  Decoy-state quantum key distribution is a standard tool for long-distance
quantum communications. An important issue in this field is processing the
decoy-state statistics taking into account statistical fluctuations (or
"finite-key effects"). In this work, we propose and analyze an option for decoy
statistics processing, which is based on the central limit theorem. We discuss
such practical issues as an inclusion of the failure probability of the
decoy-states statistical estimates in the total failure probability of a QKD
protocol and also taking into account the deviations of the binomially
distributed random variables used in the estimations from the Gaussian
distribution. The results of numerical simulations show that the obtained
estimations are quite tight. The proposed technique can be used as a part of
post-processing procedures for industrial quantum key distribution systems.
