Apple vs the FBI: why I'm with Apple

I’ve read Tim Cook’s letter to customers about four times since last Tuesday night, and the court order once, slowly, which I recommend if you’re going to argue about this at lunch. A lot of the arguing I’ve seen is about a version of the case that isn’t the one in front of the judge.

What the FBI is asking for is narrower than “decrypt this phone”. The phone is an iPhone 5C that Syed Rizwan Farook used, owned by his employer, San Bernardino County. It’s locked with a passcode, and iOS has two protections against guessing: after ten wrong tries it can wipe itself, and it makes you wait longer and longer between attempts. The order, from a magistrate judge in Riverside, tells Apple to write and sign a special version of iOS that turns off the auto-erase, removes the delays, and lets the FBI submit passcodes electronically instead of tapping them on the screen. Apple wouldn’t have to break any encryption. The FBI would then guess the passcode the slow way, at computer speed.

How slow is slow? Apple’s own security guide says the passcode is tangled with a key in the hardware, and that each attempt takes about 80 milliseconds to check, on the device, no way around it. A 4-digit passcode is 10,000 combinations, so about 13 minutes to try them all. Six digits is a million, about 22 hours. A six-character alphanumeric passcode would take five and a half years, which is the number Apple likes to quote. So if Farook used a short numeric code, and most people do, the FBI is a day away from getting in once the software exists.

That’s the FBI’s best argument, and I don’t think it’s a bad one. Jim Comey’s open letter on Sunday says, more or less, we’re not asking for a master key, we want the chance to guess the passcode without the phone self-destructing. It’s one phone, owned by the county, which has consented, in a case where fourteen people were murdered. If you’d asked me in the abstract whether a company should help police get into a dead terrorist’s work phone, I’d probably have said yes.

But the abstract isn’t the case, and there are two things that keep me on Apple’s side.

The first is that the thing they’re asking Apple to build is the dangerous part, whatever it’s used on. A firmware image that removes the passcode limits and is signed by Apple is the single most valuable piece of software an attacker could steal from Apple. The order says it should be tied to this phone’s unique ID, and I believe Apple could do that. But the protection then rests on the code being kept secret and on Apple’s signing process, and once the first one exists, the next request just changes the ID. Cook’s letter says “this software — which does not exist today” would have the potential to unlock any iPhone in someone’s physical possession, and I think that’s roughly right. I’ve done enough reverse engineering to have a lot of respect for code signing, and the whole value of a signature is that the people holding the key will say no.

The second is that “next request”. The government’s legal theory here is the All Writs Act, from 1789, which lets courts issue orders that are necessary to carry out their other orders. If that’s enough to make a company write new software to defeat its own security, I don’t see where the limit is. The Manhattan DA has said publicly that he has a pile of locked iPhones of his own. Other countries will ask for the same thing, and some of them won’t be asking about terrorists.

We’ve had this argument before, too. In 1993 the government’s answer was the Clipper chip, an encryption chip with a key held in escrow for law enforcement, and the next year Matt Blaze found a way around its escrow mechanism. “Only the good guys can use it” was the promise then. It’s the promise now, and I don’t believe anybody can keep it. I don’t think the FBI is acting in bad faith here, but keys and tools leak, and they leak from careful organizations too.

A couple of other things are bothering me about how this has gone. On Friday the government revealed in a filing that the iCloud password on the account was reset a day after the shooting, and the FBI has since said the county did it at the FBI’s request. Apple says that if it hadn’t been reset, they might have been able to get a fresh backup off the phone by connecting it to a known Wi-Fi network, without any of this. And the government went to court publicly, with a motion that reads a lot like a press release, which makes it hard to believe this is only about one phone.

One last technical point, because it’s interesting. A 5C is a 2013 design with an A6 chip, which is from before Apple added the Secure Enclave. On newer iPhones the escalating delays are enforced by that separate processor, not by iOS itself. Whether a signed update could weaken the Secure Enclave too is being argued about by people who know a lot more than I do, and I don’t think Apple has said. If it can’t, newer phones are out of reach of this trick anyway, and what’s left to fight over is mostly the precedent.

Apple’s formal response to the order is due in the next few days.