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Ask HN: Do you encrypt your laptop's hard disk?

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Re: Ask HN: Do you encrypt your laptop's hard disk?

#111

Post by tptacek »

all wrote: post #109
tptacek wrote: post #79

Earlier quoted context omitted.

Remanence isn't a realistic attack in his threat model; attackers have mere minutes to get the RAM out of his system, cool it, and siphon the data off. If he's worried about losing the Plans to the Empire when his ship is captured, sure. But if he leaves his bag in the back of a cab, he'll be fine. The notion that any "reasonably good tech thief" could pull this off is also hard to take seriously. So far as I know, t…

The threat is not against the Plans to the Empire but the password for the encryption system. That, as the video shows, can be done and without any particular haste. As the article suggests, freezing the RAM lengthens the decay process. The method is likely to have been known by three-letter agencies for some time now. The good guys are seldom, if ever, ahead of the bad guys, so it seems likely that the latter know i…

I think you're misunderstanding both the attack and full-disk encryption. The decryption key is not in RAM every time the machine starts; you have to enter material to derive the key at bootup. And the attacker does in fact have minutes to recover whatever's in RAM once the machine shuts down --- which means that if you shut your machine down before leaving the office (which you have to do), remanence simply isn't a threat at all.

Everyone "shreds" their hard disk if they lose the password. That is the point.

Also, the Plans are to the Death Star, not the whole Empire.

Re: Ask HN: Do you encrypt your laptop's hard disk?

#112

Post by gojomo »

all wrote: post #109
tptacek wrote: post #79

Earlier quoted context omitted.

Remanence isn't a realistic attack in his threat model; attackers have mere minutes to get the RAM out of his system, cool it, and siphon the data off. If he's worried about losing the Plans to the Empire when his ship is captured, sure. But if he leaves his bag in the back of a cab, he'll be fine. The notion that any "reasonably good tech thief" could pull this off is also hard to take seriously. So far as I know, t…

The threat is not against the Plans to the Empire but the password for the encryption system. That, as the video shows, can be done and without any particular haste. As the article suggests, freezing the RAM lengthens the decay process. The method is likely to have been known by three-letter agencies for some time now. The good guys are seldom, if ever, ahead of the bad guys, so it seems likely that the latter know i…

The OP is worried about thieves, not three-letter-agencies.

Re: Ask HN: Do you encrypt your laptop's hard disk?

#113

Post by donw »

all wrote: post #109
tptacek wrote: post #79

Earlier quoted context omitted.

Remanence isn't a realistic attack in his threat model; attackers have mere minutes to get the RAM out of his system, cool it, and siphon the data off. If he's worried about losing the Plans to the Empire when his ship is captured, sure. But if he leaves his bag in the back of a cab, he'll be fine. The notion that any "reasonably good tech thief" could pull this off is also hard to take seriously. So far as I know, t…

The threat is not against the Plans to the Empire but the password for the encryption system. That, as the video shows, can be done and without any particular haste. As the article suggests, freezing the RAM lengthens the decay process. The method is likely to have been known by three-letter agencies for some time now. The good guys are seldom, if ever, ahead of the bad guys, so it seems likely that the latter know i…

You're looking at a different threat model. Hard drive encryption isn't there to stop the government, the police, or the Girl Scouts.

It's there so that when the Pink Panther walks away with your laptop, he doesn't get instant access to to all of your data. If Mr. Laptop Thief wants your home directory, he's going to need to do a hell of a lot more work than reinstalling the OS and throwing the machine up on eBay.

If your drive isn't encrypted, I'll wager that a laptop thief would take a few minutes to poke around and look for something interesting, like that file 'Corporate Strategy 2010.doc', or "My Affair With The Underaged Intern, Oh God I Hope This Doesn't Get Leaked Onto The Pirate Bay.avi".

Re: Ask HN: Do you encrypt your laptop's hard disk?

#114

Post by woodall »

all wrote: post #109
tptacek wrote: post #79

Earlier quoted context omitted.

Remanence isn't a realistic attack in his threat model; attackers have mere minutes to get the RAM out of his system, cool it, and siphon the data off. If he's worried about losing the Plans to the Empire when his ship is captured, sure. But if he leaves his bag in the back of a cab, he'll be fine. The notion that any "reasonably good tech thief" could pull this off is also hard to take seriously. So far as I know, t…

The threat is not against the Plans to the Empire but the password for the encryption system. That, as the video shows, can be done and without any particular haste. As the article suggests, freezing the RAM lengthens the decay process. The method is likely to have been known by three-letter agencies for some time now. The good guys are seldom, if ever, ahead of the bad guys, so it seems likely that the latter know i…

isn't a realistic attack in his threat model

Under different circumstances your solution would be 100% correct, however, in this situation we are worried about "everyday" type criminals. These are the guys/girls that find a laptop in an unlocked locker and snatch it; small window of opportunity. In your analogy the description of the criminals is much more sophisticated; Oceans 11 types.

Stealing RAM can potentially tip someone off to a threat, a better solution IMO is the Stone-Cold Bootkit[1]. The bootkit can hook into Windows in order to gain unrestricted access. It does this by writing to the MBR unrestricted; haven't we seen this before[2]? Once installed it will log your decryption password and do what ever with it.

A BIOS password(windows) and HHD encryption will be enough to keep the NSA out for a while, and a normal criminal out indefinitely.

It would be nice to have a mobo with some type of secure memory encryption programs could write to- digitally signed. Of course that could be owned too, but it's a start. In the words of Bruce Schneier, "[sic] it is very difficult to secure data when the attacker has physical control of the machine the data is stored on."[3]

Now I am thinking about the /boot partition in linux; where GRUB is stored.

[1] http://www.stoned-vienna.com/

[2] http://news.ycombinator.com/item?id=1643451

[3] http://www.schneier.com/blog/archives/2008/02/cold_boot_atta...

[4] PSA: http://zedomax.com/blog/2009/02/23/linux-boot-hack-how-to-pa...

Re: Ask HN: Do you encrypt your laptop's hard disk?

#115

Post by gojomo »

abalashov wrote: post #91
abalashov wrote: post #88

I would be much more concerned about laptop being arbitrarily seized at an airport by customs or TSA personnel, or by law enforcement otherwise, than it being stolen per se. e.g. http://www.daniweb.com/news/story218174.html http://ezinearticles.com/?Business-Travel-Tip---Avoid-Having... http://www.businesstravelnews.com/Business-Travel/Travel-Man... You can lose a lot to thieves, but you can lose even more to state t…

You know, if you disagree, you can reply instead of downvoting.

I agree with your political point, and I downvoted it, because it injects an unnecessary political element to the thread. The OP is worried about thieves and hasn't mentioned cross-border travel. The best comments will be directly responsive to that request, rather than inject another tangentially-related politically-charged sentiment into the thread.

Your comment was ranking above other comments that were more helpful to the original poster -- and was at +3 when I voted. (I wouldn't have voted your comment down to 0 -- it wasn't inappropriate -- just less-appropriate than other better comments lagging below it.)

I've often suggested comments should have two rating dimensions -- up-promote/down-demote and left-agree/right-disagree -- and some people have said the agree+demote combination would never be used. Well, I would have used it here.

Re: Ask HN: Do you encrypt your laptop's hard disk?

#116

Post by tptacek »

woodall wrote: post #114
all wrote: post #109

Earlier quoted context omitted.

The threat is not against the Plans to the Empire but the password for the encryption system. That, as the video shows, can be done and without any particular haste. As the article suggests, freezing the RAM lengthens the decay process. The method is likely to have been known by three-letter agencies for some time now. The good guys are seldom, if ever, ahead of the bad guys, so it seems likely that the latter know i…

isn't a realistic attack in his threat model Under different circumstances your solution would be 100% correct, however, in this situation we are worried about "everyday" type criminals. These are the guys/girls that find a laptop in an unlocked locker and snatch it; small window of opportunity. In your analogy the description of the criminals is much more sophisticated; Oceans 11 types. Stealing RAM can potentially…

You've cited Schneier citing the same Felton paper that 'all cited. This research, while interesting, does not mean what 'all think it means. It is simply not the case that an attacker who captures your powered-down machine is going to be able to use remanence attacks to recover your encryption key.

The real-world attack Felton's paper implicates is this: an attacker captures your powered-on laptop, because you left it sleeping in your bag and your full-disk encryption software can't reliably wipe keys when it wakes from sleep. The attacker restarts the system and uses remanence to dd the previous RAM contents into a drive for analysis.

This very well may be an attack that government agencies are prepared to use against laptops, but since it's not going to work against anyone who knows how full-disk encryption works, it's simply not going to be in the arsenal of someone who steals your bag out of a bar.

Re: Ask HN: Do you encrypt your laptop's hard disk?

#117

Post by gojomo »

jackolas wrote: post #107
ams6110 wrote: post #99

Earlier quoted context omitted.

Regarding the FBI, "almost certainly yes" You need to add "assuming you are willing to go to jail" because a warrant can compel you to disclose your password, and if you refuse you'll be jailed for contempt of court.

That'd be thrown out of courts as a violation of your 5th Amend. rights. At least here in the states, in the UK crypto keys can be requisitioned with the penalty of jail time if refused.

I believe some rulings support that view, but others have disagreed. It might depend on the judge/district and I don't think it's ever been considered by the Supreme Court.

Re: Ask HN: Do you encrypt your laptop's hard disk?

#118

Post by gojomo »

paolomaffei wrote: post #24
paolomaffei wrote: post #15

Not meaning to be a jackass but realize that maybe if you downloaded (and maybe already deleted!) that porn video with that girl that might or not might be 18 you could be in big troubles if you don't have your full disk encrypted. Edit: or other things that would be ok but can be used against you by law enforcement, for example what about your collection of pirated MP3s or DivX? Is this more acceptable than accident…

Also, I remember I have read an article about some guy that had some pics of their little childrens sometimes naked in an "innocent" way on a trip. They had their children taken away because they went to a photo shop to have the film developed and the clerk called the police.

You're probably thinking of this incident:

http://www.salon.com/life/feature/2006/07/18/photos/index.ht...

I recall other vaguely-similar cases reported in less detail in earlier years. The clerks may not have good judgment, and the incentives for the clerks and many of the agencies involved are to err on the side of assuming-the-worst.

The stigma of even having been accused may make people in such a situation unwilling to talk about it even after being cleared afterwards. After all, many will assume law enforcement would only get involved if "the pictures weren't so 'innocent'".

Re: Ask HN: Do you encrypt your laptop's hard disk?

#119

Post by alextingle »

abalashov wrote: post #91
abalashov wrote: post #88

I would be much more concerned about laptop being arbitrarily seized at an airport by customs or TSA personnel, or by law enforcement otherwise, than it being stolen per se. e.g. http://www.daniweb.com/news/story218174.html http://ezinearticles.com/?Business-Travel-Tip---Avoid-Having... http://www.businesstravelnews.com/Business-Travel/Travel-Man... You can lose a lot to thieves, but you can lose even more to state t…

You know, if you disagree, you can reply instead of downvoting.

That's not the Hacker News way.

Re: Ask HN: Do you encrypt your laptop's hard disk?

#120

Post by nonane »

tptacek wrote: post #111
all wrote: post #109

Earlier quoted context omitted.

The threat is not against the Plans to the Empire but the password for the encryption system. That, as the video shows, can be done and without any particular haste. As the article suggests, freezing the RAM lengthens the decay process. The method is likely to have been known by three-letter agencies for some time now. The good guys are seldom, if ever, ahead of the bad guys, so it seems likely that the latter know i…

I think you're misunderstanding both the attack and full-disk encryption. The decryption key is not in RAM every time the machine starts; you have to enter material to derive the key at bootup. And the attacker does in fact have minutes to recover whatever's in RAM once the machine shuts down --- which means that if you shut your machine down before leaving the office (which you have to do), remanence simply isn't a…

Rarely does one shutdown a laptop anymore. Usually people just close the lid and the computer is put to sleep. In sleep state the contents of RAM is preserved AFAIK and should give the attacker more time to think their plan through.
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