The problem with perceptual hashes

Oliver Kuederle, who works with the image hashing technology used by Apple’s new technology that’s going to scan the photos on your iOS device continuously, explains that it is far, far from foolproof:

Perceptual hashes are messy. The simple fact that image data is reduced to a small number of bits leads to collisions and therefore false positives. When such algorithms are used to detect criminal activities, especially at Apple scale, many innocent people can potentially face serious problems.

My company’s customers are slightly inconvenienced by the failures of perceptual hashes (we have a UI in place that lets them make manual corrections). But when it comes to CSAM detection and its failure potential, that’s a whole different ball game. Needless to say, I’m quite worried about this.

This is just one of the many, many problems with what Apple announced yesterday.


  1. 2021-08-07 8:27 am
    • 2021-08-07 1:26 pm
  2. 2021-08-07 6:31 pm