C2PA Standard

The core of the standard is a manifest—a JSON-LD data structure containing assertions about the content. This manifest is hashed and signed using asymmetric cryptography (typically X.509 certificates). The manifest includes:

• Assertions: Claims about the asset (e.g., creation date, creator identity, equipment used).
• Claim Signatures: Digital signatures that bind the assertions to the asset's hash.
• Ingredient References: Links to parent assets, enabling a chain of provenance for derivative works. This structure ensures that any subsequent modification without re-signing is immediately detectable.

C2PA establishes a hard binding between a manifest and the asset's binary data. The manifest stores a cryptographic hash of the final asset. To verify, the system recalculates the hash and compares it to the signed value in the manifest. For derivative works, the manifest includes an ingredient assertion that points to the hash and manifest of the source file. This creates a directed acyclic graph (DAG) of provenance, allowing a verifier to trace an image back through multiple edits to the original camera capture.

C2PA does not define a single global trust list. Instead, it uses a decentralized trust model based on X.509 Public Key Infrastructure (PKI). Signers are identified by certificates issued by Certificate Authorities (CAs). The standard defines a Trusted Timestamp mechanism to prove data existed before a specific time. Verifiers can apply custom validation logic, such as checking if a signer's certificate is on an approved list, to determine if the provenance chain is trustworthy for their specific use case.

To support privacy-sensitive workflows, C2PA supports manifest redaction. This allows specific assertions (e.g., GPS coordinates, photographer's name) to be removed from a manifest without breaking the cryptographic signature chain. The process uses a Merkle tree structure for assertions. A redactor can prune specific leaves of the tree and provide a cryptographic proof that the remaining assertions are intact and unchanged, preserving the integrity of the provenance chain while hiding sensitive metadata.

The user-facing representation of a C2PA manifest is called a Content Credential. This is a visual overlay, typically a 'cr' pin, that users can click to inspect the provenance data. The standard defines how this information should be rendered to be human-readable, including the display of the signing entity, the recording device, and the edit history. This bridges the gap between raw cryptographic data and user trust, making verification accessible to non-technical audiences.

C2PA is designed for real-world distribution channels where metadata is often stripped. The manifest can be embedded directly into file formats like JPEG and PNG, or stored in a remote cloud location with a recovery link in the asset. The validation process is graceful: if a manifest is missing or a signature fails, the system reports a specific error code (e.g., 'assertion.missing', 'signature.mismatch') rather than a generic failure. This allows platforms to make nuanced policy decisions based on the type of validation failure.