Journal of Advanced Computer Science and Technology Research Vol.2 No.4, November 2012, 159-165 Lightweight Block Ciphers: a Comparative Study Sufyan Salim Mahmood AlDabbagh 1,a , Imad Al Shaikhli 2,b 1 Department of information systems, International Islamic University of Malaysia, Malaysia 2 Department of Computer, International Islamic University of Malaysia, Malaysia a sufyansalim_77@yahoo.com, b imadf@iium.edu.my Article Info Received: 7 th July 2012 Accepted: 3 rd September 2012 Published online: 15 th November 2012 ISSN: 2231-8275 © 2012 Design for Scientific Renaissance All rights reserved ABSTRACT Although the AES is an excellent and preferred choice for almost all block cipher applications, it is not suitable for extremely constrained environments such as RFID (Radio-Frequency IDentification) tags and sensor networks. Therefore lightweight cryptography has become very vital and a strong demand. This paper meant to be a reference (for the cryptographic designers) on the lightweight block ciphers. It starts by doing a survey to collect the latest proposed ciphers, then to study them in terms of their algorithms specifications, hardware implementation and attacks. Finally, after the explanation and comparison, this research can be the basement for starting point to improve the lightweight block cipher in many directions like number of clock cycle, size of memory, number of Chosen Plaintext, Gate equivalence ( GE), throughput and attacks. Keyword: Lightweight block ciphers, RFID, RFID tag and AES 1. Introduction The pervasive computing like smart cards, RFID tags and sensor nodes that are used for public transport, smart electricity meters and anti-counterfeiting is become the main point for wireless communication and embedded systems. So, the choice of security algorithms of resource-limited devices should be very careful by consideration of the implementation costs, amount of power and Symmetric-key algorithms especially block ciphers still play an important role for the security of the embedded systems. For security and performance concerns, typically sensors are equipped with hardware implementation of AES-128. But for resource-constrained devices, AES could be too expensive despite the various approaches that have been proposed to reduce the costs of AES hardware and software implementations. So a compact hardware and software efficient block cipher could be the most promising candidate for security in such those devices. Therefore we introduce new branch of cryptography called lightweight cryptography. The main idea of lightweight cryptography is finding a compromise between low resource requirements, performance and strength of cryptographic primitives. In this paper, we present a selection of recently published