Well, presumably at that point, someone in that position would just reveal their own files with the hash an prove to the public that they weren't illegal. Sure, it would be shitty to be forced to reveal your private information that way, but you would expose a government agency as fabricating evidence and lying about the contents of the picture in question to falsely accuse someone. It seems like that would be a scandal of Snowden-level proportions.
> Who would a company hire: the candidate with a trial for CP due to a false positive or the candidate without ?
First time I've seen it abbreviated like that; took me a while to grasp. Well, more of a plausible "Enemy of society" than what I came up with: https://news.ycombinator.com/item?id=28060995
Well, not all hashing algorithms but all interesting or considered useful hashing algorithms, probably.
When dealing with say countable infinite sets you can certainly create a provable unique hash for each item in that set. The hash won't be interesting or useful. E.g. a hash that indexes all the integers n with a hashing function h(n+1)... so every integer you hash will be that value plus one. But this just being pedantic and wanting to walk down the thought.
In the past the FBI used some cryptographic hash. Collisions with a secure cryptographic hash are functionally unobservant in practice (or else the hash is broken).
The use of the perceptual hash is because some people might evade the cryptographic hash by making small modifications to the image. The fact that they'd discarded the protection of cryptographic hashing just to accommodate these extra matches is unsurprising because their behavior is largely unconstrained and unbalanced by competing factors like the public's right to privacy or your security against being subject to a false accusation.
Would a court be compelled to provide that hash to your defence? Arguable as it could be used by criminals to clean their collection. And by that time your life is ruined anyway.
