Mostafa Belkasmi

Said Nouh, Mostafa Belkasmi

In this paper we present a new method for finding the weight enumerator of binary linear block codes by using genetic algorithms. This method consists in finding the binary weight enumerator of the code and its dual and to create from the famous MacWilliams identity a linear system (S) of integer variables for which we add all known information obtained from the structure of the code. The knowledge of some subgroups of the automorphism group, under which the code remains invariant, permits to give powerful restrictions on the solutions of (S) and to approximate the weight enumerator. By applying this method and by using the stability of the Extended Quadratic Residue codes (ERQ) by the Projective Special Linear group PSL2, we find a list of all possible values of the weight enumerators for the two ERQ codes of lengths 192 and 200. We also made a good approximation of the true value for these two enumerators.

Rkia Aouinatou, Mostafa Belkasmi

Because of the revolution and the success of the technique IBE (Identification Based Encryption) in the recent years. The need is growing to have a standardization to this technology to streamline communication based on it. But this requires a thorough study to extract the strength and weakness of the most recognized cryptosystems. Our first goal in this work is to approach to this standardization, by applying a study which permit to extract the best cryptosystems. As we will see in this work and as Boneh and Boyen said in 2011 (Journal of Cryptology) the BB1 and BB2 are the most efficient schemes in the model selective ID and without random oracle (they are the only schemes traced in this model). This is right as those schemes are secure (under this model), efficient and useful for some applications. Our second goal behind this work is to make an approvement in BB2 to admit a more efficient schemes. We will study the security of our schemes, which is basing on an efficient strong Diffie-Hellman problem compared to BB1 and BB2. More than that our HIBE support s+ID-HIBE compared to BBG (Boneh Boyen Goh). Additionally the ID in our scheme will be in Zp instead of Zp* as with BBG. We will cite more clearly all these statements in in this article.