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This is already possible using other services (Google Drive, gmail, Instagram, etc.) that already scan for CP.
by new_realist 5y ago
This is already possible using other services (Google Drive, gmail, Instagram, etc.) that already scan for CP.
- t0mas88 5y agoDoes Google scan all files you upload to them with an algorithm like the one now proposed? Or do they have only a list of exact (not perceptual) SHA hashes of files to flag on? The latter I think is also used for pirated movies etc being removed under DMCA?
- bccdee 5y agoI'm pretty sure they use perceptual hashes for matching CSAM. A lot of cloud services do this sort of thing.
- acdha 5y agoYes: it’s called PhotoDNA and is used by many, many services. See https://en.wikipedia.org/wiki/PhotoDNA https://en.wikipedia.org/wiki/PhotoDNA SHA hashes aren’t suitable for this: you can change a single bit in the header to bypass a hash check. Perceptual hashes are designed to survive cropping, rotation, scaling, and embedding but all of those things mean that false-positives become a concern. The real risk would be if someone figured out how to many plausibly innocent collisions where you could send someone a picture which wasn’t obviously contraband or highly suspicious and attempt to convince them to save it.