Cosign vs GPG: Signing Artifacts and Containers
Both sign artifacts, but for different eras. GPG is the long-standing general signing tool with long-lived keys you manage; Cosign (Sigstore) is built for containers and supply chain, with keyless signing via OIDC and a public transparency log.
Cosign and GPG both prove an artifact came from you and was not tampered with. GPG is general and mature but puts key management on you; Cosign targets container images and OCI artifacts and can sign without you holding long-lived keys. Here is the honest comparison.
| Cosign | GPG | |
|---|---|---|
| Built for | Containers, OCI artifacts, supply chain | General-purpose signing/encryption |
| Keys | Keyless (OIDC) or key pairs | Long-lived key pairs you manage |
| Transparency log | Yes (Rekor) | No |
| Container support | First-class (signs images by digest) | Manual, not container-native |
| Key management burden | Low with keyless | Higher (rotation, distribution) |
| Maturity | Newer, widely adopted | Decades old, ubiquitous |
Key management vs keyless
GPG relies on long-lived private keys you generate, protect, rotate, and distribute, which is powerful but operationally heavy, especially in ephemeral CI runners where storing a signing key is risky. Cosign keyless signing uses short-lived certificates tied to an OIDC identity (for example your CI job identity), so there is no long-lived secret to leak, and each signature is recorded in the Rekor transparency log.
Container-native by design
Cosign signs and verifies container images by digest and stores signatures alongside images in the registry, which GPG was never designed to do. For OCI images and supply-chain attestations (SBOMs, provenance), Cosign is the natural fit. GPG remains excellent for signing releases, commits, and packages in traditional workflows.
In CI
Cosign keyless signing pairs perfectly with CI: the runner OIDC token becomes the signer identity, with no secret to manage, and verification policies can require signatures before deploy. If you already sign releases with GPG, that can continue in parallel.
The verdict
Choose Cosign for signing container images and supply-chain artifacts, especially with keyless CI signing and transparency logging; keep GPG for general signing, release artifacts, and commits. They address different needs and often coexist.