Prove a document existed.
Independent proof of when. No account, no custody.
Anchor Suite lets you prove that a file or data artifact existed at a specific point in time, without trusting any single authority and without revealing the file to anyone.
This tool is for engineers, compliance teams, and the agents that work for them: anyone who needs durable, independently verifiable proof of existence for a file or a data artifact.
How it works
- Hash locally. Drop any file into the Anchor page. SHA-256 is computed in your browser using WebCrypto. Nothing leaves your machine.
- Timestamp the hash. Send the 32-byte hash to one or more independent timestamp authorities (RFC 3161). They receive only the hash, not the file.
- Verify forever. The signed receipt is a self-contained DER file. Verify it with our page, with OpenSSL, or with any RFC 3161 tool.
Why choose two or more authorities?
RFC 4998 recommends anchoring with at least two independent timestamp authorities. If one authority is compromised or shuts down, the other still proves your timestamp. The Anchor page makes selecting multiple authorities easy; the receipt captures all of them.
Works offline after first load
All cryptography runs in your browser using WebCrypto and committed vendored libraries. There are no external CDNs, no analytics scripts, and no server-side storage. Once the page has loaded, disconnect from the network: hashing and verification still work.
OpenChainGraph support
Drop an OpenChainGraph artifact and the tool anchors its execution_hash directly,
then re-emits the artifact with anchor_bindings attached per OCG v0.7 section 20.
The anchor sits outside the hash scope so the artifact integrity proof is unchanged.
Post Oak Labs never sees your document, never stores your hash, and is not the timestamp authority. The authorities are named in your receipt. Read the verification recipe.