A compact 128/192/256-bits symmetric cryptography hardware module Ot´avio de Souza Martins Gomes a1 , Robson Luiz Moreno b2 a Instituto Federal de Minas Gerais, Formiga, MG, Brazil b Universidade Federal de Itajub´ a, MG, Brazil Abstract This article describes the implementation of Twofish - one of the Advanced Encryption Standard (AES) finalists, in Field Programmable Gate Array - FPGA. The core was implemented in Altera Quartus Cyclone board. The code is totally portable and can be used in any FPGA. The algorithm was implemented for 128-bit word and 128, 192 and 256-bit keys. The main goal of this work was the implementation of an efficient, compact and modular Twofish hardware module that can find a wide range of applications as an alternative from AES-Rijndael. Keywords: Cryptography, Twofish, AES, FPGA, Communication. I. Introduction In 1997, the NIST (National Institute of Standards and Technology) released a contest to choose a new symmetric cryptograph algorithm that would be called Advanced Encryption Standard (AES) to be used to protect confidential data in the USA. The algorithm should meet few requirements such as copyright free, faster than the 3DES, cryptograph of 128 bit blocks using 128, 192 and 256 bit keys, possibility of hardware and software im- plementation, among others. The three finalists were Rijndael, Twofish and Serpent. Each one has its own design features to achieve the require- ments. In 2000, after analysis by cryptography experts, Rijndael was the winner[1][2]. With the advance of technology and the increment of hardware utilization for cryptography interfaces, it is interesting to analyze Twofish implementation in comparison with the winner, Rijndael. Some researchers are re-evaluating the characteristics of the finalists to achieve the best algo- rithm for their applications [3][4][5][6]. This work was implemented in FPGA due to its flexibility and reconfiguration capability [7]. A reconfigurable de- vice is very convenient for a cryptography algorithm since it allows cheap and quick alterations. Section II provides a brief introduction of Twofish 1 otavio.gomes@ifmg.edu.br 2 moreno@unifei.edu.br