Patent ID: 7609839
Filing Date: 2009-10-27
Classification: G11B,H03M,H04L

Abstract:
1. A quantum key distribution method employed on a quantum cryptosystem including a first communication apparatus that transmits photons onto a quantum communication path and a second communication apparatus that measures the photons, comprising: a check matrix creation step of each of the first communication apparatus and the second communication apparatus creating the same parity check matrices H(n×k); a random number generation step of the first communication apparatus generating a random number sequence (transmission data) and randomly determining a predetermined transmission code (base) by the first communication apparatus, and the second communication apparatus randomly determining a predetermined reception code (base); a photon transmission step of the first communication apparatus transmitting a photon onto the quantum communication path while the photon is in a quantum state specified by a combination of the transmission data and the transmission code; a photon reception step of the second communication apparatus measuring the photon transmitted on the quantum communication path to obtain reception data specified by the combination of the reception code and measurement result; a data deletion step of each of the first communication apparatus and the second communication apparatus deciding whether the measuring has been performed with an appropriate measuring apparatus, saving the reception data of n bits if the measuring has been performed with the appropriate measuring apparatus and transmission data that corresponds to the reception data, and discarding other pieces of the data; an error correction information notification step of the first communication apparatus notifying the second communication apparatus through a public communication path of error correction information of k bits based on the parity check matrix H and the transmission data of n bits; an error correction step of the second communication apparatus correcting the error of the reception data based on the parity check matrix H, the reception data of n bits, and the error correction information; and a cryptographic key creation step of each of the first communication apparatus and the second communication apparatus discarding a part of pieces of the common information after correction according to public error correction information, creating a cryptographic key using information that has remained after discarding, wherein the amount of information remaining is n−k bits, and setting the cryptographic key as a common key which is shared between first communication apparatus and the second communication apparatus.