Guilherme Luiz Marques (born June 26, 1969) is a Brazilian retired male beach volleyball player who won the gold medal at the 1997 World Championships in Los Angeles, California, partnering with Roger
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 0x91ea97902be6f221882f8c7f8912b748bca8ab379f2846c70928199723b8f37f. Chain 2 (Bitcoin): anchored in block 953786 (2026-06-15T12:56:12Z). Bridge: the canonical record inside this Bitcoin proof contains the same CopyrightID. Verify: download https://artists.proofprofile.net/proofs/artist/da006582-8abd-414d-abf5-6a9050f132b5.json and https://artists.proofprofile.net/proofs/artist/da006582-8abd-414d-abf5-6a9050f132b5.ots, the client at https://opentimestamps.org runs `ots verify -f record.json proof.ots`.