back to article Stray electronic-magnetic leaks used to harvest PC crypto keys

Israeli security researchers have been able to extract encryption keys from a nearby computer by analysing stray electromagnetic radiation. The attack by computer scientists from Tel Aviv University shows that TEMPEST-style side channel attacks are no longer just the preserve of Mission Impossible and three-letter spy agencies …

  1. Dan Wilkie

    So am I understanding correctly that to pull off this attack, they had to get the target to decrypt a carefully chosen cyphertext first, several times, and THEN they could decrypt whatever it was?

    It seems a little impractical for anything beyond nation states who can already do this, or is that just me?

    1. Andy Non

      How practical an attack is this? If I'm reading it right the eavesdroppers would need to give a know file to their target and ask them to encrypt it using the same key as they use for their other files, then obligingly decrypt it several times so they can pick up the key, then the attackers could access the other files.

  2. Anonymous Coward
    Anonymous Coward


    preserve of Mission Impossible and three-letter spy agencies.


    Thats GCHQ of the hook then?

    1. Rich 11 Silver badge

      Thats GCHQ of the hook then?

      It ain't off the 'ook if you drop yer aitches.

  3. Mark Allen

    White noise jamming

    Surely this is trivial to jam? My office is full of various PCs and electronics - often without cases. Are they going to pick out that one signal of the encryption being decoded? And what happens when I turn on my Plasma TV - that blasts MW and LW radio in a wide area.

    This seems a little too much of "proving a theory" but not being practical in real world use.

    1. Charles 9 Silver badge

      Re: White noise jamming

      Radio antennae can be made highly directional and highly frequency-selective (like a Yagi), allowing you to zero in on your target with enough precision to penetrate most of the noise.

      As for getting enough iterations, just use a commonly-used encrypted target and hit the sniffer each time it's being decrypted (you can hide the device in a box in a closet, maybe).

      1. druck Silver badge

        Re: White noise jamming

        The most effective jamming is by having a multi-core CPU and to make sure the other cores are all active doing something else while the decryption is taking place.

  4. x 7

    its how the Enigma crack worked.......because the Germans tended to send routine identical signals at similar times of day it was possible to presume what a message held and then brute force it

    for instance every weather message would have a preface indicating time / location, once thats cracked the rest is open - especially as weather reports follow a predictable format

    in this case, if the PC next door was also send messages in a predictable format (stock reports, bank details, sales reports) then cracking it should be relatively trivial.

  5. td0s

    Van Eck Phreaking

    This is very similar in principle to:

    which I first heard about in the Neal Stephenson novel Cryptonomicon.

    Just off to wrap my laptop in chickenwire now.

  6. James 51 Silver badge

    Would desktops in completely metal cases be less susceptible to this attack then?

    1. herman Silver badge

      No. The whole case and cables will still radiate. It is very difficult to screen equipment successfully.

      1. Jack of Shadows Silver badge

        Yes, you have to TEMPEST certified when working on the computers so you wouldn't leave one vulnerable. That's on top of 2M (Micro-Miniature) cert.

  7. x 7

    This is going to sound daft, but back when I worked for Time Computers the meeting rooms had windows with a metal coating, secondary glazing and fixed blinds, all in an attempt to stop electronic or lazer eavesdropping.

    What the brothers were worried about is anyone's guess......the only real secrets were the true ownership of all the companies in the fraud......,and just who in Dubai got all the money

    (thinks in background.....Bin Ladin, Bin Ladin). Totally no proof of course

    1. herman Silver badge

      That would not have helped if the walls were brick.

    2. Anonymous Coward
      Anonymous Coward

      I worked for Time as well.

      In the meadowhall retail park (flagship) store...Back from 2000 to about 2007 as they started to make techies redundant..

      You are right, they were a right bunch of crooks.

  8. Chris G Silver badge

    Tinfoil hats all round

    Including a grounded one around your PC!

  9. a_yank_lurker Silver badge

    A technical question

    My question is how close must the snooper be for this to work? Depending on the circumstances these types of attacks are very troubling but if the distance is 5 to 10 meters not as much.

    1. herman Silver badge

      Re: A technical question

      How close? Depends on the quality of the antenna and pre-amplifier. In practice within a few kilometers.

  10. Anonymous Coward
    Anonymous Coward

    decryption keys in applications using the libgcrypt11 library might be harvested.

    I think the might is the operative word here unless they can pack all their equipment down into something smaller than a shoe box they are going to be found out rather quickly.

    1. Charles 9 Silver badge

      They're working on that part. It's already small enough IIRC that you could stuff it in a box and hide it in a closet somewhere.

    2. Jack of Shadows Silver badge

      How's a Pita sandwich grab you. About that small. Nation states could get one-offs smaller, of course.

  11. Spaceman Spiff

    Antique tech! This technique has been used for decades to capture information from "secure" systems. That's why the US DOD came up with Tempest for truly secure terminals and computer systems that could not be eavesdropped on via stray EM signals!

    1. Charles 9 Silver badge

      Point being TEMPEST is such onerous that only the most important of computers are given the treatment. Now, these researchers are saying it can be done ANYWHERE, with inexpensive, not-too-hard-to-conceal equipment, meaning practically nothing is safe. Imagine the effect on business budgets if every single piece of electronics in their firms had to be given TEMPEST-level hardening.

    2. Jack of Shadows Silver badge

      Back then the custom gear required a van parked nearby.

  12. Anonymous Coward
    Anonymous Coward

    Not read the paper then?

    I see most people have not looked at the paper to see how they did it with largeish equipment without being detected from a few feet away, through the adjoining wall.

    There is even a nice picture showing the set-up if you click the link in the article.

    1. Anonymous Coward
      Anonymous Coward

      Re: Not read the paper then?

      The paper? Did not even read the article!

      Now let me give you my opinion...

    2. DropBear Silver badge

      Re: Not read the paper then?

      Oh, we're operating here according to strict clean-room article-reading principles: we pass judgement strictly based on El Reg articles, avoiding contamination by the original material...

      1. Tom 13

        Re: according to strict clean-room article-reading principles

        I prefer the double clean, skip the article and comment strictly based on other comments. That's the meat of it anyway, right?

  13. Anonymous Coward
    Anonymous Coward

    Maybe my priorities are wrong

    But what I found interesting about the presentation on their website is that, in the first picture's caption, they list items from left to right. Native Israelis (and the rest of the Middle East) tend to enumerate things from right to left.

    Most confusingly, the "first" item in a shelf may be the rightmost or the leftmost one from the point of view of the same person, purely depending on whether they are speaking Hebrew* or English or Russian.

    * I haven't seen this with Arabic speakers, but I presume the same phenomenon would hold for a native bilingual.

  14. Blacklight


    Soooo, if they (currently) require multiple runs to capture/identify the signals - presumably any machine running "other code" at the same time (as most machines do?) might well create obfuscation? Also, why not simply build in random calls during the decrypt, for optional "secure decryption" - every X operations, head -Y /dev/random into /dev/null (or /tmp/file), and use a decent RNG to generate X & Y. It'd slow the process down, but theoretically create enough chaff to hide things, and wouldn't be the same on any replay?

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