[Interop] Independent check: FURUI day record 2026-11-03 and its Bitcoin anchor (block 974617)

[Open Verifiable AI Consortium]

> Hello all,
> 
> This is the first post on this list: an independent check of one public record, so that anyone can repeat it.
> 
> Subject of the check: the FURUI day record for 2026-11-03, published by The HORIZONs Co., Ltd. (HORIZON SHIELD), and its Bitcoin anchor.
> 
> Record: https://ledger.horizonshield.dev/furui-check-day/280f70f3688bdc18f3a5f8f735889f30d4a52be8e394c98601a160fcaf229f3f
> Ledger entry: https://ledger.horizonshield.dev/ledger/250
> Proof: https://ledger.horizonshield.dev/ledger/250/ots
> Key: https://ledger.horizonshield.dev/.well-known/furui-check-keys.json
> 
> What we checked, with our own code (Python, PyNaCl, the opentimestamps library) and not with the publisher's verifier:
> 
> 1. Record bytes. SHA-256 of record_canonical = 280f70f3688bdc18f3a5f8f735889f30d4a52be8e394c98601a160fcaf229f3f, equal to the name in the URL. The record states day 2026-11-03, n = 2, root e5f2c113384eebfaae94e438c5bba359b848fbdb0c2f0644cdbcce6f4906c313 (RFC 6962, SHA-256).
> 2. Signature. Ed25519 by key runner-1 (OwaxB47EcLw8lxVBl3BeSjUKUbEAsdXuVW1wFOWHzYc=) verifies over the bytes "furui-check-day-v0\n" followed by the canonical JSON of the record without its signatures field (keys sorted, no whitespace). Result: valid.
> 3. Batch. Ledger entry 250 is a nenrin-agreement-batch-v1 record of 20 records. Its bytes hash to a56363c9b01f652f7fb377fb67c04ec2ebc9bfdf6f1f5794293a6971f0509221, and the list contains the day record hash above.
> 4. Anchor. Executing the OpenTimestamps proof from a56363... ends in a Bitcoin block header attestation at height 974617. The computed Merkle root, 9cad0a051dbd3c6aa47c4f6410416f7ad033bcb56855a7eda918c9d2720f56ce, equals the Merkle root of block 974617 (block time 2026-11-05 03:31:45 UTC) as served by a public block explorer (Blockstream).
> 
> Result: the record is unaltered, signed by the key the ledger serves, included in batch entry 250, and that batch existed no later than Bitcoin block 974617.
> 
> Limits, as the record itself states: this does not check any envelope, content or check behind the root (only the runner holds the leaves), and the anchor bounds the time from above and settles nothing else. We read the block header from one explorer; a check against your own Bitcoin node is stronger.
> 
> Corrections and repeat runs with other tools are welcome on this list.
> 
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> 
> With warm regards,
> The OVAIC team
> Open Verifiable AI Consortium
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