Why can't the FBI read the key embedded in the iPhone's secure chip/ROM directly from hardware (silicon)?

Question

As far as I understand, the 4 digit passcode is combined (in some fashion) with a key stored in secure read only memory (e.g. secure enclave chip or similar), where it is directly embedded into silicon wiring to help prevent unauthorized reads.

But no matter how strong or multi-layered or complicated the security is, wouldn't it still be possible to read the key directly from the silicon wiring of the secure chip or ROM, using some electron microscopy technique or similar? If so, surely the FBI could develop the technology for this, without asking Apple for help.

Answer 1

Yes, it is possible. However, that runs the risk of destroying the device without getting the data off first, which is undesirable. It also does not achieve the political goals of forcing Apple to assist in decrypting the device, paving the way with precedent for the flurry of future requests of this sort to come, some of which are certain to have less favorable facts and thus are not as suitable as test cases.

Answer 2

What makes you think that they haven't already?

This case is about setting a precedent to obtain access whenever the government desires. They chose this case because America's fear of terrorism will give more popular support for setting this precedent than, say, busting a pot grower or catching a tax cheat.

What would be even better? Privacy advocates pointed out that existing spying operations haven't provided useful count-terrorism intelligence. What if this iPhone contains some golden nuggets of counter-terror intel? Officials will be vindicated, and have a much easier time racheting back privacy protections further in the future.

Maybe the FBI is taking a page from the good lawyer's handbook, and asking questions they can already answer.

Answer 3

It doesn't scale

While the general consensus is that such technology exists and would be available to FBI, it's not an appropriate general solution because it might be applicable to this case but (unlike a legal battle with Apple) it doesn't scale to all the other cases where they would want to do the same thing.

• It is expensive - this case might be important enough to warrant the expense, but doing it for all the phones they'd want to read is even more expensive than, say, a prolonged legal battle with lots of lawyers involved;
• It risks destruction of evidence - there is a significant risk of failure, and failure would mean permanently destroying the key and any means to recover it ever.

A solution that allows FBI to decrypt such phones safely and cheaply would be very desirable to them, so even if they are able read the embedded key from the chip, it is worth a try to get Apple to do it instead.

Answer 4

You are assuming the problem is technical. It might be political / legal. Let's assume the government already has the technical capability of extracting this information from phones, without Apple providing them a back door. The government, for both legal and technical reasons, can't admit that. Legally, because it might tip its hand to other investigations in which data was used obtaining this not-yet-legal method, which would taint those investigations.

Once, however, the courts force Apple to provide them a backdoor, then they can use their own backdoor with impunity, or just use Apple's.

Answer 5

Yes, it is possible. Secure enclave chip is tamper-resistant, but with Advanced (expensive) semi-invasive attack, this chip is vulnerable.

A good link that covers all aspects of attacks on tamper-resistant hardware (note: Dr Sergei Skorobogatov attacks military chips and we know that secure enclave chip of iPhone is weaker than military chip) http://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-630.html

intercept report a real hardware attack by CIA on iPhone and below paragraph is from theintercept:

At the 2011 Jamboree conference, there were two separate presentations on hacking the GID key on Apple’s processors. One was focused on non-invasively obtaining it by studying the electromagnetic emissions of — and the amount of power used by — the iPhone’s processor while encryption is being performed. Careful analysis of that information could be used to extract the encryption key. Such a tactic is known as a “side channel” attack. The second focused on a “method to physically extract the GID key.”

But Apple-FBI backdoor is a part of a battle between government departments and crypto for privacy, so the goal of FBI is limiting all crypto-software with passing new law and Apple-FBI backdoor doesn't mean that FBI can't!

See more at: Delicate Hardware Hacks Could Unlock Shooter’s iPhone by threatpost:

“It’s been known they(NSA) have a semiconductor [fabrication] since January 2001. They can make chips. They can make software. They can break software. Chances are they can probably break hardware ”

Answer 6

They can, but that's not the problem they're facing.

As you've mentioned, the encryption key is generated from a mix of the PIN number and the private key. The problem is the PIN number.

iPhones allow only a maximum of 10 tries to enter PINs after which it will refuse to accept any additional PIN input. Furthermore, users can configure the phone to delete all data on disk if the 10th attempt fails*. Now, I'm not sure if the specific phone they're trying to unlock has been configured this way but it's too big a risk to take if the data on the phone is important.

A 4 digit PIN has 10000 combinations. So being able to try just 0.1% of all possible combinations is unlikely to work.

What the FBI is asking is basically for Apple to install a custom OS on that phone without the 10-entry limit so that they can try all 10000 PIN combinations.

*Note: When configured to delete data on disk on failed attempts the iPhone won't actually format the disk, it would just delete the private key thereby making any further cracking attempt all but impossible.

Answer 7

No, even if you were theoretically able to get the embedded key in the hardware, you would still not have the 4 digit code that is combined with the embedded key. Of course, at this point it would be trivial to bruteforce (especially at just 4 digits long).

This answer is geared more towards the original question although other answers are doing well to expand on the discussion regarding the implications of the court's decision.

Answer 8

My understanding is that reading anything "directly from silicon" is not practically possible in general case. While it is theoretically possible to determine silicon structure using an electron microscope (destroying a dozen of identical chips in the process), I'm not aware of any readily available methods to read flash memory contents.

Think about it: if it was possible to reliably read any chip's contents, why would the FBI bother to ask Apple for assistance?