Sigma 7 may refer to: the callsign of the spacecraft used in the 1962 Mercury-Atlas 8 mission the SDS Sigma 7 computer, made by Scientific Data Systems (SDS), later known as Xerox Data Systems (XDS)
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 0xb51562fcd7757e320bfd88ae897bea70bfc527b9e0fd27526d27118fc7049ac6. Chain 2 (Bitcoin): anchored in block 954342 (2026-06-19T03:22:39Z). Bridge: the canonical record inside this Bitcoin proof contains the same CopyrightID. Verify: download https://artists.proofprofile.net/proofs/artist/86e008aa-839b-497e-bc79-9e4019817043.json and https://artists.proofprofile.net/proofs/artist/86e008aa-839b-497e-bc79-9e4019817043.ots, run `ots verify -f record.json proof.ots` (https://opentimestamps.org).