An Improved Rao-Nam Cryptosystem Based on Fractional Order Hyperchaotic System and EDF-QC-LDPC

A Rao-Nam cryptosystem based on error correction code is proposed to provide both security and reliability. Since its security is drastically constrained by the limited error syndromes, in this paper, an improved Rao-Nam cryptosystem based on fractional order hyperchaotic system and Extended Difference Family-Quasi-Cyclic-Low-Density Parity-Check (EDF-QC-LDPC) codes is proposed to improve the security. A four-dimensional fractional order hyperchaotic system is constructed and is used to generate an excellent pseudorandom sequence. By replacing error syndromes with the pseudorandom sequence and permuting the coded message dynamically, the security of the Rao-Nam cryptosystem is enhanced greatly. The ability of the improved Rao-Nam cryptosystem against known attacks is analyzed and the error correction performance with different parameters is simulated. The results show that the proposed cryptosystem has a significant advantage of resisting the chosen-plaintext attack. Moreover, the proposed cryptosystem retains high capacity of error correction.