Quasi-cyclic subcodes of cyclic codes

On the decoding of quasi-BCH codes

In this paper we investigate the structure of quasi-BCH codes. In the first part of this paper we show that quasi-BCH codes can be derived from Reed-Solomon codes over square matrices extending the known relation about classical BCH and Reed-Solomon codes. This allows us to adapt the Welch-Berlekamp algorithm to quasi-BCH codes. In the second part of this paper we show that quasi-BCH codes can ...

On the Grobner Basis of a Family of Quasi-Cyclic LDPC Codes

Cryptanalysis of Two McEliece Cryptosystems Based on Quasi-Cyclic Codes

We cryptanalyse here two variants of the McEliece cryptosystem based on quasi-cyclic codes. Both aim at reducing the key size by restricting the public and secret generator matrices to be in quasi-cyclic form. The first variant considers subcodes of a primitive BCH code. The aforementioned constraint on the public and secret keys implies to choose very structured permutations. We prove that thi...

Reducing Key Length of the McEliece Cryptosystem

The McEliece cryptosystem is one of the oldest public-key cryptosystem ever designated. It is also the first public-key cryptosystem based on linear error-correcting codes. The main advantage of the McEliece cryptosystem is to have a very fast encryption and decryption functions but suffers from a major drawback. It requires a very large public key which makes it very difficult to use in many p...

A Linear Algebraic Approach to Subfield Subcodes of GRS Codes

The problem of finding subfield subcodes of generalized Reed–Solomon (GRS) codes (i.e., alternant codes) is considered. A pure linear algebraic approach is taken in order to derive message constraints that generalize the well known conjugacy constraints for cyclic GRS codes and their Bose– Chaudhuri–Hocquenghem (BCH) subfield subcodes. It is shown that the presented technique can be used for fi...