Audit chain + TSA anchoring
Every action in a session — joins, snapshots, whiteboards, recording starts, ends — lands in a per-session SHA-256 hash chain. The chain head is anchored at multiple independent timestamp authorities the moment the session closes. Tampering is detectable; the proof survives without trusting us.
How it works
Fiecare eveniment de audit poartă hash-ul SHA-256 al evenimentului anterior plus propriul conținut canonic, iar un blocaj de scriere serializează evenimentele astfel încât două capturi concurente să nu poată intra în competiție pe lanț. Reordonați ulterior un singur eveniment și fiecare hash următor nu se mai potrivește — verificarea eșuează la primul rând divergent.
| Field | Purpose |
|---|---|
| sequence | Contor monoton per sesiune. Append-only, impus la nivelul bazei de date. |
| prev_hash | SHA-256 al hash-ului canonic al evenimentului anterior. Primul eveniment folosește un prefix format numai din zerouri. |
| payload_jsonb | Canonical-JSON event data. Sorted keys, no whitespace — so the hash is reproducible. |
| hash | SHA-256 over (sequence ‖ prev_hash ‖ kind ‖ canonical payload ‖ occurred_at). |
| occurred_at | Stamped on the server. Client clocks don't drive ordering. |
Multi-backend anchoring
On session end, the chain head is submitted to two independent timestamp authorities in parallel. One outage doesn't break the proof — the verifier accepts any token whose backend cross-check passes.
Public-ledger anchor
Chain head is committed to a smart contract on Tezos. Finality lands in 15–20 minutes; the receipt carries the block hash + depth. Anyone with the session's chain head can verify against the public ledger without our cooperation.
Qualified time-stamp
Synchronous timestamp request to a qualified TSA — DataSure (ANSSI-qualified, eIDAS Art. 42) on managed deployments, or FreeTSA for self-host pilots. The TSR is a signed ASN.1 token that any RFC 3161 verifier can validate offline.
The backend interface is swappable — Sectigo, DigiCert, OpenTimestamps and other qualified TSPs drop in with a config change. Customers on managed deployments inherit DataSure; self-host operators pick their own.
What verification looks like
Every session ships with a public verify URL (HMAC-pinned, expires in 90 days). The auditor opens it, sees the chain head, the TSA receipts, and a chain-integrity check — no login, no API key, no special tooling. The verifier re-hashes every event row and cross-checks the TSA witnesses; both must pass.
| Check | What it proves |
|---|---|
| chain_integrity.ok | Every row's hash matches the re-computed hash. No middle row was edited. |
| tokens[].ok | Each TSA receipt cross-checks against the chain head it claims to anchor. |
| event_count | Compared to the count the operator saw at close — detects truncation. |
| issuing_org_name | Identity of the org that ran the session — for the auditor's case file. |
Why this matters in court
eIDAS Art. 42 establishes legal presumption for qualified electronic timestamps in EU courts — a court must accept the timestamp as genuine unless the opposing party proves otherwise. Pair that with an immutable hash chain over the session events and the burden of proof flips: instead of "we recorded this, take our word for it," you have a cryptographic witness that's independent of us, independent of you, and verifiable years later without trusting either side.
See a chain you can poke at
The demo seeder mints a real session with a real audit chain anchored at real TSAs. Get a public verify URL, change a byte in the event log, watch the proof break.