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Reviewed by Jennifer Montecillo, MD, medical reviewer. Non-practicing medical reviewer.

© 2026 Fonteum, Inc. All rights reserved.

The U.S. healthcare graph AI can cite — every fact carries its source.

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Trust → Integrity → Chain

Attestation chain head.

Every snapshot Fonteum publishes is SHA-256 hashed at write time and appended to a Certificate-Transparency-style log. The head of that log — the most recent attestation — is published below. Once the per-snapshot previous_link_hash backfill lands under §sprint3-attestation-chain, every row will additionally chain backwards to the prior row, making any tampering detectable by a single recomputation.

Current head
snapshot_id
154
source_id
source_manifest
snapshot_date
2026-06-10
content_hash (SHA-256)
558af460a5e8b853b89961fd5879b53d4782e3c4aefb4e7632deea49321821ad
attested_at
2026-06-10T06:15:16.018209+00:00
previous_link_hash
(deferred — §sprint3-attestation-chain)
signing_key
(STH signing key publishes with first signed tree head)

Total attestations on file: 110

Witness co-signatures — snapshot 154

No witness signatures on file for this snapshot.

Verify this snapshot programmatically: /api/attestation/verify/154

How the chain works

  1. Each upstream archive is downloaded, SHA-256 hashed, and written to snapshot_attestations with the source archive URL preserved verbatim.
  2. Each new row carries a previous_link_hashfield set to the prior row's content_hash (or all-zero for the first row in a source family). Tampering with any historical row breaks every downstream link.
  3. A periodic STH (Signed Tree Head) seals the chain head with Fonteum's chain-signing public key. Verifiers fetch the STH, walk the chain backwards, and confirm every link.
/verify — re-hash any attested snapshot →/trust/integrity — full attestation index →/docs/cache — 90-day source mirror →

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