Аннотация
This paper investigates the diffusion properties of lightweight encryption algorithms designed for deployment in resource-constrained systems. Modern schemes intended for environments with strict limitations on computational complexity and energy consumption are evaluated. Particular attention is paid to the analysis of isolated round functions ‒ particularly their behavior prior to the application of round keys. This approach enables the assessment of internal structural properties independently of the key scheduling procedures and identifies basic diffusion characteristics determined exclusively by the employed bitwise transformations. Specifically, the impact of flipping a single bit in the input block on the distribution of changes in the output data is analyzed, facilitating an evaluation of the quality of internal transformations and their resistance to cryptanalytic attacks. For quantitative evaluation, classical measures of avalanche behavior – the Avalanche Effect and the Strict Avalanche Criterion (SAC) – are used to assess how rapidly and uniformly information propagates within a block after the application of round transformations. All algorithms are evaluated using a unified round-by-round experimental procedure under identical conditions. This ensures a consistent and objective comparison of their diffusion characteristics across successive encryption rounds. The results reveal distinct advantages and limitations in diffusion speed, stabilization behavior, and uniformity among the evaluated lightweight cipher constructions. The comparison shows that schemes based on cyclic rotations and bitwise operations exhibit high diffusion rates with minimal computational complexity. This analysis demonstrates the effectiveness of approaches relying on simple bitwise transformations. The obtained results provide valuable practical design insights for the selection or design of lightweight cryptographic primitives for microcontrollers, sensor networks, and other devices with limited computational capabilities.