摘要: In this chapter, the use of QC-LDPC codes in public key cryptosystems inspired to McEliece and Niederreiter systems is studied. Both case which private code are permutation equivalent that such an equivalence absent considered. It shown kind may expose system new attacks, can be very dangerous if not suitably designed. The countermeasures used against these attacks described, some practical instances code-based achieving specific security levels provided. chance also digital signature schemes symmetric briefly discussed.