Sjaak is a given name and a nickname. Notable people with the name include: Jacobus Nicolaas Sjaak Brinkkemper (born 1958), Dutch computer scientist, and professor Jakob Frederik Sjaak Köhler (1902
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
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0x0782f1e06060081bcf6f1b03493f91d4c0aa22960b6fbf483286154dd1eb4f7e. Chain 2 (Bitcoin): anchored in block 953408 (2026-06-12T19:28:13Z). Bridge: the canonical record inside this Bitcoin proof contains the same CopyrightID. Verify: download https://artists.proofprofile.net/proofs/artist/a7fa8a6e-0845-4d18-ac49-7559395a16aa.json and https://artists.proofprofile.net/proofs/artist/a7fa8a6e-0845-4d18-ac49-7559395a16aa.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
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0xa8cdb3f0b202d5d00e88fb03142d522d8e60d61c4cd3ff451635c74cc71bd0c5. 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/NLG661800280.
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0xb0e712ed924400bfadeda70d7eeb15c557ca58e5429a620e5bff1c1d075553a7. Chain 2 (Bitcoin): anchored in block 956312 (2026-07-02T05:09:12Z), 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/NLG661800229.
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0x0b9b4045a3c5454bf06fecbda4d479cdbcbab81a8c21444d1f190e9ae5f16b11. 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/NLG661800306.
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0x6edec29ee15c591f00a699e562d52cbfb430dc927709155ae8abe88c53f92f32. Chain 2 (Bitcoin): anchored in block 953528 (2026-06-13T15:41:10Z), 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/NLG661800308.
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0x34b700e1ab3ed1528919eae7e1da305e27204e1e6998dc3f43c7c05799c4a6f3. 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/NLG661800309.
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0x281257da4b7a0ac093eff2c86f213c8b403556c1520b799152235df9ffa766a1. Chain 2 (Bitcoin): anchored in block 953528 (2026-06-13T15:41:10Z), 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/NLG661800310.
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0x66cfd3b0edda3b555155497b33228d78ad12fdb2d6f271c0148b40a6039c0206. Chain 2 (Bitcoin): anchored in block 957124 (2026-07-08T03:53:27Z), 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/NLG661800313.
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0x9ffeb8f471dbd45eafca8e2e1b4b13eba6419599affee617578e5ec7fafcab16. Chain 2 (Bitcoin): anchored in block 960264 (2026-07-30T14:36:16Z), 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/NLG661800305.
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 0x29bf71b3328b0d2377a52c8f6c7b702c446f59fa4f7edfbaec8ed55ef1e24417. Chain 2 (Bitcoin): anchored in block 960220 (2026-07-30T07:28:30Z), 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/NLG661800312.
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0x29fbfcde840a4b7c407a6d86a5922df50eb873295ea484ac45c4204608d244c0. 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/NLG661800314.
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0x40fa02722d48de7afdbbf491f7cf0356bf6ae9b55f3776ad58b9c20dd70174f0. Chain 2 (Bitcoin): anchored in block 960321 (2026-07-30T22:27:30Z), 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/NLG661800315.
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0x0ddb80d6ba7f3c5371aece7d03388d18d3e090068abc890a47ded116988cfdfa. Chain 2 (Bitcoin): anchored in block 956304 (2026-07-02T03:55:08Z), 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/NLD682102817.
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0x2c62ab54df7d701d72e440bf9155bf2d8cd2f829179182e911e1e1da2aeae95d. Chain 2 (Bitcoin): anchored in block 960485 (2026-08-01T00:10:46Z), 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/NLD682102816.
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0xfa1571c1f7ca9f0ae28740b79cc9a763e061f906b9370843b1ff48ed6dfc3c5d. Chain 2 (Bitcoin): anchored in block 953513 (2026-06-13T12:47:07Z), 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/TCAEL1994584.
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0x7f85a1a74815a41048fe37cb69f6b2201d617f1ce0d7049b9d5ee42b53cf9bbd. Chain 2 (Bitcoin): anchored in block 953536 (2026-06-13T17:25:41Z), 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/NLYN51300058.
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0xccbb217bf941934a6e05d83463e143db027122321647ab4a4837043f9d31c3bc. Chain 2 (Bitcoin): anchored in block 956302 (2026-07-02T03:30:09Z), 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/NLG661900440.
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0x03fc8711b5fce69e02e0af5d07433e62ccba795141c5d0ffd81f336b3896da06. Chain 2 (Bitcoin): anchored in block 957124 (2026-07-08T03:53:27Z), 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/NLF711811333.
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0xa9f60ce8b5196eb5c533e7fe669cab194d8e1b456616fbc65354c5624967c901. Chain 2 (Bitcoin): anchored in block 960383 (2026-07-31T09:50:37Z), 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/NLF711807524.