Git Commit Signing and Image Signing
Intro: Signing does not replace review, but it improves provenance and auditability. The goal is not symbolic cryptography. The goal is to make high-value code and release events harder to forge and easier to verify.
Commit signing
Use commit or tag signing when you need stronger confidence that privileged changes came from expected identities.
Good use cases:
- protected repositories that control infrastructure, CI/CD, or authentication logic;
- release tags and hotfix branches;
- repositories where emergency or admin-only changes must be attributable.
Image signing
Use image signing and verification when promotion or admission decisions depend on provenance.
Good use cases:
- promotion from build to staging or production registries;
- admission control in Kubernetes;
- evidence-backed releases with SBOMs or attestations.
Practical guidance
- sign the smallest set of truly sensitive repositories first;
- treat signing keys, identities, and verification policy as an operational system, not a checkbox;
- verify signatures at promotion or admission time, not only at build time;
- pair signing with branch protection, review policy, and artifact immutability.
Use with
- provenance-aware release evidence;
- SLSA / attestation discussions;
- Harbor or admission controller policy;
- emergency-change attribution.