Information security has become a major issue during the last decades where new algorithms based on algebraic methods or chaotic dynamics were suggested for encryption. This paper presents an algorithm for encoding binary images using one-dimensional chaotic maps. In order to perform pixel value permutation, the approach presented uses the diffusion property of chaotic maps, where local information is spread out. Comparison in terms of the correlation between the initial image and the transformed images is provided for different degrees of chaocity which corresponds to different values of positive Lyapunov exponent. Since images present a special kind of data where the size may be much larger than text data, an algorithm is suggested that emphasizes fast calculation in order to be implemented in real time for binary images encryption.