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Locking of accessible information and implications for the security of quantum cryptography

Robert Koenig·Renato Renner·Andor Bariska·Ueli Maurer
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Abstract

The unconditional security of a quantum key distribution protocol is often defined in terms of the accessible information, that is, the maximum mutual information between the distributed key S and the outcome of an optimal measurement on the adversary's (quantum) system. We show that, even if this quantity is small, certain parts of the key S might still be completely insecure when S is used in applications, such as for one-time pad encryption. This flaw is due to a locking property of the accessible information: one additional (physical) bit of information might increase the accessible information by more than one bit.

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Robert Koenig, Renato Renner, Andor Bariska, Ueli Maurer. 2006-01-11. Locking of accessible information and implications for the security of quantum cryptography. https://doi.org/10.1103/physrevlett.98.140502

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