest MCP

attest-mcp

Listed on the official MCP Registry as io.github.SPAZIO-GENESI/attest-mcp.

MCP server and CLI for Spazio Genesi's attestation service — attest, verify, and check the existence of digital works from any MCP-capable AI agent (Claude Code, Claude Desktop, etc.) or straight from a terminal / CI pipeline.

Full privacy: file bytes never leave your device. The fingerprint (SHA-256) is computed locally, streamed from disk — only the hash and optional metadata are sent.

📖 English documentation: attestazione.spaziogenesi.org/en — site, developer docs, and tiers/terms are all available in English.

What it does

The attestation service timestamps a file's SHA-256 fingerprint, signs it (HMAC), and can produce a signed PDF certificate plus an OpenTimestamps proof anchored in Bitcoin. This server exposes that service as MCP tools, so an agent can attest and verify works on your behalf without a browser.

Why this, not just an OpenTimestamps wrapper

Several MCP servers can submit a hash to an OpenTimestamps calendar. As far as we know, this is the only one that hands back a complete proof of existence — a signed PDF certificate, a recognized RFC 3161 timestamp, and a Bitcoin anchor — for free, with the file's bytes never leaving the caller's machine. No account, no upload, no paid notarization chain. If you know of another MCP server with the same combination (full certificate + free + local hashing), we'd genuinely like to hear about it — open an issue.

Built for the European legal and regulatory context

Spazio Genesi is an Italian non-profit (ETS – *Ente del Terzo Settore*). The attestation service behind this package was designed with the EU regulatory environment in mind, not adapted to it afterwards:

• GDPR-first, privacy by design: the file itself never reaches our servers — only its SHA-256 fingerprint (and any metadata you choose to declare) is sent.
• EU data residency: certificates and proofs are archived on Cloudflare R2 under EU jurisdiction.
• Recognized timestamping, no single point of trust: every certificate carries an RFC 3161 timestamp from an AATL-rooted authority (trusted by Adobe and most PDF readers) *and* an independent Bitcoin anchor via OpenTimestamps.
• Honest about eIDAS: this is not (yet) an eIDAS qualified trust service — the signer identity is currently self-signed, and a qualified electronic seal is a planned but unimplemented upgrade. See the technical whitepaper for the full, unvarnished breakdown of what is and isn't guaranteed.

Full tiers and terms: attestazione.spaziogenesi.org/en/condizioni.

Install

Claude Desktop — one command, no manual JSON editing:

npx -y @spazio-genesi/attest-mcp-setup

This finds your claude_desktop_config.json (Windows/macOS/Linux), adds the attest-mcp entry, and backs up the original file first. It refuses to touch anything if the existing file isn't valid JSON — it never guesses. Restart Claude Desktop afterwards. To remove it again: add --uninstall. To preview without writing: add --dry-run.

Claude Code:

claude mcp add attest-mcp -- npx -y @spazio-genesi/attest-mcp

Manual / other clients — add this to your MCP client's config:

{

"mcpServers": { "attest-mcp": { "command": "npx", "args": ["-y", "@spazio-genesi/attest-mcp"] } } }

Authentication

Two ways to authenticate, matching the underlying service:

1. API key (for partner integrations, issued manually by Spazio Genesi): set the IMGAUTH_API_KEY environment variable.
2. Device flow (for personal/agent use): call the authorize tool with no arguments. It returns a URL — open it, approve with the human-verification widget, then call authorize again with the returned code. The session token (24h, 20 attestations) is saved to ~/.config/attest-mcp/credentials.json (permissions 600 where supported) and used automatically after that.

Either way, the credential only unlocks the anti-bot check on attestation — the server-side timestamp, cryptographic signature, and rate limits are unchanged.

Tools

CLI (sg-attest)

Same package, no separate install. The CLI is a bin alongside the MCP server, sharing the same hashing/API/config code — same full privacy (streamed local hash, file bytes never sent), same credentials.

npx -y -p @spazio-genesi/attest-mcp sg-attest attest ./work.png

npx -y -p @spazio-genesi/attest-mcp sg-attest verify ./work.png --hash

(-p is required: sg-attest is a secondary bin of the package, and plain npx -y @spazio-genesi/attest-mcp runs the MCP server instead.)

One advantage over the site: no 1 GB cap. The browser is limited by WebCrypto (which loads the whole file into memory); this CLI streams from disk on Node, so it can attest files of any size.

Every command accepts --json (emits one JSON object on stdout, for scripting) and --quiet (reduces non-essential human-readable output). Errors go to stderr; the CLI never prints a credential (API key or session token) to stdout, stderr, or --json output — same discipline as the MCP server.

Exit codes (a stable contract, for CI/scripting):

Authentication is the same as the MCP server: IMGAUTH_API_KEY env var, or a session token saved by sg-attest authorize (device flow). There is no --key flag — a credential on the command line ends up in shell history; use the env var (or a CI secret) instead.

A GitHub Action that uses this CLI to attest build artifacts in CI lives in a companion repo: attest-action.

Standalone binaries (no Node required)

For a machine or CI runner without Node.js, download a pre-compiled sg-attest executable from the Releases page — same commands, same behavior, nothing to install.

Each release also includes SHA256SUMS.txt. Verify the download before running it:

sha256sum -c SHA256SUMS.txt --ignore-missing   # Linux/macOS

(Get-FileHash .\sg-attest-windows-x64.exe -Algorithm SHA256).Hash   # compare by eye to SHA256SUMS.txt

⚠️ The binaries are not code-signed: expect an "unknown publisher" warning from Windows SmartScreen or macOS Gatekeeper the first time you run one. The checksum above is the integrity guarantee in the meantime — the binary is built and published by GitHub Actions directly from this repo's source, nothing hand-uploaded.

Usage is identical to the npm-installed CLI, just call the file directly:

chmod +x ./sg-attest-linux-x64          # Linux/macOS only

./sg-attest-linux-x64 attest ./work.png --pdf cert.pdf ./sg-attest-linux-x64 status

npx/npm remain the primary distribution channel (and what attest-action uses in CI) — the binaries are an additional channel, not a replacement.

Build provenance (SLSA/in-toto)

The checksum above answers "is this file intact?" — it says nothing about *where the bytes came from*. Every release since v0.4.2 also carries a signed build provenance attestation (actions/attest-build-provenance, job release in release-binaries.yml): cryptographic proof that the file was built by this repo's own workflow, from a specific commit and tag, not hand-uploaded or swapped afterward.

The GitHub CLI can verify it, but gh attestation verify requires an authenticated gh session even on this public repo (confirmed: it fails with "please run gh auth login" without one) — a real gap if the point is a check anyone can run with zero setup:

gh attestation verify sg-attest-linux-x64 --repo SPAZIO-GENESI/attest-mcp

scripts/verify-provenance.mjs does the same verification with no GitHub credentials at all — only the public attestations REST endpoint (confirmed reachable unauthenticated, even on this public repo) and the sigstore library, which checks the signature against Sigstore's own public infrastructure (Rekor, Fulcio, TUF — no account needed there either):

git clone https://github.com/SPAZIO-GENESI/attest-mcp

cd attest-mcp && npm install node scripts/verify-provenance.mjs ./sg-attest-linux-x64 \ --repo SPAZIO-GENESI/attest-mcp --tag v0.4.2

Exits 0 on success, 1 if the file doesn't match anything the workflow actually built (e.g. a single altered byte makes the digest — and therefore the lookup key itself — no longer match any attestation).

Configuration

Troubleshooting

If your client reports "Server disconnected", check its log first: this server writes diagnostics to stderr, which MCP clients capture. On Claude Desktop the log lives in %APPDATA%\Claude\logs\mcp-server-attest-mcp.log (Windows) or ~/Library/Logs/Claude/mcp-server-attest-mcp.log (macOS).

You should see one line per lifecycle event:

[attest-mcp 2026-07-21T11:14:12.948Z]