AxLEA: Approximate ARX-based Lightweight Encryption Algorithm for Resource Constrained Devices

Our daily lives are increasingly dependent on small, resource-limited devices that often handle sensitive information, emphasizing the need for robust security measures. However, many lightweight cryptographic algorithms compromise speed and efficiency to conserve resources. To overcome this challenge, we introduce the AxLEA cryptosystem, the first to apply approximation techniques to a reversible cryptographic system. AxLEA improves computational efficiency by mitigating carry propagation overhead through approximation. We design an invertible 32-bit approximate adder and integrate it into the round function and round key generation process. This integration reduces delay by 80% and decreases area and power consumption by 9% in rolled implementations, while unrolled implementations achieve overall 50% performance improvement. Also, the proposed design achieves a 5 × reduction in energy consumption in both rolled and unrolled implementations, demonstrating improved efficiency over LEA across different architectural configurations. AxLEA meets critical security requirements, satisfying the avalanche effect and randomness tests specified by the NIST and ENT test suites. Additionally, it demonstrates strong resistance to linear and differential cryptanalysis. These results make AxLEA an efficient and secure solution for highly resource-constrained devices.