RSA Key Extraction via Low-Bandwidth Acoustic Cryptanalysis(cs.tau.ac.il)
cs.tau.ac.il
RSA Key Extraction via Low-Bandwidth Acoustic Cryptanalysis
http://www.cs.tau.ac.il/~tromer/acoustic/
24 comments
The single coolest thing in the paper (other than Shamir's name): "On many laptops (e.g., most Lenovo ThinkPad models), the chassis potential can be easily reached by a
human hand, through metal connectors and conductive coating on metal surfaces. Thus, an attacker can
measure the chassis potential by merely touching the laptop chassis with his hand. Surreptitiously,
the attacker can simultaneously measure his own body potential relative to the room’s ground potential,
e.g., by having a concealed differential probe touching both his body and some nearby conductive
grounded surface in the room. Perhaps surprisingly, even this circuitous measurement offers sufficient
signal-to-noise ratio for the key extraction attack."
I wonder whether this is specific to laptops (running from battery or otherwise not grounded) or if it also works with properly grounded desktop computers.
My HP notebook from ~2000 had measurable (although very high impedance) 110V AC between exposed metal parts and PE in wall outlet when connected to charger. Modern thinkpads (and probably all non-Apple laptops sold in Europe) does not seem to have this problem as ground is connected through in charger, not only AC coupled to both hot and neutral.
My HP notebook from ~2000 had measurable (although very high impedance) 110V AC between exposed metal parts and PE in wall outlet when connected to charger. Modern thinkpads (and probably all non-Apple laptops sold in Europe) does not seem to have this problem as ground is connected through in charger, not only AC coupled to both hot and neutral.
I have been finally able to download and read their full paper and it seems to answer this question: they observe that grounding thru AC charger does increase SNR of measured signal.
Macbooks can be grounded, too. The round metal thing that's holding the plug in place also serves as a connection for ground. It is moot if you're using the small plug which doesn't have ground but if you connect the cable instead of the plug, or use a UK plug, the computer is properly grounded.
[deleted]
Playing loud music when encrypting/decrypting/typing in your password will defend against acoustic attacks, right?
This other type of attack, however, isn't so easily guarded against:
Beyond acoustics, we demonstrate that a similar low-bandwidth attack can be performed by measuring the electric potential of a computer chassis. A suitably-equipped attacker need merely touch the target computer with his bare hand, or get the required leakage information from the ground wires at the remote end of VGA, USB or Ethernet cables.
This serves as a reminder that it's pretty much impossible to defend against an attacker that has physical access to your box.
This other type of attack, however, isn't so easily guarded against:
Beyond acoustics, we demonstrate that a similar low-bandwidth attack can be performed by measuring the electric potential of a computer chassis. A suitably-equipped attacker need merely touch the target computer with his bare hand, or get the required leakage information from the ground wires at the remote end of VGA, USB or Ethernet cables.
This serves as a reminder that it's pretty much impossible to defend against an attacker that has physical access to your box.
> Playing loud music when encrypting/decrypting/typing in your password will defend against acoustic attacks, right?
Probably. The answer to Q11 says "The interesting acoustic signals are mostly above 10KHz". They don't say what the high end of the range is. But I would guess that sufficiently loud music (which usually contains frequencies up to about 22kHz) would mask the sound generated by the CPU.
Probably. The answer to Q11 says "The interesting acoustic signals are mostly above 10KHz". They don't say what the high end of the range is. But I would guess that sufficiently loud music (which usually contains frequencies up to about 22kHz) would mask the sound generated by the CPU.
From the article:
Noisy environment. One may expect that placing the machine in a noisy machine will foil the attack.
However, the energy of noise generated in a typical noisy environment (such as outdoors or a noisy room)
is typically concentrated at low frequencies, below 10kHz. Since the acoustic leakage is usually present
well above this rage, such noises can be easily filtered out during the data acquisition process using a
suitable high-pass filter (as we did in our experiments). Also, the signal would be observe during any
pauses in ambient noise (e.g., music). Note also that the attacker may, to some extent, spectrally shift
the acoustic signal to a convenient notch in the noise profile, by inducing other load on the machine (see
below). Thus, a carefully-designed acoustic noise generator would be required for masking the leakage."Thus, a carefully-designed acoustic noise generator would be required for masking the leakage."
Like dubstep.
Like dubstep.
EDM to save the world (by blocking government snooping)!
http://www.youtube.com/watch?v=Da4V5vKcGl8
http://www.youtube.com/watch?v=Da4V5vKcGl8
They have an electribe ER1 and they modulate so that's gold.
of COURSE we can f@cking modulate this
@kevincennis: A counter-argument to that is that an attacker could run shazam/soundcloud to fingerprint the music, and then subtract the music from the recorded signal. It would be more work, certainly, but I don't think e.g. just playing the radio would be enough to mask the side-channel.
That's a really interesting point. I hadn't thought about phase cancellation at all. You certainly couldn't remove everything, since the signal you picked up would be influenced by the speakers/room/microphone/converters/etc, but you still might be able to remove a significant portion of the music that way.
Filtering out a signal that's in the same band is notoriously difficult.
If the signal you're subtracting is known to you, you can simply lock the phases and subtract. That's pretty trivial.
But knowing the name of the song doesn't necessarily give you a known signal to subtract. Conceivably, you could be working with a version of the song that was compressed differently than the one playing on the target computer. In which case, the two signals might not have the same waveform, and they wouldn't cancel.
To the listener's ear, the signals may sound identical. A good example of this principle is musical instruments. Have a skilled violinist play the same note twice with the same articulation for the same duration under the same conditions. Record each sample the same way. Most listeners would say these two samples are identical. But if you invert one and then mix them, they won't cancel, because they didn't actually have the same waveform.
But it's definitely an interesting approach, and potentially viable, if a good filtering algorithm can be worked out. My suspicion is that such an algorithm exists or is at least possible. But I'm not an audio engineer, so I'm not certain.
If the signal you're subtracting is known to you, you can simply lock the phases and subtract. That's pretty trivial.
But knowing the name of the song doesn't necessarily give you a known signal to subtract. Conceivably, you could be working with a version of the song that was compressed differently than the one playing on the target computer. In which case, the two signals might not have the same waveform, and they wouldn't cancel.
To the listener's ear, the signals may sound identical. A good example of this principle is musical instruments. Have a skilled violinist play the same note twice with the same articulation for the same duration under the same conditions. Record each sample the same way. Most listeners would say these two samples are identical. But if you invert one and then mix them, they won't cancel, because they didn't actually have the same waveform.
But it's definitely an interesting approach, and potentially viable, if a good filtering algorithm can be worked out. My suspicion is that such an algorithm exists or is at least possible. But I'm not an audio engineer, so I'm not certain.
I suspect that, in practice, playing music will provide enough of a barrier to mitigate attacks using these side-channels. But then again, in practice, I'd hope that attacks using these side-channels are pretty infrequent to begin with.
Besides, in practice, upgrading to GnuPG 1.4.16 (released today) is supposed to also mitigate the key extraction attack using this side channel.
The naive approach I suggested would be easily defeated by playing two songs from two different sources; which itself would be defeated by setting up soundcloud on two devices in both places and carefully setting up/analyzing/modelling the room so that you can adjust the signal you're subtracting to account for the distance the sound waves travel and whatnot. I think after a while you just get increasing complexity and diminishing returns -- i.e. it becomes an arms race.
Besides, in practice, upgrading to GnuPG 1.4.16 (released today) is supposed to also mitigate the key extraction attack using this side channel.
The naive approach I suggested would be easily defeated by playing two songs from two different sources; which itself would be defeated by setting up soundcloud on two devices in both places and carefully setting up/analyzing/modelling the room so that you can adjust the signal you're subtracting to account for the distance the sound waves travel and whatnot. I think after a while you just get increasing complexity and diminishing returns -- i.e. it becomes an arms race.
Certainly you also can't assume that a recording of a sound played via crappy laptop speakers will even closely resemble the original waveform. Playing back (distortion by differing air pressure etc) and recording (environment & A/D noise anyone?) will completely distort it.
I believe this would only mask the direct sound waves, not the reflections caused by the room. Perhaps masking the direct sound is enough, but maybe not if the reflections have sufficient energy.
If you've got enough information to cancel the main signal, then you've also got enough information to cancel the reflections. It will take a more computational power though, which is okay if you're doing the analysis on a recording.
The brute force way is to do an exhaustive search, repeatedly correlating the signal you are looking to cancel and the received signal, whilst "sliding" the known signal across the received signal, which means adding a delay to the known signal between each correlation. Correlation peaks can be picked out and used to cancel the reflections. Similar techniques are regularly used in radio communications, to combat multipath fading, which is a fancy way of saying that the received radio signal contains reflections.
Edit: remove cruft at end of comment.
The brute force way is to do an exhaustive search, repeatedly correlating the signal you are looking to cancel and the received signal, whilst "sliding" the known signal across the received signal, which means adding a delay to the known signal between each correlation. Correlation peaks can be picked out and used to cancel the reflections. Similar techniques are regularly used in radio communications, to combat multipath fading, which is a fancy way of saying that the received radio signal contains reflections.
Edit: remove cruft at end of comment.
I saw that too, but I think they sort of side-step the issue of music. The bit about noise typically being below 10kHz doesn't really apply to most music. If you go run pretty much any modern record through a spectrum analyser, you'll see tons of content above 10kHz.
Anyway, I'm certainly not claiming to know with any certainty that loud music would work as a preventative measure against this kind of attack. I just don't think the paper sufficiently proves that it wouldn't be.
Anyway, I'm certainly not claiming to know with any certainty that loud music would work as a preventative measure against this kind of attack. I just don't think the paper sufficiently proves that it wouldn't be.
But laptop speakers are notoriously shitty. I don't think laptop speaker output has tons of content above 10kHz.
This is complicated by the human ear's variation in loudness perception over the frequency spectrum, and the effect this has on music. The stuff over 10k is typically mixed quieter than the stuff under 10k, though it doesn't sound that way. Records with lots of energy above 12-13khz tend to sound pretty awful.
https://en.wikipedia.org/wiki/Equal-loudness_contours
EDIT: also pitch is logarithmic with respect to frequency. 8khz sounds really high pitched.
https://en.wikipedia.org/wiki/Equal-loudness_contours
EDIT: also pitch is logarithmic with respect to frequency. 8khz sounds really high pitched.
Playing loud music when encrypting/decrypting/typing in your password will defend against acoustic attacks, right?
I recommend "Wrecking Ball" by Miley Cyrus. The strength of the attacker's cryptanalysis will be moot because no one will go near you.
I recommend "Wrecking Ball" by Miley Cyrus. The strength of the attacker's cryptanalysis will be moot because no one will go near you.
"Puberty Love" can be an ... um ... lethal option, too.
http://en.wikipedia.org/wiki/Attack_of_the_Killer_Tomatoes
http://en.wikipedia.org/wiki/Attack_of_the_Killer_Tomatoes
or... it may increase people's interest in you, you know, for national security.
Well, by Bradley Manning's account, he listened to Lady Gaga while leaking classified military documents, so maybe hit pop songs are not as innocent as they seem. :)
In my opinion, changing software in response to emissions (be it audio or EMI/RFI) and power side-channel attacks is mostly futile and correct solution involves just making sure by means of physical security and/or shielding that attacker cannot access places where it's possible to implement such attacks.
On the other hand timing attacks are something that anyone implementing anything security related has to be aware of and actively prevent as they can be conducted from mostly anywhere.
On the other hand measurement of potential on chassis seems interesting as that can possibly be measured pretty far away (eg. PC -> STP cable -> Cable modem -> CATV).
On the other hand timing attacks are something that anyone implementing anything security related has to be aware of and actively prevent as they can be conducted from mostly anywhere.
On the other hand measurement of potential on chassis seems interesting as that can possibly be measured pretty far away (eg. PC -> STP cable -> Cable modem -> CATV).
Ah, the Maginot Line[1] argument. Given the sheer number of possible emissions channels, are you proposing they all be universally protected against in hardware? Or that there should be special classes of 'protected against $FOO' hardware for specific threats?
The concept of defence-in-depth suggests that you should take all[2] possible measures to avoid sensitive data leakage. If an attacker does get into your secret computer-bunker, but can't get past the cage or case-level defences, they could potentially still use such an attack as this. Also, how do you test that your shielding is working? The paper notes that their probable noise source was a faulty electrolytic capacitor, which presumably wasn't [as] faulty when QA'd at the factory. So you'd need to periodically retest, which could get pricey fast.
Likewise, the engineering tradeoffs of shielding everything make it pretty impractical for mobile/portable devices, or ones that might be used in unsecured areas.
The main issue I see is that if this (or similar improvements) is truly something that could be implemented with a mobile phone or small MEMS microphone bug in the general vicinity, it's potentially cheap enough to make it not just a "how do I protect against the NSA?" problem, but one within the means of corporate or organised crime espionage groups.
[1] https://en.wikipedia.org/wiki/Maginot_Line
[2] well, as many as economically feasible anyway.
The concept of defence-in-depth suggests that you should take all[2] possible measures to avoid sensitive data leakage. If an attacker does get into your secret computer-bunker, but can't get past the cage or case-level defences, they could potentially still use such an attack as this. Also, how do you test that your shielding is working? The paper notes that their probable noise source was a faulty electrolytic capacitor, which presumably wasn't [as] faulty when QA'd at the factory. So you'd need to periodically retest, which could get pricey fast.
Likewise, the engineering tradeoffs of shielding everything make it pretty impractical for mobile/portable devices, or ones that might be used in unsecured areas.
The main issue I see is that if this (or similar improvements) is truly something that could be implemented with a mobile phone or small MEMS microphone bug in the general vicinity, it's potentially cheap enough to make it not just a "how do I protect against the NSA?" problem, but one within the means of corporate or organised crime espionage groups.
[1] https://en.wikipedia.org/wiki/Maginot_Line
[2] well, as many as economically feasible anyway.
> and correct solution involves just making sure by means of physical security and/or shielding that attacker cannot access places where it's possible to implement such attacks
This is addressed in the linked page.
This is addressed in the linked page.
The attack requires the victim to encrypt/decrypt many chosen messages, no? Configure your laptop to only encrypt or decrypt messages when you want it to.
Some people have GPG configured to sign every email they send. Would that be enough activity to compromise the key?
Not if the attacker doesn't control the contents. They would need to send you the email, and then you would need to open/decrypt it while they're listening. afaik.
This serves as a reminder that it's pretty much impossible to defend against an attacker that has physical access to your box.
... or is able to hack into your phone.
... or is able to hack into your phone.
So a scenario would be what, when two people bring their laptops to do a deal via Bitcoin?
It won't - you find the tracks with shazam and then just subtract them from the recording.
Uhh... When people say physical access to your box, they mean someone can physically tamper with it in arbitrary ways. This is not the same as being near the box. Otherwise we would just say that all phones/laptops are insecure.
Important stuff:
> Q9 How vulnerable is GnuPG now? We have disclosed our attack to GnuPG developers under CVE-2013-4576, suggested suitable countermeasures, and worked with the developers to test them. New versions of GnuPG 1.x and of libgcrypt (which underlies GnuPG 2.x), containing these countermeasures and resisting our current key-extraction attack, were released concurrently with the first public posting of these results. Some of the effects we found (including RSA key distinguishability) remain present.
> Q9 How vulnerable is GnuPG now? We have disclosed our attack to GnuPG developers under CVE-2013-4576, suggested suitable countermeasures, and worked with the developers to test them. New versions of GnuPG 1.x and of libgcrypt (which underlies GnuPG 2.x), containing these countermeasures and resisting our current key-extraction attack, were released concurrently with the first public posting of these results. Some of the effects we found (including RSA key distinguishability) remain present.
This is really impressive work. After skimming through the detailed paper it looks as if they are not picking up sound emitted from the CPU itself, but from the switching power supply circuit.
The frequency variation is caused by load differences. So they are in fact doing an indirect power analysis. A switching power supply will always change frequency as a reaction to variations in supply current, this is inherent to its design. I also believe that it will be very difficult to "muffle" all the inductors and capacitors as they are subjected to very high pulse loads. Magnetics will always find a way to emit sound...
It's interesting to note that the biggest difference seems to be between register and memory instructions. This seems reasonable as memory instruction may, in the worst case, require powering the external bus, which is very power hungry. This will only get worse in future CPUs, as more and more clock gating is introduced.
So, I guess some countermeasures could be:
- If the CPU supports SMT or HT, load the other cores with a thread accessing random memory positions.
- Optimize the RSA code so that it's memory access and runtime pattern does not depend on the key or clean text.
- Try to localize the RSA code as much as possible to reduce memory accesses. If memory access is required, do it all at once, for example by swapping entire cache pages.
Some of these are highly CPU dependent.
The frequency variation is caused by load differences. So they are in fact doing an indirect power analysis. A switching power supply will always change frequency as a reaction to variations in supply current, this is inherent to its design. I also believe that it will be very difficult to "muffle" all the inductors and capacitors as they are subjected to very high pulse loads. Magnetics will always find a way to emit sound...
It's interesting to note that the biggest difference seems to be between register and memory instructions. This seems reasonable as memory instruction may, in the worst case, require powering the external bus, which is very power hungry. This will only get worse in future CPUs, as more and more clock gating is introduced.
So, I guess some countermeasures could be:
- If the CPU supports SMT or HT, load the other cores with a thread accessing random memory positions.
- Optimize the RSA code so that it's memory access and runtime pattern does not depend on the key or clean text.
- Try to localize the RSA code as much as possible to reduce memory accesses. If memory access is required, do it all at once, for example by swapping entire cache pages.
Some of these are highly CPU dependent.
This is the patch they used to mitigate it afaict.
http://git.gnupg.org/cgi-bin/gitweb.cgi?p=libgcrypt.git;a=co...
http://git.gnupg.org/cgi-bin/gitweb.cgi?p=libgcrypt.git;a=co...
Nobody mentioned TEMPEST yet in this comment thread. It's old (60s) but very interesting stuff. https://en.wikipedia.org/wiki/Tempest_%28codename%29 It includes acoustical leaks as one side channel.
Also see: http://www.nsa.gov/public_info/_files/cryptologic_spectrum/t...
It's cool that they were able to demonstrate it that well.
Came in here to make this exact comment -- the amount of things looked into as ways to leak secrets was insane, even going as far as detecting screen radiation IIRC.
Check out this researcher's papers: http://www.cl.cam.ac.uk/~mgk25/ esp. "Optical Time-Domain Eavesdropping Risks of CRT Displays"
Using multiple cores turns out to help the attack (by shifting down the signal frequencies).
I don't understand how this would be, maybe because I don't understand what they mean by "using multiple cores."
You'd think that running a decoy thread on another core would mask things pretty effectively.
I don't understand how this would be, maybe because I don't understand what they mean by "using multiple cores."
You'd think that running a decoy thread on another core would mask things pretty effectively.
Disclaimer: I never worked with the sound side-channel, so maybe what I'm going to say is not entirely true, but the general idea should be right.
Actually I think the job of the other core would be more difficult than just doing random noises to mask the noise from the actual secret computation. Simply doing random computations (and thus, random noises) of the other core is not effective since random noise would "easily" be canceled using statistical tools (for instance, looking at the variance of the data instead of looking at it directly will already reduce some type of noises).
What would be more effective would be to balance the noise for instance, maybe running the same computation with opposite data would balance it more effectively. To picture what I'm saying better, here is a completely fanciful example (just to provide an idea). Imagine that during the RSA exponentiation (where the private key is exposed), the operation that is done when the bit of the secret key is 1 makes the sound "s_s_" and when it is 0 the sound is "_p_k". If you do the the same computation as the secret one on the other core exactly at the same time, but with the opposite secret key, then whatever the key is the attacker will always ear "spsk" at each clock cycle. And that will be harder to attack than random noises (but is also more difficult to achieve, of course).
That said, I don't know why the use of multiple cores would help the attack (but I didn't read the paper, just a few sample of the linked web page).
Actually I think the job of the other core would be more difficult than just doing random noises to mask the noise from the actual secret computation. Simply doing random computations (and thus, random noises) of the other core is not effective since random noise would "easily" be canceled using statistical tools (for instance, looking at the variance of the data instead of looking at it directly will already reduce some type of noises).
What would be more effective would be to balance the noise for instance, maybe running the same computation with opposite data would balance it more effectively. To picture what I'm saying better, here is a completely fanciful example (just to provide an idea). Imagine that during the RSA exponentiation (where the private key is exposed), the operation that is done when the bit of the secret key is 1 makes the sound "s_s_" and when it is 0 the sound is "_p_k". If you do the the same computation as the secret one on the other core exactly at the same time, but with the opposite secret key, then whatever the key is the attacker will always ear "spsk" at each clock cycle. And that will be harder to attack than random noises (but is also more difficult to achieve, of course).
That said, I don't know why the use of multiple cores would help the attack (but I didn't read the paper, just a few sample of the linked web page).
I understood it as the general tendency for more cores resulting in lower per core clock speed.
The lower the clock speed, the more you can hear in the audible frequencies.
The lower the clock speed, the more you can hear in the audible frequencies.
What's interesting are old school spy acounstic methods. http://en.wikipedia.org/wiki/Laser_microphone <-- great primer. This played out in micro surface vibration in a cup of coffee in the movie Eagle Eye (terrible movie btw). Either way, kind of a neat way to spy on embassy windows from a far w/o even having to be in the room. A little off topic was the KGB's bugging a government office with passive radio transmission - virtually undetectable http://en.wikipedia.org/wiki/Thing_(listening_device) This stuff is so damn cool. :)
Just to be clear, I believe this is from 2004.
This was originally presented was in 2004, but since then has been refined in a number of ways. The detailed paper that includes the full key extraction attack was only released today, coinciding with the GnuPG security update that mitigates against the attack.
It took 9 years to fix GPG?
GnuPG 2.x wasn't vulnerable, just the old 1.x:
http://lists.gnupg.org/pipermail/gnupg-announce/2013q4/00033...
"GnuPG 1.4.16 avoids this attack by employing RSA blinding during
decryption. GnuPG 2.x and current Gpg4win versions make use of
Libgcrypt which employs RSA blinding anyway and are thus not vulnerable."
RSA blinding seems to protect against timing attacks, how does RSA blinding protect against this acoustic attack?
Random comment: Could similar attacks be used to extract the private key for Bitcoin accounts?
These attacks are specifically for the operations involved in repeated use of long-term RSA keys, and Bitcoin uses ECDSA keys a relatively small number of times, so the attacks would be materially different.
However, I would not bet against the fact that your machine outputs "compromising emanations" (be they acoustic or RF or otherwise) leaking _some_ information about your bitcoin keys.
There is less opportunity to execute such an attack in the bitcoin universe, though, as bitcoin-qt doesn't reuse keys that much. (When you send a payment, the "change" difference is sent to a new key.)
It's something to think about, but the attack surface is a lot smaller. Perhaps there's something specific in the ECDSA algorithm that may make it easier or harder? I don't have the requisite mathematical understanding of elliptic curves to know how they're executed in-CPU.
However, I would not bet against the fact that your machine outputs "compromising emanations" (be they acoustic or RF or otherwise) leaking _some_ information about your bitcoin keys.
There is less opportunity to execute such an attack in the bitcoin universe, though, as bitcoin-qt doesn't reuse keys that much. (When you send a payment, the "change" difference is sent to a new key.)
It's something to think about, but the attack surface is a lot smaller. Perhaps there's something specific in the ECDSA algorithm that may make it easier or harder? I don't have the requisite mathematical understanding of elliptic curves to know how they're executed in-CPU.
I've read the linked document, but this feels like magic to me. Is the general idea something like : i can hear the CPU is doing 10 additions, then 20 substractions, twenty times in a row, so i can tell by knowing the algorithm used that the CPU is computing a public key and that it must be between 1 billion and 1.5 billion ?
No, more like the CPU will, in some cases, need to do more work if the key is X and less work if the key is Y, and we specially craft our plain-text to have many X/Y pairs as possible, so that we can hear the capacitors working harder when decrypting.
Without taking party, I am deeply impressed at an increasing rate and with honest respect to the ingenuity of the research that's coming from Tel Aviv, Israel and from Switzerland. There is no other country except the USA which makes such leaps in technological progress. That's my honest image of the research. I'm personally reading many of their publications and from various other journals too.
If three academic types can come up with this, just imagine what the NSA or other foreign intelligence groups can find with a budget like they have.
Interesting for sure.
Interesting for sure.
If that attack is available for us to know, I wonder what can possibly be happening inside NSA?
I even wonder how these big guys/heroes like Julian and Snowden feel when they find out about it. I mean, maybe they just don't care about the stuff they have being accessed without their consent, it is supposed to be released anyways, but what about their conversations that are supposed to be highly confidential?
I even wonder how these big guys/heroes like Julian and Snowden feel when they find out about it. I mean, maybe they just don't care about the stuff they have being accessed without their consent, it is supposed to be released anyways, but what about their conversations that are supposed to be highly confidential?
When I started reading I thought this must be a joke. As a dev with what I like to think is a solid understanding of computer hardware I don't often think of new tech as spooky/sci-fi-esque, but this is so unbelievably cool. I have no words.
Fixed GnuPG 1.4.16 version released:
http://lists.gnupg.org/pipermail/gnupg-announce/2013q4/00033...
A good enough solution might be using appliances designed with older cpus with little to no power management features but it is only practical for high stakes stuff like military comms I guess.
Some motherboards have programmable/adjustable VRMs. I wonder if the settings can be changed to mitigate the threat.
I remember being able to hear a program run on an HP 32S (RPN) by placing it up to my ear, so this isn't surprising.
What about computers located in the datacenter, next to other people's computers?
[deleted](1)
I really want to call B.S. on most of their claims, but I withhold any judgement until there is a live demo performed. Have they announced a timetable for a live demo?
Just go to any conference about cryptosystems' implementation security (like CHES), or to any exhibition on this topic (like CARTES) and you will be bluffed by demos of side-channel attacks, which are very real.
This sounds like BS, smells like BS.. But then again he is Shamir.. Still I think it is BS
This is a really well written fake.
Use some common sense.
Are you only doing one thing on your computer? No.
Does your Memory vibrate when the data is stored? No.
Can data be transferred via acoustics over a 2 conductor 16 gauge wire at the speeds memory is accessed or is sent to the CPU? No.
Think of something you have heard "hum". Is the noise pattern of your Amp and another the same if the "hum is anything other than 60hz? No. Because manufacturing tolerances are not such that the flaws are the same.
This is really great FUD. Likely designed to get People to think that they are constantly at risk, and have the CIA and FBI spend billions buying acoustic shields for their computers.
If this is real. And does work, fine, just run a background task that puts multiple random RSA's through the paces in alternate threads so the extraction can't take place because of garbled data.
EDIT: Apparently I forgot that HackerNews You get downvoted if you present common sense in face of a fallacy that those with limited understanding want to hold true, as seen by the mass of links to wikipedia made by those with out the foggiest about audio, capacitance, RSA, or Electrical engineering.
-Brandon Wirtz SMPTE
Use some common sense.
Are you only doing one thing on your computer? No.
Does your Memory vibrate when the data is stored? No.
Can data be transferred via acoustics over a 2 conductor 16 gauge wire at the speeds memory is accessed or is sent to the CPU? No.
Think of something you have heard "hum". Is the noise pattern of your Amp and another the same if the "hum is anything other than 60hz? No. Because manufacturing tolerances are not such that the flaws are the same.
This is really great FUD. Likely designed to get People to think that they are constantly at risk, and have the CIA and FBI spend billions buying acoustic shields for their computers.
If this is real. And does work, fine, just run a background task that puts multiple random RSA's through the paces in alternate threads so the extraction can't take place because of garbled data.
EDIT: Apparently I forgot that HackerNews You get downvoted if you present common sense in face of a fallacy that those with limited understanding want to hold true, as seen by the mass of links to wikipedia made by those with out the foggiest about audio, capacitance, RSA, or Electrical engineering.
-Brandon Wirtz SMPTE
This is a very weak dismissal. Have you read the actual details they claim?
Side-channel attacks (like power analysis) in the presence of other activity are well established.
Electrical signals causing audible frequency output are also well established. Look up the piezoelectric effect[1], or magneto/electrostiction[2][3]. The demand for miniaturisation of everything means even at low voltages, there are quite substantial electric fields across small distances, which are enough to flex the material audibly.
On the magnetostriction side, the flyback transformer in old CRT televisions is a perfect example. Myself and many people have been able to tell whether the TV was powered up (even if totally muted) from outside the room (and yes, double-blind tested repeatedly).
What does wire gauge have to do with anything?
On the practicality/data rate issue, a nice quote from the very intro of their paper states:
> In a nutshell, the key extraction attack relies on crafting chosen ciphertexts that cause numerical cancellations deep inside GnuPG’s modular exponentiation algorithm. This causes the special value zero to appear frequently in the innermost loop of the algorithm, where it affects control flow. A single iteration of that loop is much too fast for direct acoustic observation, but the effect is repeated and amplified over many thousands of iterations, resulting in a gross leakage effect that is discernible in the acoustic spectrum over hundreds of milliseconds.
(emphasis mine)
It seems that the main focus of their work is to fingerprint the crypto and identify that a particular key was used (but not necessarily what the key is), which is a much easier problem than the one they talk about here, which requires specially crafted input over a substantial period of time.
Your solution might work, or it might just lower the SnR of the signal and require filtering larger quantities of data to extract the desired signal again.
The road to crypto-hell is paved with people who thought that they could use their "common sense" to reason intuitively about their problem. But to paraphrase Feynman, Mother Nature is not swayed by persuasive arguments.
[1] https://en.wikipedia.org/wiki/Piezoelectricity
[2] https://en.wikipedia.org/wiki/Magnetostriction
[3] https://en.wikipedia.org/wiki/Electrostriction
Side-channel attacks (like power analysis) in the presence of other activity are well established.
Electrical signals causing audible frequency output are also well established. Look up the piezoelectric effect[1], or magneto/electrostiction[2][3]. The demand for miniaturisation of everything means even at low voltages, there are quite substantial electric fields across small distances, which are enough to flex the material audibly.
On the magnetostriction side, the flyback transformer in old CRT televisions is a perfect example. Myself and many people have been able to tell whether the TV was powered up (even if totally muted) from outside the room (and yes, double-blind tested repeatedly).
What does wire gauge have to do with anything?
On the practicality/data rate issue, a nice quote from the very intro of their paper states:
> In a nutshell, the key extraction attack relies on crafting chosen ciphertexts that cause numerical cancellations deep inside GnuPG’s modular exponentiation algorithm. This causes the special value zero to appear frequently in the innermost loop of the algorithm, where it affects control flow. A single iteration of that loop is much too fast for direct acoustic observation, but the effect is repeated and amplified over many thousands of iterations, resulting in a gross leakage effect that is discernible in the acoustic spectrum over hundreds of milliseconds.
(emphasis mine)
It seems that the main focus of their work is to fingerprint the crypto and identify that a particular key was used (but not necessarily what the key is), which is a much easier problem than the one they talk about here, which requires specially crafted input over a substantial period of time.
Your solution might work, or it might just lower the SnR of the signal and require filtering larger quantities of data to extract the desired signal again.
The road to crypto-hell is paved with people who thought that they could use their "common sense" to reason intuitively about their problem. But to paraphrase Feynman, Mother Nature is not swayed by persuasive arguments.
[1] https://en.wikipedia.org/wiki/Piezoelectricity
[2] https://en.wikipedia.org/wiki/Magnetostriction
[3] https://en.wikipedia.org/wiki/Electrostriction
>What does wire gauge have to do with anything?
If you have to ask any of the rest of your arguments are invalidated.
If you have to ask any of the rest of your arguments are invalidated.
Thanks for your constructive reply. Your exact statement was:
> Can data be transferred via acoustics over a 2 conductor 16 gauge wire at the speeds memory is accessed or is sent to the CPU? No
Which is of course true, if you're talking about >GB/s signals over wide buses.
But we're not. So I don't see why it's relevant here.
These attacks are not "sniff the actual data the CPU is flinging around by coupling to signal traces", so they don't need anything like full data-rate capability.
Edit: On re-reading your claim again, I noticed the phrase "transferred via acoustics over a 2 conductor 16 gauge wire" is a bit ambiguous. Do you mean transferred electrically over those wires, but limited to the typical acoustic frequency band (say, 0-20kHz)? Or do you mean actually acoustically coupled as mechanical vibrations of the wire itself? I can't imagine it makes any difference to my argument above, but I do wonder.
> Can data be transferred via acoustics over a 2 conductor 16 gauge wire at the speeds memory is accessed or is sent to the CPU? No
Which is of course true, if you're talking about >GB/s signals over wide buses.
But we're not. So I don't see why it's relevant here.
These attacks are not "sniff the actual data the CPU is flinging around by coupling to signal traces", so they don't need anything like full data-rate capability.
Edit: On re-reading your claim again, I noticed the phrase "transferred via acoustics over a 2 conductor 16 gauge wire" is a bit ambiguous. Do you mean transferred electrically over those wires, but limited to the typical acoustic frequency band (say, 0-20kHz)? Or do you mean actually acoustically coupled as mechanical vibrations of the wire itself? I can't imagine it makes any difference to my argument above, but I do wonder.
I am one of those people who can hear a CRT television from a room or two over. Comes across as a very distinctive high pitched squeal. I always assumed that other people couldn't hear it simply because it was too high.
It actually seemed worse when my LCD TV broke last year and I pulled out my old CRT to watch a movie in the meantime. I don't know if I had just grown unaccustomed to hearing it or what, but it was annoying me even through the sounds of the movie.
It actually seemed worse when my LCD TV broke last year and I pulled out my old CRT to watch a movie in the meantime. I don't know if I had just grown unaccustomed to hearing it or what, but it was annoying me even through the sounds of the movie.
Whoa, I had to reread your comment twice to understand it properly. In the context of RSA, and particularly speaking about its weaknesses, for me "CRT" automatically stands for "Chinese Remainder Theorem"… :-D.
If that interest someone, look for the BellCoRe attack on CRT-RSA [1,2]. I'm also working on the countermeasure as part of my PhD [3,4], and it's quite some fun!
[1] http://cryptome.org/jya/smart.pdf
[2] http://eprint.iacr.org/2012/553
[3] http://eprint.iacr.org/2013/506
[4] http://eprint.iacr.org/2013/810
If that interest someone, look for the BellCoRe attack on CRT-RSA [1,2]. I'm also working on the countermeasure as part of my PhD [3,4], and it's quite some fun!
[1] http://cryptome.org/jya/smart.pdf
[2] http://eprint.iacr.org/2012/553
[3] http://eprint.iacr.org/2013/506
[4] http://eprint.iacr.org/2013/810
Apparently you didn't read it, but nevermind.
Specifically this:
>just run a background task that puts multiple random RSA's through the paces in alternate threads so the extraction can't take place because of garbled data.
Adding randomness does not remove detectable, statistically-significant information. It just takes more trials to extract it. This is the basis of many side-channel attacks. Super-trivial example: if you roll a super-weighted die and it shows 6 every time it's obvious, but if it's only barely weighted it'll still be detectable with enough rolls, to the same level of confidence (since getting 6 one hundred times in a row is not impossible with a fair die).
Specifically this:
>just run a background task that puts multiple random RSA's through the paces in alternate threads so the extraction can't take place because of garbled data.
Adding randomness does not remove detectable, statistically-significant information. It just takes more trials to extract it. This is the basis of many side-channel attacks. Super-trivial example: if you roll a super-weighted die and it shows 6 every time it's obvious, but if it's only barely weighted it'll still be detectable with enough rolls, to the same level of confidence (since getting 6 one hundred times in a row is not impossible with a fair die).
Roll a 24 sided di a 6 sided di a 12 sided di and 2 dozen di picked of random sizes each roll, and a Di that always rolls 6 but is only included once every Random rolls.
Determine a method given only the SUM of the di to determine the value of the weighted di.
Determine a method given only the SUM of the di to determine the value of the weighted di.
Since the attacker has control over when the weighted die is added in this case (an on/off switch that includes it once in every 6 rolls, but we don't know how many rolls it takes to "use" it), yes, you can.
Roll the die with it "off" a few billion times. You now have a very-consistent prediction about the range and probability of each value. Throw the switch to "on", roll a few times until you're sure it has been used up, then turn it off. Repeat a few billion times. Since the computation finishes at some point, the weighted die's influence will exist most-strongly at the beginning.
You're left with a crap-ton of random-ish fluctuations that over time shows a slight bias to being larger at the start (compared to "off"), after you turned it on. Since you know it's included once every 6 times (I'm assuming random here, to make it harder), it will be the distribution for 1/6th the size of the weighted value (or something similar, I forget exactly). If it wasn't randomly included, then you should see spikes every 6th round.
--
Note that this does not require knowing that you had dice at all, nor knowing how many, nor knowing that there is always a 6, 12, and 24 sided die in the mix and 2 dozen others. If you knew that, you could be more confident about what a normal distribution looked like, so you could finish earlier.
Roll the die with it "off" a few billion times. You now have a very-consistent prediction about the range and probability of each value. Throw the switch to "on", roll a few times until you're sure it has been used up, then turn it off. Repeat a few billion times. Since the computation finishes at some point, the weighted die's influence will exist most-strongly at the beginning.
You're left with a crap-ton of random-ish fluctuations that over time shows a slight bias to being larger at the start (compared to "off"), after you turned it on. Since you know it's included once every 6 times (I'm assuming random here, to make it harder), it will be the distribution for 1/6th the size of the weighted value (or something similar, I forget exactly). If it wasn't randomly included, then you should see spikes every 6th round.
--
Note that this does not require knowing that you had dice at all, nor knowing how many, nor knowing that there is always a 6, 12, and 24 sided die in the mix and 2 dozen others. If you knew that, you could be more confident about what a normal distribution looked like, so you could finish earlier.
No. The attacker has control over what time period, not how many rolls.
You don't have the level of control you think. You are assuming that you will know exactly. When in truth you will only know approximately.
The human analogy falls down because we are slow. But with computers you would be controlling it from a distance, and latency would mean you wouldn't know exactly when.
You don't have the level of control you think. You are assuming that you will know exactly. When in truth you will only know approximately.
The human analogy falls down because we are slow. But with computers you would be controlling it from a distance, and latency would mean you wouldn't know exactly when.
Latency is just another bit of randomness. There have already been examples of using latency across the internet to extract encryption keys because e.g. someone didn't compare the checksum to the entire string and simply stopped once it was clear it wasn't valid. That's detecting nanosecond differences across a hundred-millisecond extremely noisy channel.
Besides, if you can get the output, you can tell how many rolls occurred, so it doesn't really matter. And this is a "chosen cyphertext" example, so the attacker has some idea of how long the computation will take under certain circumstances.
Besides, if you can get the output, you can tell how many rolls occurred, so it doesn't really matter. And this is a "chosen cyphertext" example, so the attacker has some idea of how long the computation will take under certain circumstances.
I don't think Adi Shamir is interested in writing fake articles and a fake paper about the same topic:
http://www.tau.ac.il/%7Etromer/papers/acoustic-20131218.pdf
http://www.tau.ac.il/%7Etromer/papers/acoustic-20131218.pdf
> Can data be transferred via acoustics over a 2 conductor 16 gauge wire at the speeds memory is accessed or is sent to the CPU? No.
Of course you can.
Of course you can.
Really? That's why we took so many years building HDMI? You can send that kind of data over the air as sound? and down a cable? What were we thinking? All this bother with radio waves, and compression, and hundreds of conductors?
Telephone with two cans and a string works. But not well enough that you can convert your Vinyl to OGG.
Telephone with two cans and a string works. But not well enough that you can convert your Vinyl to OGG.
Of course you don't need anything approaching OGG or HDMI fidelity in the attack described.
Do some reading about processing on cyclostationary signals. Correlation is basically God's own free lunch.
I most certainly hear noises other than 60Hz hums, coming from capacitors which correspond to what the computer is doing, including from my current PC. It's called the piezoelectric effect: http://product.tdk.com/capacitor/mlcc/en/faq/faq00031.html
And again, if you your only doing one thing at a time that might work. But if you are doing multiple things you aren't going to extract that.
If you had an old 286 you might be able to hear peizo's but your laptop doesn't have many of the old style caps that hum with any appreciable noise. Your power isn't clean enough that you can separated the other noises, and with Wifi enabled you have all sort of other noises.
What is described here isn't possible with acoustics. Anyone with even a rudimentary understanding of Audio can see that.
Brandon Wirtz SMPTE Committee Member for the H.264 and VC1 audio and video standards (someone with rudimentary understanding of audio)
If you had an old 286 you might be able to hear peizo's but your laptop doesn't have many of the old style caps that hum with any appreciable noise. Your power isn't clean enough that you can separated the other noises, and with Wifi enabled you have all sort of other noises.
What is described here isn't possible with acoustics. Anyone with even a rudimentary understanding of Audio can see that.
Brandon Wirtz SMPTE Committee Member for the H.264 and VC1 audio and video standards (someone with rudimentary understanding of audio)
Have you read the paper yet? You might be interested in figures 7-9, which show spectrographic measurements of exactly what you're claiming is impossible. Sections 4 and 5 go on to describe how you can use these measurements to get fairly accurate timing information about individual RSA key operations. What you seem to be missing is that, even though the audio bandwidth isn't nearly high enough to resolve individual CPU instructions, aggregated timing measurements can still leak a substantial amount of information. This is well-established in the crypto literature, and it's now standard practice to write code robustly to this sort of attack by making the timing data-independent.
As a side note: it's not clear to me what being an "SMPTE committee member" entails, or why it confers any special expertise about cryptographic side-channel attacks. I only point that out because you've mentioned it in two separate comments now, and I don't see why it's relevant.
As a side note: it's not clear to me what being an "SMPTE committee member" entails, or why it confers any special expertise about cryptographic side-channel attacks. I only point that out because you've mentioned it in two separate comments now, and I don't see why it's relevant.
SMPTE in this case is relevant because the claims aren't defensible under the rules of Physics. You can't push the stuff they are claiming though Air, or with microphones. There is one claim in there about the capacitance of a human that I can't provide counter claims for, because I really don't know, but basically you can't move the kinds of data they are talking about via Air, sound, and mic cables.
Once you realize that doesn't work everything else is irrelevant.
Once you realize that doesn't work everything else is irrelevant.
If you can name a single specific claim that you don't think is defensible, I might be inclined to take your argument more seriously. But so far, everything you've said is a vague generality that continues to support my theory that you haven't read the paper and don't understand the method being described.
The claim that there is a significant difference in the emitted sound from a capacitor based on the value of an RSA Key. May or may not be true.
That that sound is significant enough that you can use a microphone, to pick it up from a distance greater than a fraction of an inch is implausible.
That the sound difference is such that it can be captured with any of the setups pictured in the paper is impossible. There are systems designed for frequency isolation that do megahertz sampling rates which you could convince me are capable of reading the 1's and 0's out of a 286. The frequencies of modern electronics that is simply not possible.
That that sound is significant enough that you can use a microphone, to pick it up from a distance greater than a fraction of an inch is implausible.
That the sound difference is such that it can be captured with any of the setups pictured in the paper is impossible. There are systems designed for frequency isolation that do megahertz sampling rates which you could convince me are capable of reading the 1's and 0's out of a 286. The frequencies of modern electronics that is simply not possible.
>That the sound difference is such that it can be captured with any of the setups pictured in the paper is impossible. There are systems designed for frequency isolation that do megahertz sampling rates which you could convince me are capable of reading the 1's and 0's out of a 286. The frequencies of modern electronics that is simply not possible.
They are claiming to pick up a rather large algorithm change in code that runs for dozens of milliseconds to extract a single bit. A loop taking a bit over 26 vs. a bit over 28 microseconds in the example (or something reasonably close to that description). Why would this need such high-end equipment to pick up?
They are claiming to pick up a rather large algorithm change in code that runs for dozens of milliseconds to extract a single bit. A loop taking a bit over 26 vs. a bit over 28 microseconds in the example (or something reasonably close to that description). Why would this need such high-end equipment to pick up?
That's a claim that the authors aren't making. As has been repeatedly pointed out, the attack depends on timing the execution of blocks of code which take much longer than a single instruction, so the 44.1kHz sampling rate described in the paper is sufficient.
I'll add that it is obvious when certain types of calculation start, too. It's neat to be able to point to this and say I wasn't crazy to a few friends who didn't believe me.
On an older computer an animated gif on a web page caused my speakers to feedback differently than playing video (and this worked even when the sound card was muted). And the signals never fully masked each other. I always suspected it was a grounding fault, but it was subtle and generally unobtrusive so I never tried to fix it (it's almost a feature, like a blinking hard drive light).
Notably it is far easier to hear through the amplifier that is the sound card, but even with no speakers, a quiet room will still show the same. As others noted above, CRT monitors are notoriously loud, and you can definitely hear different image patterns.
On an older computer an animated gif on a web page caused my speakers to feedback differently than playing video (and this worked even when the sound card was muted). And the signals never fully masked each other. I always suspected it was a grounding fault, but it was subtle and generally unobtrusive so I never tried to fix it (it's almost a feature, like a blinking hard drive light).
Notably it is far easier to hear through the amplifier that is the sound card, but even with no speakers, a quiet room will still show the same. As others noted above, CRT monitors are notoriously loud, and you can definitely hear different image patterns.
I can also get a good idea whether the CPU is idle or doing some particular task just by listening to the motherboard. This isn't any sort of paranormal effect, it's quite audible. I suspect most of it comes from the inductors on the CPU vcore DC-DC converter.
For me, the sounds I hear are somewhat like this: Animated GIF = chuff-chuff-chuff, one chuff per frame transition Scrolling terminal window = low hissing, like someone slowly breathing out Dragging window around the screen = high-pitched whine CPU stress test = very high-pitched whistling Loading a big app = a more noisy hiss than scrolling the terminal window, interspersed with HDD sounds
I was tested at a young age to have above-average hearing range, so maybe that also has a factor in how well you can hear these things; I don't listen to loud music or subject myself to loud noises either.
For me, the sounds I hear are somewhat like this: Animated GIF = chuff-chuff-chuff, one chuff per frame transition Scrolling terminal window = low hissing, like someone slowly breathing out Dragging window around the screen = high-pitched whine CPU stress test = very high-pitched whistling Loading a big app = a more noisy hiss than scrolling the terminal window, interspersed with HDD sounds
I was tested at a young age to have above-average hearing range, so maybe that also has a factor in how well you can hear these things; I don't listen to loud music or subject myself to loud noises either.
> Are you only doing one thing on your computer? No.
You seem to be implying that doing multiple things on a computer means that every single side channel will be masked by noise indistinguishable from random. This is obviously false. Cryptographically secure random data doesn't just appear out of nowhere.
I'm not even concerned with the credibility of this article; side channel attacks are old news and will continue to be a threat for a long time (I'm guessing we don't even understand physics well enough yet to eliminate them completely, so there will still be new breaks all the time for the near future). Luckily, everyone is still too busy trying to remove their remote code vulnerabilities to deal with real issues like side channel attacks.
You seem to be implying that doing multiple things on a computer means that every single side channel will be masked by noise indistinguishable from random. This is obviously false. Cryptographically secure random data doesn't just appear out of nowhere.
I'm not even concerned with the credibility of this article; side channel attacks are old news and will continue to be a threat for a long time (I'm guessing we don't even understand physics well enough yet to eliminate them completely, so there will still be new breaks all the time for the near future). Luckily, everyone is still too busy trying to remove their remote code vulnerabilities to deal with real issues like side channel attacks.