Image encryption and distribution method based on LFSR and counters

In the conditions of processing large amounts of graphic data, the task arises of developing a reliable image encryption scheme with reduced computing costs. The purpose of the study was to develop a deterministic scheme for encrypting and evenly distributing vectorised images using a shift register with linear feedback and counters. Methods of research included converting a pixel matrix to a sequence of bytes using a row-wise traversal rule, splitting the index space into equal subranges, generating pseudo-random indexes based on shift register states, and using reversible counters. The results of statistical testing demonstrate the stable characteristics of the proposed image encryption method. Encrypted test images were also evaluated for attack resistance by determining correlation coefficients between the incoming image and the encrypted one. In particular, for coloured images with a size of 512 × 512, when divided into eight subranges, the number of pixel change rate reached 99.61%, and the unified average intensity of pixel change was 32.28%, which corresponds to the upper cluster of estimates of advanced methods. The entropy of encrypted data was close to the theoretical maximum of 7.999, and the correlation between neighbouring pixels was significantly reduced and approaches zero values. Image distribution and restoration was performed without errors. The algorithm was characterised by low computational costs. The practical significance of the study consisted in ensuring reproducibility of the distribution and high cryptographic stability using mathematically simple operations, pseudo-randomness, and expanding the image encryption space to the full volume, making the proposed approach suitable for systems requiring accurate recovery and operating under limited computational resources