Chain of Custody

Binds an identity to an action through public-key cryptography. Every transfer, access, or transformation event is signed by the responsible actor's private key, making it computationally infeasible for that actor to deny their involvement.

• Technology: Sigstore, Cosign, or X.509 certificates
• Key Concept: A verifiable assertion of 'who did what and when'
• Example: A data scientist signs a dataset with their OIDC-backed workload identity before it is ingested into a training pipeline.

Moves beyond static logging to active, policy-based enforcement. Before an artifact is deployed or consumed, its chain of custody is automatically validated against a transparency log and a set of codified rules.

• Enforcement Point: Admission controllers in Kubernetes or binary authorization gateways
• Policy Engine: Open Policy Agent (OPA) to codify 'only artifacts signed by the CI system are allowed'
• Example: A production cluster rejects a container image because its attestation log is missing a required vulnerability scan signature.

Secures the handoff points where an artifact crosses a trust boundary, such as from a vendor to a client. An in-toto layout cryptographically verifies that all agreed-upon steps were performed by the correct functionaries before the artifact is accepted.

• Challenge: Preventing supply-chain attacks during third-party model integration
• Solution: A signed attestation bundle that includes the SBOM, CVE scan results, and training provenance
• Example: A financial institution verifies a vendor's model provenance attestation against a pre-agreed policy before deploying it to a shadow environment.

Relies on append-only, cryptographically verifiable ledgers to store the chain of custody records. This prevents a malicious actor with root access from deleting or modifying the audit trail itself.

• Implementation: Transparency logs like Rekor or immutable cloud storage with object lock
• Principle: Separation of duties between the system operator and the auditor
• Example: Every signature generated by a CI/CD pipeline is automatically uploaded to a public Rekor transparency log, providing an independent, auditable record of all build events.

A formal, machine-readable inventory of all components, libraries, and dependencies that constitute a software artifact. An SBOM is the foundational data layer for a Chain of Custody report, enabling precise vulnerability and license management. Without an SBOM, you cannot verify what you are tracking.

• Standard formats include CycloneDX and SPDX
• Acts as a manifest for dependency graph analysis

A framework that cryptographically attests to the integrity of every step in a software supply chain. It creates a verifiable, end-to-end record of who performed what action and what materials were used, directly establishing a non-repudiable Chain of Custody.

• Links Supply-chain Levels for Software Artifacts (SLSA) steps together
• Uses link and layout metadata to verify expected workflows

An open-source project enabling automated, free digital signing and verification of software artifacts using short-lived certificates issued via OpenID Connect identities. Cosign is the core tool that signs containers and blobs, creating a verifiable link in the custody chain.

• Keyless signing eliminates long-term key management risks
• Entries are recorded in a public Transparency Log (Rekor) for auditing

A security framework (Supply-chain Levels for Software Artifacts) providing a graded checklist of controls to prevent tampering and improve integrity. It formalizes the Chain of Custody by requiring provenances that describe how an artifact was built.

• Defines levels from basic build scripting to hermetic, isolated builds
• Requires Reproducible Builds and non-falsifiable provenance at higher levels

An append-only, cryptographically verifiable public ledger that records digital events, such as code signatures and attestations. It makes the issuance of certificates auditable and detectable if compromised, providing the immutable backbone for a Chain of Custody audit trail.

• Rekor is the primary implementation in the Sigstore ecosystem
• Enables monitoring for unauthorized artifact signings

A deterministic compilation process that allows independent parties to recreate a bit-for-bit identical software artifact from the same source code. This verifies that no tampering occurred during the build, serving as a critical control to prove the integrity of the Chain of Custody.

• Removes the build environment as a trusted component
• Essential for achieving SLSA Level 4 compliance