Sigstore

Eliminates the operational burden of long-lived signing keys by binding signatures to OpenID Connect (OIDC) identities. Developers authenticate via their existing email or platform account, and the Fulcio certificate authority issues a short-lived X.509 certificate valid for only 10 minutes. This ephemeral credential is used to sign the artifact and is then discarded, removing the need for key distribution, rotation, or secure storage.

• Uses OIDC tokens from providers like Google, GitHub, or Microsoft
• Certificates expire in 10 minutes, minimizing exposure
• No private key management required by the developer

An immutable, append-only ledger that records every signing event. Each entry contains the signed artifact's hash, the public key from the ephemeral certificate, and a timestamp. This creates a tamper-evident record that allows anyone to verify when and by whom a signature was created. Rekor uses a Merkle tree structure to enable efficient cryptographic proofs of inclusion without exposing the entire log.

• Built on the Trillian verifiable data structure framework
• Supports pluggable record types for different artifact formats
• Enables monitoring for unauthorized or unexpected signing events

A CLI tool purpose-built for signing and verifying OCI (Open Container Initiative) container images. Cosign stores signatures directly in the same OCI registry as the image, eliminating the need for a separate signature server. It supports multiple signing modes, including keyless signing via Fulcio, traditional key-pair signing, and hardware token integration with PKCS#11 devices.

• Signatures stored as OCI artifacts alongside images
• Supports SBOM attachment and verification
• Integrates with Kubernetes admission controllers via Policy Controller

A root CA that issues short-lived code-signing certificates after validating an OIDC identity token. Fulcio embeds the verified identity—such as an email address or workload identity—directly into the X.509 certificate's Subject Alternative Name (SAN) extension. This cryptographically binds the signer's identity to the signature without requiring a pre-existing public key infrastructure.

• Operates as a transparent CA with all certificates logged in Certificate Transparency
• Supports custom OIDC issuers for enterprise identity providers
• Certificates are never reused across signing events

A Kubernetes admission controller that enforces signature verification policies before allowing container images to be deployed. It integrates with OPA/Gatekeeper and Kyverno to define rules such as requiring all images from a specific registry to be signed by a trusted identity. This prevents unsigned or tampered images from running in production clusters.

• Validates signatures against the Rekor transparency log
• Supports CUE and Rego policy languages
• Blocks deployment of images that fail verification

Provides RFC 3161 compliant trusted timestamps for signing events. The timestamp authority cryptographically binds a signature to a specific point in time, proving that the artifact was signed while the ephemeral certificate was still valid. This is critical for long-term signature verification, as it allows a verifier to confirm that a signature was created before the certificate expired, even years after the event.

• Enables long-term non-repudiation of signatures
• Prevents backdating attacks
• Operated as a public, free service by the Sigstore community

A root Certificate Authority that issues short-lived code-signing certificates bound to OpenID Connect identities. Unlike traditional CAs, Fulcio does not require manual key management—certificates are automatically generated and valid for only 10 minutes, eliminating the need for long-lived private keys. The CA verifies the developer's OIDC token from providers like Google, GitHub, or Microsoft, then issues an X.509 certificate with the identity embedded in the SAN extension.

An immutable, append-only ledger that records signed metadata about software artifacts. Built on the Merkle Tree data structure, Rekor provides cryptographic proof of inclusion, enabling anyone to verify that a signature existed at a specific point in time. Key properties:

• Tamper-evident: any alteration to a logged entry is cryptographically detectable
• Publicly auditable: anyone can monitor the log for unauthorized entries
• Verifiable timestamps: proves artifact signing occurred before certificate expiry

A CLI tool for signing and verifying container images using Sigstore's keyless infrastructure. Cosign stores signatures in the same OCI registry as the image, eliminating separate signature storage. Capabilities include:

• Keyless signing with OIDC-based identity verification
• SBOM attestation for software bill of materials
• Vulnerability scan attestation binding scan results to specific images
• Support for in-toto attestations for supply chain integrity

Sigstore leverages Certificate Transparency (CT) principles through Rekor, creating a cryptographically verifiable chain from developer identity to signed artifact. When Fulcio issues a certificate, it is logged in a CT-compatible structure. This enables:

• Real-time monitoring for misissued certificates
• Public auditability of all signing events
• Cross-ecosystem verification with existing CT monitors The integration ensures that any compromise of Fulcio would be publicly detectable within the certificate's 10-minute validity window.

A metadata format and verification protocol that Sigstore integrates to provide end-to-end supply chain integrity. In-toto collects cryptographically signed metadata about each step in a software pipeline—from source code checkout to compilation to deployment. Combined with Sigstore's keyless signing:

• Each pipeline step receives a verifiable attestation
• Layout policies define which steps must occur and who must perform them
• Final verification ensures no step was skipped, tampered with, or performed by an unauthorized identity

Supply-chain Levels for Software Artifacts (SLSA) is a security framework that Sigstore directly supports. Sigstore provides the provenance generation and verification primitives required for SLSA compliance:

• SLSA Level 2: requires signed provenance, achievable via Cosign attestations
• SLSA Level 3: requires non-falsifiable provenance, enabled by Rekor's immutable log
• SLSA Level 4: requires hermetic builds with two-person review, verifiable through in-toto attestations stored in Rekor Sigstore's keyless model removes the key management burden that historically hindered SLSA adoption.