Timestamping

What is Timestamping?

Timestamping in electronic signing is the process of securely and verifiably recording when a document was signed. While a simple timestamp (just recording the current time) can be useful, a trusted timestamp from a timestamp authority (TSA) provides much stronger evidence because it is issued by an independent, trusted third party and is cryptographically secured against manipulation.

A trusted timestamp is created by sending a hash of the signed document to a timestamp authority. The TSA combines this hash with the current time from a trusted clock, signs the combination with its own private key, and returns the timestamp token. This token proves that the document existed in its exact form at the stated time — because the TSA has no stake in the transaction and uses a verified time source.

Trusted timestamps are important for several reasons. They provide evidence of when a signature was applied, which is legally relevant for contracts with deadlines, statutes of limitation, or time-sensitive obligations. They also extend the validity of digital signatures beyond the expiration of the signing certificate — a concept called Long-Term Validation (LTV). Without timestamps, a digital signature could become unverifiable once the signer's certificate expires.

Under eIDAS, qualified electronic timestamps are those issued by a qualified trust service provider using an approved time source. Qualified timestamps enjoy a presumption of accuracy of the date and time they indicate, and a presumption of integrity of the data to which the date and time are bound.