> Why haven't I made my whitepaper about PhotoDNA public? In my view, who would it help? It would help bad guys avoid detection and it will help malcontents manufacture false-positives. The paper won't help NCMEC, ICACs, or related law enforcement. It won't help victims.
Making it public would allow the public to scrutinize it, attack it, if you will, so that we can get to the bottom of how bad this technology is. Ultimately my sincere guess is that we’d end up with better technology to do this not some crap system that essentially matches on blurry images. Our government is supposed to be open source, there’s really no reason we can’t as a society figure this out better than some anti CP cabal with outdated crufty image tech.
PhotoDNA is a very simple algorithm. Reproducing what OP did to "reverse engineer" is not hard. If you really have the guts to try this go ahead and you'll be surprised. I'm living in the US with a greencard so I'm not touching the problem even with a laser pointer.
The techno-legal framework is worse than just "reversing the hashes is possible". You could brute force creation of matching images using a cloud service or online chat as an "oracle".
Making it public would allow the public to scrutinize it, attack it, if you will, so that we can get to the bottom of how bad this technology is. Ultimately my sincere guess is that we’d end up with better technology to do this not some crap system that essentially matches on blurry images. Our government is supposed to be open source, there’s really no reason we can’t as a society figure this out better than some anti CP cabal with outdated crufty image tech.