Assertion
Definition
A single provenance statement inside a C2PA claim. Examples include the camera make and model, GPS coordinates at capture, an AI-training or AI-generated flag, a crop action, or a colour-grade action. Each assertion is individually hashed so that selective tampering is detectable.
- Standard
- C2PA (Coalition for Content Provenance and Authenticity)
- Integrity method
- Each assertion individually hashed
- Example fields
- Camera make/model, GPS, AI-generated flag, edit actions
- Container
- Bundled inside a signed C2PA claim
Common questions
What happens if someone edits an image after a C2PA assertion is recorded?+
Because each assertion is hashed individually, an edit after capture either appends a new assertion recording the edit action, or invalidates the hash of any assertion it tampers with, making the alteration detectable without needing to compare against a separate original file.
Can an assertion be selectively removed without breaking the whole manifest?+
Removing or altering one assertion breaks its own hash and the claim's overall signature, so the manifest as a whole fails verification. Selective tampering is detectable even if only one assertion, such as GPS data, is the target.
Related terms
- C2PA Manifest
- The structured provenance record embedded in or associated with a media file. Contains one or more signed claim blocks, each holding a...
- C2PA Trust List
- A curated list of trusted root certificate authorities whose chains can anchor a C2PA claim signature. Maintained by the C2PA organisation. A...
- Claim Signature
- An X.509-based digital signature over the hashes of all assertions in a claim plus the content binding hash. Produced by the signer's...
- Hard Binding
- A content binding that stores SHA hashes of specific byte ranges of the media file inside the signed manifest. Any modification to...
- Soft Binding
- A content binding using a perceptual fingerprint or watermark embedded in the signal rather than the file bytes. Designed to survive format...