McEliece cryptosystem

Abstract: We describe a probabilistic algorithm, which can be used to discover words of small weight in a linear binary code. The work-factor of the algorithm is asymptotically quite large but the method can be applied for codes of a medium size. Typical instances that are investigated are codewords of weight 20 in a code of length 300 and dimension 150.

Abstract: It is shown that the problem of computing the minimum distance of a binary linear code is NP-hard, and the corresponding decision problem is NP-complete. This result constitutes a proof of the conjecture of Berlekamp, McEliece, and van Tilborg (1978). Extensions and applications of this result to other problems in coding theory are discussed.

Abstract: In this work, we propose two McEliece variants: one from Moderate Density Parity-Check (MDPC) codes and another from quasi-cyclic MDPC codes. MDPC codes are LDPC codes of higher density (and worse error-correction capability) than what is usually adopted for telecommunication applications. However, in cryptography we are not necessarily interested in correcting many errors, but only a number which ensures an adequate security level. By this approach, we reduce under certain hypotheses the security of the scheme to the well studied decoding problem. Furthermore, the quasi-cyclic variant provides extremely compact-keys (for 80-bits of security, public-keys have only 4801 bits).

Abstract: An algorithm for finding minimum-weight words in large linear codes is developed. It improves all previous attacks on the public-key cryptosystems based on codes and it notably points out some weaknesses in McEliece's (1978) cipher. We also determine with it the minimum distance of some BCH codes of length 511.