"Leider" (German for Unfortunately) is a song by German Neue Deutsche Härte band Eisbrecher and the first single from their album Antikörper. On 22 August 2006, a double-single titled "Leider/Vergissm
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 0x7224a1d26d765a47f9941b6f4b6db3cef4ad8717b3a558ffdc1a880ee1f11ff7. Chain 2 (Bitcoin): anchored in block 954131 (2026-06-17T19:19:19Z). Bridge: the canonical record inside this Bitcoin proof contains the same CopyrightID. Verify: download https://artists.proofprofile.net/proofs/artist/7cbe03cb-2c76-4f64-a2b0-8b52bd621e6a.json and https://artists.proofprofile.net/proofs/artist/7cbe03cb-2c76-4f64-a2b0-8b52bd621e6a.ots, run `ots verify -f record.json proof.ots` (https://opentimestamps.org).