XAC may refer to: the IATA code for Arcachon - La Teste-de-Buch Airport, France the ISO 639-3 code for the Kachari language Xinyang Agricultural College Xi'an Aircraft Industrial Corporation, als
1. Compute SHA-256 of OTSCanonicalRecord value → must equal OTSHash 2. Open OTSProofURL → extract Bitcoin block number → must equal OTSBitcoinBlock 3. GET OTSBitcoinBlockVerifyURL → returns the Bitcoin block hash at height OTSBitcoinBlock; GET https://blockstream.info/api/block/{that hash} → its timestamp must match OTSTimestamp 4. Read CopyrightID inside OTSCanonicalRecord → must equal the CopyrightID above 5. GET OTSVerificationAPI → pre-computed 6-check result from server 6. If all match: this entity was registered on CopyrightChains at OTSTimestamp, independently verifiable on Bitcoin Note: an OTS proof may carry multiple Bitcoin attestations; OTSBitcoinBlock is the earliest confirmed one — a later attestation inside the proof corroborates it and is not a mismatch
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0xaa131fcb2da62fc4ceb1ea435c24c3693500ee26ac90cc2476acfdcc888be3cd. Chain 2 (Bitcoin): anchored in block 954017 (2026-06-16T23:38:33Z). Bridge: the canonical record inside this Bitcoin proof contains the same CopyrightID. Verify: download https://artists.proofprofile.net/proofs/artist/371c9271-2055-4443-88fc-95e456307afd.json and https://artists.proofprofile.net/proofs/artist/371c9271-2055-4443-88fc-95e456307afd.ots, run `ots verify -f record.json proof.ots` (https://opentimestamps.org).