Sigstore

Eliminates the need for long-lived private keys by binding signatures to OpenID Connect (OIDC) identities. A developer or automated pipeline authenticates via an OIDC provider (e.g., Google, GitHub, Microsoft), and Sigstore issues an ephemeral key pair.

• Ephemeral Keys: The private key is generated and discarded immediately after signing, eliminating key management risk.
• Identity Binding: The signing certificate records the OIDC identity, providing a direct link between a verified identity and the signed artifact.
• Use Case: An MLOps pipeline authenticates via its cloud provider's identity to sign a newly trained model artifact.

An append-only, immutable, and publicly auditable ledger that records a cryptographic proof of every signing event. This provides a verifiable timeline of artifact provenance.

• Tamper-Evident Record: Once a signature is logged in Rekor, any attempt to alter or delete the record is cryptographically detectable.
• Monitoring: Organizations can monitor the log for their own identities to detect unauthorized signing events in real-time.
• Verification: Verifiers check Rekor to confirm a signature was publicly recorded at a specific time, enabling non-repudiation for AI audit trails.

A root Certificate Authority (CA) that issues short-lived code-signing certificates bound to an OIDC identity. These certificates are valid for only 10 minutes, drastically reducing the window of compromise.

• Short-Lived Credentials: Certificates expire in minutes, making them useless to an attacker after the fact.
• No CRL/OCSP Required: Because certificates are so short-lived, complex revocation infrastructure is unnecessary.
• Transparency by Default: All issued certificates are automatically logged in a Certificate Transparency log, providing a public record of the CA's operation.

Sigstore can be integrated into MLOps pipelines to sign model weights, datasets, and AI Bills of Materials (AI BOMs). This creates a verifiable chain of custody from training to deployment.

• Model Integrity: A signed model artifact proves it has not been tampered with since the signing event.
• Provenance Attestation: Sign an in-toto attestation that describes the model's training data, hyperparameters, and build environment.
• Compliance: Satisfies EU AI Act requirements for technical documentation and traceability of high-risk AI systems.

The cosign CLI tool is the primary client for signing and verifying OCI (Open Container Initiative) artifacts and arbitrary blobs. It integrates directly with container registries and cloud storage.

• OCI Support: Sign container images, Helm charts, and other OCI-compliant artifacts stored in registries.
• Blob Signing: Sign any file, such as a serialized model or a dataset archive, and store the signature alongside it.
• Verification: cosign verify checks the signature, the identity in the certificate, and the inclusion proof in the Rekor transparency log in a single command.

Sigstore integrates with Kubernetes admission controllers (like Kyverno or OPA/Gatekeeper) to enforce that only signed and verified artifacts can be deployed into a cluster.

• Admission Control: A webhook validates the signature and identity of every container image before it is allowed to run.
• Trusted Identities: Policies define which OIDC identities are authorized to sign artifacts for a specific environment (e.g., only the production CI pipeline).
• Runtime Assurance: Prevents the deployment of unsigned or tampered AI inference servers, ensuring the integrity of the production environment.

The identity layer on top of OAuth 2.0 that Sigstore uses for keyless signing. Instead of managing long-lived private keys, developers authenticate via an OIDC provider (like Google, GitHub, or Microsoft) to receive a short-lived signing certificate.

• Ephemeral Keys: The signing key is generated on the fly and discarded immediately after use.
• Identity Binding: The resulting certificate binds the software artifact directly to the developer's verified identity and the source repository.
• Workflow Integration: Commonly used in CI/CD pipelines to prove that a container image was built by a specific GitHub Actions workflow.

An append-only, immutable ledger that records signed metadata about software artifacts. Rekor provides a public, verifiable record of the signing event, enabling monitoring and auditability.

• Cryptographic Proof: Stores a Merkle tree commitment of all entries, allowing efficient inclusion proofs.
• Tamper Detection: Any attempt to alter or delete a log entry is immediately detectable by monitors.
• Audit Trail: For AI governance, Rekor can serve as the immutable log for model signatures, ensuring non-repudiation of model provenance.

A root Certificate Authority (CA) that issues short-lived code-signing certificates bound to OIDC identities. Fulcio eliminates the need for developers to manage, rotate, or protect private keys.

• Short-Lived Credentials: Certificates are valid for only 10 minutes, drastically reducing the window of key compromise.
• Zero Key Management: The private key is generated in-memory and never stored on disk.
• Transparent Issuance: All issued certificates are logged in the Rekor transparency log, creating a public audit trail of who signed what and when.

The CLI tool that performs the actual signing and verification of Open Container Initiative (OCI) artifacts, including container images and AI model blobs. Cosign integrates directly with Fulcio and Rekor.

• Keyless Signing: cosign sign authenticates via OIDC, obtains a certificate from Fulcio, and uploads the signature to Rekor in a single command.
• Verification: cosign verify checks the signature against the transparency log and validates the identity binding.
• AI Model Signing: Can sign any OCI artifact, making it suitable for cryptographically attesting to the integrity of serialized model files stored in registries.

A specification for secure software update systems that protects against key compromise and repository attacks. Sigstore's root of trust is distributed using TUF to ensure the integrity of the root CA and log public keys.

• Multi-Signature Thresholds: Requires multiple trusted parties to sign the root metadata, preventing a single compromised key from undermining the entire trust system.
• Key Rotation: Provides a secure mechanism for rotating root keys and recovering from compromise.
• Trust Bootstrap: Sigstore clients use TUF to securely obtain the initial trusted root of trust, ensuring they are verifying against the authentic Fulcio and Rekor instances.

Applying Sigstore's keyless signing paradigm to machine learning artifacts creates a cryptographic chain of custody from training to deployment. This addresses the EU AI Act's requirements for traceability.

• AI Bill of Materials (AI BOM): Sign the model weights, training dataset hash, and hyperparameters together as an OCI artifact.
• Inference Attestation: Generate a Model Inference Hash for each prediction and log it to Rekor for non-repudiable audit trails.
• Supply Chain Integrity: Verifiably link a deployed model back to its exact training run, source code, and the engineer who initiated it.