5 ms·

How to Break Cryptography With Your Bare Hands

36 points by cgtyoder 12y ago

tptacek 12y ago
The actual journal article this is taken from was on HN a few days back, and has some comments: https://news.ycombinator.com/item?id=8153670 https://news.ycombinator.com/item?id=8153670
linuxlizard 12y ago
Obligatory XKCD apropos to "bare hands." https://xkcd.com/538/ https://xkcd.com/538/
- bitL 12y ago
  That was the first thing that popped up in my mind when I read the title ;-)
valarauca1 12y ago
The biggest issue with this is reliability. There are dozens if not hundreds of ways to break crypto on hardware that can be done in laboratory conditions. But these are in laboratory conditions, not somebody touching your laptop in a coffee shop.
- sp332 12y ago
  These guys grabbed a signal of ~1 picowatt after filtering in a noisy environment https://www.blackhat.com/presentations/bh-usa-09/BARISANI/BHUSA09-Barisani-Keystrokes-SLIDES.pdf https://www.blackhat.com/presentations/bh-usa-09/BARISANI/BH... While this doesn't say anything about reliability of the current experiment, it probably works better than you'd think.
  - valarauca1 12y ago
    Okay read the slides. Its cool but completely impractical. The problem is if two keyboards share the same ground plane and have roughly the same frequency (I.E.: same manufacturer), their signals will interfere with each other constructively and destructively based on who is typing what. They say the ground plane is noisy, but not noisy in the frequency they are looking. Which is idiotic. The EM frequency band all around us is noisy, but in certain spectrum ranges its completely dead. If you sample the entire band its noisy... They didn't test something directly interfering with the device. Which would roughly be equal to two radio stations broadcasting on the same channel, you couldn't hear anything sensible. :.:.: Not to mention their signals are still VERY noisy. I've worked/around signal processing so you have to understand that if you want to predictably read what is written. http://i.imgur.com/sJ90YPu.png http://i.imgur.com/sJ90YPu.png As you can see that's 3 different triggers of on/off. Dynamic filtering is I guess possible, but you need to know what your searching for to start with. And build a model of likely signals, so you can compare post filtered with what you got post filter to check correctness, and repeat until you get within the tolerance of acceptable correctness. If its a computer generated encryption key then your looking for psuedo random bit pattern, and your just fucked. Secondly http://i.imgur.com/gDvd7M1.png http://i.imgur.com/gDvd7M1.png See, if you assume which trigger you use upper or lower this signal will actually change from 00100110001 to 00100111001. :\ The only way you can know which is correct is if you know what was given to start with. :.:.: I don't want to say its completely unreliable because of that, but if that literally the best example they had to put on a slide then their can't be many more good samples.
    - short_circut 12y ago
      Idk when I see talks like this one. https://www.youtube.com/watch?v=5N1C3WB8c0o https://www.youtube.com/watch?v=5N1C3WB8c0o
      - valarauca1 12y ago
        Look, one university researcher stands up and says "Hey I was looking for this conjecture, So I designed a single experiment and confirmed it!" You wouldn't quote it as scientific fact. In fact they'd be laughed out of the journal. So why do we do that for defcon talks?
    - tptacek 12y ago
      No. You're posing an argument against a set of slides at Black Hat, but we're talking about a paper submitted at CRYPTO. Two totally different teams. You need to read Eran Tromer's article. It gets into the details of how they acquire signals, what filtering they use, and what their noise thresholds are. You are much, much too quick to dismiss this work. That's understandable, because you're reading a crappy MIT Press article about the work, and not the work itself. Unfortunately for you (at least rhetorically), that dumb article has left you trying to dismiss the work of someone who is essentially one of the godfathers of sidechannel cryptanalysis. If you're not going to read the original paper, just take my word for it: they've worked in signal processing too.
- tptacek 12y ago
  The "bare hands" thing is a gimmick. The actual Tromer paper is much, much more interesting than that. See the link posted elsewhere in the thread.
Fando 12y ago
Mind blow.
markbernard 12y ago
For this to work they have to have the correct key in the first place. If I encrypt something with my key and send it down the wire and they intercept it and try it on a machine they own they wouldn't be able to decrypt it. This requires them to be hooked to my machine while I am decrypting to get at the key.

36 points by cgtyoder 12y ago

The actual journal article this is taken from was on HN a few days back, and has some comments: https://news.ycombinator.com/item?id=8153670 https://news.ycombinator.com/item?id=8153670

linuxlizard 12y ago

Obligatory XKCD apropos to "bare hands." https://xkcd.com/538/ https://xkcd.com/538/

bitL 12y ago
That was the first thing that popped up in my mind when I read the title ;-)

valarauca1 12y ago

The biggest issue with this is reliability. There are dozens if not hundreds of ways to break crypto on hardware that can be done in laboratory conditions. But these are in laboratory conditions, not somebody touching your laptop in a coffee shop.

sp332 12y ago
These guys grabbed a signal of ~1 picowatt after filtering in a noisy environment https://www.blackhat.com/presentations/bh-usa-09/BARISANI/BHUSA09-Barisani-Keystrokes-SLIDES.pdf https://www.blackhat.com/presentations/bh-usa-09/BARISANI/BH... While this doesn't say anything about reliability of the current experiment, it probably works better than you'd think.
- valarauca1 12y ago
  Okay read the slides. Its cool but completely impractical. The problem is if two keyboards share the same ground plane and have roughly the same frequency (I.E.: same manufacturer), their signals will interfere with each other constructively and destructively based on who is typing what. They say the ground plane is noisy, but not noisy in the frequency they are looking. Which is idiotic. The EM frequency band all around us is noisy, but in certain spectrum ranges its completely dead. If you sample the entire band its noisy... They didn't test something directly interfering with the device. Which would roughly be equal to two radio stations broadcasting on the same channel, you couldn't hear anything sensible. :.:.: Not to mention their signals are still VERY noisy. I've worked/around signal processing so you have to understand that if you want to predictably read what is written. http://i.imgur.com/sJ90YPu.png http://i.imgur.com/sJ90YPu.png As you can see that's 3 different triggers of on/off. Dynamic filtering is I guess possible, but you need to know what your searching for to start with. And build a model of likely signals, so you can compare post filtered with what you got post filter to check correctness, and repeat until you get within the tolerance of acceptable correctness. If its a computer generated encryption key then your looking for psuedo random bit pattern, and your just fucked. Secondly http://i.imgur.com/gDvd7M1.png http://i.imgur.com/gDvd7M1.png See, if you assume which trigger you use upper or lower this signal will actually change from 00100110001 to 00100111001. :\ The only way you can know which is correct is if you know what was given to start with. :.:.: I don't want to say its completely unreliable because of that, but if that literally the best example they had to put on a slide then their can't be many more good samples.
  - short_circut 12y ago
    Idk when I see talks like this one. https://www.youtube.com/watch?v=5N1C3WB8c0o https://www.youtube.com/watch?v=5N1C3WB8c0o
    - valarauca1 12y ago
      Look, one university researcher stands up and says "Hey I was looking for this conjecture, So I designed a single experiment and confirmed it!" You wouldn't quote it as scientific fact. In fact they'd be laughed out of the journal. So why do we do that for defcon talks?
  - tptacek 12y ago
    No. You're posing an argument against a set of slides at Black Hat, but we're talking about a paper submitted at CRYPTO. Two totally different teams. You need to read Eran Tromer's article. It gets into the details of how they acquire signals, what filtering they use, and what their noise thresholds are. You are much, much too quick to dismiss this work. That's understandable, because you're reading a crappy MIT Press article about the work, and not the work itself. Unfortunately for you (at least rhetorically), that dumb article has left you trying to dismiss the work of someone who is essentially one of the godfathers of sidechannel cryptanalysis. If you're not going to read the original paper, just take my word for it: they've worked in signal processing too.
tptacek 12y ago
The "bare hands" thing is a gimmick. The actual Tromer paper is much, much more interesting than that. See the link posted elsewhere in the thread.

Fando 12y ago

Mind blow.

markbernard 12y ago

For this to work they have to have the correct key in the first place. If I encrypt something with my key and send it down the wire and they intercept it and try it on a machine they own they wouldn't be able to decrypt it. This requires them to be hooked to my machine while I am decrypting to get at the key.