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Researchers Simplify Quantum Cryptography
Stony Stevenson writes "Quantum cryptography, the most secure method of transmitting data, has taken a step closer to mainstream viability with a technique that simplifies the distribution of keys. Researchers at NIST claim that the new 'quantum key distribution' method minimizes the required number of detectors, the most costly components in quantum crypto. Four single-photon detectors are usually required (these cost $20K to $50K each) to send and decode cryptography keys. In the new method, the researchers designed an optical component that reduces the required number of detectors to two. (The article mentions that in later refinements to the published work, they have reduced the requirement to one detector.) The researchers concede that their minimum-detector arrangement cuts transmission rates but point out that the system still works at broadband speeds."
Either this post is first or it isn't. I won't know until I press submit.
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The big deal is that the cracking time for non-quantum algorithms reduces to O(n) for length n keys. OTOH, for quantum encryption, the cracking time minimum threshold is O(n^n) for length n keys. Hyperbolically, the linear analog is also true in that with quantum decryption, it is possible to crack non-quantum algorithms in O(n) time (again for length n keys), but quantum algorithms require O(n^n) to decrypt. Note that without the correct key, the quantum algorithm requires O(n^n) regardless of whether the cracker is employing spherical numerical analysis techniques or advanced quantum distribution array matrices.
The fact of the matter is that quantum encryption provides much greater security than standard algorithmic encryption.
I think you've misunderstood something. "Quantum encryption" is something of a misnomer. It's actually a physical process that can be used by Alice and Bob to establish a commonly shared secret that is random (and unknown to even Alice and Bob before the process starts). This secret is then typically used as a one-time pad.
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The sexy part is that if there is a third party who tries to eavesdrop, the attempt will both fail and can be detected by the two communicating parties, and that the security of quantum cryptography has nothing to do with the lack of ability to factor large numbers, but is instead based on physical principles (quantum mechanics). Of course, the sensitivity to eavesdropping means that the system is probably vulnerable to a denial of service attack, depending on how the two communicating parties relate to eavesdropping.
Otherwise, you are perfectly correct. Many cryptographers, including Bruce Schneier, believe that quantum cryptography is a solution to the wrong problem. Nowadays, most probably, the least secure part of your communication system isn't in your key distribution scheme, but is somewhere else --- like in social engineering, or the computer systems which deal with the decrypted cleartext.
You also failed to mention that it is impossible to eavesdrop on the communication of the keys. This is probably the most important part because it can make one time pad encryption useful on computer networks. Without quantum cryptography, your one time pad is only as safe as how you send it (RSA encryption, chaos encryption, snail mail). Additionally, quantum cryptography can't be reverse engineered to find the algorithm for your one time pad.
This is all nice, but it is going to be tricky to implement it in the future. How do you send a photon from one computer to another a long distance away without using repeaters or branches? It will be a little tricky. Would this require a fiber optic connection between every computer that wants to communicate with quantum encryption? Or can you adjust the medium so that photons are transmitted and branched undisturbed?
The reason Eve can't just generate a new pad is because there are two methods of generating a photon and two methods of measuring a photon. Each method of generating a photon has a matched way of measuring it. If you use the matched measurement method you correctly get the bit Alice sent. If you use the incorrect method you get a random 0 or 1 no matter what bit Alice sent. Eve (and Bob too) has no way of telling which method Alice used. In quantum key distribution, after sending the photons, Alice would contact Bob over a different channel. They would tell which method they used, and if they used matching methods keep that bit. If they used different methods they would throw out the bit. If Eve regenerated the bits, she could not have used the same methods as Alice since she doesnt know which methods were used. So Alice and Bob's keys won't match up which will result in any information passed between them to be undecodable and they will know someone eavesdropped.
Quantum Key Distribution is, in its most naive form, still vulnerable to man in the middle attacks. It makes it a little more difficult because you must be able to intercept information on two different channels (the quantum channel and the classical electronic channel), but it is still doable. (There are, however, cryptographic methods of detecting man in the middle attacks, but thats a subject for another time).
The laws of probability forbid it!
...quantum cryptography now requires 30% less cats and 46% fewer radioactive isotopes.
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