Matthew Green, a Cryptography professor at Johns Hopkins University: "The question is, what kind of data, and what kind of measurements are they applying it to, and what are they doing with it. It’s a really neat idea, but I’ve never really seen it deployed. It ends up being a tradeoff between accuracy of the data you are collecting and privacy. The accuracy goes down as the privacy goes up, and the tradeoffs I’ve seen have never been all that great. I’ve never really heard of anyone deploying it in a real product before. So if Apple is doing this they’ve got a custom implementation, and they made all the decisions themselves."Apple did appear to have an expert on its side during the keynote, displaying a slide in which Aaron Roth, an associate professor of computer science at the University of Pennsylvania, called it ‘visionary’ and said that it ‘positions Apple as the clear privacy leader among technology companies today.’ But Federighi admitted that Roth had been given only a ‘quick peek’ at the technology, and Roth told Wired that he couldn’t comment on anything specific that Apple’s doing with differential privacy’ though he did think the company was ‘doing it right.’
