I'm a cryptographer, so I do understand the system fairly well. What Apple is doing is applying an automated hash-based image matching system to all photos in y

I'm a cryptographer, so I do understand the system fairly well. What Apple is doing is applying an automated hash-based image matching system to all photos in your library, and triggering an alert (plus a low-resolution photo) to a human being when 30 photos match. Except for the use of cryptography and the "30" threshold, this is functionally identical to what existing providers do on the server side. As an expert in this field I'm thrilled to see the use of fancy cryptography, but the use of a 2PC protocol does not change the underlying functionality at all. What is different about the Apple system is that unlike many companies (as of 2019) [0] they are not simply scanning shared photos intended for distribution. They are scanning all photos in your library, even unshared ones. This to me is much more significant than the use of PSI or adding a threshold of 30 reports. You can agree or disagree but it's much more helpful to argue this based on the merits than to be rude about it. [0] page 8: https://www.europarl.europa.eu/RegData/etudes/BRIE/2020/659360/EPRS_BRI(2020)659360_EN.pdf https://www.europarl.europa.eu/RegData/etudes/BRIE/2020/6593...