Beating the PNS attack in practical quantum cryptography

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  • 8 November 2004
Abstract
In practical quantum key distribution, weak coherent state is often used and the channel transmittance can be very small therefore the protocol could be totally insecure under the photon-number-splitting attack. We propose an efficient method to verify the upper bound of the fraction of multi-photon pluses and the lower bound of the fraction of single-photon pulses transmitted to from Alice to Bob, given whatever type of Eve's action. The protocol simply uses two coherent states for the signal pulses and vacuum for decoy pulse. Our verified upper bound is sufficiently tight for QKD with very lossy channel, in both asymptotic case and non-asymptotic. The coherent states with mean photon number from 0.2 to 0.5 can be used in practical quantum cryptography.

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