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Twofish: A 128Bit Block Cipher
 in First Advanced Encryption Standard (AES) Conference
, 1998
"... Twofish is a 128bit block cipher that accepts a variablelength key up to 256 bits. The cipher is a 16round Feistel network with a bijective F function made up of four keydependent 8by8bit Sboxes, a fixed 4by4 maximum distance separable matrix over GF(2 8 ), a pseudoHadamard transform, bit ..."
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Cited by 58 (8 self)
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Twofish is a 128bit block cipher that accepts a variablelength key up to 256 bits. The cipher is a 16round Feistel network with a bijective F function made up of four keydependent 8by8bit Sboxes, a fixed 4by4 maximum distance separable matrix over GF(2 8 ), a pseudoHadamard transform, bitwise rotations, and a carefully designed key schedule. A fully optimized implementation of Twofish encrypts on a Pentium Pro at 17.8 clock cycles per byte, and an 8bit smart card implementation encrypts at 1660 clock cycles per byte. Twofish can be implemented in hardware in 14000 gates. The design of both the round function and the key schedule permits a wide variety of tradeoffs between speed, software size, key setup time, gate count, and memory. We have extensively cryptanalyzed Twofish; our best attack breaks 5 rounds with 2 22.5 chosen plaintexts and 2 51 effort.
Constructing symmetric ciphers using the CAST design procedure
 DESIGNS, CODES, AND CRYPTOGRAPHY
, 1997
"... This paper describes the CAST design procedure for constructing a family of DESlike SubstitutionPermutation Network (SPN) cryptosystems which appear to have good resistance to differential cryptanalysis, linear cryptanalysis, and relatedkey cryptanalysis, along with a number of other desirable ..."
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Cited by 22 (1 self)
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This paper describes the CAST design procedure for constructing a family of DESlike SubstitutionPermutation Network (SPN) cryptosystems which appear to have good resistance to differential cryptanalysis, linear cryptanalysis, and relatedkey cryptanalysis, along with a number of other desirable cryptographic properties. Details of the design choices in the procedure are given, including those regarding the component substitution boxes (sboxes), the overall framework, the key schedule, and the round function. An example CAST cipher, an output of this design procedure, is presented as an aid to understanding the concepts and to encourage detailed analysis by the cryptologic community.
A Family of Trapdoor Ciphers
 Fast Software Encryption, LNCS 1267, E. Biham, Ed., SpringerVerlag
, 1997
"... . This paper presents several methods to construct trapdoor block ciphers. A trapdoor cipher contains some hidden structure; knowledge of this structure allows an attacker to obtain information on the key or to decrypt certain ciphertexts. Without this trapdoor information the block cipher seems to ..."
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Cited by 7 (2 self)
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. This paper presents several methods to construct trapdoor block ciphers. A trapdoor cipher contains some hidden structure; knowledge of this structure allows an attacker to obtain information on the key or to decrypt certain ciphertexts. Without this trapdoor information the block cipher seems to be secure. It is demonstrated that for certain block ciphers, trapdoors can be builtin that make the cipher susceptible to linear cryptanalysis; however, finding these trapdoors can be made very hard, even if one knows the general form of the trapdoor. In principle such a trapdoor can be used to design a public key encryption scheme based on a conventional block cipher. 1 Introduction Researchers have been wary of trapdoors in encryption algorithms, ever since the DES [9] was proposed in the seventies [15]. In spite of this, no one has been able to show how to construct a practical block cipher with a trapdoor. For most current block ciphers it is relatively easy to give strong evidence th...
Higher Order Differential Attack of a CAST Cipher
 Proceedings of the Fifth International Workshop on Fast Software Encryption
, 1998
"... Abstract. This paper proposes a new higher order differential attack. The higher order differential attack proposed at FSE’97 by Jakobsen and Knudsen used exhaustive search for recovering the last round key. Our new attack improves the complexity to the cost of solving a linear system of equations. ..."
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Abstract. This paper proposes a new higher order differential attack. The higher order differential attack proposed at FSE’97 by Jakobsen and Knudsen used exhaustive search for recovering the last round key. Our new attack improves the complexity to the cost of solving a linear system of equations. As an example we show the higher order differential attack of a CAST cipher with 5 rounds. The required number of chosen plaintexts is 2 17 and the required complexity is less than 2 25 times the computation of the round function. Our experimental results show that the last round key of the CAST cipher with 5 rounds can be recovered in less than 15 seconds on an UltraSPARC station. 1
Resistance of a CASTLike Encryption Algorithm to Linear and Differential Cryptanalysis
, 1997
"... Linear cryptanalysis and differential cryptanalysis are two recently introduced, powerful methodologies for attacking privatekey block ciphers. In this paper, we examine the application of these two cryptanalysis techniques to a CASTlike encryption algorithm based on randomly generated sboxes. It ..."
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Cited by 5 (1 self)
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Linear cryptanalysis and differential cryptanalysis are two recently introduced, powerful methodologies for attacking privatekey block ciphers. In this paper, we examine the application of these two cryptanalysis techniques to a CASTlike encryption algorithm based on randomly generated sboxes. It is shown that, when randomly generated substitution boxes (sboxes) are used in a CASTlike algorithm, the resulting cipher is resistant to both the linear attack and the differential attack. 1 Introduction As the need for privacy and authentication is now generally recognized by the telecommunications community, a widely adopted privatekey encryption algorithm is becoming an increasingly important objective in the development and analysis of cryptographic algorithms. For some time, the Data Encryption Standard (DES) [16] has been the most widely used and trusted encryption algorithm. However, DES is about twenty years old and has recently become vulnerable to cryptanalysis due to its smal...
Cryptanalysis of RijmenPreneel trapdoor ciphers
 Proceedings of ASIACRYPT’98, LNCS 1514
, 1998
"... Abstract. Rijmen and Preneel recently proposed for the rst time a family of trapdoor block ciphers [8]. In this family of ciphers, a trapdoor is hidden in Sboxes and is claimed to be undetectable in [8] for properly chosen parameters. Given the trapdoor, the secret key (used for encryption and decr ..."
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Abstract. Rijmen and Preneel recently proposed for the rst time a family of trapdoor block ciphers [8]. In this family of ciphers, a trapdoor is hidden in Sboxes and is claimed to be undetectable in [8] for properly chosen parameters. Given the trapdoor, the secret key (used for encryption and decryption) can be recovered easily by applying Matsui's linear cryptanalysis [6]. In this paper, we break this family of trapdoor block ciphers by developing an attack on the Sboxes. We showhow to nd the trapdoor in the Sboxes and demonstrate that it is impossible to adjust the parameters of the Sboxes such that detecting the trapdoor is di cult meanwhile nding the secret key by trapdoor information is easy. 1
A Comparative Study Of Two Symmetric Encryption Algorithms Across Different Platforms.
"... Abstract: The world of digital communications is expanding day by day, For secure communications over the unsecure mediums, Cryptography plays a crucial role and Symmetric Encryption algorithms do the real part of encoding data before transmission. The deep analysis of their security and speed becom ..."
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Abstract: The world of digital communications is expanding day by day, For secure communications over the unsecure mediums, Cryptography plays a crucial role and Symmetric Encryption algorithms do the real part of encoding data before transmission. The deep analysis of their security and speed become the necessity of safe digital communication. In this paper, we study the two popular symmetric cryptographic algorithms BLOWFISH and CAST. We analyze their security issues and then compare their efficiency for encrypting text, image and sound with the official encryption standard AES(Advanced Encryption Standard) across different widely used Operating Systems like Windows XP, Windows Vista and Windows 7. The simulation results reveal Which algorithm performs better on Which Operating system for encrypting What kind of data.
Nonlinearity of the round function by
"... Abstract: In the paper we present the results which enable to calculate the nonlinearity of the round function with quite large dimensions, e.g. 32 × 32 bits, which are used in some block ciphers. It can be used to estimate resistance of these ciphers against linear cryptanalysis. We give the applic ..."
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Abstract: In the paper we present the results which enable to calculate the nonlinearity of the round function with quite large dimensions, e.g. 32 × 32 bits, which are used in some block ciphers. It can be used to estimate resistance of these ciphers against linear cryptanalysis. We give the application to linear cryptanalysis of the TGR block cipher.