Abstract
Dynamic substitution boxes (S-boxes) are a vital building block of many cryptosystems. The general process of the dynamic construction of a bijective S-box consists of two main components: a random number generator, and a construction algorithm. In this paper, we study the effect of the choice of the construction algorithm on various aspects of the dynamic S-box, including its randomness and it cryptographic strength. We identify the different algorithms found in the literature and present a comparative analysis of their computational complexity and effective key space. Moreover, we study the cryptographic characteristics of the resulting S-boxes. We conclude with some guidelines to help cipher designers choose the S-box construction method most suited for their design objectives.