C2PA

C2PA constructs a verifiable provenance chain—a complete, end-to-end sequence of cryptographically linked manifests tracing an asset's entire history. Ingredient assertions document each piece of source media used in creating a composite asset, forming a directed acyclic graph of dependencies. When an asset is edited, the new manifest references the previous one via a cryptographic hash chain, ensuring that altering any historical version invalidates all subsequent signatures.

• Edit History Graph: Visual representation of all actions and ingredients
• Action Assertions: Describe operations like cropping, resizing, or color correction
• Re-signing: New signature applied when a party takes custody or edits the asset

C2PA's Identity Assertion cryptographically links content to a verified real-world identity, typically backed by an X.509 certificate from a trusted Certificate Authority. The underlying Provenance Data Model aligns with the W3C PROV standard, representing entities, agents, and activities as an abstract graph. This alignment ensures interoperability with broader web standards, including potential integration with W3C Verifiable Credentials for privacy-respecting identity claims.

• X.509 Certificate: Standard format binding a public key to a verified identity
• Content Credential Schema: Machine-readable definition ensuring interoperable validation
• W3C PROV Alignment: Graph-based model for entities, agents, and activities

A critical challenge for any provenance system is surviving common content transformation pipelines—such as social media uploads—that routinely strip non-essential metadata. C2PA addresses this through hard binding strategies that embed manifests deep within file structures and through complementary techniques like invisible watermarking. The goal is metadata stripping resistance: ensuring that provenance data persists even when content passes through aggressive re-encoding or resizing operations that would normally discard attached metadata.

• Hard Binding: Embeds manifest directly into the file's binary structure
• JUMBF Container: Survives within standard-compliant file format parsers
• Complementary Watermarking: Provides redundancy when structural metadata is removed

A structured, digitally signed statement within a C2PA manifest that makes a specific claim about the content. Each assertion is a discrete unit of provenance data, such as:

• Creative Work Assertion: Declares the author and creation date
• Action Assertion: Describes an edit operation like cropping or filtering
• Ingredient Assertion: Documents source media used in a composite asset Assertions are cryptographically bound together and signed to prevent selective tampering.

Two methods for attaching a provenance manifest to digital content:

Hard Binding embeds the signed manifest directly into the asset's binary structure, such as in the JUMBF box of a JPEG file. This ensures the provenance data travels with the file through downloads and re-uploads.

Soft Binding stores the manifest externally as a sidecar file or cloud URL, referenced by a content hash. This is used when direct embedding is technically infeasible, but risks metadata loss if the sidecar becomes separated.

A cryptographically signed, curated list of trusted issuers, Certificate Authorities, and validators that a verifier application consults to determine if a content credential is trustworthy. Trust lists solve the key question: 'Who is authorized to sign provenance claims?' They are maintained by governance bodies and distributed to validator engines, creating a trust anchor hierarchy that prevents malicious actors from self-signing fraudulent credentials.

The software component that performs the complete cryptographic verification of a C2PA content credential. The engine executes a series of checks:

• Signature validation: Verifies each claim signature against the signer's public key
• Certificate chain verification: Validates the X.509 certificate path to a root CA
• Revocation check: Queries the CA's OCSP responder to ensure no certificate has been revoked
• Trust list membership: Confirms the signer appears on an authorized trust list
• Hash integrity: Recomputes asset hashes to detect any content modification

The complete, end-to-end sequence of cryptographically linked manifests and assertions that traces a digital asset's entire history from initial capture through all subsequent edits. Each link in the chain contains:

• A hash of the previous manifest
• New assertions describing the latest action
• A fresh digital signature from the current custodian This creates a tamper-evident edit history graph where altering any past version immediately invalidates all downstream cryptographic proofs.