Interview Security & DevSecOps

What is artifact signing, and what is Sigstore/cosign? [Intermediate]

Answer

Artifact signing cryptographically signs a build artifact or image digest so consumers can verify integrity and publisher identity. Sigstore and cosign make this practical for containers by supporting keyless signing, transparency logs, and signature verification in CI/CD and Kubernetes admission.

Technical explanation

Signing mutable tags is weaker; sign immutable digests so the signature binds to exact content.

Keyless signing can bind an artifact to an OIDC identity from CI, reducing long-lived signing-key risk.

Verification should happen before promotion and again before deployment.

Hands-on example

Hands-on:

cosign sign --keyless registry.example.com/checkout@sha256:abc

cosign verify --certificate-identity-regexp 'https://github.com/org/repo/.github/workflows/.*' \

--certificate-oidc-issuer https://token.actions.githubusercontent.com \

registry.example.com/checkout@sha256:abc

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