Zero-Knowledge SHA-256 Document Timestamp & Integrity Notary
Prove that an exact contract, board resolution, multisig descriptor, codicil, or archive existed at a specific UTC timestamp without exposing its contents. Your file is hashed strictly inside local browser memory—only the 64-character hexadecimal SHA-256 digest crosses the network.
1. Compute Local SHA-256 & Anchor Existence Proof
Select or drop any local file (up to 250 MB in browser RAM), or enter text below to compute its deterministic SHA-256 fingerprint. Filenames stay exclusively in your browser for optional local certificate printing and are never transmitted.
SHA-256 Timestamp Notary Certificate
| Document SHA-256 Digest | — |
|---|---|
| First Anchored Timestamp (UTC) | — |
| Notary Reference / Mode | — |
| Local Reference Filename | Not provided (client-side only; never transmitted) |
| Decentralized Mainnet Anchor | — |
| Custody & Registry Jurisdiction | — |
| HMAC-SHA256 Attestation | — |
Verification Procedure: Any third party, auditor, or court expert holding the unmodified original file can recompute its SHA-256 digest offline (`shasum -a 256 <file>` or `Get-FileHash -Algorithm SHA256`) and verify the anchored timestamp at https://zerocanary.com/tools/sha256-notary. Modifying even a single bit produces a completely different SHA-256 digest.
2. Verify an Existing SHA-256 Proof Digest
Already have a 64-character SHA-256 digest from a ZeroCanary Deposit Certificate or standalone Notary Receipt? Verify its immutable UTC registration timestamp below.
Need your family, co-founder, or counsel to receive the file itself if something happens to you?
A SHA-256 timestamp proves a file existed, but it stores zero bytes of the document. To encrypt the actual confidential file or multi-file archive (up to 50 MB) with AES-256-GCM and release it automatically when your Dead Man’s Switch expires—complete with a standalone air-gapped Offline Recovery File (.html)—seal a deposit in the ZeroCanary Vault Console.