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Tweakable block ciphers
, 2002
"... Abstract. We propose a new cryptographic primitive, the “tweakable block cipher. ” Such a cipher has not only the usual inputs—message and cryptographic key—but also a third input, the “tweak. ” The tweak serves much the same purpose that an initialization vector does for CBC mode or that a nonce do ..."
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Cited by 102 (4 self)
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Abstract. We propose a new cryptographic primitive, the “tweakable block cipher. ” Such a cipher has not only the usual inputs—message and cryptographic key—but also a third input, the “tweak. ” The tweak serves much the same purpose that an initialization vector does for CBC mode or that a nonce does for OCB mode. Our proposal thus brings this feature down to the primitive blockcipher level, instead of incorporating it only at the higher modesofoperation levels. We suggest that (1) tweakable block ciphers are easy to design, (2) the extra cost of making a block cipher “tweakable ” is small, and (3) it is easier to design and prove modes of operation based on tweakable block ciphers.
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 54 (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.
Unbalanced Feistel Networks and BlockCipher Design
 Fast Software Encryption, 3rd International Workshop Proceedings
, 1996
"... We examine a generalization of the concept of Feistel networks, which we call Unbalanced Feistel Networks (UFNs). Like conventional Feistel networks, UFNs consist of a series of rounds in which one part of the block operates on the rest of the block. However, in a UFN the two parts need not be of eq ..."
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Cited by 50 (5 self)
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We examine a generalization of the concept of Feistel networks, which we call Unbalanced Feistel Networks (UFNs). Like conventional Feistel networks, UFNs consist of a series of rounds in which one part of the block operates on the rest of the block. However, in a UFN the two parts need not be of equal size. Removing this limitation on Feistel networks has interesting implications for designing ciphers secure against linear and differential attacks. We describe UFNs and a terminology for discussing their properties, present and analyze some UFN constructions, and make some initial observations about their security. It is notable that almost all the proposed ciphers that are based on Feistel networks follow the same design construction: half the bits operate on the other half. There is no inherent reason that this should be so; as we will demonstrate, it is possible to design Feistel networks across a much wider, richer design space. In this paper, we examine the nature of the...
Recent Developments in the Design of Conventional Cryptographic Algorithms
 Computer Security and Industrial Cryptography  State of the Art and Evolution, LNCS
, 1998
"... This paper examines proposals for three cryptographic primitives: block ciphers, stream ciphers, and hash functions. It provides an overview of the design principles of a large number of recent proposals, which includes the global structure, the number of rounds, the way of introducing nonlinearity ..."
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Cited by 10 (2 self)
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This paper examines proposals for three cryptographic primitives: block ciphers, stream ciphers, and hash functions. It provides an overview of the design principles of a large number of recent proposals, which includes the global structure, the number of rounds, the way of introducing nonlinearity and diffusion, and the key schedule. The software performance of about twenty primitives is compared based on highly optimized implementations for the Pentium. The goal of the paper is to provided a technical perspective on the wide variety of primitives that exist today.
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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Cited by 2 (0 self)
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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