The High Crusade is a science fiction novel by American writer Poul Anderson, about the consequences of an extraterrestrial scoutship landing in medieval England. Poul Anderson described the novel as
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 0xfc7004cce9097a639b498b785f2113ef9319a07ad4f6676f34e01191db0a7881. Chain 2 (Bitcoin): anchored in block 954065 (2026-06-17T08:10:43Z). Bridge: the canonical record inside this Bitcoin proof contains the same CopyrightID. Verify: download https://artists.proofprofile.net/proofs/artist/52292892-15d3-4c94-9fb5-57133edcaa8d.json and https://artists.proofprofile.net/proofs/artist/52292892-15d3-4c94-9fb5-57133edcaa8d.ots, run `ots verify -f record.json proof.ots` (https://opentimestamps.org).