Timestamp Authority
A Timestamp Authority (TSA) is a trusted third party that issues signed timestamps — cryptographic tokens that prove a specific piece of data (typically a document hash) existed at a particular point in time.
What it means
A TSA timestamp token is issued per RFC 3161. The signing application sends the document hash to the TSA, and the TSA returns a signed token containing that hash plus the current time, signed with the TSA's own certificate. This token is embedded in the document signature, providing legally recognized proof of the signing time that is independent of the signer's own clock.
Why it matters for e-signatures
SignOwl embeds a trusted timestamp in every signature. This is critical for long-term validity: if a signing certificate is later revoked, the timestamp proves the signature was created before the revocation, keeping the signature valid.
Related terms
Frequently asked questions
Why can't I just use the system clock for the signing time?
System clocks can be manipulated by the signer. A TSA timestamp is signed by a trusted third party and cannot be forged, providing legally credible evidence of the signing time.
Is a TSA timestamp required for all e-signatures?
No. It is required for PAdES-T and above, and for qualified signatures under eIDAS. For simple e-signatures, a logged timestamp from the platform is typically sufficient.
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