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The concept of checking images against a hash list is not unique to Apple or even new. https://en.m.wikipedia.org/wiki/PhotoDNA https://en.m.wikipedia.org/wiki
by snowwrestler 5y ago
The concept of checking images against a hash list is not unique to Apple or even new.
https://en.m.wikipedia.org/wiki/PhotoDNA https://en.m.wikipedia.org/wiki/PhotoDNA
What Apple announced is a way to do it on the client device instead of the server. That has some security implications, but they’re more specific than just “hashes might collide.”
- heavyset_go 5y agoThey're not just checking against a hash list, they're using perceptual hashing, which is inexact and unlike cryptographic hashing or checksumming. Then, they use a fuzzy metric like hamming distance to determine if one image is a derivative of an illegal image. The problem is that the space for false positives is huge when you use perceptual hashing, and it gets even larger when you start looking for derivative images, which they have to do otherwise criminals would just crop or shift color channels in order to bypass filters.