Technologies Behind the Apple's CSAM Detection System

Apple wants to help protect children from people who use communication tools to recruit and exploit them, and limit the spread of CSAM files. On the other side, Apple's plan has been particularly controversial and has prompted concerns about the system potentially being abused by governments as a form of mass surveillance. But rather than analyzing the benefits and drawbacks of this new feature, I would like to say a few words about the cryptographic techniques and protocols used for this system implementation. Before explaining these technologies, let's step back for a moment and take a quick look at the whole process of CSAM detection and its steps to get some more context around this. NeuralHash is a perceptual hashing function that maps images to numbers. The system computes these hashes by using an embedding network to produce image descriptors and then converting those descriptors to integers using a Hyperplane LSH (Locality Sensitivity Hashing) process.