# Design Trends and Comparative Analysis of Lightweight Block Ciphers for IoTs
## 4 Related Work
### Feistel Network (FN)
When evaluated on both software and hardware platforms, TED demonstrated significantly reduced CPU cycles and memory footprint compared to other ciphers such as PRESENT while maintaining robust resistance to differential and linear cryptanalysis. The cipher also performed well in terms of security, with strong resistance to structural attacks and high avalanche effects. Additionally, TED's energy efficiency was improved by 14.85% through an area-optimized design, making it ideal for resource-constrained IoTs applications. The TED algorithm has higher computational complexity due to its 26 encryption rounds and increased energy consumption compared to SPECK and SIMON. Its side-channel attack resistance needs further validation, and its complex key scheduling may add processing overhead. The real-time bit permutation calculation reduces memory usage but increases computational cost. Additionally, the bit-sliced S-box implementation may complicate deployment in constrained environments. This paper presents a lightweight design of the SM4 [38] cryptographic algorithm with hardware implementation aimed at improving efficiency in resource-constrained environments. By replacing the original 8-bit S-box with a 4-bit cyclic shift S-box as presented in Figure 30, the design reduces hardware resource consumption while maintaining the cryptographic properties of the SM4 algorithm. A threshold scheme based on secret sharing is also introduced to enhance resistance against side-channel attacks, particularly first-order and second-order differential power analysis (DPA) attacks. The implementation involves transforming operations from GF(2\({}^{4}\)) to GF(2\({}^{2}\)) using a multiplier and square, further reducing circuit consumption. The system is implemented using FPGA and demonstrates a significant reduction in hardware resource usage, achieving a lightweight cryptographic solution with a total of 2803 logic elements while maintaining robust security. Figure 22:1 Single round of TED block cipher. The improved SM4 algorithm has reduced security due to the 4-bit S-box, making it potentially vulnerable. Its resistance to side-channel attacks still needs further validation. The implementation complexity increases due to composite field transformations and secret sharing. It is hardware-optimized, limiting software efficiency, and software performance remains untested. Despite being lightweight, it still requires 2803 logic elements, which may be a constraint for ultra-low-power devices. LWBC the paper proposes M-XXTEA [39], a modified version of the original XXTEA block cipher, designed to enhance the security and performance of lightweight cryptography for IoTs smart devices. M-XXTEA, as evidenced by Figure 31, builds on the unbalanced Feistel structure of XXTEA and introduces two key improvements: an enhanced S-box (based on AES but modified using Fibonacci numbers and prime factors) to strengthen non-linearity and resistance to cryptanalysis, and a chaotic key generator that dynamically changes the encryption key for each block, emulating a one-time pad. The algorithm supports flexible block sizes (multiples of 32 bits, minimum 64 bits) and uses a 128-bit key. Experimental results show that M-XXTEA achieves significantly better encryption and decryption speed compared to AES (by 60% and 57%, respectively), while maintaining strong avalanche properties and passing all NIST statistical randomness tests. Its design is suitable for real-time data protection in IoTs systems, smart cities, and e-health applications. Despite its advantages, M-XXTEA has a few limitations. The increased encryption complexity--due to dynamic key generation and non-linear substitutions--adds slight performance overhead compared to the original XXTEA, particularly for large messages or high key sizes (192 or 256 bits). Its reliance on chaotic key generation also introduces challenges in synchronizing sender and receiver seed values in practical deployments.