Stream Encryption Cryptographic Systems Based on Asymmetric Cet Operations with an Accuracy of Permutation
Serhii Semenov, Volodymyr Rudnytskyi, Nataliia Lada, Volodymyr Krivtsun, Tymofii Korotkyi, Vitalii Zazhoma, Olga Wasiuta · Applied Sciences · 2026
This paper addresses the problem of constructing adaptive stream encryption transformations based on dynamically generated Boolean mappings. A formal framework for modeling and modifying asymmetric two-operand Conditional Elementary Transformations (CETs) is proposed, where new operations are obtained through permutation-driven modification of operands and transformation results. The main contribution of the study is the development of a method for generating groups of CET-based transformations and corresponding generator models that enable the construction of pseudorandom sequences of dynamically varying substitution rules. The proposed approach ensures preservation of bijectivity and establishes formal relationships between direct and inverse operations under transformation modifications. Experimental evaluation demonstrates that the generated CET-based transformations produce output sequences with entropy close to the theoretical maximum (H ≈ 1) while providing enhanced diffusion properties. In particular, the CET_base configuration achieves an avalanche effect of approximately 0.79 compared to ≈0.5 for the classical XOR baseline. At the same time, permutation-based variants introduce additional structural diversity, enabling flexible trade-offs between diffusion strength and variability of transformation behavior. The obtained results confirm that the proposed framework enables systematic construction of large families of Boolean mappings, including up to 16 and 64 S-box transformations for 2Ci- and 3Ci-quanta operations, respectively, exceeding the capabilities of fixed XOR-based schemes. The proposed approach is intended as a flexible design paradigm for adaptive and lightweight cryptographic systems. However, the current study is limited to structural and statistical analysis, and a formal evaluation of resistance to established cryptanalytic attacks remains a subject of future research.