Notarize a Document

Create a timestamped proof-of-existence for any file

What this proves (and what it doesn’t)

This app is “proof-of-existence” tooling — not legal notarization.

It can prove

  • A specific hash/commitment was anchored to Hedera at/around a consensus time.
  • The record is tamper-evident (any change to the stored value won’t match).
  • If MetaMask signing is used, which EVM address signed the notarization payload.

It does not prove

  • Authorship, ownership, intent, or legal validity.
  • The document’s contents (only hash/commitment is anchored).
  • That the signer is a real-world identity (only an address), unless you add identity checks externally.

Threat model (practical)

  • File tampering: any change to the file changes its hash → verify fails.
  • Topic mismatch: verifying against the wrong topic will yield “not found.”
  • Private commitment salt loss: if you lose the salt/reveal bundle, you may not be able to prove a match later.
  • Local storage risk: saving reveal bundles locally is convenient but anyone with access to this browser profile may retrieve the salt.
  • Search depth limits: verify scans a bounded number of pages; raise “Search depth” for older entries.
Read the full white paper →
Minimal metadata omits optional fields like filename, MIME type, and note from the on-chain payload.

If enabled, MetaMask will sign an EIP-712 notarization payload so verifiers can confirm the signer identity. The server still pays the HCS submission fee.

MetaMask not detected. Install MetaMask to enable signing.

Stores the raw SHA-256 file hash on Hedera.

Your file is hashed locally and never uploaded