Sigstore and signed software

In short: Sigstore is a project that makes signing software and containers simple and free, without having to manage long-lived keys.

In more detail: A signature proves who built a program and that it is unchanged since. Until now this often failed on key management.

In Depth

• Cosign: Signs container images and files and verifies signatures.
• Keyless: You sign in via OIDC (for example with GitHub). The certificate authority Fulcio issues a short-lived certificate for that identity, and after signing the key is discarded.
• Rekor: A public, tamper-evident log (“transparency log”) recording every signature. This later proves that it was valid at the time.
• Context: Against supply-chain attacks. Complements SBOMs (bills of materials of the components) and the SLSA standard, which describes levels of build trust.
• Use: Kubernetes policies can admit only signed images. npm and PyPI show provenance attestations.
• Limit: A signature says who built it, not that the software is free of defects.

See also: reproducible builds