In the same year, Rotor-based Humming Bird was proposed by Revere Security. However, these algorithms have been revealed to be vulnerable to chosen-IV attacks and chosen message attacks. Two years later, HummingBird2 [5], an improved version of HummingBird, was proposed. In 2011, Guo et al. [6] proposed a lightweight cipher LED, with a structure similar to AES, but it does not perform key scheduling.Both lightweight block ciphers and methods to optimize legacy block ciphers have been studied. Moradi et al. [7] optimized AES and reduced the gate count to 2,400 GE (gate equivalent). Poschmann et al. [8] implemented DES with 1,848 GE.Recently, the Electronics and Telecommunications Research Institute in Korea announced a new lightweight block cipher called LEA [9].

The focus of LEA design is a ��software-oriented lightweightness�� for resource-constrained small devices. It is intended to have a small code size and consume low power. Therefore, it is extremely efficient when it is implemented in software. LEA has three key sizes of 128, 192, or 256 bits and a 128-bit block size. Every inner operation of the LEA is 32 bits wide, since 32-bit microprocessors are more popular than 8-bit ones these days. Further, it does not employ a complex operation such as S-Box, and only uses simple operations such as addition, rotation, and XOR (ARX).Usually, small chip size and reasonably fast encryption is preferred for cryptographic hardware for small devices in resource constrained environments such as RFID tags or smart meters for smart grids.

In this paper, we propose several Batimastat methods to optimize LEA hardware for all key sizes and present implementation results in terms of time and chip area cost. This work is the first that studies a comprehensive hardware implementation of LEA. LEA was originally designed for software implementation, but we aim to demonstrate that it is also efficient when implemented in hardware.The rest of this paper is organized as follows: We introduce the LEA algorithm in Section 2, and then present elemental techniques for implementing LEA in hardware in Section 3. Section 4 presents hardware structures for the 128, 192, and 256 key version of LEA, and corresponding implementation results are presented in Section 5. We conclude this paper in Section 6.2.?LEA AlgorithmIn this section, we introduce the LEA block cipher.

LEA has 128 bit long message blocks and 128, 192, or 256 bit long keys. We denote each version of this algorithm as LEA-128, LEA-196, and LEA-256 according to key length.2.1. NotationsWe present notations and corresponding descriptions required to explain the LEA algorithm in Table 1.Table 1.Notations used to explain LEA algorithm.2.2. Key Schedule2.2.1. Constants4, 6, and 8 constant values that are 32 bits long are used for each version of the LEA key schedule.