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(IJCSIS) International Journal of Computer Science and Information Security, Vol. 8, No. 6, September 2010 A Performance Study on AES Algorithms B.D.C.N.Prasad1 P E S N Krishna Prasad2 Dept. of Computer Applications, Dept. of Computer Science & Engineering P V P Siddardha Institute of Technology Aditya Engineering College Vijayawada, India Kakinada, India bdcnprasad@gmail.com surya125@gmail.com P Sita Rama Murty3 K Madhavi4 Dept. of Computer Science & Engineering Dept. of CSE Sri Sai Aditya Institute of Science & Technology Dadi Institute of Technology Kakinada, India Anakapalli, India psramam@yahoo.co.in kolukulurimadhavi@yahoo.co.in Abstract— The Aim of this project is to find the performance Cryptography, over the ages, has been practiced by many comparative analysis of AES algorithms such as MARS, RC6, who have devised ad-hoc techniques to meet some of the Rijndael, Serpent, Twofish algorithms in terms of speed, information security requirements. The last twenty years memory, time, encryption and decryption, key setup time, have been period of transition as the discipline to a broader number of rounds, key sizes and also hardware considerations. area. There are now several international scientific Most of the AES algorithms, especially symmetric block conferences denoted exclusively to cryptography and also ciphers, are based on the principle of substitution and and International Association for Crypto-logic Research transposition to encrypt a plain-text message and to produce a (IACR), aimed at fostering research in the area. cipher-message. Those transformations are based on well- understood Mathematical problems using non-linear functions There are two general types of cryptographic algorithms. and linear modular algebra. 1. Symmetric algorithms. Implementation of cryptographic algorithms mainly uses bit- 2. Asymmetric algorithms. level operations and table look-ups. Bit-wise operators (XORs, AND/OR, etc.), substitutions, logical shifts and permutations The current Digital Encryption Standard (DES) does no are quite common operations. Such operations are well suited longer satisfy the need for data security because of its short for their fast execution in hardware platforms. Furthermore, 56-bit key. Such short keys can today be broken by brute currently abundant memory resources in hardware platforms force attacks. We are looking for newer and more flexible enhance encryption speed for the operations like substitution. algorithms to replace DES. Some of the candidates for the These operators play an important role in analysis and Advanced Encryption Standard (AES) are MARS encryption comparison of the performance of the above mentioned AES algorithm, RC6, Serpent, Rijndael, and Twofish. These are algorithms, to evaluate simple, effective and efficient outcomes symmetric key block ciphers use 128 bit blocks and supports and also the information might be more secure. variable key sizes (from 128 to 1248 bits). These use addition and subtractions, S-boxes, fixed and data dependent Keywords-AES algorithms; Mars; RC6; Rijndeal; Sarpent; Two fish; rotations, and multiplications. The final AES selection was made on the basis of several additional characteristics: I. INTRODUCTION Security is a broad topic and covers a multitude of sins, computational efficiency and memory in its simplest form. It is concerned with making sure that requirements on a variety of software and nosy people cannot read, or worse yet, modify message hardware, including smart cards intended for other recipients. It is concerned with people flexibility, simplicity and ease of trying to access remote services that they are not authorized implementation to use. Security also deals with people trying to deny that they sent certain message. The existing system consisted of files with literally no file security standards like AES algorithms such as MARS, Network security problems can be divided roughly into RC6, Rijndael, Serpent, and Twofish. AES algorithms are four intertwined areas: symmetric cipher algorithms which are far better than DES Confidentiality, algorithms, since DES algorithms are limited key size with fixed number of blocks. So, we have chosen for finding the Authentication and Integrity control comparison of AES algorithms to provide the security for Data as well as networks and files. AES algorithms are to be Denial of service 128 http://sites.google.com/site/ijcsis/ ISSN 1947-5500 (IJCSIS) International Journal of Computer Science and Information Security, Vol. 8, No. 6, September 2010 implemented due to the following factors against which CBC mode within ESP. This mode requires an Initialization several security measures had to be taken up: Vector (IV) that is the same size as the block size. Use of a randomly generated IV prevents generation of identical 1. Reading data cipher text from packets which have identical data that spans 2. Manipulating and modifying data the first block of the cipher algorithm's block size. 3. Illegal use of files The IV is XOR'd with the first plaintext block before it is encrypted. Then for successive blocks, the previous cipher 4. Corrosion of data files text block is XOR'd with the current plaintext, before it is 5. Distortion of data transmission encrypted. For the use of CBC mode in ESP with 64-bit ciphers. The main issue of (1) is secrecy and confidentiality. Confidentiality has always played an important role in 2) Key Size diplomatic and military matters. Often Information must Some cipher algorithms allow for variable sized keys, store or transferred from one place to another without being while others only allow specific, pre-defined key sizes. The exposed to an opponent or enemy. Key management is also length of the key typically correlates with the strength of the related to Confidentiality. This deals with generating, algorithm; thus larger keys are usually harder to break than distributing and storing keys. Items (2-4) are primarily shorter ones. This article stipulates that all key sizes MUST concerned with reliability. Often the expression integrity is be a multiple of 8 bits. used as a measure of genuineness of data. Also computer The default key size that implementations MUST support files and networks must be protected against intruders and 128 bits. In addition, all of the ciphers accept key sizes of Unauthorized. Item 5 is different aspect of the security of the 192 and 256 bits. information. A. AES Algorithms TABLE II. KEY SIZES AES algorithms are symmetric cipher algorithms Algorithm Key Sizes(bits) Default with variable key sizes and blocks, also with number of MARS 128 – 448* 128 rounds to encrypt and decrypt the data than DES algorithms. RC6 Variable up to 2040 128 Rijndael 128,192,256 128 There are numerous algorithms in AES. From them we have Serpent Variable up to 256** 128 chosen the following algorithms for finding the performance Two fish Variable up to 256*** 128 analysis on time, memory, key sizes, key setup time, encryption, and decryption and so on. MARS key lengths must be multiples of 32 bits. The Chosen algorithms are as: ** Serpent keys are always padded to 256 bits. The MARS encryption algorithm padding consists of a "1" bit followed by "0" bits. RC6 Algorithm *** Twofish keys, other than the default sizes, are always Rijndael Algorithm padded with "0" bits up to the next default size. Serpent Algorithm 3) Weak Keys Some cipher algorithms have weak keys or keys that Twofish Algorithm MUST not be used due to their interaction with some aspect of the cipher's definition. If weak keys are discovered for the TABLE I. GENERAL STRUCTURE AES or any of the other finalists, then weak keys SHOULD be checked for and discarded when using manual key Cipher Type Rounds Using management. When using dynamic key management, weak MARS Extended 32 Variable Rotation, key checks SHOULD NOT be performed as they are seen as Feistel Multiplication Non Cryptic Rounds an unnecessary added code complexity that could weaken the RC6 Feistel 20 Variable Rotation, intended security. Multiplication Rijndael Square 10,12,14 4) Block Size and Padding Serpent SP Network 32 Bitslice All of the algorithms described in this document use a Twofish Feistel 16 block size of sixteen octets (128 bits), mandatory for the AES. Some of the algorithms can handle larger block sizes as well. Padding is required by the algorithms to maintain a 1) Mode 16-octet (128-bit) blocksize. Padding MUST be added, such No operational modes are currently defined for the that the data to be encrypted has a length that is a multiple of AES cipher. The Cipher Block Chaining (CBC) mode is 16 octets. Because of the algorithm specific padding well-defined and well-understood for symmetric ciphers, and requirement, no additional padding is required to ensure that is currently required for all other ESP ciphers. This article the cipher text terminates on a 4-octet boundary (i.e. specifies the use of the AES cipher and the other finalists in maintaining a 16-octet blocksize guarantees that the ESP Pad 129 http://sites.google.com/site/ijcsis/ ISSN 1947-5500 (IJCSIS) International Journal of Computer Science and Information Security, Vol. 8, No. 6, September 2010 Length and Next Header fields will be right aligned within a 1) RC6 4-octet word RC6 is the submission of MIT (Massachusetts Institute of Technology) and the RSA-Laboratories. Similar to MARS it 5) Rounds splits the 128 bit blocks into four words in the algorithm, but This variable determines how many times a block is the algorithm is designed in a way that you can easily change encrypted. While this variable MAY be negotiated, a default to two 64 bit words in newer architectures. RC6 is also a value MUST always exist when it is not negotiated. Feistel network. It uses the same type of operations except Algorithm Negotiable Default of Rounds from look-up tables and fixed rotations. The algorithm is MARS yes 32 more flexible than MARS about blocksize and number of RC6 yes 20 rounds. The AES submission is optimized for 128 bit blocks Rijndael yes 10,12,14 and 20 rounds. Several performance test showed that RC6 is Serpent yes 32 Twofish yes 16 slower than MARS for encryption and for the key setup. But it uses less memory because there are no look-up tables. B. MARS Algorithm 2) Rijndael MARS is a shared-key block cipher that works with Rijndael is the submission of the Belgium Proton World a block size of 128 bit and a variable key size. The algorithm Int. and the Katholieke Universities Leuven, Belgium. This is a type-3 Feistel network which is word (32 bit) oriented. algorithm is quite different from MARS. It works with The word orientation should bring a performance for Galois Field GF(128) arithmetic and handles the input blocks software implementations on most computer architectures as matrices of bytes. They define several operations to these available today. A fully optimized implementation is matrices as ByteSub, ShiftRow, MixColumn and expected to run at 100Mbit/second and hardware can achieve AddRoundKey. For detailed information about these an additional 10x speedup factor. operations consult [Rijndael99]. Several combinations of 1) Operations these operations define a round. Depending on the key length MARS algorithm uses a big variety of different which is in the range from 128 to 256 bits a fixed number of operations: rounds has to be executed. This cipher is not a Feistel network. Several performance tests showed that Rijndael is Additions, subtractions and xors: These simple about the same speed in encryption and decryption as operations are used to mix data and key values together. MARS. But the key expansion for keys of the same length is Because xors are interleaved with additions and subtractions significant slower. these operations do not commute with each other. 3) Serpent Table look-up: Similar to the S-boxes in DES has also Serpent is a submission from three universities MARS cipher a table look-up. It uses a single table of 512 (Cambridge University, England; Technion, Haifa, Israel; 32-bit words, simple called S-box. A problem of the table University of Bergen, Norway). Therefore it's the only look-up is the slow software implementation (at least 3 algorithm where no company stands behind. The algorithm is instructions per look-up). That's why S-box look-up is only pretty similar to DES, it uses permutations, xors, fixed used sparely in MARS where fast avalanche of the key bits is rotations and shifts and constant table look-up's. The first needed. version of the algorithm even used the same S-boxes as DES. Fixed rotations: Data-dependent rotations: Data The key can vary from 128 to 256 bit. The algorithm works dependent rotations may lead to differential weaknesses. internally also with 4 words as RC6 and MARS. This problem is solved in MARS by combining these Performance tests that the encryption of Serpent is about rotations with multiplications. 25% faster than the MARS encryption. But the key expansion is significant slower. An implementation of Multiplications: All multiplications in MARS are modulo Serpent also uses a lot of memory because of the look-up 232 which suits most modern computer architectures. tables. Multiplications used to be a problem in cryptographic algorithms because they were slow. Today is this no longer 4) Twofish the case. Most architecture can complete a multiplication in 2 Twofish is the submission from a company called clock cycles. MARS algorithms uses 16 multiplications per Counterpane. It is a 16 round Feistel cipher that works with block. This should not be a big deal. For hardware key dependent 8x8 bit look-up tables, 4 by 4 matrices over realizations we have the problem that a multiplicator needs the Galois field GF(128), a pseudo-Hadamard transform, much more chip-space than adders or logical units. permutations and rotations. The detailed description of these functions can be found in [Twofish]. The key length varies C. Comparison with other AES Candidates also from 128 bit to 256 bit as in most other AES candidates. Performance tests showed that the encryption speed of There are 4 other candidates for AES in the last Twofish is about the same as for MARS, but the Twofish key round. So they are all 128 bit block ciphers with variable key setup is significant faster. length from 128 bit to at least 192 bit. All designs claim to be secure against all known attacks like differential, linear, known plaintext or cipher text and other attacks. 130 http://sites.google.com/site/ijcsis/ ISSN 1947-5500 (IJCSIS) International Journal of Computer Science and Information Security, Vol. 8, No. 6, September 2010 D. Performance Analysis Initialization The performance analysis can be done with various 35 measures such as speed comparison with encryption and 30 decryption cycles, key setup and key initialization, analysis 25 of various key sizes and fair speed/security comparisons. The 20 performance analysis will be presented in the form of tables c Initialization and figures below. 15 10 1) Speed Comparisons 5 0 MARS RC6 Rijndael Serpent TwoFish TABLE III. SPEED Key Setup Figure 3. Key Initialization Encrypt Decrypt Cipher (Cycles) (Cycles) Encrypt Decrypt Init 2) Analysis on various Key Sizes MARS 1600 1580 4780 5548 18 a) Encryption RC6 1436 1406 5186 5148 30 TABLE IV. ENCRYPTION Rijndael 1276 1276 17742 18886 28 Serpent 1800 2102 13154 12648 14 Algorithm Encry128 Encry192 Encry256 TwoFish 1254 1162 18846 18634 20 MARS 3738 3707 3733 RC6 4698 4740 4733 2500 Rijndael 4855 4664 4481 2000 Serpent 1843 1855 1861 1500 Encryption(Cycles) Twofish 1749 1749 1744 Decryption(Cycles) 1000 b) Decryption 500 TABLE V. DECRYPTION 0 MARS RC6 Rijndael Serpent TwoFish Algorithm Encry128 encry192 encry256 Figure 1. Graph for Encryption and Decryption (Cycles) MARS 3965 3965 3936 20000 RC6 4733 4698 4740 18000 16000 Rijndael 4819 4624 4444 14000 12000 Serpent 1873 1897 1896 Encryption 10000 Decryption 8000 Twofish 1781 1775 1761 6000 4000 Encryption 2000 6000 0 MARS RC6 Rijndael Serpent TwoFish 5000 4000 Algorithm Kbits/sec Encry128 3000 Figure 2. Graph for Key setup Encryption and Decryption encry192 2000 encry256 1000 0 1 2 3 4 5 6 Figure 4. Encryption 131 http://sites.google.com/site/ijcsis/ ISSN 1947-5500 (IJCSIS) International Journal of Computer Science and Information Security, Vol. 8, No. 6, September 2010 Decryption algorithms. But MARS is one among the chosen algorithms 6000 is some what better as considered reports. 5000 It won't be an easy decision to choose one of the 4000 Kbits/sec Encry128 3000 encry192 finalists as AES. There is no known weakness in all these encry256 2000 algorithms, so other factors as performance, needed 1000 0 hardware or flexibility must be used for the decision. MARS h nt el 6 S cipher is for sure a good candidate. It has the largest is C R da pe of R A ijn Tw er M S R available key length of all of them and it is expandable to Figure 5. Decryption larger block sizes than 128 bit. Another advantage of MARS is that it comes from a well known company that is in this c) Fair Speed/ Security Comparisons business for a long time which means they have a lot of experience and have proven their trustworthiness. TABLE VI. FAIR SPEED/ SECURITY COMPARISONS Original Time F. References Cipher (cycles) Rounds Minimal Rounds (Cycles) [1] Cryptography and Network Security -“William Stallings” ,Third MARS 1600 32 20 1000 Edition. [2] The Laws of Cryptography with JAVA Code -“Neal R.Wagner”. RC6 1436 20 20 1436 [3] MARS: C.Burwick, D.Coppersmith, E.D'Avignon, R.Gennaro, S.Halevi, C.Jutla, S.Matyas, L.O'Connor, M.Peyravian, D.Safford, N.Zunic, "MARS - a candidate cipher for AES", IBM Corporation, Rijndael 1276 10 8 1021 September 1999. [4] TweakIBM99 - Shai Halevi, "Detailed discussion of the MARS Serpent 1800 32 17 956 "tweak" for Round 2", IBM Corporation, Mai 1999. [5] RC6: Ronald L. Rivest, M.J.B. Robshaw, R. Sidney, Y.L. Yin, "The Twofish 1254 16 12 940 RC6 Block Cipher", M.I.T. Laboratory for Computer Science, RSA Laboratories. [6] Rijndael: Joan Daemen, Vincent Rijmen, "AES Proposal: Rijndael", Proton World Int.l, Belgium, Katholieke Universiteit Leuven, 2000 Belgium, September 1999. 1800 [7] Serpent: Ross Anderson, Eli Biham, Lars Knudsen, "Serpent: A 1600 Proposal for the Advanced Encryption Standard", Cambridge 1400 University, England; Technion, Haifa, Israel; University of Bergen, Original (cycles) Norway. 1200 Rounds [8] Twofish: Bruce Schneier, John Kelsey, Doug Whiting, David 1000 800 Minimal Rounds Wagner, Chris Hall, Niels Ferguson, "Two sh: A 128-Bit Block Time(Cycles) Cipher", Counterpane Systems, University of California Berkeley. 600 [9] E Biham, “ A Note Comparing AES Candidates, NIST,1999. 400 200 [10] P. Preneel, V Rijmen and A Bosselaers, “ Principles and Performance of Cryptographic Algorithms”, Dr. Dobb’s journal. 0 MARS RC6 Rijndael Serpent Twofish [11] B. Schneier, J Kelsey, D. Whiting, D Wagner, C. Hall and N Ferguson, “Performance Comparison of the AES Candidate conference,1999. Figure 6. Fair speed / security comparisons E. Conclusion A performance comparison can be made among various AUTHORS PROFILE AES Algorithms such as MARS, RC6, Rijndael, Serpent, Dr. B D C N Prasad, currently is a Professor & Head of Twofish. The Performance analysis reports were presented Department of Computer Applications at Prasad V. Potluri in the specified contents. It is concluded that all the above Siddardha Institute of Science and Technology, Vijayawada, Andhra Pradesh, India. He received Ph.D. in specified algorithms have almost similar speed rate and Applied Mathematics from Andhra University, timings while using java tool for execution of these Visakhapatnam,India in 1984. His research interests 132 http://sites.google.com/site/ijcsis/ ISSN 1947-5500 (IJCSIS) International Journal of Computer Science and Information Security, Vol. 8, No. 6, September 2010 includes Machine Intelligence, Data Mining, Rough Sets and Information Security in Computer Science and Boundary value problems and Fluid Dynamics in Mathematics. He has several publications in mathematics and computer science in reputed national and international journals. He is a member of ISTAM , ISTE and also he is a national executive member of Indian Society for Rough Sets. Mr. P E S N Krishna Prasad, currently is a Research Scholor under the guidance of Dr. BDCN Prasad in the area of Machine Intelligence and Neural Networks. He is working as Associate Professor in the Department of CSE, Aditya Engineering College, Kakinada, Andhra pradesh, India. He is a member of ISTE. He has presented and published papers in several national and International conferences and journals. His areas of interest are Artificial Intelligence, Neural Networks and Machine Intelligence. Mr. P Sita Rama Murty, currently is a Research Scholor, in the area of ATM networks and Information Secuirty. He is working as Assistant Professor in the department of CSE, Sri Sai Aditya Institute of Science and Technology, Kakinada, Andhra Pradesh, India . 133 http://sites.google.com/site/ijcsis/ ISSN 1947-5500

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