A Feistel-based modification of the PRESENT lightweight block cipher

The PRESENT block cipher is commonly used in constrained devices, such as IoT nodes, low-power wireless sensors, and RFID tags, due to its low power consumption, small hardware footprint, and acceptable security margin. However, PRESENT’s substitution layer depends on a fixed S-box, which can reduce resistance against specific analytical attacks (linear and differential analysis). In the proposed version, the static S-box is replaced with a dynamic, key-dependent S-box created by rounds of a lightweight Feistel network. The modified variant eliminates repetitive patterns in the substitution layer. In this study, we evaluate the security strength of the proposed method using differential analysis, linear analysis, avalanche rate, algebraic interpolation attacks, and integral/square attacks. Additionally, we measure the time and hardware complexity. The results demonstrate that the introduced version achieves an average avalanche value of 30.92 flipped bits with a standard deviation of 4.7, indicating strong diffusion with increased variability compared to PRESENT, while maintaining moderate computational and hardware complexity. The improved security of the introduced scheme is attained at the expense of a modest increase in hardware area, consistent with current lightweight cipher design trade-offs.