This paper examines the generation of key-dependent S-boxes using sponge functions. In this study, we render 8-bit key-dependent S-boxes employing a novel approach that contrasts previous techniques using a mixing strategy. We test the efficiency and security of the resultant S-boxes by performing a sequence of experiments. We consider the integration of the keyed S-boxes into a symmetric cipher and determine the probability of differential cryptanalysis. We found that the maximum differential distribution is approximately 12/256 or ≈ 2–6, with a mean of roughly 11/256 and a standard deviation of 1.2/256. Our review of other methods concludes that they have the same maximum differential distribution, while our generation method is significantly faster. We conclude by characterising future research on keyed S-boxes in a white-box context.