I told you so.

Verify

Check a copy you have

Choose a file you saved earlier: an entry's entry.txt, or a file one links to, such as a talk's PDF. It is hashed here and matched against every receipt.

Or check any entry

Every entry here is fingerprinted and timestamped when it is filed. This page checks those receipts in your browser. Nothing is uploaded; files you check never leave your machine.

For each entry it checks four things:

  1. The text. The SHA-256 of the entry, and of any files it links, must equal the fingerprint taken at filing.
  2. DigiCert’s timestamp and 3. FreeTSA’s timestamp. Each is an RFC 3161 token over the fingerprint. The signature must verify, and the signing certificate must chain to that authority’s root, which is built into the verifier rather than taken from the token.
  3. The Bitcoin anchor. The OpenTimestamps proof is replayed to the Merkle root of a Bitcoin block, and that root is compared with the real block, fetched from blockstream.info (or mempool.space). If the site’s copy of the proof is still pending, the OpenTimestamps calendars are asked directly.

The checks run in a WebAssembly module built from Rust, published with the rest of the tools. Because this page comes from the same site it checks, it is a convenience, not an independent witness. For that, run the same checks yourself with openssl and ots, as described on the About page.