Theory and performance analyses in quantum stream cipher based on bitwise NOT operation

Abstract

Because of the realization of physical layer security, the Quantum Stream Cipher (QSC) is getting more and more attention. However, the error rate of each bit of ciphertexts is different from 0.5 for Eve in QSC. This drawback provides Eve with an opportunity to break QSC system possibly through some attacks, such as fast correlation attacks. Thus, to increase the bit error rate of ciphertexts in the higher bit positions to cope with this kind of attacks, this paper proposes a ciphertext mapping method based on Bitwise NOT Operation (BNO). According to parity of bases, BNO-based mapping performs bitwise NOT operation for some bit positions of ciphertext to expand the difference between adjacent bit positions of ciphertexts in QSC. Besides, BNO-based QSC can be directly employed in multi-bit plaintext mapping in QSC for different modulation formats, such as PSK/QSC and QAM/QSC. The security and transmission performance of QSC based on BNO are mainly investigated with different intensity ASE noises and the number of bases in optical back-to-back simulation. The simulation results demonstrate that bit error rate in each bit position of ciphertext is close to 0.5 by BNO method in QSC. Thus, BNO method can expand the impact of noise on the higher bit positions of ciphertext. In addition, BNO method has little influence on transmission performance of receiver in QSC system.