On Decoding Schemes for the MDPC-McEliece Cryptosystem

In this paper, classical (iterative) decoding schemes for moderate-density parity-check (MDPC) codes are considered. The algorithms are analyzed with respect to their errorcorrection capability as well as their resilience against a recently proposed reaction-based key-recovery attack on a variant of the MDPC-McEliece cryptosystem by Guo, Johansson and Stankovski (GJS). New message-passing decoding algorithms are presented and analyzed. The proposed decoding algorithms have an improved error-correction performance compared to existing hard-decision decoding schemes and can reduce the effectiveness of the GJS reaction-based attack for an appropriate choice of the algorithm’s parameters