Update draft-birkholz-cose-tsa-tst-header-parameter.md

Co-authored-by: Thomas Fossati <[email protected]>

draft-birkholz-cose-tsa-tst-header-parameter.md

@@ -73,7 +73,7 @@ A second use case is the notarization of a signed document by registering it at
 This is common for accountability and auditability of issued documents.
 Once a document is registered at a Transparency Service's append-only log, its log entry cannot be changed.
 In certain cases, the registration policy of a Transparency Service may add a trustworthy timestamp to the signed document.
-This is done to enhance confidence in the authenticity of the document at the time of registration, enshrining that a signature was successfully validated.
+This is done to lock the signature to a specific point in time.
 To achieve this, the Transparency Service acquires a TST from a TSA when its registration policy is met, bundles it alongside the signed document, and then registers it.
 A relying party that wants to ascertain the authenticity of a document at a certain time does not have to trust the Transparency Service's clock, which may have been maliciously altered or can simply be inaccurate.