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The White House wants to 'cryptographically verify' videos of Joe Biden so viewers don't mistake them for AI deepfakes
(www.businessinsider.com)
this post was submitted on 11 Feb 2024
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Depending on the implementation, there are two cryptographic functions that might be used (perhaps in conjunction):
Cryptographic hash: An arbitrary amount of data (like a video file) is used to create a “hash”—a shorter, (effectively) unique text string. Anyone can run the file through the same function to see if it produces the same hash; if even a single bit of the file is changed, the hash will be completely different and you’ll know the data was altered.
Public key cryptography: A pair of keys are created, one of which can only encrypt data (but can’t decrypt its own output), and the other, “public” key can only decrypt data that was encrypted by the first key. Users (like the White House) can post their public key on their website; then if a subsequent message purporting to come from that user can be decrypted using their public key, it proves it came from them.
A note on this. There are other videos that will hash to the same value as a legitimate video. Finding one that is coherent is extraordinarily difficult. Maybe a state actor could do it?
But for practical purposes, it'll do the job. Hell, if a doctored video with the same hash comes out, the White House could just say no, we punished this one, and that alone would be remarkable.
You’d need to find one that was not just coherent, but that looked convincing and differed in a way that was useful to you—and that likely wouldn’t be guaranteed, even theoretically.
Pigeon hole principle says it does for any file substantially longer than the hash value length, but it's going to be hard to find