A kontra (, 'three-stringed viola') is a Hungarian, Czech, Polish, Romanian, Slovak and Romani instrument common in Transylvania. Construction The kontra can be constructed new, but is most often a c
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 0x3736b63de1ba5e3d08033fa4469a02226bb24a1f548fd8d5e1f334b3c6ad6f2a. Chain 2 (Bitcoin): anchored in block 953617 (2026-06-14T09:00:45Z). Bridge: the canonical record inside this Bitcoin proof contains the same CopyrightID. Verify: download https://artists.proofprofile.net/proofs/artist/1be88a65-6c25-443b-ba22-ccb682963c53.json and https://artists.proofprofile.net/proofs/artist/1be88a65-6c25-443b-ba22-ccb682963c53.ots, the client at https://opentimestamps.org runs `ots verify -f record.json proof.ots`.