Transmitter, receiver, quantum key distribution (QKD) system and quantum key distribution method

1. A transmitter that transmits first transmission key data and second transmission key data as quantum information, comprising:

an error correction encoding unit configured to generate first additional information by performing error correction encoding of the first transmission key data;

an error correction decoding unit configured to generate decoded key data by correcting errors contained in the second transmission key data using second additional information generated based on second reception key data corresponding to the second transmission key data;

a first privacy amplifier configured to generate first secure key data by performing privacy amplification on the first transmission key data to remove information that has possibly been acquired by an eavesdropper of the first transmission key data; and

a second privacy amplifier configured to generate second secure key data by performing privacy amplification on the decoded key data to remove information that has possibly been acquired by an eavesdropper of the second reception key data.

2. A receiver that obtains first reception key data and second reception key data corresponding to first transmission key data and second transmission key data by receiving quantum information, comprising:

an error correction encoding unit configured to generate second additional information by performing error correction encoding of the second reception key data;

an error correction decoding unit configured to generate decoded key data by correcting errors contained in the first reception key data using first additional information generated based on the first transmission key data;

a first privacy amplifier configured to generate first secure key data by performing privacy amplification on the decoded key data to remove information that has possibly been acquired by an eavesdropper of the first transmission key data; and

a second privacy amplifier configured to generate second secure key data by performing privacy amplification on the second reception key data to remove information that has possibly been acquired by an eavesdropper of the second reception key data.

3. A quantum key distribution system, comprising:

a transmitter that transmits first transmission key data and second transmission key data as quantum information; and

a receiver that obtains first reception key data and second reception key data by receiving the quantum information, wherein

the transmitter comprises

a first error correction encoding unit configured to generate first additional information by performing error correction encoding of the first transmission key data,

a first error correction decoding unit configured to generate first decoded key data by correcting errors contained in the second transmission key data using second additional information,

a first privacy amplifier configured to generate first secure key data by performing privacy amplification on the first transmission key data to remove information that has possibly been acquired by an eavesdropper of the first transmission key data, and

a second privacy amplifier configured to generate second secure key data by performing privacy amplification on the first decoded key data to remove information that has possibly been acquired by an eavesdropper of the second reception key data,

the receiver comprises

a second error correction encoding unit configured to generate the second additional information by performing error correction encoding of the second reception key data,

a second error correction decoding unit configured to generate second decoded key data by correcting errors contained in the first reception key data using the first additional information,

a third privacy amplifier configured to generate third secure key data by performing privacy amplification on the second decoded key data to remove information that has possibly been acquired by the eavesdropper of the first transmission key data, and

a fourth privacy amplifier configured to generate fourth secure key data by performing privacy amplification on the second reception key data to remove information that has possibly been acquired by the eavesdropper of the second reception key data.

4. The system according to claim 3 , wherein the transmitter and the receiver makes a remote data backup using the first secure key data, the second secure key data, the third secure key data, and the fourth secure key data.

5. A quantum key distribution method, comprising:

transmitting, by a transmitter, first transmission key data and second transmission key data as quantum information;

obtaining, by a receiver, first reception key data and second reception key data by receiving the quantum information;

generating, by the transmitter, first additional information by performing error correction encoding of the first transmission key data;

generating, by the transmitter, first decoded key data by correcting errors contained in the second transmission key data using second additional information;

generating, by the transmitter, first secure key data by performing privacy amplification on the first transmission key data to remove information that has possibly been acquired by an eavesdropper of the first transmission key data;

generating, by the transmitter, second secure key data by performing privacy amplification on the first decoded key data to remove information that has possibly been acquired by an eavesdropper of the second reception key data;

generating, by the receiver, the second additional information by performing error correction encoding of the second reception key data;

generating, by the receiver, second decoded key data by correcting errors contained in the first reception key data using the first additional information;

generating, by the receiver, third secure key data by performing privacy amplification on the second decoded key data to remove information that has possibly been acquired by the eavesdropper of the first transmission key data; and

generating, by the receiver, fourth secure key data by performing privacy amplification on the second reception key data to remove information that has possibly been acquired by the eavesdropper of the second reception key data.