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Perceptual hashes aren't cryptographic. The Twitter thread has examples of engineered collisions for a simpler perceptual hash.
by pseudalopex 5y ago
Perceptual hashes aren't cryptographic. The Twitter thread has examples of engineered collisions for a simpler perceptual hash.
- zepto 5y agoSo we know they are using perceptual hashing and what kind?
- pseudalopex 5y ago"Hashes using a new and proprietary neural hashing algorithm Apple has developed, and gotten NCMEC to agree to use."
- zepto 5y agoThat sounds like we know it’s perceptual but not what kind, and therefore we don’t know the collision characteristics.
- pseudalopex 5y agoWe know perceptual hashing and cryptography have incompatible requirements. Think of an image, the same image with 1 pixel changed, and a very different image. A perceptual hash should say 1 and 2 were related and not 3. Cryptographers call that failing a chosen plaintext attack.
- zepto 5y agoAgreed, but we don’t know the collision characteristics of this algorithm so knowing this difference is moot in this context.