Image encryption algorithms using non-chaotic substitutions and permutations

This paper presents substitution and/or permutation symmetric-key encryption algorithms based on non-chaotic generators. While the substitution algorithm is based on fractals with delay and multiplexer elements, permutations are achieved via a chess-based algorithm. A comparison of four different cases; substitution-only, permutation-only, substitution-permutation and permutation-substitution; is introduced taking into consideration their encryption analysis results and sensitivity. Three different standard images; Lena, pepper and airplane; are tested for each algorithm to validate the comparisons. Moreover, a comparison between the encryption key for each algorithm is presented. Each algorithm is evaluated using standard analyses such as histogram distributions, correlation coefficients between pixels, differential attack measures, Mean Square Error (MSE), entropy, sensitivity analyses and the 15 statistical tests of the National Institute of Standards and Technology (NIST) SP-800-22 test suite.