# Design Trends and Comparative Analysis of Lightweight Block Ciphers for IoTs
###### 1 Introduction  
In recent years, the demand for secure communication in low resource environments has grown significantly due to the rapid expansion of embedded systems and the Internet of Things (IoTs). These systems, which encompass sensors, RFID tags, mobile devices, and wireless sensor networks, often function with limited computational power, memory, and energy resources. Traditional cryptographic algorithms such as AES, while highly secure, are generally inappropriate for these scenarios due to their high resource demands [1].  
To tackle these challenges, lightweight block ciphers (LWBCs) have emerged as a vital area of research and development. LWBCs are designed to meet the stringent requirements of constrained devices by minimizing gate area, power consumption, and computational complexity while ensuring a reasonable level of cryptographic security. These ciphers are used in a variety of applications, including secure data transmission, device authentication, and privacy protection [2].  
The development of LWBCs has been driven by several factors, including the need for scalable security solutions, the limitations of traditional encryption standards in constrained environments, and the increasing threat of cyberattacks on pervasive technologies. Researchers have proposed a wide range of LWBCs, each employing different structural approaches such as Feistel networks, substitution-permutation networks (SPNs), and generalized Feistel networks (GFNs), often incorporating unique optimization techniques for specific environments [3].  
Figure 1 highlights the fundamental challenges in IoTs environments and maps them to corresponding security requirements, many of which are directly addressed through lightweight cryptography. Issues such as limited computational resources, long-term device support, and the integration of diverse technologies underscore the need for cryptographic solutions that are both efficient and robust. Lightweight block ciphers play a vital role in meeting core security requirements such as confidentiality, data integrity, and authentication without overwhelming constrained devices. Their low area, energy, and latency footprints make them ideal for enforcing privacy, securing record updates, and ensuring availability across a wide range of interconnected IoTs systems. By aligning cryptographic design with the outlined requirements, particularly in addressing cyber threats and ensuring secure interoperability, lightweight cryptography serves as a foundational tool for building secure, scalable IoTs ecosystems.  
This survey provides a comprehensive overview of notable LWBCs proposed between 2018 and 2025. We categorize the ciphers by their underlying structural models and evaluate them based on various criteria, including hardware efficiency (measured in Gate Equivalents), cryptographic strength, and adaptability to different platforms. By comparing  
Figure 1: Challenges of IoTs and its security requirements.  
these ciphers, we aim to highlight the design trade-offs involved and provide guidance for selecting suitable cryptographic solutions for diverse constrained environments.  
This paper is organized as follows: Section 2 introduces the structural taxonomy and classification of the 58 lightweight block ciphers based on their internal architecture. Section 3 provides a summary literature review of LWBCs and their drawbacks. Section 4 offers a comparative analysis across all designs, emphasizing trade-offs between performance, cost, and security. Section 5 discusses current trends and observations across cipher types, highlighting practical design choices. Finally, Section 6 outlines key conclusions and identifies future research directions for lightweight cryptographic development.