4 ms·

> Most security experts that I know agree that if an intruder has physical access to a device, it can be considered compromised because it is just a matter of t

> Most security experts that I know agree that if an intruder has physical access to a device, it can be considered compromised because it is just a matter of time. Anyone who says this is not a security expert. That hasn't been true since full disk encryption became available. A properly encrypted device is a brick if stolen, which is the only reason to have full disk encryption in the first place.

gjmulhol 13y ago
Most people outside of this community are not using disk encryption. With that said and the caveat that I am not an encryption expert myself: given an infinite amount of computing power and an infinite amount of time, can full disk encryption not be broken? If so, then it is just a question of computing power and time, not of whether it is possible to get to the data.
- unimpressive 13y ago
  >given an infinite amount of computing power and an infinite amount of time, can full disk encryption not be broken? Sure. But the difference between "infinite" and "a couple billion years" from a human perspective is minute.
- lawnchair_larry 13y ago
  Yeah, just a matter of time. Bring a flashlight though, because the sun is projected to burn out far sooner than the largest supercomputer will be able to brute force a 256 bit key.
- quchen 13y ago
  Combinatorical problems tend to grow in the amount of effort to try out all possible elements quite quickly, and quickly growing things in turns often hit physical limits. The following post on Security.Stackexchange explains it quite nicely; excerpt: the sun doesn't emit enough energy over its lifetime to power an extremely efficient computer able to try all combinations. http://security.stackexchange.com/a/25878/25947 http://security.stackexchange.com/a/25878/25947 So basically we need some new form of computer (one that's not flipping individual physical bits), and not "just faster" ones, to crack certain encryptions by brute force.
MichaelGG 13y ago
No, the physical access statement still holds true, even with FDE. First, if the machine is powered on, they can just extract the keys from RAM. Second, if you continue to use the device after it has been tampered with, you also lose (aka evil maid attack).
erichocean 13y ago
I take it you're not a security researcher either, because "A properly encrypted device is a brick if stolen, which is the only reason to have full disk encryption in the first place" is insufficient, too. Cold boot attacks, copying the drive and hacking the bootloader to get the drive password the next time you log in are two trivial methods, both of which have been used already. Once you lose physical access to your hardware, it's game over. You simply cannot trust your computer after that point if you care AT ALL about maximizing security.
- lawnchair_larry 13y ago
  I like how you refer to things that you have never tried as "trivial". And the defense against those is easy. Don't reuse it after it was stolen then returned. That's a different threat.

gjmulhol 13y ago

Most people outside of this community are not using disk encryption. With that said and the caveat that I am not an encryption expert myself: given an infinite amount of computing power and an infinite amount of time, can full disk encryption not be broken? If so, then it is just a question of computing power and time, not of whether it is possible to get to the data.

unimpressive 13y ago
>given an infinite amount of computing power and an infinite amount of time, can full disk encryption not be broken? Sure. But the difference between "infinite" and "a couple billion years" from a human perspective is minute.
lawnchair_larry 13y ago
Yeah, just a matter of time. Bring a flashlight though, because the sun is projected to burn out far sooner than the largest supercomputer will be able to brute force a 256 bit key.
quchen 13y ago
Combinatorical problems tend to grow in the amount of effort to try out all possible elements quite quickly, and quickly growing things in turns often hit physical limits. The following post on Security.Stackexchange explains it quite nicely; excerpt: the sun doesn't emit enough energy over its lifetime to power an extremely efficient computer able to try all combinations. http://security.stackexchange.com/a/25878/25947 http://security.stackexchange.com/a/25878/25947 So basically we need some new form of computer (one that's not flipping individual physical bits), and not "just faster" ones, to crack certain encryptions by brute force.

MichaelGG 13y ago

No, the physical access statement still holds true, even with FDE. First, if the machine is powered on, they can just extract the keys from RAM. Second, if you continue to use the device after it has been tampered with, you also lose (aka evil maid attack).

erichocean 13y ago

I take it you're not a security researcher either, because "A properly encrypted device is a brick if stolen, which is the only reason to have full disk encryption in the first place" is insufficient, too. Cold boot attacks, copying the drive and hacking the bootloader to get the drive password the next time you log in are two trivial methods, both of which have been used already. Once you lose physical access to your hardware, it's game over. You simply cannot trust your computer after that point if you care AT ALL about maximizing security.

lawnchair_larry 13y ago
I like how you refer to things that you have never tried as "trivial". And the defense against those is easy. Don't reuse it after it was stolen then returned. That's a different threat.