RFC 3161 TSA
The cryptographic proof-of-existence that underpins the evidentiary value of B2B documents.
Definition
The client sends a document's hash in a TimeStampReq; the TSA returns a TimeStampResp containing a signed token binding that hash to the reference time. These tokens underpin long-term signatures (XAdES/CAdES) and e-invoice retention.
Origin
Defined by IETF RFC 3161, "Internet X.509 Public Key Infrastructure Time-Stamp Protocol (TSP)", complemented by RFC 5816.
Example in context
<TimeStampResp><status>granted</status><timeStampToken>…</timeStampToken></TimeStampResp> — a TSA's response to a timestamp request.