Notation vs OpenPubkey

Notation is a command-line tool for signing and verifying container images and other artifacts in OCI registries, including software bills of materials. It implements the Notary Project specifications, which are intended to help secure software supply chains. Its signatures can move between OCI registries and be validated in connected, intermittently connected, or disconnected environments without additional server infrastructure. The specifications define signature envelopes using COSE or JWS. Notation can integrate with existing key management systems through a plugin model, with instructions for Azure Key Vault and AWS Signer. Developers and CI/CD pipelines can create signatures and store them alongside signed artifacts. The project provides a quick start for signing and validating a container image. Notation runs on Linux, macOS, and Windows and is free under the Apache 2.0 license. Cloud signing, trusted timestamping, and CI/CD signing are listed capabilities; a certificate is not provided. The specifications repository lists a 2023 security audit, and the project overview describes continuous fuzz testing across three repositories.

OpenPubkey binds a user or workload identity established through OpenID Connect to a public key, so the identity can sign messages or artifacts. A PK Token represents control of an OIDC identity and its related private key at a particular time, provided the verifier trusts the identity provider. The project lists Google, Azure/Microsoft, Okta, OneLogin and Keycloak as compatible without changes to those providers; however, its client and verifier currently create and verify tokens from Google for users and GitHub for workloads. Current workload identity use requires GQ signatures. For user identity, they are unnecessary when the PK Token is not public. GQ signatures allow the identity provider’s signature to be stripped from an ID Token while preserving proof of that signature, preventing use against OIDC resource providers. OpenPubkey says it needs no additional certificate authority because the OpenID Provider fulfills that role. Public PK Tokens can reveal claims from an OIDC ID Token, potentially including a name or email address. The project is free under the Apache 2.0 license and is a Linux Foundation project; its repository says it is being prepared for version 1.0. The project directs technical questions to GitHub issues and offers a community Slack channel.