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I am not a security expert, but my understanding is that the main problems for the FBI are: a) There is a timed delay for trying new passwords after enough unsu

by ilyanep 11y ago

I am not a security expert, but my understanding is that the main problems for the FBI are: a) There is a timed delay for trying new passwords after enough unsuccessful attempts and b) The phone will wipe itself after 10 unsuccessful attempts. It's pretty much only sufficient to have (a) since the delays will make it take years to guess the password by brute force. I just ctrl-f'd for "delay" in the security guidelines[0], which claim that the secure enclave is the one that enforces the timed delay[1], so I guess the only attack vector would be if you could somehow backdoor code onto the chip. I can't find anything in the guide from a quick skim, but I'd suspect the code is on a ROM chip or is somehow prevented from an upgrade without an unlock? [0] https://www.apple.com/business/docs/iOS_Security_Guide.pdf https://www.apple.com/business/docs/iOS_Security_Guide.pdf [1] Page 12

mikeash 11y ago
> I can't find anything in the guide from a quick skim, but I'd suspect the code is on a ROM chip or is somehow prevented from an upgrade without an unlock? This is the big unanswered question. I suspect the same, but so far have not been able to find anything that actually says so. The code is not in ROM, as it can be updated, but it could wipe data if updated without an unlock. But I can't find anything saying whether it actually is. The mere fact that it's possible isn't enough, and their silence is a bit odd.
- ilyanep 11y ago
  Seems like it'd be a pretty huge oversight if that vector were open, but I agree with you that it's not very confidence-inspiring if nothing about this is out there.
  - mikeash 11y ago
    Depends on your threat model. It's possible that the Secure Enclave was just intended to be a defense in depth against malware and common criminals, not something that could keep Apple themselves out. If so, I'm sure they're re-evaluating that now.

by ilyanep 11y ago

mikeash 11y ago

> I can't find anything in the guide from a quick skim, but I'd suspect the code is on a ROM chip or is somehow prevented from an upgrade without an unlock? This is the big unanswered question. I suspect the same, but so far have not been able to find anything that actually says so. The code is not in ROM, as it can be updated, but it could wipe data if updated without an unlock. But I can't find anything saying whether it actually is. The mere fact that it's possible isn't enough, and their silence is a bit odd.

ilyanep 11y ago
Seems like it'd be a pretty huge oversight if that vector were open, but I agree with you that it's not very confidence-inspiring if nothing about this is out there.
- mikeash 11y ago
  Depends on your threat model. It's possible that the Secure Enclave was just intended to be a defense in depth against malware and common criminals, not something that could keep Apple themselves out. If so, I'm sure they're re-evaluating that now.