Users
Handle a duplicity proof
What a duplicity proof is, how to check one, and what it obliges you to do.
A duplicity proof is what a witness returns instead of a cosignature when a chain presents the same index with two different heads. It contains both signed tuples, so the contradiction is in the submitter's own signatures.
You get one from a POST /v1/anchor that conflicts:
Check it
auths artifact verify --offline duplicity.json
It verifies with no trust in the witness that emitted it and no network — the proof is self-contained.
Treat one as disqualifying
There is no innocent reading of two histories at one index. The proof is portable: attach it to a dispute, publish it, hand it to a counterparty.
Where they come from
Watchers — the market among them — scan witness logs for exactly these collisions and publish what they find. You don't have to be the one who catches it.
If it doesn't verify: a proof that fails offline verification proves nothing; it may be a malformed or fabricated artifact. Discard it.