[judge2020]

> Who via digital signature

the voice data signature can be removed, unless you mean something like an audio watermark

> What via hash

audio remuxing will destroy the hash, especially since it's already done by pretty much every social media company. Even with some sort of lossy audio hash, just put some clapping or cheering behind the voice and you've probably created a new audio hash.

> When via timestamp

file timestamps can change

This solves nothing unless your user either doesn't care about sharing the original file, or is malicious but too dumb to ffmpeg -i original.ogg out.mp3.

[surrealize]

There's an original, canonical version of the audio, and the hash of that version goes on chain. That establishes who posted it originally, when, and the exact version. Then any subsequent (potentially doctored) version can be compared with the canonical original. The on-chain timestamp and hash can't be changed after the fact, in the same way that past bitcoin blocks can't be changed (without creating a fork).

It could at least address some kinds of misleading editing. In the political use case, maybe the candidate posts all their event audio and records the hashes on chain. Then they can't change the content of any of it without getting caught. And if someone else posts an edited version, the edit will have a later timestamp, and the candidate can point to their original earlier version and prove that it's the original. That lets everyone else determine which version is the original and which version is the edit.