Abstract
A simple and general proof is given for the information theoretic (unconditional) security of the Kirchhoff-law–Johnson-noise key exchange system under practical conditions. The unconditional security for ideal circumstances, which is based on the second law of thermodynamics, is found to prevail even under slightly non-ideal conditions. This security level is guaranteed by the continuity of functions describing classical physical linear, as well as stable non-linear, systems. Even without privacy amplification, Eve’s probability for successful bit guessing is found to converge toward 0.5—i.e., the perfect security level—when ideal conditions are approached.
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Acknowledgments
L.K. is grateful to Horace Yuen, Vadim Makarov, Vincent Poor, and Renato Renner for helpful discussions about relevant security measures.
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Kish, L.B., Granqvist, C.G. On the security of the Kirchhoff-law–Johnson-noise (KLJN) communicator. Quantum Inf Process 13, 2213–2219 (2014). https://doi.org/10.1007/s11128-014-0729-7
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DOI: https://doi.org/10.1007/s11128-014-0729-7