Linear Approximations Representation of Moamagar Block Cipher

The security of block ciphers is assessed through their resistance to known attacks. One of the most important attacks is linear cryptanalysis. In this paper, we describe a model for presenting linear approximations for Moamagar block cipher. This graph shows the whole space of linear approximations for the block cipher algorithm is presented through its obtained multi-level weighted directed graph, such that the problem of searching for the best linear characteristic is equivalent to searching for the minimum weight path in the directed graph. We first show how to present linear approximations for different components used in this block cipher through graphs. Then we present split and merge graphs which are used to define the sequential and parallel combination operations. These operations join the obtained graphs of components to construct the graph for one round of the cipher. At last the graph for the cipher with both SPN and DES-like structure will be obtained. At the end, we use the ant colony optimization to search for efficient linear characteristics of Moamagar block cipher and we show the obtained results.