Two Countermeasures against Reaction Attacks on LEDApkc and other QC-MDPC and QC-LDPC based McEliece Cryptosystems in ARQ Setting Heuristic Discussion

two new countermeasures against reaction attacks on LEDApkc and other similar McEliece cryptosystems using quasi-cyclic low-density parity-check codes and quasi-cyclic moderate density parity-check codes in automatic repeat request setting are presented in this manuscript. In this scenario it is supposed that the attacks are enabled for Eve by gaining information from Bob's decryption failures via negative acknowledgements on the feedback channel used in the automatic repeat request transmission technique. The two countermeasures proposed in this manuscript are trying to make this information needed for the attacks useless or completely unavailable. In the first one this information is camouflaged by stochastically generated negative acknowledgements, which are sent in the feedback channel. In the second, an outer fountain code makes the feedback channel redundant.