Proof · Pillar 2

Bitemporal history & attestation chain

Every fact Fonteum publishes traces to a specific government file with a known SHA-256. The chain below shows how: a claim records when the source asserted it (valid-time) and when we recorded it (system-time). Anyone can re-download the source file and confirm the hash — no login required.

How the chain works

1
Claim — A fact about a facility or provider (e.g. star rating at CCN 460057). Has valid_from, valid_to, and recorded_at columns (bitemporal).
2
Source — The exact government CSV fetched at a specific date. Fonteum stores the SHA-256 of the raw file so you can re-download and confirm it.
3
Snapshot + witness — An aggregate snapshot of the ingest is signed with an Ed25519 key (methodology: in-toto-witness/v1). The signed payload contains the SHA-256 of the snapshot contents.

Bitemporal columns

Column	Axis	Meaning
valid_from	Valid-time start	When the source asserted this fact became true
valid_to	Valid-time end	When the fact stopped being true; null = still current
recorded_at	System-time	When Fonteum first wrote this row to the database

Backfill note: valid_from ← asserted_at; recorded_at ← created_at. No valid-time was fabricated.

Worked example — real claim

Claim

id:b5f3b055-abb5-4dbe-8a6b-745b2fa49455
claim_key:facility.09002f.star_rating.2026q2
metric:star_rating
value:3 rating_1_5
valid_from:2026-06-04T16:50:27.482+00:00
valid_to:— (current)
recorded_at:2026-06-04T16:50:31.286726+00:00

Source

name:CMS Hospital General Information 2026-04-28
publisher:Centers for Medicare & Medicaid Services
retrieved:2026-06-04T16:45:19.411+00:00
sha256:83c98b2e8687580e0482b13e1e9acd5813534be243e5ccd9f55556a869595d40

Point-in-time diff

Check any claim

Paste a provenance_claims UUID to see its attestation chain.

Methodology

Witness signature algorithm: Ed25519 (Node.js crypto module)
Canonical payload format: {"methodology_version":"...","sha256":"...","signed_at":"...","snapshot_id":...} — Keys always sorted alphabetically for determinism.
Methodology version pinned: in-toto-witness/v1
Source hash: SHA-256 of the raw downloaded file, stored in provenance_sources.content_sha256

Compliance posture