Comment by cwoolfe

It is possible to detect CSAM in end-to-end encrypted messaging by doing it on-device on the client side before it is encrypted and/or on the receiving client side after it is decrypted. iMessage already does this in the latest release. Most smart phones have AI-enabled chips that would be able to run images/videos against classification algorithms. The tricky part would be enforcing that users use clients which do this, so the task becomes regulating allowed messaging clients, which might be impossible. That being said, one could probably knock out 80% of the problem by legally forcing the hand of all the major platforms to do client-side scanning. At that point, only the truly dedicated would move their comms to another platform. Mobile users are very susceptible to nudges.