A STUDY OF MARS, RC6 AND SERPENT NEETA WADHWA, SYED ZEESHAN HUSSAIN & S. A. M RIZVI Department of Computer Science, Jamia Millia Islamia, New Delhi, India ABSTRACT After DES [Data Encryption Standard] was cracked, the new symmetric encryption standard hunt was started in 1999 and finished in 2001. The process was comprised of two rounds.This paper presents the study of 3 out of 5 finalists of second round of AES [Advanced Encryption Standard] process: MARS, RC6 and SERPENT. It analyzes the structure and working of these algorithms. It also analyzes the three algorithms on the basis of their encryption and decryption time. KEYWORDS: AES, DES, MARS, RC6, SERPENT, Symmetric Cryptography INTRODUCTION When digital communication systems developed, everyone had been using cryptography in his own ways secretly for their personal use. Due to the two major inventions in the world of digital communication, this art became science. First, The publication of the draft DES in the U.S. Federal Register on 17 March 1975. It started the development of Symmetric Cryptography. Second, The publication of the paper „New Directions in Cryptography‟ by Whitfield Diffie and Martin Hellman in 1976. This key exchange protocol gave birth to the Asymmetric Cryptography. This work focuses only on Symmetric cryptography. DES was criticized because of its small key length and cracked by bruteforce attack in late 90‟s. Then AES process started. First round screened out 15 algorithms and the second round shortlisted 5 algorithms. In final round, the winner, RIJNDAEL, got 86 votes at the third AES conference while SERPENT got 59 votes, TWOFISH got 31 votes, RC6 got 23 votes and MARS got 13 votes. So NIST [National Institute of Standards and Technology] selected Rijndael as the AES. The present study analyzes the following three algorithms. STRUCTURE Mars MARS [1] designed by IBM, it was one of the finalists of AES competition but could not win. Like all AES candidates, it uses 128-bit blocks and supports key sizes of 128, 192 or 256 bits. It uses a variant of the Feistel structure which designers call a "type 3 Feistel network"; it is word oriented cipher, the 128-bit block is treated as four 32-bit sub- blocks or words; each round uses one sub-block as input and modifies all of the other three sub-blocks. It uses data- dependent rotations like RC6. One 9*32 S-box is used; for some operations it is treated as two 8*32 S-boxes. MARS supports user key lengths from 128 bits to 448 bits. The key expansion procedure expands the user-supplied key array k0, …, kn-1, into a 40-word internal key array K0, …, K39. The range of n is from 4 to 4 32 bit words. The key expansion procedure guarantees that the key words which are used for multiplication do not have any obvious weaknesses. This procedure keeps these words “random”, in the sense that no single word has probability much larger than in the uniform distribution. Due to the structure of the key expansion procedure, the performance of MARS is essentially independent of the key-length used. International Journal of Computer Science and Engineering (IJCSE) ISSN 2278-9960 Vol. 2, Issue 3, July 2013, 89-94 © IASET