Create and verify digital signatures using RSA-PSS or ECDSA with the WebCrypto API.
Digital Signature Tool creates RSA-PSS or ECDSA signatures from an entered message and a compatible private key, then checks a signature against the original message and corresponding public key. Its cryptographic operations run through Web Crypto in the browser, so key material and message contents are not uploaded. The common surprise is that a valid signature is not encrypted text and does not, by itself, identify a person; it only validates the supplied combination.
Signing requires a private key whose type matches the selected scheme. For RSA-PSS, the salt length is part of the signing parameters; the key also carries its RSA hash settings. For ECDSA, the EC key's named curve and the selected digest must be compatible. The browser signs the encoded message bytes and returns signature bytes.
Verification requires the original message, signature, corresponding public key, and matching algorithm parameters. The verification operation yields true or false. A false result does not diagnose which item is wrong. Changed whitespace, a different text encoding, another RSA-PSS salt length, or an ECDSA parameter mismatch can all prevent validation.
Do not expect byte-for-byte reproduction. RSA-PSS deliberately incorporates a salt, so repeated signing can produce different signature bytes. ECDSA signatures should also be treated as values to verify, not as reproducible message hashes. The meaningful test is verification against the unchanged message, corresponding public key, and matching scheme parameters.
No. A valid result shows that the signature, message, public key, and parameters are mathematically consistent. It does not name the key holder, show when signing occurred, or prove that the expected person controlled the private key. Identity depends on independently authenticating the public key, such as through a trusted certificate or verified fingerprint.
The behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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