OpenPubkey vs Sigstore

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.

Sigstore is a free, open source project for signing and verifying software artifacts to improve supply chain security. It supports release files, container images, binaries, software bills of materials, and more. Signatures use temporary keys, so developers do not have to manage signing keys; events are recorded in a tamper-resistant public log for audit. Its components include Cosign, Fulcio, Rekor, OpenID Connect, and Policy Controller. Cosign signs and verifies artifacts and stores signatures in an OCI registry. Fulcio issues temporary certificates to authorized identities, while Rekor keeps signed metadata in a searchable ledger. OpenID Connect authenticates users through providers such as GitHub and Google. The trust root uses The Update Framework and is maintained by five keyholders from different companies and academic institutions. Sigstore provides GitHub Actions, documents GitLab CI installation, and offers official clients for Go, Java, JavaScript, Python, Ruby, and Rust. It supports API, Linux, macOS, Windows, and self-hosted environments. One integration caveat is that Cosign has no API stability guarantees, does not follow semantic versioning, and is not recommended for application integration because of its dependencies.