Key generation device and method

A key generation device, comprising:

• a key generator configured to generate a first key;
• a modulator coupled to the key generator and configured to modulate the first key to a first light source signal to obtain a modulated optical signal;
• a first beam splitter coupled to the modulator and configured to split the modulated optical signal to obtain a first sub-modulated optical signal and a second sub-modulated optical signal;
• an attenuator coupled to the first beam splitter and configured to:
• attenuate the first sub-modulated optical signal in a manner that a quantity of photons comprised in each period of the attenuated first sub-modulated optical signal is less than a preset value;
• and
• send the attenuated first sub-modulated optical signal to a receive-end device;
• a data obtainer comprising a heterodyne detector, a first analog-to-digital converter, and a processor, wherein the data obtainer is coupled to the first beam splitter and configured to obtain, after a bit error occurs when the first key is modulated to the first light source signal, a second key carried in the second sub-modulated optical signal;
• and
• a memory coupled to the data obtainer and configured to store the second key in the memory for communication with the receive-end device.