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You argued that somehow Apple blindly followed “elite consensus” to end up with the system they announced. I pointed out that the system they announced question

You argued that somehow Apple blindly followed “elite consensus” to end up with the system they announced. I pointed out that the system they announced questions every aspect of “elite consensus” about how to scan for CSAM in a cloud service. Now you’re waving your hands and saying they’re practically the same when there is a 14 page security threat model on Apple’s website which lists the many ways in which it’s not. How many of the incumbent systems make their perceptual hash available or let clients inspect the data used for manual review in an associated data packet? Where does Dropbox publish its root hash for the known CSAM database? I could go on. Next, arriving at “practically the same solution” is a necessary but not sufficient condition for having the same assumptions. Arguing about practical functionality doesn’t even prove your point. Finally, I explained why it’s a bad take so I’m not sure what you find unhelpful.

matthewdgreen 5y ago
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...
- shuckles 5y ago
  This comment has nothing to do with your original theory about elite consensus which is problematic for many reasons including this one: > arriving at “practically the same solution” is a necessary but not sufficient condition for having the same assumptions. Your evidence doesn’t even prove your point.

matthewdgreen 5y ago

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...

shuckles 5y ago
This comment has nothing to do with your original theory about elite consensus which is problematic for many reasons including this one: > arriving at “practically the same solution” is a necessary but not sufficient condition for having the same assumptions. Your evidence doesn’t even prove your point.