On the improvement of McEliece cryptosystem based on LDPC codes

In this paper an improvement of the McEliece cryptosystem based on QC-LDPC codes is considered. The key idea of the improvement is to use soft-decision decoding algorithm of LDPC codes in decryption step. This allows to reduce a public- key size in comparison with the McEliece cryptosystem based on QC-LDPC codes decoded by hard-decision bit-flipping decoder. In addition, the analysis of the dependence between key size and security in bits for the proposed cryptosystem was conducted.