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Move Over, Quantum Cryptography: Classical Physics Can Be Unbreakable Too
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."
Johnson noise.
Give me Classic Slashdot or give me death!
Unbreakable encryption that can be decrypted is much harder.
"Have you ever thought about just turning off the TV, sitting down with your kids, and hitting them?"
I remember when this was posted on Slashdot 7 years ago.
The basic idea of the key exchange is a variant of an older key exchange idea. The very basic idea involves Alice and Bob having a wire that goes between them. Each of the two has two resistors one with very low resistance and one with high resistance. To gain a series of random bits, Alice and Bob both randomly choose a resistor and connect it to the wire and then measure the resistance through the whole system. If they both used the high or both used the low resistance resistors they throw out those exchanges. Whenever they have one medium and one high, they will both know which one had a low and which one had a high because they'll know their own. But Eve the evil eavesdropper even if she has a connection into the line won't be able to get this just from knowing the total resistance. In some weak respects this resembles a physical analog of the Diffie-Hellman http://en.wikipedia.org/wiki/Diffie%E2%80%93Hellman_key_exchange. The process being proposed here though, a Kish key exchange http://en.wikipedia.org/wiki/Kish_cypher does some clever stuff with the thermodynamics end to deal with man-in-the-middle and other related attacks.
I don't know about y'all, but I like my cats dead when I open the box.
As someone pointed out, this was on Slashdot 7 years ago. Here's the referenced paper.
The idea is simple. At both ends of the wire, random data modulated with content is being emitted. At any point on the wire, you see the sum of two random sources. But each end knows their own random data, and can subtract it out.
To break the system, you need two taps on the wire, some distance apart. Now you get to see the sums of the signals from each end, but with different time shifts between them due to propagation delay. With that data, you can separate out what's coming from each end. This allows recovering the original signals.
"No new encryption system is worth looking at unless it comes from someone who has already broken a very hard one." - Friedman.
The resistor stuff solves an orthogonal problem to OTP. OTP gives you perfect secrecy when you share an unknown secret key with the other party you are communicating with. This "resistor stuff" is how you get an unknown shared secret key with the other party. OTP still requires key distribution, which is what this does. The two are complementary, neither replaces the other.