Sigstore

Sigstore is an open-source project hosted by the Cloud Native Computing Foundation (CNCF) that aims to improve software supply chain security by making it easier to sign, verify, and audit software artifacts. Its approach centers on cryptographic signing with short-lived credentials and a public, tamper-evident record of signatures.

The project comprises three main components: Fulcio, Cosign, and Rekor. Fulcio is a certificate authority that issues short-lived X.509 code signing certificates bound to a developer’s identity, typically via an OpenID Connect (OIDC) provider. Cosign is a signing and verification tool (and library) used to sign artifacts such as container images and binaries, producing signatures and optional attestations. Rekor is a transparency log that records signatures and attestations to provide an auditable, tamper-evident history of provenance.

How Sigstore works in practice: a developer authenticates with an identity provider, Fulcio issues a ephemeral certificate, and Cosign signs the target artifact using a corresponding private key. The signature, certificate, and any attestations are stored and verifiable, with Rekor offering a public log entry that can be consulted to confirm provenance. Cosign can attach signatures to OCI-compatible container registries, enabling verification during deployment or runtime.

Adoption and scope: while commonly used to sign container images, Sigstore’s tooling supports signing of various artifact types and integrates with CI/CD pipelines and supply-chain workflows. It promotes practices such as verifiable provenance, SBOMs, and alignment with supply-chain security frameworks like SLSA, while reducing key-management risk through short-lived credentials and public transparency.