A signing key gets retired — rotated out after a laptop theft. A year later, someone who kept a copy of that old key sets their computer's clock back, signs a contract, and presents it as “signed back when the key was valid.” The cryptography checks out perfectly. The lie isn't in the signature — it's in the date.
That's the weakness in every system where the signer stamps their own time: the person holding the pen also holds the clock. TrustDID closes it by letting an independent time authority counter-seal the signature with the real moment it was made — a stamp the signer can't move, forward or back.
“Trust my clock”
The timestamp comes from the signer's own computer. Fine for everyday intent — worthless the day someone has a reason to lie about a date.
“A third party saw it”
An independent authority seals the real moment over the signature itself. Rewinding the clock changes nothing — the counter-seal already exists.
Why it matters to you: contracts and approvals are exactly the documents that get disputed years later, after keys have rotated and people have moved on. Provable time is what lets a five-year-old agreement stand on its own in front of an auditor, a court, or a counterparty — no “take our word for it” required.
Part of every seal's long life
Provable time works hand-in-hand with signatures that verify forever: the key history says which keys were valid when, and the timestamp proves which “when” applies. Together they make your documents provable for decades — patent-pending, and built on the same open, no-blockchain foundations as everything else here.
Live today, on every signing plan
Every TrustDID signing plan stamps its seals with the TrustDID Time-Stamp Authority,
did:web:tsa.trustdid.ca, as part of signing — no extra step, no extra fee. The verifier
reads the authority's time as the signing time; the signer's own clock is only a claim.
Don't trust the authority either — check it
Every stamp the authority issues goes into a public, append-only transparency log.
trustdid-verify --audit proves a stamp is in that log and that the log has never rewritten its
past. See how it works, and check it yourself →