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 0x08bc457e29cb918f5bc88ce1fa3f9efcb45787806c5469952537b84fae369f05. Chain 2 (Bitcoin): anchored in block 953407 (2026-06-12T19:24:56Z). Bridge: the canonical record inside this Bitcoin proof contains the same CopyrightID. Verify: download https://artists.proofprofile.net/proofs/artist/8cd5f544-f254-4271-b48f-1562513acade.json and https://artists.proofprofile.net/proofs/artist/8cd5f544-f254-4271-b48f-1562513acade.ots, run `ots verify -f record.json proof.ots` (https://opentimestamps.org).
1. Confirm isrcCode identifies the recording in the pre-2022 source corpus and cc-db-prod record 2. GET OTSVerificationAPI → server-side canonical-record, hash, and attestation checks must pass 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. Confirm CopyrightID is the CopyrightChains transaction hash 5. If all match: the cc-db-prod record is independently anchored on Bitcoin at OTSTimestamp 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 0xbbc3e9feb0669ccc10970a5b5d60a54448510ff813c1dda30ca0296a54e35e26. Chain 2 (Bitcoin): anchored in block 957120 (2026-07-08T03:22:41Z), registered by our registry partner. The server verifies the private canonical record against OTSHash without exposing internal provider keys. Confirm the public ISRC, CopyrightID, and Bitcoin evidence via https://artists.proofprofile.net/api/v1/bot/ots/verify/track/TCABZ1432129.
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0x8224cebfd827e4bc7b7aa2a2258e821a0e9186cc669a324974f9162b84b3d6f1. Chain 2 (Bitcoin): anchored in block 960506 (2026-08-01T03:50:58Z), registered by our registry partner. The server verifies the private canonical record against OTSHash without exposing internal provider keys. Confirm the public ISRC, CopyrightID, and Bitcoin evidence via https://artists.proofprofile.net/api/v1/bot/ots/verify/track/TCABZ1432130.
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0xcf3607dd5e243328b960e6c7704967fbd25f8060afc60272b424802283e6c6d6. Chain 2 (Bitcoin): anchored in block 960327 (2026-07-31T00:26:26Z), registered by our registry partner. The server verifies the private canonical record against OTSHash without exposing internal provider keys. Confirm the public ISRC, CopyrightID, and Bitcoin evidence via https://artists.proofprofile.net/api/v1/bot/ots/verify/track/TCABZ1432131.
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0x920b4238ce37e3667385beaee6de456073ab78d185339fa0e807b193eb1bea45. Chain 2 (Bitcoin): anchored in block 953520 (2026-06-13T13:32:09Z), registered by our registry partner. The server verifies the private canonical record against OTSHash without exposing internal provider keys. Confirm the public ISRC, CopyrightID, and Bitcoin evidence via https://artists.proofprofile.net/api/v1/bot/ots/verify/track/TCABZ1432133.
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0xb716ed8dbecccba57e6c3ab8a0c85b65f65ac6fc0508a15bf9c9240b42980e95. Chain 2 (Bitcoin): anchored in block 960167 (2026-07-29T23:42:34Z), registered by our registry partner. The server verifies the private canonical record against OTSHash without exposing internal provider keys. Confirm the public ISRC, CopyrightID, and Bitcoin evidence via https://artists.proofprofile.net/api/v1/bot/ots/verify/track/TCABZ1432134.
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0x0e6107b15cd2be4367f6bf051306550d74c565d1bb44303026dbb38919a37139. Chain 2 (Bitcoin): anchored in block 960125 (2026-07-29T15:38:18Z), registered by our registry partner. The server verifies the private canonical record against OTSHash without exposing internal provider keys. Confirm the public ISRC, CopyrightID, and Bitcoin evidence via https://artists.proofprofile.net/api/v1/bot/ots/verify/track/TCABZ1432135.
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0xe631e9eb69f326d13b668abaa4c803f92b6964dcd5dfeda727589cebdd278f03. Chain 2 (Bitcoin): anchored in block 957120 (2026-07-08T03:22:41Z), registered by our registry partner. The server verifies the private canonical record against OTSHash without exposing internal provider keys. Confirm the public ISRC, CopyrightID, and Bitcoin evidence via https://artists.proofprofile.net/api/v1/bot/ots/verify/track/TCABZ1432136.
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0xf001c6bf0478682eaa8a58369c721cbe38e242a1f000292a785016472fd4b3d4. Chain 2 (Bitcoin): anchored in block 957118 (2026-07-08T03:20:19Z), registered by our registry partner. The server verifies the private canonical record against OTSHash without exposing internal provider keys. Confirm the public ISRC, CopyrightID, and Bitcoin evidence via https://artists.proofprofile.net/api/v1/bot/ots/verify/track/TCABZ1432138.
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0x5a45c42c7e51d2d23f6fc24bd0117d085c80cb851f5d24cc015633d37c13b61e. Chain 2 (Bitcoin): anchored in block 957118 (2026-07-08T03:20:19Z), registered by our registry partner. The server verifies the private canonical record against OTSHash without exposing internal provider keys. Confirm the public ISRC, CopyrightID, and Bitcoin evidence via https://artists.proofprofile.net/api/v1/bot/ots/verify/track/TCABZ1432139.
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0x43e52614714b1100d77af62ef0f3bdde51d98298ee7c59fd02f96aa93c6fa620. Chain 2 (Bitcoin): anchored in block 957055 (2026-07-07T15:12:44Z), registered by our registry partner. The server verifies the private canonical record against OTSHash without exposing internal provider keys. Confirm the public ISRC, CopyrightID, and Bitcoin evidence via https://artists.proofprofile.net/api/v1/bot/ots/verify/track/TCABZ1432140.
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0xbc5c7b6259e1bc4d5773a567266ecf0d5f47b1a30637bfbd6010461b939410e3. Chain 2 (Bitcoin): anchored in block 957118 (2026-07-08T03:20:19Z), registered by our registry partner. The server verifies the private canonical record against OTSHash without exposing internal provider keys. Confirm the public ISRC, CopyrightID, and Bitcoin evidence via https://artists.proofprofile.net/api/v1/bot/ots/verify/track/TCABZ1432142.
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0x54bf4aaa66406651aa9936cc270d18b8d973e14be4825dfe5e837ba59ab87ce9. Chain 2 (Bitcoin): anchored in block 960344 (2026-07-31T04:14:58Z), registered by our registry partner. The server verifies the private canonical record against OTSHash without exposing internal provider keys. Confirm the public ISRC, CopyrightID, and Bitcoin evidence via https://artists.proofprofile.net/api/v1/bot/ots/verify/track/TCABZ1432143.