6 ms·

Most likely it's already been fixed. The iPhone 5C in question uses an A6 processor. It encrypts data by comingling the passcode with the unique device ID to c

by abalone 11y ago

Most likely it's already been fixed. The iPhone 5C in question uses an A6 processor. It encrypts data by comingling the passcode with the unique device ID to create a a strong 256-bit key, so you can't just pull and brute force the flash memory chip. Meanwhile the OS will wipe the key if you guess a wrong passcode too many times, making the data forever inaccessible. However there is one vulnerability with the A6 that some have theorized.[1] If you could somehow get around the wiping part, you could keep guessing passcodes. A typical 4 or 6 digit passcode could be guessed in under a day. So it may be possible to copy the flash memory into a soldered-in test rig that is effectively wipe-proof. It would restore the contents every time it's wiped. So that's the best guess I know of for what happened here. But starting with the A7 Apple added the secure enclave. This now enforces at the hardware level an escalating time delay with each wrong passcode guess. It goes all the way up to a one hour delay.[2] That's also where the (unreadable) unique device ID resides, so there's no swapping out the processor with a rig. The key is forever wedded to this protection against brute forcing. That is pretty darn spiffy from a security standpoint. If it works as designed, about the only hope anyone has of getting at data from an A7 or later device is through iCloud backups.[3] [1] https://www.aclu.org/blog/free-future/one-fbis-major-claims-iphone-case-fraudulent https://www.aclu.org/blog/free-future/one-fbis-major-claims-... see also http://blog.cryptographyengineering.com/2014/10/why-cant-apple-decrypt-your-iphone.html http://blog.cryptographyengineering.com/2014/10/why-cant-app... [2] https://www.apple.com/business/docs/iOS_Security_Guide.pdf https://www.apple.com/business/docs/iOS_Security_Guide.pdf [3] Either that or some kind of peek into the secure enclave. It's specifically designed to inhibit this at a hardware level, but perhaps a nation-state could figure it out (e.g. verrrrry carefully grinding it down without destroying it and looking at state with an electron microscope).

nodesocket 11y ago
That's an interesting point that I haven't heard mentioned. What if the FBI got to the data not from the phone, but iCloud. That honestly actually seems easier.
- xupybd 11y ago
  I think they attempted that, however due to a mistake wiped the iCloud data.
  - abalone 11y ago
    They didn't wipe it. They got a six week old backup. What they did prevented triggering a newer backup.
    - ikeboy 11y ago
      Would not have been backed up anyway http://www.theverge.com/2016/3/10/11195772/apple-fbi-icloud-backup-shut-off-password-changed http://www.theverge.com/2016/3/10/11195772/apple-fbi-icloud-...
      - nitrogen 11y ago
        They could have mentioned that just like they could have mentioned that they asked for the password to be changed.
  - bigiain 11y ago
    Due to a mistake, or "accidentally on purpose" so they could punt with this law suit…
  - tga_d 11y ago
    It wasn't wiped, it was disabled. They actually did get the iCloud backup data, but from about a month and a half before the phone was seized. Instead of waiting for another iCloud backup to occur, they reset the password, which disables these backups. The FBI then lied about this, saying that resetting the password was done against their will by the county. The county disputed this claim, and the FBI eventually admitted that they had actually instructed the county to do so, leaving open the question of why they did this. source: just search "San Bernardino iCloud" and you'll get a whole bunch of articles on the subject
cromwellian 11y ago
I wouldn't assume that nation-state attackers would be thwarted by the Secure Enclave. Organizations which can deploy taps on undersea fiber optic cables from nuclear submarines, attack centrifuges deep inside air-gapped underground nuclear facilities, etc would likely be able to mount the kinds of specialized attacks needed to break into HW trusted computing models. Something that is tamper-resistant isn't tamper-proof. It will likely take some time to develop a capacity to attack these chips, but it is not impossible in principle nor intractable.
- abalone 11y ago
  Hey, I updated my comment with a footnote on exactly that. Not sure if you saw it. I agree it may be possible to develop an attack against the secure enclave with a big enough budget and access to lots of sample chips to practice on. But keep in mind secure enclaves are designed to self-destruct under these circumstances, so I almost think it may entail pushing the frontier of electron microscopy and/or techniques for exposing it that are more delicate that grinding down the chip. In other words yes, I'd bet money there's a "secure enclaves" team at the NSA with a few million bucks to play with. Or teams.
  - cromwellian 11y ago
    Another possibility is a tailored-access type attack further upstream the supply chain. For example, Apple relies on Samsung or TSMC to fab chips. It's possible the chips could be modified before manufacture, or after, to contain a flaw. I've read about such attacks demonstrated in principle already. There was a worry about the Chinese government executing such attacks for example. One of the downsides of the way global manufacturing works today that there's so many stages in which components can be intercepted. You don't know that the device you bought actually consists of unmodified versions of the components that were part of the original design. Could the NSA partner with the Korean government and Samsung to put a backdoor into components? I wouldn't rule it out.
    - dogma1138 11y ago
      It would be considerably cheaper to just replicate the ASIC you want to attack in your own silicon. The secure enclave isn't so magic it's just a secondary processor that handles cryptography it has it's own memory to store variable such as failed attempts. Attacking the SOC might be more complex and expensive but eventually it's exactly the same as attacking the NAND or any other integrated circuit. For all we know the NSA could (and most likely does) develop their own in circuit debuggers for common ASIC/SOC's and just dumps what ever unique values the target SOC stores and takes a crack at it. This also isn't out of the realm of possibilities for companies that specialize in in-circuit emulation, hardware design, and forensics to create as a turn key solution.
diskcat 11y ago
>It encrypts data by comingling does the use of the word 'comingling' here implies any kind of special combination technique??
- abalone 11y ago
  I'm just using the term casually. Technically I think it's a hierarchy of keys wrapping keys. It's all explained here: https://www.apple.com/business/docs/iOS_Security_Guide.pdf https://www.apple.com/business/docs/iOS_Security_Guide.pdf
molecule 11y ago
> That is pretty darn spiffy from a security standpoint. If it works as designed, about the only hope anyone has of getting at data from an iPhone 6 or later is through iCloud backups. Isn't that 5S or later? Touch ID and Secure Enclave were introduced w/ the 5S model.
- abalone 11y ago
  Sorry, yes. Updated.
awqrre 11y ago
Just get the data while the device is in use and unencrypted, using a warrant? (wirelessly, before you apprehend the suspect)
nxzero 11y ago
Phone is just locked, key is not wiped.
Someone 11y ago
"If you could somehow get around the wiping part, you could keep guessing passcodes" In the 80's, one could do that by cutting a single line in the connector between motherboard and hard disk. I would guess something similar is possible between motherboard and flash. It would be more complex because 'write' now isn't a single signal, but part of a protocol and because one would have to des older the flash, but that shouldn't stop the FBI. So, I guess one can get rid of the "restore the contents every time it's wiped" step, speeding up the process. As to the A7: as you indicate, people will try to do essentially the same thing to the flash storage inside it. Cut one open and try to figure out where its memory is, try cutting that loose from the CPU part, etc. The scale will be smaller, and the challenge (a lot, if the A7 has anti-tamper devices on-board) harder, but impossible?
studentrob 11y ago
Hmm the executive branch remains unfixed. Obama and the DOJ still think they can compel all encrypted messaging platforms to provide the US government with decryptable data.
makomk 11y ago
The Secure Enclave supposedly has the same problem - the information about how many guesses have been attempted is stored entirely in external flash memory that can be rolled back to give unlimited tries. Additionally, Apple have the ability to sign and load new software for the Secure Enclave that doesn't have the escalating time delay, leaving only the same 80ms per check hardware limit that the A6 had.
sllabres 11y ago
Potentially this might not only possible for nation-state actors. This is for not for an iPhone, but for an secure element (TPM): https://www.youtube.com/watch?v=h-hohCfo4LA https://www.youtube.com/watch?v=h-hohCfo4LA https://en.wikipedia.org/wiki/Christopher_Tarnovsky#Acts_of_hacking https://en.wikipedia.org/wiki/Christopher_Tarnovsky#Acts_of_...

by abalone 11y ago

nodesocket 11y ago

That's an interesting point that I haven't heard mentioned. What if the FBI got to the data not from the phone, but iCloud. That honestly actually seems easier.

xupybd 11y ago
I think they attempted that, however due to a mistake wiped the iCloud data.
- abalone 11y ago
  They didn't wipe it. They got a six week old backup. What they did prevented triggering a newer backup.
  - ikeboy 11y ago
    Would not have been backed up anyway http://www.theverge.com/2016/3/10/11195772/apple-fbi-icloud-backup-shut-off-password-changed http://www.theverge.com/2016/3/10/11195772/apple-fbi-icloud-...
    - nitrogen 11y ago
      They could have mentioned that just like they could have mentioned that they asked for the password to be changed.
- bigiain 11y ago
  Due to a mistake, or "accidentally on purpose" so they could punt with this law suit…
- tga_d 11y ago
  It wasn't wiped, it was disabled. They actually did get the iCloud backup data, but from about a month and a half before the phone was seized. Instead of waiting for another iCloud backup to occur, they reset the password, which disables these backups. The FBI then lied about this, saying that resetting the password was done against their will by the county. The county disputed this claim, and the FBI eventually admitted that they had actually instructed the county to do so, leaving open the question of why they did this. source: just search "San Bernardino iCloud" and you'll get a whole bunch of articles on the subject

cromwellian 11y ago

I wouldn't assume that nation-state attackers would be thwarted by the Secure Enclave. Organizations which can deploy taps on undersea fiber optic cables from nuclear submarines, attack centrifuges deep inside air-gapped underground nuclear facilities, etc would likely be able to mount the kinds of specialized attacks needed to break into HW trusted computing models. Something that is tamper-resistant isn't tamper-proof. It will likely take some time to develop a capacity to attack these chips, but it is not impossible in principle nor intractable.

abalone 11y ago
Hey, I updated my comment with a footnote on exactly that. Not sure if you saw it. I agree it may be possible to develop an attack against the secure enclave with a big enough budget and access to lots of sample chips to practice on. But keep in mind secure enclaves are designed to self-destruct under these circumstances, so I almost think it may entail pushing the frontier of electron microscopy and/or techniques for exposing it that are more delicate that grinding down the chip. In other words yes, I'd bet money there's a "secure enclaves" team at the NSA with a few million bucks to play with. Or teams.
- cromwellian 11y ago
  Another possibility is a tailored-access type attack further upstream the supply chain. For example, Apple relies on Samsung or TSMC to fab chips. It's possible the chips could be modified before manufacture, or after, to contain a flaw. I've read about such attacks demonstrated in principle already. There was a worry about the Chinese government executing such attacks for example. One of the downsides of the way global manufacturing works today that there's so many stages in which components can be intercepted. You don't know that the device you bought actually consists of unmodified versions of the components that were part of the original design. Could the NSA partner with the Korean government and Samsung to put a backdoor into components? I wouldn't rule it out.
  - dogma1138 11y ago
    It would be considerably cheaper to just replicate the ASIC you want to attack in your own silicon. The secure enclave isn't so magic it's just a secondary processor that handles cryptography it has it's own memory to store variable such as failed attempts. Attacking the SOC might be more complex and expensive but eventually it's exactly the same as attacking the NAND or any other integrated circuit. For all we know the NSA could (and most likely does) develop their own in circuit debuggers for common ASIC/SOC's and just dumps what ever unique values the target SOC stores and takes a crack at it. This also isn't out of the realm of possibilities for companies that specialize in in-circuit emulation, hardware design, and forensics to create as a turn key solution.

diskcat 11y ago

>It encrypts data by comingling does the use of the word 'comingling' here implies any kind of special combination technique??

abalone 11y ago
I'm just using the term casually. Technically I think it's a hierarchy of keys wrapping keys. It's all explained here: https://www.apple.com/business/docs/iOS_Security_Guide.pdf https://www.apple.com/business/docs/iOS_Security_Guide.pdf

molecule 11y ago

> That is pretty darn spiffy from a security standpoint. If it works as designed, about the only hope anyone has of getting at data from an iPhone 6 or later is through iCloud backups. Isn't that 5S or later? Touch ID and Secure Enclave were introduced w/ the 5S model.

abalone 11y ago
Sorry, yes. Updated.

awqrre 11y ago

Just get the data while the device is in use and unencrypted, using a warrant? (wirelessly, before you apprehend the suspect)

nxzero 11y ago

Phone is just locked, key is not wiped.

Someone 11y ago

"If you could somehow get around the wiping part, you could keep guessing passcodes" In the 80's, one could do that by cutting a single line in the connector between motherboard and hard disk. I would guess something similar is possible between motherboard and flash. It would be more complex because 'write' now isn't a single signal, but part of a protocol and because one would have to des older the flash, but that shouldn't stop the FBI. So, I guess one can get rid of the "restore the contents every time it's wiped" step, speeding up the process. As to the A7: as you indicate, people will try to do essentially the same thing to the flash storage inside it. Cut one open and try to figure out where its memory is, try cutting that loose from the CPU part, etc. The scale will be smaller, and the challenge (a lot, if the A7 has anti-tamper devices on-board) harder, but impossible?

studentrob 11y ago

Hmm the executive branch remains unfixed. Obama and the DOJ still think they can compel all encrypted messaging platforms to provide the US government with decryptable data.

makomk 11y ago

The Secure Enclave supposedly has the same problem - the information about how many guesses have been attempted is stored entirely in external flash memory that can be rolled back to give unlimited tries. Additionally, Apple have the ability to sign and load new software for the Secure Enclave that doesn't have the escalating time delay, leaving only the same 80ms per check hardware limit that the A6 had.

sllabres 11y ago

Potentially this might not only possible for nation-state actors. This is for not for an iPhone, but for an secure element (TPM): https://www.youtube.com/watch?v=h-hohCfo4LA https://www.youtube.com/watch?v=h-hohCfo4LA https://en.wikipedia.org/wiki/Christopher_Tarnovsky#Acts_of_hacking https://en.wikipedia.org/wiki/Christopher_Tarnovsky#Acts_of_...