3 ms·

I thought quality hashing algorithms have no known collisions? Like, it's theoretically possible, it just has never happened, anywhere, not even once. Why woul

• ensignavenger 3y ago
  Cryptographic hashes aren't supposed to have collisions... the types of hashing that PhotoDNA and other similar systems use are not cryptographic. In fact, some say they aren't even real hashes. The reason for this is because they want images that have been altered to still match, whereas with a cryptographic has, even a minor change will change the hash. So it is more a a "similarity" check than a proper hash.
• yencabulator 3y ago
  You're confusing hashing as in SHA-256 with perceptual hashing, which is more like a blurry thumbnail of an image converted into numbers. Any minor alteration to an image will change it's cryptographic hash completely, making those pretty poor tools for finding images that might want to be hidden. Perceptual hashing should match e.g. resized versions of the image, but with them two "blurry thumbnail hashes" can match accidentally.