Provenance System Flaws Highlight Need for Alternative Approach

The Content Credentials (C2PA) system, aimed at verifying media provenance and trust, has been criticized for its structural flaws. The system binds provenance to the asset and roots trust in a central authority, which can be compromised by an adversary.

C2PA's primary mechanism is the 'hard binding,' a cryptographic hash of the asset attached to the file's metadata. However, this method has limitations: embedded metadata can be detached from the file through routine operations like re-encoding or screenshotting.

The authors argue that C2PA's designers know about these limitations and have introduced 'soft bindings', invisible watermarks or content fingerprints for recovering a manifest when metadata is stripped. However, this approach also has its weaknesses: it relies on the presence of the manifest repository being online, honest, and well-governed.

The deeper problem lies in where trust actually lives: C2PA signatures are only as meaningful as one's willingness to trust the entity that issued them. The authors propose an alternative approach: 'provenance as a property of the system,' rather than a sticker on the file, with four key properties:

* Provenance held by the system, not attached to the asset.

* Tamper-evident and chained: each entry cryptographically linked to the previous one.

* Verifiable without a central authority: no trust list or issuer hierarchy.

* Held locally, by the operator: the record lives on hardware controlled by the accountable party.