Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!


Forgot your password?
Encryption Network Security Science

Move Over, Quantum Cryptography: Classical Physics Can Be Unbreakable Too 126

MrSeb writes "Researchers from Texas A&M University claim to have pioneered unbreakable cryptography based on the laws of thermodynamics; classical physics, rather than quantum. In theory, quantum crypto (based on the laws of quantum mechanics) can guarantee the complete secrecy of transmitted messages: To spy upon a quantum-encrypted message would irrevocably change the content of the message, thus making the messages unbreakable. In practice, though, while the communication of the quantum-encrypted messages is secure, the machines on either end of the link can never be guaranteed to be flawless. According to Laszlo Kish and his team from Texas A&M, however, there is a way to build a completely secure end-to-end system — but instead of using quantum mechanics, you have to use classical physics: the second law of thermodynamics, to be exact. Kish's system is made up of a wire (the communication channel), and two resistors on each end (one representing binary 0, the other binary 1). Attached to the wire is a power source that has been treated with Johnson-Nyquist noise (thermal noise). Johnson noise is often the basis for creating random numbers with computer hardware."
This discussion has been archived. No new comments can be posted.

Move Over, Quantum Cryptography: Classical Physics Can Be Unbreakable Too

Comments Filter:
  • by PatDev ( 1344467 ) on Friday June 15, 2012 @01:43PM (#40337131)

    The important point that people seem to be missing is that quantum encryption *is* one-time pad. The system of quantum encryption consists of using entangled particles to be the shared source of randomness. Because both parties would be aware if anyone besides the two of them were observing the shared randomness, they can't exactly communicate via entanglement, but they can reach an arbitrary (ie. not decided by either of them) consensus on the values in a random stream. This random stream is then used as the key of a one-time-pad where the ciphertext is transported over a traditional channel of communication.

    For this reason, I consider the term "quantum encryption" to be a bit of a misnomer - nothing about the actual en/de cryption is quantum. A better name would be "quantum key distribution" or "quantum consensus generation"

  • Re:Still breakable (Score:4, Interesting)

    by MozeeToby ( 1163751 ) on Friday June 15, 2012 @01:50PM (#40337209)

    Maybe I'm just being silly, but if you also encrypt the message using standard means it will look identical to random noise, making it impossible to tell if you stumbled upon the correct current and voltage in the first place. Alternatively, Alice and Bob are able to detect your trying to intercept their communications, which means they can alter their behavior long before you stumble upon the correct settings.

  • by Ancient_Hacker ( 751168 ) on Friday June 15, 2012 @03:07PM (#40338131)

    A ridiculouos idea, if you're an electrical engineer, for many reasons:

    (1) The noise on the wire, for reasonable values of resistors and bandwidth, is down in the low microvolts. If the cable is unshielded, it's going to pick up several microvolts of radio signals per foot. Even if it's really well shielded, we're still talking microvolts per kilometer.

    (2) Eve can put a probe signal on the wire, it just has to be random noise. Alice and Bob have no way of proving that a small spike of random noise, only half a standard deviation above the average, isn't perfectly fine Johnson noise coming from the other end. Eve knows the amplitude of the noise she is putting on the wire, so she can subtract that amount, and the difference reveals the values of the resistors.

    (3) For any moderately long wire, in the kilometer range, there is a time delay, allowing Eve to inject short bursts of noise and get the resistor info from each end coming back, spread out in time.

    (4) Bell Labs proposed this idea, the part about injecting noise inn from both ends, back around 1955.

  • by jmorris42 ( 1458 ) * <jmorris@NOSPAM.beau.org> on Friday June 15, 2012 @04:14PM (#40338815)

    > send someone over with a flash drive full of random bits

    No, they would just have to send a mailman over every few years with a new credit card which they already do. I just did some back of the envelope math and if you assume a transaction could be sent in 64 bytes and you store only 1Gib of random pad in the card you could almost make a transaction per minute with it and even with a 5year expiration date you wouldn't have to reuse the pad and break the security. The problem is Visa would need to retain that gigabit of data until the card expires and it might cost a bit to keep that much key material secure but it would be a very secure system. Apparently they believe the fraud losses are cheaper.

    Something to keep in mind next time you hear em whining. Or hear a Lifelock ad. It is only cheaper for them because they offload so much of the expense for their being cheap bastards onto us.

God doesn't play dice. -- Albert Einstein