How it works

Hash → Merkle root → Monero tx_extra → block → proof.

1. Hash: each file is hashed (SHA-256).
2. Merkle root: batch hashes form one Merkle tree; the root is the commitment.
3. Commit: the root is embedded in tx_extra of a self-send. The amount returns to your wallet; only the fee is lost.
4. Anchor: after ≥10 confirmations, anchored .xmrts proofs are written (block height + hash + timestamp).
5. Verify: re-hash, check the Merkle path, then confirm the transaction on-chain. Crypto first, chain second.

What's in a proof?

A .xmrts file binds your file to a chain position:

• File hash + Merkle path to the batch root
• Transaction ID carrying the commitment
• Block height, block hash, block timestamp
• Network (mainnet / stagenet)

Sharing a proof only reveals the txid: already public on-chain.

Confirmations & reorgs

Monero averages a block every ~2 minutes. stamp defaults to 10 confirmations (~20 minutes), matching Monero's own 10-block output lock.

Treat 10 as a minimum

On 2025-09-14 mainnet saw an 18-block reorg that overwhelmed 10 confirmations. Wait for 20+ before relying on high-value timestamps:

xmrts stamp --min-confirmations 20 contract.pdf
xmrts verify contract.pdf contract.pdf.xmrts --min-confirmations 20

Authorship: sign first, then stamp

Timestamping proves existence, not authorship. For authorship, sign first: stamp --sign-with anchors a detached GPG signature in the same batch:

xmrts stamp --sign-with <gpg-key> file
xmrts verify file file.xmrts --sig file.sig

GPG verifies the signature (fingerprint printed), and file.sig.xmrts must anchor in the same transaction as the file proof: a later signature still passes GPG but fails the binding. Proofs living away from the files (e.g. --out-dir) pass --sig-proof.