Security analysis method of continuous variable quantum key distribution protocol based on optimal bias threshold detection

The invention discloses a security analysis method for a continuous variable quantum key distribution protocol based on optimal bias threshold detection. The method comprises the following steps: step 1, in a CV-QKD protocol, Alice modulates and sends a coherent state signal according to a random bit string; 2, Bob uses a Kennew receiver based on threshold detection to carry out signal detection, and Eve uses a beam splitting attack method to obtain information about a sent signal; step 3, Bob optimizes the bias value of the bias detector; 4, for different channel transmission efficiencies, further optimizing the amplitude value of the transmitted coherent state signal so as to maximize the mutual information amount of two legal parties; and step 5, based on the optimal offset value and the amplitude of the transmitted coherent state signal, adopting a post-selection method, enabling Bob to only retain a measurement result that the information amount of Bob is greater than that of an eavesdropper, and respect