Integrity

How a sealed evidence package makes a later modification detectable.

An evidence package is only as valuable as the certainty that it was not modified after it was produced. That certainty is what sealing provides.

The principle behind sealing

Before any fingerprint is computed, the package's content — job metadata, control results, measured durations, and everything else it contains — is put into a single canonical form: a stable, unambiguous representation of that data. It is on this canonical form that a cryptographic fingerprint (a hash) is computed.

This construction has a direct consequence: any modification made to the package after sealing changes its canonical form, and therefore its fingerprint. A later modification — even a minor one — becomes detectable this way, since the recomputed fingerprint would no longer match the one recorded at the moment of sealing.

What the signature guarantees, and what it does not

The sealed package is signed by RestorSignal or by the agent that produced the result. This signature guarantees the package's integrity within the scope of the key used to produce it, and identifies who performed the sealing. Its scope needs to be stated precisely: this signature does not constitute a certification of the backup itself. It attests that the package's content has not been altered since it was sealed, and by whom it was sealed — nothing more, and that is already a lot.

The integrity elements a package documents

Beyond the package's overall hash, an evidence package typically documents several complementary integrity elements: the fingerprint of the restored artifact itself, the digest of the runner image used, that runner's version, the version of the normative reference framework applied at the time of the test, and the version of the technical schema used to structure the package. Taken together, these elements make it possible to reconstruct exactly under which technical and normative conditions a given result was obtained, and to verify afterward that none of them were substituted.

For how sealing relates to timestamping the package, see Timestamping.