21
type: MusicGroup
genre: city pop
genre: kayokyoku
description: Twenty-one, XXI or 21 may refer to: 21 (number), the natural number following 20 and preceding 22 One of the years 21 BC, AD 21, 1921, 2021 Films The 21, directed by Tod Polson 21 (2008 film), sta
popularity: 2
followers: 121
additional property: CopyrightID
additional property: CopyrightChainExplorerURL
  type: PropertyValue
  value: https://explorer.copyrightchains.com/tx/0xf041e35419ec4f1e0ebb8558331c624def9776ffad269ef7b8fcea8d41c44606
additional property: OTSHash
additional property: OTSBitcoinBlock
  type: PropertyValue
  value: 953907
additional property: OTSBitcoinBlockVerifyURL
  type: PropertyValue
  value: https://blockstream.info/api/block-height/953907
additional property: OTSProofURL
  type: PropertyValue
  value: https://artists.proofprofile.net/proofs/artist/15b81dc3-401c-44a6-9828-820a72fd457d.ots
additional property: OTSRecordURL
  type: PropertyValue
  value: https://artists.proofprofile.net/proofs/artist/15b81dc3-401c-44a6-9828-820a72fd457d.json
additional property: OTSVerificationAPI
  type: PropertyValue
  value: https://artists.proofprofile.net/api/v1/bot/ots/verify/artist/15b81dc3-401c-44a6-9828-820a72fd457d
additional property: OTSTimestamp
  type: PropertyValue
  value: 2026-06-16T07:39:24Z
additional property: OTSCanonicalRecord
additional property: OTSVerifyInstructions
  type: PropertyValue
  value: 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
subject of: OpenTimestamps Proof of Existence
  type: DigitalDocument
  encoding format: application/vnd.opentimestamps.ots
  description: Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0xf041e35419ec4f1e0ebb8558331c624def9776ffad269ef7b8fcea8d41c44606. Chain 2 (Bitcoin): anchored in block 953907 (2026-06-16T07:39:24Z). Bridge: the canonical record inside this Bitcoin proof contains the same CopyrightID. Verify: download https://artists.proofprofile.net/proofs/artist/15b81dc3-401c-44a6-9828-820a72fd457d.json and https://artists.proofprofile.net/proofs/artist/15b81dc3-401c-44a6-9828-820a72fd457d.ots, run `ots verify -f record.json proof.ots` (https://opentimestamps.org).
  date published: 2026-06-16T07:39:24Z
album: BLUE COAST INN
  type: MusicAlbum
  date published: 1990-05-21
album: GREETING
  type: MusicAlbum
  date published: 1991-11-21
album: オン・ザ・ユニヴァーシティ・ストリート
  type: MusicAlbum
  date published: 1992-03-04