Prototypes SignetP2 · Signed documents

Sign a file, and check that it is unchanged

Sign any file with a key kept in this browser, and hand the signature on. Whoever gets both drops them here and sees whether a single byte changed, and for a text file, which lines.

Sign a file

Drop a file to signor press to choose one. The file stays on this computer.

Check a file

Drop the file and its signatureDrop both at once, or one after the other. Signature files end in .signature.json.

Try it without files

Sign the sample agreement, then change a word below and watch the check.

Sign the sample first

Your signing key

PartValue
MethodMaking a key
Fingerprint
Made
KeptIt is kept in this browser, in IndexedDB, and the private key cannot be exported.
How Signet is built
  1. The signature file holds the file’s name, size and SHA-256, the time, the public key, and a signature over all of it made with Ed25519.
  2. For a text file it also holds a salted hash of every line. The salt is new for every signature, so nobody can guess a line from its hash.
  3. The check verifies the signature with the public key in the file, then compares the hashes. When the hashes of the whole file differ, the line hashes show which lines were changed, added or removed.
  4. A signature proves the file matches what the key signed. Compare the fingerprint with the signer to know whose key it is.