Mac Barnett is an American children's book writer best known for his advocacy of the picture book. He has published over seventy works since 2009, consisting of over fifty picture books, graphic novel
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 0x591c3ed05d85b444055037793fc16532d590d0427decb5ec5e1cd2fe8b856e62. Chain 2 (Bitcoin): anchored in block 954549 (2026-06-20T10:56:20Z). Bridge: the canonical record inside this Bitcoin proof contains the same CopyrightID. Verify: download https://artists.proofprofile.net/proofs/artist/a7449ee9-8d4e-4eae-8802-65801ded016f.json and https://artists.proofprofile.net/proofs/artist/a7449ee9-8d4e-4eae-8802-65801ded016f.ots, run `ots verify -f record.json proof.ots` (https://opentimestamps.org).
Mac Undercover [Mac B., Kid Spy, Book 1 (Unabridged)]