Slashdot Mirror
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."
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?"
Yes, that's true in a trivial sense. What that essentially amounts to is that one has unbreakable encryption if one has a shared source of randomness that the eavesdropper lacks. So if you can do things like have physical couriers carry bits back and forth between set locations you can do that sort of thing. The problem is that such situations aren't very common. Most encryption contexts that would be much too inefficient or outright impossible (you don't want to be in a situation where in order to securely give your credit card number to Amazon they have to send someone over with a flash drive full of random bits). The key is making practical and close to unbreakable or outright unbreakable crypto that doesn't rely on such ridiculously strong assumptions.
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.
But given that the noise is fundamentally based on quantum mechanical events, can this really claim to be classical rather than a clever way to generate a quantum key?
Please consider this account deleted, I just can't be bothered with the spam anymore.