Smartphone can use its microphone to extract RSA decryption key from laptop

https://www.schneier.com/blog/archives/2013/12/acoustic_crypta.html

by BrandonMarc • 13 years ago

156 36 13 years ago

schneier.com

ColinWright2• 13 years ago

Substantial discussion:

https://news.ycombinator.com/item?id=6927905 (tau.ac.il) (92 comments)

Other submissions:

https://news.ycombinator.com/item?id=6940827 (theregister.co.uk)

https://news.ycombinator.com/item?id=6938536 (dailymail.co.uk)

https://news.ycombinator.com/item?id=6935289 (tau.ac.il)

https://news.ycombinator.com/item?id=6933255 (slashdot.org)

https://news.ycombinator.com/item?id=6932445 (slideshare.net)

BrandonMarc• 13 years ago

Thanks. I'm with the first commenter on the Schneier post - remove your phone's battery (and the corollary: try not to own a phone which you can't confidently remove the battery ... though, is that even possible anymore?)

petercooper• 13 years ago

I submitted it as well with a suffixed URL to force a repost. Your list is proof, if any, that it's really down to chance now even if excellent stuff makes it to the front page anymore..

CaveTech• 13 years ago

But it did make the front page... The first time it was submitted.

cpleppert• 13 years ago

A brief glance at this thread and the other discussion showed only 1 substantive comment that told me something I didn't know after a cursory read through(that I saw at least). The amount of people who didn't even read the paper is mindblowing

rubyrescue• 13 years ago

I just don't believe this is reproducible... seems fake.

kevingadd2• 13 years ago

Read the paper. The mechanisms are explained in detail and they present data and examples.

yelnatz• 13 years ago

One of the authors of this paper is Adi Shamir.

One of the guys who wrote the RSA algorithm in 1977.

RSA -> Ron Rivest, Adi Shamir and Leonard Adleman

This is legit.

jodrellblank2• 13 years ago

"This will be reproducible because the author is famous".

(Appeal to authority fallacy?)

mrinterweb• 13 years ago

Looks like a security patch to GnuPG 1.x has already been released that addresses this and GnuPG 2.x is not vulnerable to this hack according to this article. http://lists.gnupg.org/pipermail/gnupg-announce/2013q4/00033...

pflanze• 13 years ago

Interesting. Reminds me of the times long ago when pocket calculators were a new thing and I was also owning an AM/FM radio and held it close to the calculators to listen to what they were "doing". You would hear a lot more in the radio than the bit of whining and buzzing that you can hear acoustically from nowaday's computers.

So, I was wondering, what about the FM radio built into many (if not most) mobile phones? Connected my earbuds (they also function as antenna), turned on the phone loudspeaker, laid the earbud cable over my laptop, tuned the FM radio to some frequency where there is no radio station (thus statics playing), and voilà, I can clearly hear correlation between noise and activity. Even when I'm placing my earbuds/phone a foot away from the laptop I can still clearly hear when I'm opening some new window. The sounds are not as 'colorful' as they were on an AM radio when listening to calculators, but I'd wager a guess that it's better than an acoustic attack.

So much for thinking that making acoustic noise like playing music would dwarf the attack vector "mobile phone".

PS: what might prevent this attack is that on some (most?) phones the output of the FM radio can't be captured directly. It could be played through the speaker and recorded through the mic, though. The attack as carried out by Genkin/Shamir/Tromer is sending tons of encrypted emails and would probably arouse suspicion anyway if the computer was attended, thus this indirection may not pose a problem.

Sami_Lehtinen• 13 years ago

Totally true and old common knowledge, check this out: https://en.wikipedia.org/wiki/Tempest_%28codename%29 When chips and devices were slower and used more energy, it was just easier to observe those differences. I also have had many mobile phones which leaked information as audio, I think most of that leak was from RF tramsitter unit power consumption and speaker amplifier power not being properly filtered. But it's just perfect example of acoustic information leak.

sillysaurus22• 13 years ago

I love that Shamir keeps doing work that makes people say "... this can't be true!"

Once again, this is a reminder that any adversary that has physical access to your box can extract all your secrets, and there's almost nothing you can do about it.

For defending against acoustic attacks when encrypting/decrypting/typing in your password, play loud music. I recommend "What does the fox say?" by Ylvis since it has a wide range of powerful frequencies.

(There are other types of physical attacks than acoustic attacks, so this is more tongue in cheek than a real defense mechanism.)

kevingadd2• 13 years ago

To be clear, it's my understanding that playing music or generating artificial noise won't actually do much to stop this attack. Listening to some good tunes will definitely help distract you from worrying about attackers stealing your private keys, though!

sillysaurus22• 13 years ago

Heh. Even loud music? Why not?

Now I really want to repeat Shamir's experiment with Gangnam Style blaring just to see what would happen.

Crito• 13 years ago

What about running 'loud processes' on other processors?

icegreentea• 13 years ago

It depends on which attack vector you're defending against.

If you're trying to defend against the cellphone (or chasis microphone) attack vector, then you can defintely defend with human audible noise. Your cellphone is going to have an aggressive low pass filter prior to the ADC to prevent aliasing. This will limit the cellphone range to roughly human audible range. The difficulty is in generating sufficient noise at the frequencies required. As the FAQ on the page points out the majority of this lies in +10kHz, so using normal music won't be too effective, but artificial noise is certainly possible.

The Q&A on the linked site answers all sorts relevant questions and is quite enlightening.

In the actual paper is maddening non-specific about how widespread audible range attacks are. Ultrasonic attacks are likely viable against nearly all unprotected machines, however the paper only says that 'some' machines are vulnerable to audible spectrum attacks.

venomsnake• 13 years ago

One has to wonder do proper sound proof case like Fractal Design that are lined with foam inside can thwart the attack.

anovikov• 13 years ago

How long does the full encryption of a say, typical email (kilobyte of plain text or so) takes? It shouldn't be that much long, in the range of a few milliseconds, or a few dozen samples of a microphone (44,100hz max).

What i can't understand is how you can compress a whole RSA decryption key, which is say 4096 bits, into space SMALLER than itself (source data from microphone with 16 bits per sample, mono, at 44,100 hz, will take 6ms to accumulate 4096 bits - for sure encryption of a short email will take less!). So it sounds like a hoax.

Obviously the key can't be 'comperssed' because it's ramdom data with a high quality of randomness. And you cannot pull it out of SMALLER amount of data recorded by the microphone in the time it takes to make an encryption. That is, if anything happening within the processor can make acoustic noise loud enough for microphone to detect, which i really doubt.

I believe this even less than air-powered cars, or cold fusion.

nwh• 13 years ago

Read the paper. They're using a known input ciphertext to help aid this recovery and get around the limitations you've noted. Recovery also takes an hour, byte by byte with different decryptions.

4ad2• 13 years ago

Wow, I don't want to steer this discussion into the "ye olde golden HN days" territory, but this is the lowest of the low I have read on HN recently.

Really? You dismiss a scientific claim because you, YOU cannot understand it? There's a scientific paper written by a security researcher (who by the way co-invented RSA) that goes into great detail explaining what's going on. There's data to analyse. People can try to replicate the results. Do you have anything to say about the paper?

There have been a few threads about this already. What I have learned from those, and from other threads where a paper is discussed, is that practically nobody who comments has read the paper.

ColinWright2• 13 years ago

Wonderful analysis of something completely different from the actual article. You make several good and useful points, it's just a shame that they're irrelevant.

  > I believe this even less than air-powered cars ...

Air-powered vehicles are quite common.

http://www.fastcoexist.com/1681429/this-air-powered-car-gets...

http://auto.howstuffworks.com/fuel-efficiency/vehicles/air-c...

http://www.dailymail.co.uk/news/article-2266632/Car-runs-air...

http://en.wikipedia.org/wiki/Compressed_air_car

myle• 13 years ago

This could have been prevented. Oblivious Turing Machines: http://stackoverflow.com/questions/14847080/how-does-an-obli...

drakaal2• 13 years ago

Once again Shamir puts out a bombastic paper where they tested against one device in a controlled environment and doesn't release a software or a proof that it works.

If this were real there would be a "submit your recording" or an opensource library for others to try.

The physics of this don't work.

If they did work the experiment should be documented in a way that there could be peer review. If you can't repeat it, it isn't valid.

I lost lots of Karma the last time I mentioned this, but I kind of don't care. These kinds of fake "hacks" are only designed to create fear, and keep people from working on real security issues while creating a reputation based on falsehoods for the author.

Smartphone can use its microphone to extract RSA decryption key from laptop

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