A tamper-evident AI log binds each execution to a SHA-256 commitment over canonicalised fields and an Ed25519 signature from an independent attestation node. Any later change to inputs, parameters, outputs, or metadata invalidates the certificate hash. This is what regulators, auditors, and customers mean when they ask for tamper-proof AI logs, tamper-evident is the accurate technical term.
Side-by-side comparison
| Dimension | Standard AI logs | Tamper-evident AI logs (NexArt CER) |
|---|---|---|
| Storage | Application or observability database | Portable JSON artifact, verifiable offline |
| Integrity | None; the operator can modify entries | SHA-256 canonical hash over protected fields |
| Third-party signature | None | Ed25519 signature from an independent attestation node |
| Detection of edits | Not detectable without external comparison | Any modification breaks the certificate hash immediately |
| Retention control | Controlled by the operator | Controlled by whoever holds the record |
| Verifiable by outsiders | No | Yes, with the published public key |
| Regulator-ready | No, treated as operator narrative | Yes, cryptographic evidence independent of the operator |
Why 'tamper-proof' is the wrong word
No log is truly tamper-proof; any record can be deleted from a database. What matters is tamper-evidence: can a third party detect that a record has been altered without trusting the operator? A NexArt Certified Execution Record answers yes. The certificate hash covers the exact bytes of every protected field, and the attestation node's signature commits the hash to an external key.
This distinction is what the EU AI Act Article 12 record-keeping obligations require in practice, evidence that survives the operator and can be checked by an outside party.
Frequently asked
Is a tamper-evident log the same as an immutable log?
No. An immutable log prevents modification through storage guarantees. A tamper-evident log allows deletion but makes any content modification cryptographically detectable. Tamper-evidence is a stronger practical property because it does not depend on trusting a specific storage layer.
Do I need to store raw AI inputs and outputs to have a tamper-evident log?
No. In confidential mode, sensitive fields are replaced with SHA-256 commitments before permanent storage in the confidential proof record. The commitment is what gets signed, so the record proves what executed without exposing the underlying data.
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