Provenance Verification

The validator must construct and verify a complete X.509 certificate chain from the signing certificate up to a trusted root Certificate Authority (CA) . This process confirms:

• Each certificate in the chain is within its validity period
• No certificate has been revoked (checked via OCSP or CRL)
• The issuing CA was authorized to issue the subordinate certificate
• The root CA is present in the verifier's trust list

This establishes that the signing identity is cryptographically bound to a verified, real-world organization or individual.

To prove content existed before a specific moment, the validator inspects trusted timestamps issued by a Timestamp Authority (TSA) . The verification checks:

• The TSA's digital signature on the timestamp token is valid
• The hash embedded in the timestamp matches the signed data
• The TSA's certificate chains to a trusted root
• The timestamp falls within the signing certificate's validity period

This counters backdating attacks and ensures long-term validity even after the original signing certificate expires.

For composite assets, the validator reconstructs the full provenance chain by recursively verifying each ingredient assertion. This involves:

• Confirming that each ingredient's hash matches its referenced manifest
• Validating the cryptographic hash chain linking each edit version to its predecessor
• Building a complete edit history graph showing all source media and transformations

A break anywhere in this chain—such as a missing ingredient or hash mismatch—indicates an incomplete or tampered lineage.

A critical real-time check that queries whether any certificate in the chain has been revoked before its expiration. This uses:

• Online Certificate Status Protocol (OCSP) for near-instantaneous status
• Certificate Revocation Lists (CRLs) as a periodic, batch-checked fallback
• OCSP stapling to reduce latency and privacy exposure

A revoked certificate—due to key compromise or organizational dissolution—invalidates all credentials signed with it, regardless of other valid checks.

A sequential chain of hashes linking each version of an asset to its predecessor, creating a verifiable edit history. Each link contains the hash of the previous manifest and content state.

• Uses SHA-256 or SHA-384 one-way functions
• Altering any past version invalidates all subsequent hashes
• Forms the backbone of tamper-evident provenance chains
• Enables detection of even single-bit modifications

A cryptographic digital signature generated over a set of assertions, binding them to a specific identity. Ensures integrity and non-repudiation of provenance claims.

• Typically uses ECDSA with NIST P-256 curves
• Signed by the private key corresponding to an X.509 certificate
• Validator engines verify the signature against the signer's public key
• Any post-signature tampering causes verification failure

A curated, cryptographically signed list of trusted issuers, Certificate Authorities, and validators. The verifier application consults this list to determine if a content credential is trustworthy.

• Maintained by organizations like the Content Authenticity Initiative
• Contains root CA certificates and approved signer identities
• Updated regularly with revocation data
• Prevents trust in credentials from compromised or rogue authorities

The software component that performs the full cryptographic verification of a content credential. It executes multiple checks to confirm authenticity and integrity.

• Verifies digital signatures against public keys
• Walks the X.509 certificate chain to a trust anchor
• Performs revocation checks via OCSP or CRLs
• Validates timestamp tokens from the Timestamp Authority
• Cross-references signers against the active Trust List

A standard digital certificate format that binds a public key to a verified identity. It serves as the trust anchor for signing content credentials within the C2PA ecosystem.

• Issued by a Certificate Authority after identity validation
• Contains subject identity, public key, validity period, and CA signature
• Supports chain-of-trust validation up to a root CA
• Revocation status checked via OCSP responders during verification

A process that cryptographically binds a document's hash to a specific point in time. Issued by a Timestamp Authority (TSA), it proves data existed before a certain moment.

• Compliant with RFC 3161 standard
• Counter-signs the content hash with the TSA's private key
• Provides non-repudiation of temporal existence
• Critical for proving content was created before an event, not after