This study aims to address the limitations of standard cryptographic methods in securing Internet of Things (IoT) devices by introducing a compact, hybrid lightweight encryption scheme. Focusing on symmetric-key algorithms, it combines a bit permutation approach with the PRESENT cipher, which uses a substitution-permutation network (SPN). To overcome the lack of confusion in bit permutation methods, a novel instruction was added to enhance security. The scheme was tested on ARM, MSP and AVR microcontrollers, showing improved compactness and an enhanced avalanche effect. Overall, it offers a more efficient and secure encryption solution for resource-constrained IoT environments.
The proposed hybrid lightweight encryption design combines the PRESENT cipher’s S-box with new bit permutation instructions that include the confusion property, missing in previous designs. These instructions replace the original P-layer, enabling faster and more compact 64-bit permutations using only 4 lines of code instead of 23, resulting in a more efficient and memory-saving encryption scheme suitable for IoT devices.
The proposed E-PRESENT cipher outperformed the original PRESENT and PRESENT-GRP across all evaluated IoT platforms. In scenario 0, it showed superior performance by balancing code size, RAM usage and execution time equally. Scenario 1 highlighted platform-specific differences, where E-PRESENT maintained the fastest execution time and most efficient memory use, even on constrained 8-bit devices, underlining the importance of RAM in performance. Scenario 2 confirmed E-PRESENT’s top ranking across all platforms. Overall, the results demonstrate that E-PRESENT is the most efficient and compact among the compared designs, making it a strong candidate for use in resource-limited IoT environments.
The originality of this work lies in the integration of confusion-enhanced bit permutation instructions into a lightweight symmetric encryption scheme. Unlike existing designs, the proposed E-PRESENT cipher replaces the standard P-layer of the PRESENT cipher with novel bit-level operations that are both compact and efficient. This approach not only reduces memory and computational requirements but also strengthens security through improved confusion properties. The design offers a unique balance between performance and cryptographic strength, making it highly suitable for constrained IoT environments. Its innovative structure demonstrates clear value for future lightweight cryptographic implementations.
