Enigma machines are devices that perform cryptography using pseudo-random numbers. The original enigma machine code was broken by detecting hidden patterns in these pseudo-random numbers. This paper proposes a model for a quantum optical enigma machine and shows that the phenomenon of quantum data locking makes such quantum enigma machines provably secure even in the presence of noise and loss. [Arxiv - Quantum enigma machines]
The enigma machine used for cryptography during the second world war was a device which, given a short keyword, produced a pseudorandom output which could be decoded by a second machine using the same keyword. The original enigma machine consisted of a series of rotors through which electrical current could pass in a way that depended on the relative orientation of the rotors. The path taken by the current connected an input symbol to an output system. After each key press the rotors went through a stepping motion that changed the functional relationship between input and output for the next key press. A sender and receiver who prepared their machines using the same initial setting, determined by the keyword, could then exchange encrypted messages. While the enigma machine did a pretty good job of scrambling the input, the outputs deviated sufficiently from pseudorandom sequences that the enigma code could be broken. In general, classical codes based on pseudo-random numbers are secure only if P <> NP proving the security of such codes is accordingly difficult. This paper proposes a quantum optical version of the enigma machine and shows that it is secure in principle, in the sense that amount of information that Eve can access about the message can be made arbitrarily small, even in the presence of arbitrary amounts of loss.
The security of quantum enigma machines relies on the phenomenon of quantum data locking.
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The enigma machine used for cryptography during the second world war was a device which, given a short keyword, produced a pseudorandom output which could be decoded by a second machine using the same keyword. The original enigma machine consisted of a series of rotors through which electrical current could pass in a way that depended on the relative orientation of the rotors. The path taken by the current connected an input symbol to an output system. After each key press the rotors went through a stepping motion that changed the functional relationship between input and output for the next key press. A sender and receiver who prepared their machines using the same initial setting, determined by the keyword, could then exchange encrypted messages. While the enigma machine did a pretty good job of scrambling the input, the outputs deviated sufficiently from pseudorandom sequences that the enigma code could be broken. In general, classical codes based on pseudo-random numbers are secure only if P <> NP proving the security of such codes is accordingly difficult. This paper proposes a quantum optical version of the enigma machine and shows that it is secure in principle, in the sense that amount of information that Eve can access about the message can be made arbitrarily small, even in the presence of arbitrary amounts of loss.
The security of quantum enigma machines relies on the phenomenon of quantum data locking.
Read more »
