Proof, compliance and data
Timestamping
Timestamping attaches a certain date and time to a document, attested by a third party, proving that the document existed in that form at that moment.
A timestamping service receives the document's fingerprint, not the document itself, and adds the time from a reliable source, all sealed with its signature. Any later change to the document breaks the match. The European eIDAS regulation gives a qualified timestamp a presumption of accurate date and integrity.
Why it matters for fax
The time printed by a fax machine comes from its own clock, set by its owner. A timestamp issued by a third party, applied to the document and the sending report, provides a date the sender could not choose.