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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!
I want to know if the Laszlo in this story also has an underground room where he prepares and sends in entries to the publishers clearing house sweepstakes. And who's dorm room closet does he come out of?
Is it just my observation, or are there way too many stupid people in the world?
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.
Is it a coincidence that Johnson-Nyquist noise sounds exactly like an accordion and bagpipe duo playing La Marseillaise?
Claude Shannon proved in the 1940's that the Vernam cipher with a key the same size as the message, aka one time pad, has perfect security. The USA built the world first digital audio system during WWII in order to give such perfect security to voice communications between Roosevelt and Churchill, among others.
This approach assumes that only Alice and Bob know the current and voltage of the power source. This can be brute forced until a tangible message is found. Next...
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.
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.