Sigstore and in-toto answer related questions. Sigstore helps a verifier check a signature and its signing identity. in-toto provides formats and a framework for describing software supply-chain steps and evaluating evidence against policy. Teams can use them together.
What is Sigstore?
Sigstore is an open-source signing and verification ecosystem. It includes clients such as Cosign, the Fulcio certificate authority, and the Rekor transparency log. Public services are one deployment option; the project is not simply a hosted signature database.How does Sigstore work?
In a typical keyless flow, a client generates an ephemeral key and authenticates to an identity provider. Fulcio issues a short-lived certificate binding the public key to the authenticated identity. The client signs an artifact or statement. Verification checks the signature, the expected identity and issuer, the trusted certificate chain, and the required transparency or timestamp evidence.
A valid signature does not say that the signed software is safe. An authorized signer can sign malicious software or an inaccurate statement. Identity verification is one part of a trust decision.
What is in-toto?
in-toto is an open-source project for software supply-chain integrity. Its attestation format connects a statement about an artifact to that artifact's digest and a typed predicate. Its framework also supports defining authorized steps and checking supplied evidence against a policy.How does in-toto work?
Consider a release that requires a build and a vulnerability scan. Evidence can record the build's inputs and output digest, then associate the scan result with that same output. A verifier checks the expected producers, the artifact bindings, and the required results before accepting the release.
The verifier still needs an explicit trust model. A compromised builder that controls both the work and the evidence can make false statements. Independent observation, protected signing identities, and isolated execution can strengthen that boundary; a format alone cannot.
Key differences between in-toto and Sigstore
- Signing and identity: Sigstore helps sign and verify artifacts and statements.
- Evidence structure: in-toto statements describe an artifact and a claim about it.
- Policy: a verifier decides which producers, steps, and results are acceptable.
- Storage: retaining an attestation is separate from signing or accepting it. A transparency log is not a private evidence warehouse.
Both are open-source ecosystems. Neither is a certificate that an entire product or organization is compliant.
Why high-compliance organizations use in-toto
A control owner needs to know which test ran, what it examined, and what result it produced. Artifact-bound evidence can support that review and make repeated checks easier. The organization must still establish the control's scope, the producer's trustworthiness, and whether the test actually addresses the requirement.
How in-toto detects tampering
Verification can detect a mismatch between an artifact's bytes and its recorded digest, an invalid signature, or evidence that fails a configured policy. It cannot detect every malicious action, reconstruct work that was never observed, or establish the truth of a claim solely because it is signed.
Getting started with in-toto
Start with one decision: for example, accepting a release only when an approved scanner has examined the exact artifact. Define the producer you trust, capture the scan, retain its signed result, and test the verifier with a changed artifact, a missing result, and an unexpected signer.
