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US 7,609,839 B2Granted
Quantum key distribution method and communication device
AssigneeMitsubishi Electric Corporation
InventorsYoudai Watanabe, Wataru Matsumoto
Life of this patent
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Abstract
In order to create a highly-secured common key while a data error on a transmission path is corrected by an error correction code having remarkably high characteristics, in a quantum key distribution method of the invention, at first a communication apparatus on a reception side corrects the data error of reception data by a deterministic, stable-characteristics parity check matrix for a “Irregular-LDPC code.” The communication apparatus on the reception side and a communication apparatus on a transmission side discard a part of pieces of the common information according to public error correction information.
Claims24
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.
6 more elements
A communication apparatus on transmission side that transmits photons onto a quantum communication path, comprising:
- a check matrix creation unit that creates a parity check matrix H(n×k) identical to a communication apparatus on reception side;
- a transmission unit that generates a random number sequence (transmission data), randomly determines a predetermined transmission code (base), transmits the 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, decides whether the measuring has been performed with an appropriate measuring apparatus in the communication apparatus on the reception side, saves the transmission data of n bits if the measuring has been performed with the appropriate measuring apparatus, and discards other pieces of the transmission data;
- an error correction information notifying unit that notifies the communication apparatus on the reception side of error correction information of k bits based on the parity check matrix H and the transmission data of n bits through a public communication path;
- and
- a cryptographic key creation unit that discards a part (k) of pieces of the common information after error correction according to public error correction information, creates a cryptographic key using information that has remained after discarding, wherein the amount of information remaining is n−k bits, and sets the cryptographic key as a common key which is shared with the communication apparatus on the reception side.
2 more elements
A communication apparatus on reception side that measures photons on a quantum communication path, comprising:
- a check matrix creation unit that creates a parity check matrix H(n×k) identical to a communication apparatus on transmission side;
- a receiving unit that randomly determines a predetermined reception code (base), measures the photons on the quantum communication path, reproduces reception data specified by a combination of the reception code and measurement result, decides whether the measuring has been performed with an appropriate measuring apparatus, saves the reception data of n bits if the measuring has been performed with the appropriate measuring apparatus, and discards other pieces of the reception data;
- an error correction unit that corrects the error of reception data based on error correction information of k bits received through a public communication path, the parity check matrix H, and the reception data of n bits;
- and
- a cryptographic key creation unit that discards a part of pieces of the common information after error correction according to public error correction information, creates a cryptographic key using information that has remained after discarding, wherein the amount of information remaining is n−k bits, and sets the cryptographic key as a common key which is shared with the communication apparatus on the transmission side.
2 more elements
Dependencies are inferred from the claim text.