Validator Engine

The engine cryptographically validates every claim signature within a manifest to ensure non-repudiation. It uses the signer's public key, extracted from their X.509 certificate, to verify that the assertion data has not been altered since signing. A failed signature check immediately invalidates the entire credential and halts further processing.

• Validates Ed25519, ECDSA, and RSA signature schemes
• Checks signature over the complete assertion byte stream
• Flags any mismatch as a tamper-evident event

The engine constructs and validates the full X.509 certificate chain from the signer's end-entity certificate up to a configured trust anchor root CA. Each certificate in the path is checked for correct issuance, key usage extensions, and validity period. The engine must cryptographically verify that each certificate's signature was generated by the private key of its issuer.

• Enforces RFC 5280 path validation rules
• Checks Basic Constraints and Key Usage extensions
• Rejects chains with expired or not-yet-valid certificates

The engine performs a liveness check on every certificate in the chain to ensure none have been revoked. It queries the issuing Certificate Authority's revocation service, typically via OCSP (Online Certificate Status Protocol) or by fetching a CRL (Certificate Revocation List). A revoked certificate renders the signature untrustworthy, even if mathematically valid.

• Supports OCSP stapling for latency reduction
• Implements CRL parsing with delta update support
• Caches revocation responses per their validity interval

The engine recomputes the cryptographic hash of the asset and compares it against the hash recorded in the signed manifest. This confirms that the binary content has not been altered since the credential was issued. Any mismatch indicates either corruption or unauthorized modification.

• Supports SHA-256, SHA-384, and SHA-512 families
• Validates both the final asset hash and all ingredient hashes
• Detects bit-level tampering anywhere in the file

The engine consults a cryptographically signed trust list to determine whether the signer's identity and issuing CA are recognized as authoritative. Trust lists are curated XML or JSON structures that whitelist specific root certificates, intermediate CAs, and individual signers. A valid signature from an entity not on the trust list is treated as unverified.

• Parses C2PA Trust List format
• Validates the trust list's own signature before use
• Supports multiple trust lists for different policy domains

The engine traverses the complete provenance chain by resolving all ingredient assertions and their associated manifests. It verifies the cryptographic linkage between each version of the asset, ensuring the edit history forms an unbroken, tamper-evident sequence from the original capture to the final output.

• Builds a directed acyclic graph of all action assertions
• Validates each link's hash continuity
• Surfaces any break in the chain as a verification failure

The complete end-to-end process that a Validator Engine executes. It involves cryptographically validating the digital signatures, hash chains, and certificate chains within a content credential. The engine confirms the integrity of the provenance data and the authenticity of the signing identities. A failed verification at any step—such as a hash mismatch or an expired certificate—must invalidate the entire credential chain.

A curated, cryptographically signed list of trusted issuers, Certificate Authorities, and validators that a Validator Engine consults to determine if a content credential is trustworthy. The engine cross-references the signer's certificate against this list. If the signer is not a member of the active trust list, the engine must flag the credential as having an untrusted identity anchor, even if the cryptographic signatures are mathematically valid.

The process of querying a Certificate Authority's database—typically via the Online Certificate Status Protocol (OCSP) or Certificate Revocation Lists (CRLs)—to ensure the digital certificate used to sign a content credential has not been revoked. A Validator Engine must perform this check in real-time or against a cached, time-stamped status. A credential signed with a revoked certificate is cryptographically invalid.

The standard digital certificate format that binds a public key to an identity verified by a Certificate Authority (CA). This forms the trust anchor for signing content credentials. The Validator Engine parses the X.509 certificate chain, validates each certificate's signature, checks expiration dates, and verifies that the root CA is in its trusted store. Any break in this chain constitutes a validation failure.

A sequential chain of hashes linking each version of an asset to its predecessor. The Validator Engine recomputes each hash in the chain and compares it to the stored value. If a single bit of the asset has been altered, the recomputed hash will not match, and the chain is broken. This provides the engine with a tamper-evident mechanism to verify the complete edit history of a digital asset.

A process that cryptographically binds a document's hash to a specific point in time, issued by a trusted Timestamp Authority (TSA). The Validator Engine verifies the TSA's signature on the timestamp token and confirms the hash matches the content. This proves the data existed before a certain moment and countersigns the provenance record, providing non-repudiation of the temporal claim.