Quantum Cryptography Broken, and Fixed 118
schliz writes in with research out of Sweden in which researchers showed that, looking at a quantum cryptographic system as a whole, it was possible for an eavesdropper to extract some information about the QC key, thus reducing the security of the overall system. The team then proposed a cheap and simple fix for the problem. "The advanced technology was thought to be unbreakable due to laws of quantum mechanics that state that quantum mechanical objects cannot be observed or manipulated without being disturbed. But a research team at Linköping University in Sweden claim that it is possible for an eavesdropper to [get around the limitations] without being discovered. In a research paper, published in the international engineering journal IEEE Transactions on Information Theory (abstract), the researchers propose a change in the quantum cryptography process that they expect will restore the security of the technology."
Comment removed (Score:3, Informative)
Re:Fundamental Flaw in Quantum[Anything] (Score:2, Informative)
Article is a dupe... (Score:5, Informative)
Initialization vector (Score:3, Informative)
"The researchers propose an additional, non-quantum exchange of a small amount of random bits that are separate from the quantum key."
The End of The Science of Cryptography (Score:5, Informative)
This in effect means that the science of cryptography has met its end in terms of development.
Like the game of checkers, there are no more moves to make.
At the time of publication (2002?), the longest distance an encrypted quantum message sent and received was approximately 50kms and considered to be impossible to break.
Re:One time pad (Score:4, Informative)
That is exactly the point of quantum cryptography. The cryptographic key is the one time pad, negotiated between two parties, using superposition (and in some cases entanglement) in order to come to agreement on the pad and at the same time detect evesdroppers.
Re:The End of The Science of Cryptography (Score:3, Informative)
Re:Wah? (Score:4, Informative)
2. Bob reads the key, but, due to the random encoding, he can read only half of it (you can read only if the receiver is in the same state as the sender), so Bob sees some random subset of the bits. This random subset is the key. Alice does not know which subset this is.
3. Bob transmits the configuration he used to read the stream back to Alice. Alice compares the configuration to her own configuration for sending data and derives which bits Bob saw. They now both know the key.
It is impossible to read the bits without changing them, in which case Bob will see something different from what was sent, so the keys won't match.
It is also impossible to derive the key from the configuration that is sent back by Bob because it only specifies how the bits were read, not what the bits were.
This is, of course, vulnerable to a man-in-the-middle attack, however.
Re:Wah? (Score:4, Informative)
When Eve reads the message changes to 50% correct, 50% incorrect.
When Bob gets the photons his 50% will consist of 25% correct and 25% incorrect ones. (assuming true randomness)
When Alice and Bob compare there keys they will see the discrepancy.
Then the 1 and 0 are XORs with the message and then the result is sent.
http://en.wikipedia.org/wiki/Quantum_cryptography#Polarized_photons_-_Charles_H._Bennett_and_Gilles_Brassard_.281984.29 [wikipedia.org]
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Broken QC FAQ (Score:3, Informative)
Re:Article is a dupe... (Score:1, Informative)