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The Feds Can Now Probably Unlock Every iPhone Model

forbes.com

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Re: The Feds Can Now Probably Unlock Every iPhone Model

#11

Post by userbinator »

eugeniub wrote: post #9
caymanjim wrote: post #4

I'm too lazy to find a link for it, but last time I read about Cellebrite, they were cloning the data and simply trying unlock codes in sequence until one worked. They could restore the cloned data before each try, or possibly do it on custom hardware or an emulator, and start with a fresh copy each time, so they never triggered "erase after 10 failures". It's a pretty straightforward approach, but it doesn't scale w…

This is not true. You cannot just clone the data and run passcodes against it, because the data is not encrypted by your passcode. Instead, each file on iOS 11 is encrypted with a different AES 256-bit key, and cracking even one 256-bit key through exhaustive search is thought to be out of reach of humankind ( https://security.stackexchange.com/questions/6141/amount-of-... ). The file keys are wrapped by, among other…

or prying open the Secure Enclave to obtain the Unique ID

People have been cracking secure coprocessors of the type used in payment cards, TPMs, and the like for a long time, dare I say even those which were designed to a higher level of security than Apple's. The fact that there is an entire phone attached to it doesn't make much of a difference, but the technology behind this (FIB, microprobing, etc.) has been steadily dropping in price and increasing in availability for a long time.

Re: The Feds Can Now Probably Unlock Every iPhone Model

#12

Post by 908087 »

IBM wrote: post #7
eridius wrote: post #2

Bruce Schneier says¹: > There's also a credible rumor that Cellebrite's mechanisms only defeat the mechanism that limits the number of password attempts. It does not allow engineers to move the encrypted data off the phone and run an offline password cracker. If this is true, then strong passwords are still secure. ¹ https://www.schneier.com/blog/archives/2018/02/cellebrite_un...

>The story I hear is that Cellebrite hires ex-Apple engineers and moves them to countries where Apple can't prosecute them under the DMCA or its equivalents. Crazy if true. Doesn't this also create a weird incentive problem where the FBI (or any other law enforcement agency) who would normally be tasked with helping Apple with this doesn't actually want to?

1984: CIA smuggles cocaine into the US

2018: FBI smuggles Apple engineers out of the US

Re: The Feds Can Now Probably Unlock Every iPhone Model

#14

Post by gruez »

eugeniub wrote: post #9
caymanjim wrote: post #4

I'm too lazy to find a link for it, but last time I read about Cellebrite, they were cloning the data and simply trying unlock codes in sequence until one worked. They could restore the cloned data before each try, or possibly do it on custom hardware or an emulator, and start with a fresh copy each time, so they never triggered "erase after 10 failures". It's a pretty straightforward approach, but it doesn't scale w…

This is not true. You cannot just clone the data and run passcodes against it, because the data is not encrypted by your passcode. Instead, each file on iOS 11 is encrypted with a different AES 256-bit key, and cracking even one 256-bit key through exhaustive search is thought to be out of reach of humankind ( https://security.stackexchange.com/questions/6141/amount-of-... ). The file keys are wrapped by, among other…

I think he got the the idea right. Yes, you need the secret key burned into the CPU to decrypt anything, and yes, you can't easily extract the keys. but his claim is that by fully restoring the flash storage (presumably where the retry counter is stored), it's possible to bypass the "erase data after 10 failed attempts" policy by constantly resetting the counter back to its original state. It might take a while (you might have to go through the boot process each time, but for a 6 digit pin and 30 seconds each attempt, it's still less than a year.

Re: The Feds Can Now Probably Unlock Every iPhone Model

#15

Post by alwillis »

julianj wrote: post #13

I wish there was a kind of "dead man switch" app that would wipe a device if it is not unlocked for x days or met some other kind of personalized criteria.

You mean like automatically erasing the device after 10 incorrect passcode attempts?

That option has been built in to the iPhone pretty much since the beginning.

Re: The Feds Can Now Probably Unlock Every iPhone Model

#16

Post by pdkl95 »

julianj wrote: post #13

I wish there was a kind of "dead man switch" app that would wipe a device if it is not unlocked for x days or met some other kind of personalized criteria.

An app would need an environment to run in, but the main CPU/etc may not be available if the recovery process involves removing chips or other hardware modifications.

A better idea would be to put an RTC + watchdog timer[1] into the security chip that holds the keys and power it continuously with a small amount of external power. The power must be available and the watchdog timer must have time remaining to disconnect a circuit that pulls the memory holding the keys to ground.

More advanced types of tamper resistance and self-destructing chips are possible, but they tend to have significant downsides.

[1] https://en.wikipedia.org/wiki/Watchdog_timer

Re: The Feds Can Now Probably Unlock Every iPhone Model

#17

Post by julianj »

alwillis wrote: post #15
julianj wrote: post #13

I wish there was a kind of "dead man switch" app that would wipe a device if it is not unlocked for x days or met some other kind of personalized criteria.

You mean like automatically erasing the device after 10 incorrect passcode attempts? That option has been built in to the iPhone pretty much since the beginning.

No. An example would be automatically erase if the device has not been unlocked in 3 days.

Re: The Feds Can Now Probably Unlock Every iPhone Model

#18

Post by gruez »

julianj wrote: post #13

I wish there was a kind of "dead man switch" app that would wipe a device if it is not unlocked for x days or met some other kind of personalized criteria.

I think that's how some HSMs work to guard against tampering. The keys are stored on volatile memory, and there's a internal battery/capacitor. You can unplug it, but its tamper intrusion mechanisms will still be active because of the internal battery. If you trip the tamper detection mechanisms, the keys get wiped. If the battery runs out, the key gets wiped. So if you're relocating the HSM, you have x days to replug it in before you lose your keys. I imagine if you're designing a high security phone, you could possibly want this as a feature, but I doubt most people want a phone that wipes their data if the battery went flat for 7 days.

Re: The Feds Can Now Probably Unlock Every iPhone Model

#19

Post by julianj »

pdkl95 wrote: post #16
julianj wrote: post #13

I wish there was a kind of "dead man switch" app that would wipe a device if it is not unlocked for x days or met some other kind of personalized criteria.

An app would need an environment to run in, but the main CPU/etc may not be available if the recovery process involves removing chips or other hardware modifications. A better idea would be to put an RTC + watchdog timer[1] into the security chip that holds the keys and power it continuously with a small amount of external power. The power must be available and the watchdog timer must have time remaining to disconnec…

Good points. Thank you for this reading material.

Re: The Feds Can Now Probably Unlock Every iPhone Model

#20

Post by giovannibajo1 »

gruez wrote: post #14
eugeniub wrote: post #9

Earlier quoted context omitted.

This is not true. You cannot just clone the data and run passcodes against it, because the data is not encrypted by your passcode. Instead, each file on iOS 11 is encrypted with a different AES 256-bit key, and cracking even one 256-bit key through exhaustive search is thought to be out of reach of humankind ( https://security.stackexchange.com/questions/6141/amount-of-... ). The file keys are wrapped by, among other…

I think he got the the idea right. Yes, you need the secret key burned into the CPU to decrypt anything, and yes, you can't easily extract the keys. but his claim is that by fully restoring the flash storage (presumably where the retry counter is stored), it's possible to bypass the "erase data after 10 failed attempts" policy by constantly resetting the counter back to its original state. It might take a while (you…

That doesn’t work as well because the counter is kept in the Secure Enclave so it’s not part of the flash contents. Also the exponential delay in attempts is enforced by the enclave.

Previous iOS versions used to have some small window where you could race and power off after trying a passcode but before the enclave had incremented the counter, but that bug was fixed long ago. Maybe there are others unknown bugs of similar kind

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