Apple has announced plans to scan iPhones and other Apple devices for images of child sexual abuse and report them to the National Center for Missing and Exploited Children. A Johns Hopkins University expert is available to discuss how the technology works, as well as potential privacy concerns.

Matthew D. Green is an associate professor of computer science and a nationally recognized expert on applied cryptography and cryptographic engineering. A member of the Johns Hopkins Information Security Institute, he has written widely about Apple’s privacy methods and led a research team that worked with Apple to fix a security bug in the iMessage app.

“This is a really bad idea,” Green wrote on Twitter. “These tools will allow Apple to scan your iPhone for photos that match a specific perceptual hash and report them to Apple servers if too many appear.”

“The ability to add scanning systems like this to end-to-end encryption messaging systems has been a major ask by law enforcement the world over,” wrote Green. “This sort of tool can be a boon for finding child pornography in people’s phones. But imagine what it could do in the hands of an authoritarian government.”


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