Method for processing double click event for securing safety in quantum key distribution system

1. A method performed by a processor of a receiver of generating a secret key using a quantum communication, the processor to execute the method comprising:

performing a quantum key distribution (QKD) protocol to generate a sifted key;

performing a post-processing protocol based on the sifted key to generate a final key;

counting number of double click events when quantum signals are detected; and

performing privacy amplification of the final key based on the counted number of the double click events,

wherein the performing of privacy amplification comprises

calculating an amount of information open to an attacker, based on the counted number of the double click events, and

adjusting a length of the final key based on the calculated amount of information.

2. The method of claim 1 , wherein the length of the final key is adjusted by Length final =Length sifted ×{1−2·h(QBER)}−Num double , where Length sifted denotes a length of the sifted key, h(x) denotes Shannon entropy, QBER denotes a quantum bit error rate, and Num double denotes the counted number of the double click events.

3. The method of claim 1 , further comprising

discarding the QKD protocol when the counted number of the double click events exceeds a preset permissible limit.

4. The method of claim 1 , wherein information about the counted number of the double click events is shared with a transmitter before the sifted key is generated by implementing the QKD protocol.