Cryptanalysis of a public key encryption scheme based on QC-LDPC and QC-MDPC codes
This work identifies a security flaw in a proposed post-quantum cryptosystem, which is incremental as it builds on prior cryptanalysis techniques.
The authors cryptanalyzed a modified McEliece encryption scheme based on QC-LDPC and QC-MDPC codes, showing that an attack can decode ciphertexts with high probability and that weak keys are prevalent, effectively ruling out the scheme's security.
This letter presents a cryptanalysis of the modified McEliece cryptosystem recently proposed by Moufek, Guenda and Gulliver [24]. The system is based on the juxtaposition of quasi-cyclic LDPC and quasi-cyclic MDPC codes. The idea of our attack is to find an alternative permutation matrix together with an equivalent LDPC code which allow the decoding of any cipher-text with a very high probability. We also apply a recent technique to determine weak keys [4] for this scheme. The results show that the probability of weak keys is high enough that this variant can be ruled out as a possible secure encryption scheme.