Coalition for Content Provenance and Authenticity (C2PA)

A manifest is the core data structure that acts as a verifiable record of provenance for a digital asset. It is a collection of assertions and claims about the asset's origin, creation, and edit history.

• Contains a unique Claim Generator identifier, typically a Decentralized Identifier (DID) or X.509 certificate
• Stores a list of ingredients—references to parent assets from which this asset was derived
• Includes a signature over the entire manifest to ensure integrity and non-repudiation
• Can be embedded directly into supported file formats (JPEG, PNG, AVIF, etc.) or stored externally as a sidecar file

Assertions are the individual, verifiable statements about an asset that populate a manifest. Each assertion is a structured data object that makes a specific claim about the content or its provenance.

• Creative Assertions: Capture authorship information, including the creator's name, affiliation, and contact details
• Action Assertions: Record specific editing operations performed on the asset, such as cropping, color adjustment, or AI-based generative fill
• Thumbnail Assertion: Provides a cryptographically bound visual preview of the asset at the time of signing
• Metadata Assertions: Carry EXIF, IPTC, or other technical metadata in a verifiable wrapper
• Assertions can be added by multiple actors throughout the asset's lifecycle, creating a cumulative provenance chain

To prevent tampering, the C2PA specification mandates a hard binding between the manifest and the asset's binary data. This is achieved through cryptographic hashing.

• The asset's raw bytes are processed through a SHA-256 hash algorithm
• This hash is stored as a claim within the manifest before the manifest itself is signed
• Any subsequent modification to a single pixel or audio sample will produce a completely different hash, breaking the binding
• Verifiers recalculate the hash and compare it against the signed claim to detect tampering
• This mechanism ensures that the provenance data cannot be separated from the content and reattached to a forgery

C2PA does not determine what is 'true'—it verifies who said what about an asset. The specification relies on a Trust List to establish the credibility of signers.

• A Trust List is a curated, cryptographically signed list of root certificates and DIDs that a validator considers authoritative
• When a manifest is validated, the validator checks if the signer's certificate chains back to a trusted root on its list
• This model allows different communities (news organizations, social platforms, camera manufacturers) to maintain their own trust lists
• The specification defines the technical mechanism for trust, while policy decisions about who to trust remain external
• This separation of cryptographic verification from trust policy is a deliberate architectural choice

Ingredients document the lineage of a composite asset by referencing its source materials. This is critical for tracking provenance through complex editing workflows.

• An ingredient is a reference to a parent manifest, typically identified by its manifest hash or a URL
• When a designer composites multiple images in Photoshop, the final export's manifest lists each source image as an ingredient
• This creates a provenance graph—a directed acyclic structure tracing the asset back to its original capture devices
• Ingredients enable a validator to recursively verify the entire chain, not just the final step
• The specification supports redaction of sensitive ingredient data while preserving the cryptographic integrity of the remaining chain

The C2PA specification defines a rigorous, multi-step process for validating a manifest to produce a definitive trust assessment.

• Structural Validation: Parse the manifest and confirm it conforms to the C2PA data model and CBOR encoding rules
• Signature Verification: Use the signer's public key to cryptographically verify the manifest's digital signature
• Hard Binding Check: Recompute the asset's hash and compare it against the signed claim to confirm the binding is intact
• Trust List Resolution: Traverse the signer's certificate chain to determine if it anchors to a trusted root
• Ingredient Recursion: Repeat the entire process for each ingredient to validate the full provenance chain
• The output is a binary valid/invalid status, plus detailed diagnostic information about which step failed

A mathematical scheme using public-key cryptography to verify authenticity and integrity while providing non-repudiation. In C2PA, every assertion in a provenance manifest is digitally signed by the entity making the claim—whether a camera manufacturer, photo editor, or publisher. This creates an unbroken chain of cryptographic assertions that allows any downstream consumer to validate the complete edit history of a media asset.

The documented and unbroken control, transfer, and processing history of evidence that proves integrity from creation to current state. C2PA formalizes digital chain of custody through its manifest structure, which records every action taken on an asset—capture, crop, resize, export—along with the identity of each actor. This creates an auditable forensic trail that mirrors physical evidence handling protocols in the digital domain.