METHOD FOR DETECTING A DETECTOR BLINDING ATTACK IN QUANTUM CRYPTOGRAPHY SYSTEMS WITH POLARISATION ENCODING Russian patent published in 2022 - IPC H04L9/08 

FIELD: cryptography.

SUBSTANCE: invention relates to the field of quantum cryptography. The system includes a transmitting part, a receiving part including a photodetector unit, a communication line made in the form of a single-mode optical fibre and interconnecting the transmitting part and the receiving part, wherein the photodetector unit comprises two independent channels — an information channel and a control channel, an asymmetric beam splitter with one input and two outputs and separating the information and control channels, a symmetrical beam splitter with one input and two outputs, a controlled polarisation converter with two outputs, and two detectors; wherein the input emission of the receiving part is supplied to the input of the asymmetric beam splitter, the input of the polarisation converter is linked with the first output of the asymmetric beam splitter, the input of the symmetrical beam splitter is linked with the second output of the asymmetric beam splitter, the first output of the polarisation converter is linked with the first detector, the second output of the polarisation converter is linked with the second detector, the first output of the symmetrical beam splitter is linked with the first detector, the second output of the symmetrical beam splitter is linked with the second detector; wherein polarisation conversions of the input quantum states are provided in the information channel before recording by the detector by supplying control signals to the polarisation converter, polarisation conversions of the input quantum states are not used in the control channel before recording by the detector, the split coefficient of the asymmetric beam splitter is selected such that the control states and the states after the polarisation conversion have the same intensity in the first and second photodetectors when the bases of the transmitting and receiving parts match.

EFFECT: possibility of detecting false quantum states in the quantum communication channel, generated by the monitor during a detector blinding attack, in quantum cryptography systems with polarisation encoding.

1 cl, 5 dwg