Oblivious S-functions and Their Security against Rotational Cryptanalysis

This paper considers a specific class of ARX primitives: oblivious S-functions, which are distinguished by their computational states being independent of each other. We present generic analytical expressions for the rotation probabilities of oblivious S-functions, which characterize security against rotational cryptanalysis. We also examile particular classes of oblivious S-functions, including generalized NORX-like mappings and LRX-analogues for multiplication by three. For these mappings, we provide numerical values of the rotation probabilities.