Klangfarbe and C2PA: live calls, and the recording after
C2PA signs media assets. A phone call has no asset and no manifest. Klangfarbe covers the live call, and can hand its evidence to C2PA when the call becomes a recording.
C2PA (Content Credentials) and the Creator Assertions Working Group are the main ecosystem for signed media provenance. Klangfarbe is designed to sit next to them, not against them.
What C2PA and CAWG cover
C2PA defines cryptographically signed manifests that travel with an image, video or audio file and describe how it was made. Version 2.3 added live video, including audio tracks in live ISO-BMFF workflows. CAWG builds identity on top: its Identity Assertion and Organizational Identity Profile let a named organization sign as the creator of an asset.
Where a phone call falls outside
A PSTN or SIP conversation is not an asset. There is no container to attach a manifest to, the audio is transcoded on the way, and the only thing that reaches the other end is speech. That is the gap Klangfarbe targets: an identity binding for ephemeral speech streams, carried inside the audio itself.
How they fit together
| C2PA / CAWG | Klangfarbe | |
|---|---|---|
| Unit | A media asset with a manifest | A live voice session |
| Identity of | The asset's creator or signer | The AI agent, its organization and purpose |
| Travels as | Metadata attached to the file | A binding inside the speech |
| Survives a phone line | No manifest to carry | Designed to |
| Best for | Durable provenance of files | Live identity during the call |
When a call is recorded, the evidence can move across. A Klangfarbe verifier can keep an evidence bundle with the session attestation, credential, trust chain and status at the time of the call. The intended path is to express that evidence as C2PA and CAWG material, so a recording keeps a durable, standard provenance record instead of a separate format. The exact mapping is one of the open questions in the whitepaper and is waiting for expert review.
See how the protocol works or request the whitepaper to review the C2PA mapping with us.