# An optimized novel lightweight block cipher for image encryption

## TL;DR

This paper introduces a new lightweight block cipher designed for secure and efficient image encryption in resource-limited environments.

## Contribution

A novel lightweight block cipher with a multi-stage ARX structure optimized for image encryption and efficient implementation.

## Key findings

- The cipher achieves a 50% average avalanche effect and strong resistance to differential and linear cryptanalysis.
- It passes NIST statistical tests and demonstrates robustness in securing various input images.
- FPGA implementation confirms its suitability for resource-constrained environments.

## Abstract

In the era of pervasive multimedia communication, image data has become a dominant form of information exchange across embedded, mobile, and IoT platforms. This surge in visual data transmission introduces critical challenges related to confidentiality, authenticity, and tamper resistance particularly in resource-constrained environments where conventional cryptographic solutions may prove computationally intensive. To address these challenges, lightweight cryptographic algorithms tailored for image protection are essential, balancing rigorous security requirements with efficient hardware and software implementation. This paper proposes a novel lightweight block cipher optimized for image encryption, employing a multi-stage internal Addition-Rotation-XOR (ARX) structure within each round to enhance confusion and diffusion. The cipher operates on 64-bit plaintext blocks with a 64-bit master key and utilizes a customized key schedule mechanism that generates five distinct subkeys per round through bit-swapping, modular addition, and XOR operations. The cryptographic properties of the proposed cipher were evaluated using the NIST SP 800-22 statistical test suite, confirming high key randomness. Further analysis demonstrated robust security with a 50% average avalanche effect, a maximum differential probability of approximately \documentclass[12pt]{minimal}
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\begin{document}$$\lesssim 2^{-32}$$\end{document}, and a maximum linear bias below \documentclass[12pt]{minimal}
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\begin{document}$$\lesssim 2^{-8}$$\end{document}. The cipher achieves strong resistance to differential and linear cryptanalysis within five rounds, offering an optimal balance between security and efficiency. Comprehensive statistical analysis using various input images are analyzed and demonstrate the cipher’s robustness in securing visual data. The encryption algorithm was further implemented on an Artix-7 FPGA, and synthesis results confirmed its suitability for resource constrained environments. The results indicate that the proposed cipher offers a secure and efficient solution to modern image security challenges.