Applied Mathematics & Information Sciences

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South Africa


The coherent-one-way and the differential-phase-shift protocols are two of the most recent practical quantum key distribution protocols for quantum cryptography. These protocols belong to a class of so-called distributed-phase-reference quantum key distribution protocols. While security proofs for some limited attacks exist, the unconditional security proofs this class of protocol remain unrealised. The existing tools for proving security of protocols against the most general attacks fail to apply to this class of protocol in a straight forward way. One of the necessary conditions for a quantum key distribution protocol to be secure is the presence of noncommuting measurements. In this paper, the coherent-one-way protocol is formalised, and we describe Bob’s measurements by non-commuting POVM elements, showing that this security condition is met.

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