This op-ed originally appeared in the Washington Post last Saturday in response to Apple’s claims about the security of iMessage.

A lively debate is brewing over the security of Apples iMessages. I was recently quoted on this issue, but Apple has since responded, and it seems important to clarify that the argument now seems to be largely a matter of semantics.
In case you missed it, a group of researchers at Quarklab recently analyzed the iMessage protocol, including the trust model and key exchange, and found some mistakes that leave iMessages open to attacks. I had also previously demonstrated that iCloud backups, including backed-up iMessages, could easily be accessed by Apple. This news is important because previous reports suggested that iMessage encryption was a major impediment to law enforcement, and Apple specifically described iMessage data as “protected by end-to-end encryption so no one but the sender and receiver can see or read them” in response to their reported participation in the NSA’s PRISM program.

Apple stands by its claim that its software can’t be intercepted and that it is not reading iMessages. In that article, Apple spokeswoman Trudy Muller said: “iMessage is not architected to allow Apple to read messages. The research discussed theoretical vulnerabilities that would require Apple to re-engineer the iMessage system to exploit it, and Apple has no plans or intentions to do so.”

But Apple’s response that it cannot intercept messages is a bit misleading.

Apple controls the entire stack: the phone operating system (iOS), iMessage application, the SSL certificates, and key exchange. Quarklab’s researchers demonstrated that if they could obtain (or fake) a trusted Apple SSL certificate AND man-in-the-middle the iMessage key exchange, they would be in a position to intercept or tamper with iMessage. Basically, that means iMessage could be vulnerable if an actor is able to convince the application that they are authorized to carry the data and to insert themselves between the users.
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