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Time Machines, Computer Memory, and Brute Force Attacks Against Smartcards

Posted by Unknown on from the one-too-many-questions dept.

An anonymous reader writes "IEEE Spectrum reports on a method that exploits the decaying contents of unpowered computer memory to create an hourglass-like 'time machine' that rate limits brute force attacks against contactless smartcards and RFIDs. The paper takes an odd twist on the 'cold boot' attack reported four years ago at USENIX Security. Not quite as cool as a hot tub time machine though. " Full paper (PDF).

49 comments

  1. What? by jhoegl · · Score: 4, Insightful

    Why do I have to decrypt the summary?

    1. Re:What? by osu-neko · · Score: 0

      Why do I have to decrypt the summary?

      You could try reading the article, perhaps?

      --
      "Convictions are more dangerous enemies of truth than lies."
    2. Re:What? by Baloroth · · Score: 5, Informative

      SRAM looses coherency in a statistically predictable pattern for a few seconds/minutes after it looses power. That means an otherwise powerless and clockless RFID chip can detect when it was powered on recently, and deny access attempts until at least a few seconds after the last access, rendering brute-force attempts vastly less practical (those normally use thousands of access attempts a second). Also, potentially annoying the hell out of anyone for whom the card doesn't work the first time, but security has always been a tradeoff with practicality (and if it is just a matter of seconds, not a huge deal).

      --
      "None can love freedom heartily, but good men; the rest love not freedom, but license." --John Milton
    3. Re:What? by VortexCortex · · Score: 1

      Why do I have to decrypt the summary?

      You don't. That compulsion can be completely ignored. For proof, see: Nearly all the other comments.

    4. Re:What? by Anonymous Coward · · Score: 0

      Also, potentially annoying the hell out of anyone for whom the card doesn't work the first time, but security has always been a tradeoff with practicality (and if it is just a matter of seconds, not a huge deal).

      If you RTFA, you'll see it already addresses that:
      "Unlike cruder present-day RFID defense measures—such as France’s e-passports that punish every successive failed RFID read with an increasingly longer lag, causing frustrating wait times for travelers and customs officials—TARDIS would theoretically permit standard occasional communications but severely constrain the tsunami of failed attempts that are the hallmark of a hostile attack."

    5. Re:What? by Anonymous Coward · · Score: 0

      It only cost $0.00 for the company that owns the patent. An on-chip/external capacitor or even a crudely made DRAM cell on chip might be cheaper than paying the licensing fee for everyone else.

    6. Re:What? by Anonymous Coward · · Score: 0

      I think you mistyped "SPAM"...

    7. Re:What? by biodata · · Score: 1

      I don't get this. So the American public paid for this research, and now they have to pay again if they ever want to use the knowledge? The original paper says this: "This research is supported by NSF grants CNS- 0831244, CNS-0845874, CNS-0923313, CNS-0964641, SRC task 1836.074, Gigascale Systems Research Center, and a Sloan Research Fellowship.", so how does a private corporation get to own a patent on this idea?

      --
      Korma: Good
    8. Re:What? by Anonymous Coward · · Score: 0

      that happens with a lot of stuff, too.

    9. Re:What? by Threni · · Score: 1

      > So the American public paid for this research, and now they have to pay again if they
      > ever want to use the knowledge?

      Not ever, no, because it's a patent. Once it's expired you'll be free to use it.

    10. Re:What? by mcgrew · · Score: 0

      SRAM looses coherency

      How can coherency possibly be set free? You make no sense at all.

      for a few seconds/minutes after it looses power

      Oh, a non-reader. Sorry, I now see that you meant "lose". "Loose" means to set free. If it loosed power, that would be an electrical short. Your mistake completely changed the meaning of what you were trying to say. I suggest you read less internet and more edited and proofread books so you don't look so uneducated. To paraphrase Twain, an aliterate has no advantage over an illiterate.

      --
      Free Martian Whores!
  2. Neat trick... by fuzzyfuzzyfungus · · Score: 3, Interesting

    Taking advantage of the (statistically) predictable decay rate of data stored in the RFID's SRAM is a cute trick for rough timekeeping, I have to admit.

    It makes me wonder, though, and some perfunctory googling isn't giving me the immediate gratification that I demand, is there anything reasonably practical that could modify the decay rate for SRAM, ideally in a way that would be practical for an attack? Does a strong magnetic field affect contemporary transistors in any useful way? Would a hit of radiation before each attack attempt sufficiently scramble the RAM contents before it also scrambled the nonvolatile memory storing the secret being attacked?

    1. Re:Neat trick... by BradleyUffner · · Score: 1

      Taking advantage of the (statistically) predictable decay rate of data stored in the RFID's SRAM is a cute trick for rough timekeeping, I have to admit.

      It makes me wonder, though, and some perfunctory googling isn't giving me the immediate gratification that I demand, is there anything reasonably practical that could modify the decay rate for SRAM, ideally in a way that would be practical for an attack?

      I think temperature has some effect.

    2. Re:Neat trick... by chriso11 · · Score: 1

      Running the devices hotter should increase the decay rate...

      --
      No, I don't trust in god. He'll have to pay up front, like everybody else.
    3. Re:Neat trick... by Anonymous Coward · · Score: 0

      But how much of an effect will it have before you start damaging the chip?

    4. Re:Neat trick... by Anonymous Coward · · Score: 0

      Okay,I've downloaded the "payload". What's next?

      1. download PDF
      2. open document
      3. ??
      4. profit !!

      my passcode is "grenade"

    5. Re:Neat trick... by Anonymous Coward · · Score: 1

      >Running the devices hotter should increase the decay rate...

      Integrate a thermal fuse and that door is closed.

    6. Re:Neat trick... by fredprado · · Score: 2

      If you keep it hot but within working parameters that should do the trick. Working temperature ideally shouldn't get higher than 70 C.

    7. Re:Neat trick... by Baloroth · · Score: 3, Informative

      If the attacked has lengthy, exclusive access to the chip and sufficiently advanced resources, basically nothing will stop them cracking it. This technique is simply a software added trick that can be used with cheap existing RFID technology to prevent drive-by attacks, not dedicated cracking. The key is "cheap": nearly free, in fact, rather than a more complicated method (my first thought was to use a simple RCI circuit to detect if the card has had power in the last few seconds to achieve the same effect as this, but that of course would add complexity and cost and most importantly couldn't be used with existing chips. Also potentially crackable, but it would help).

      --
      "None can love freedom heartily, but good men; the rest love not freedom, but license." --John Milton
    8. Re:Neat trick... by allanw · · Score: 1

      Probably has some kind of exponential dependence on temperature as well, so I imagine there has to be a table storing the decay rate across temperature and voltage which also has to be specific for each manufactured chip.

    9. Re:Neat trick... by gweihir · · Score: 1

      Cooling will massively slow down this rate. Well known.

      --
      Most ACs are not even worth the keystrokes to insult them. Be generically insulted by this and ignored otherwise.
    10. Re:Neat trick... by leuk_he · · Score: 1

      Thermal fuse means adding components. That costs money. The trick is that this is done without adding componets (well... 50 lines of code need to be stored somewhere...)

      Rising the temperature or putting it in a microwave will increase the decay rate. But it will still hinder a brute force attack.

    11. Re:Neat trick... by Anonymous Coward · · Score: 0

      From telephone cards in the 90s I remember just doing 30 seconds of microwaving nicely reset things.

    12. Re:Neat trick... by dkf · · Score: 1

      If the attacked has lengthy, exclusive access to the chip and sufficiently advanced resources, basically nothing will stop them cracking it.

      That's actually untrue. The trick is whether the memory can be read without powering up the chip; if not, then you can put in detection code (e.g., a rate limiter) that flushes the memory with crap if an attack is detected (which it's is easy to make the circuitry for). After that, the attacker might as well give up. Preventing reading the memory in unpowered state is the trick though, and the best techniques there tend to involve burying the secure memory elements under other parts of the chip so that you can't just grind them off and peek with an electron microscope. Of course, at that point the attacker has also invested many thousands in a decent microelectronics lab, and will need to break into a lot of chips just in order to recover their costs...

      Or in other words, simple measures are actually quite sufficient.

      --
      "Little does he know, but there is no 'I' in 'Idiot'!"
    13. Re:Neat trick... by plover · · Score: 1

      Or in other words, simple measures are actually quite sufficient.

      Like anything dealing with security, that depends entirely on the value of the secret being protected.

      If this is a MiFARE card, learning the secret could get you and some friends a few free rides on the metro. If this is an access card, it might get you into a building. If this is a passport, it might get you into the country. If this is a banking card, you might get access to the customer's account. Pick the right customer, and it's suddenly very profitable. If this is a satellite card, it could be worth millions on the black market.

      The other thing to keep in mind, is that all of these activities will get you in a roughly equal amount of trouble: fraudulent devices and theft add up to about the same punishment regardless of how much money is stolen. A bad guy has incentive to hit the richest target, not the poorest, since the risk to him is the same.

      --
      John
  3. Thermite by Anonymous Coward · · Score: 0

    Thermite will work.

  4. Re:Please consider Mitt Romney by retchdog · · Score: 0, Redundant

    well, i'm sold. thanks!

    --
    "They were pure niggers." – Noam Chomsky
  5. Has nothing to do with space time manipulation. by VortexCortex · · Score: 1

    Got nothing more to do with a time machine than your average lump of matter...

    1. Re:Has nothing to do with space time manipulation. by Anonymous Coward · · Score: 0

      I think "clock" would be a better name for it. Wording is obviously to sensationalize the article.

  6. First Officer, report! by MobileTatsu-NJG · · Score: 3, Funny

    Just like putting too much air into a balloon.

    --

    "I like to lick butts!" by MobileTatsu-NJG (#32700246) (Score:5, Informative)

  7. software must live on hardware by Anonymous Coward · · Score: 0

    it's simply physics, finally

  8. Sounds like BS to me by gweihir · · Score: 1

    Far too easy to manipulate from the outside. E.g. cooling will massively slow this "clock".

    --
    Most ACs are not even worth the keystrokes to insult them. Be generically insulted by this and ignored otherwise.
    1. Re:Sounds like BS to me by Anonymous Coward · · Score: 1

      Far too easy to manipulate from the outside. E.g. cooling will massively slow this "clock".

      I thought this too, but actually the rate limiting appears to be susceptible only to pulsed cooling/heating attacks in certain cases. Cooling the chip actually makes the adversary's job even harder because it slows down the hourglass---making the rate limiting even more punishing.

    2. Re:Sounds like BS to me by Sabriel · · Score: 1

      The objective appears to be hindering remote brute-force attacks against contactless cards that are still in the physical possession of the owner, not to create some non-existent "perfect defence".

    3. Re:Sounds like BS to me by pipedwho · · Score: 1

      If the existing algorithms and implementations are so bad as to make a brute force attack take less than some time period measured in ages of the universe, then they're doing it wrong.

    4. Re:Sounds like BS to me by Anonymous Coward · · Score: 3, Insightful

      Unlike your top of line PC, there are a lot of constraints on an embedded chip especially one that cost pennies, can run on energy from the RF near field and amount of computation. Unlike white board software, this is real world Engineering where there is a trade-off between constraints/requirement/economic/physical that are opposite to each other. So might want to not mouth off without knowing the subject.

      The chip is also highly observable and a lot of information can be deduced from the amount of time for the processing and power profile during execution.

    5. Re:Sounds like BS to me by gman003 · · Score: 2

      Which makes it harder, actually.

      The "trick" is basically the card using the slow decay of unpowered memory to detect if the card has been powered on recently, and if so, force a small delay. The goal is basically to limit the rate of attacks with minimal impact on proper use (if the card reads properly every time, this has near-zero impact on proper use - it might annoy a bit if your card doesn't read right, having to wait a second or two to swipe again, but that's neither a terribly common case nor a significant impact on real users).

      Chilling it actually makes it worse for you, as the card will detect itself as "having been powered up recently" for longer than it would normally, so you limit your attack rate even more.

  9. 555 timer, not hot tub Eloi and hot tub Morlocks by tepples · · Score: 1

    Got nothing more to do with a time machine than your average lump of matter

    Yeah, it has a lot more to do with the 555 timer, which was called "The IC Time Machine" when first sold, than it does with hot tub Eloi and hot tub Morlocks.

    block dropping mini-game

    Mr. Rogers is coming to get you.

  10. Re:Mitt Romney staple = IT guys with rip off sales by CheshireDragon · · Score: 0

    excellent use of the word THERE...

    --
    "That's right...I said it."
  11. Re:Please consider Mitt Romney by CheshireDragon · · Score: 1

    I wonder when our nations checks are going to bounce. We keep writing them, but they aren't worth a dime. I want a check book like that.

    --
    "That's right...I said it."