AWS Signer vs Cosign

AWS Signer is a managed code-signing service for verifying code integrity and publisher trust. It supports signing AWS Lambda deployment packages, code for supported IoT devices, and OCI container images using Notation. Lambda verifies signatures and package integrity when signed code is deployed. For containers, Signer works with Notation in registries such as Amazon ECR, with signatures stored alongside images for verification.

Administrators control access to Signer resources and actions through AWS Identity and Access Management policies. Signing profiles can be managed in the Signer console, AWS CLI, or API. Signer manages certificates and keys for Lambda and container workflows; IoT workflows can use a code-signing certificate imported into AWS Certificate Manager. Documentation also lists integrations with AWS Certificate Manager and CloudTrail, plus Amazon EKS image verification. Notation CLI and Signer plugin installers are listed for Linux, macOS, and Windows. API actions have per-second quotas by account and Region, with no minimum request rate. Use with specified AWS services has no additional charge, though related charges may apply.

Cosign is a free tool for signing and verifying OCI container images and other software artifacts. It can store container signatures in an OCI registry and publish generic artifacts through OCI. Supported targets include blobs, binaries, scripts, configuration files, SBOMs, WASM modules, Tekton bundles, eBPF modules, and in-toto attestations whose payloads use DSSE. Its default keyless workflow uses temporary keys held in memory, short-lived certificates from Sigstore’s Fulcio certificate authority, and entries in the Rekor transparency log. Other signing options include hardware and KMS-backed keys, encrypted keypairs generated by Cosign, and user-provided PKI. Cosign supports CI/CD signing, with guidance for GitHub Actions and GitLab CI/CD. Offline verification is possible when the image and signature materials are available locally and a trusted root is supplied. The project describes Cosign as a legacy signing system and recommends Sigstore-go for verification integrations. Its CLI-focused design has no API stability guarantees, and the documentation does not recommend it for application integration.