[burself]

The algorithms and data involved are too sensitive to be discussed publicly and the reasoning is acceptable enough to even the most knowledgeable people. They can't even be pressured to prove that the system is effective at it's primary purpose.

This is the perfect way to begin opening the backend doors.

[kccqzy]

The algorithm is actually public: https://www.apple.com/child-safety/pdf/Apple_PSI_System_Secu... From an intellectual point of view it's interesting to learn about.

I agree with the rest of your points. The problem is that we don't know if Apple implemented this algorithm correctly, or even this algorithm at all, because the source code isn't subject to review and, even it were the binary cannot be proved to have been built from such source code. We also don't have proof that the only images being searched for are child abuse images as they claim.

[suizi]

Security by obscurity has never been particularly effective, and there are some articles which allege that detection algorithms can be defeated fairly easily.