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# Topic: Feistel network

 Feistel cipher - Wikipedia, the free encyclopedia In cryptography, a Feistel cipher is a block cipher with a particular structure, named after IBM cryptographer Horst Feistel; it is also commonly known as a Feistel network. Feistel networks were first seen commercially in IBM's Lucifer cipher, designed by Feistel and Don Coppersmith. Feistel networks gained respectability when the US Federal Government adopted the DES (a cipher based on Lucifer, with changes made by the NSA). en.wikipedia.org /wiki/Feistel_cipher   (472 words)

 Horst Feistel - Wikipedia, the free encyclopedia He could easily be considered the father of modern block ciphers: he was the first cryptographer to publish designs and theory on the topic. Feistel was born in Berlin in 1915, and moved to the United States in 1934. Feistel obtained a bachelor's degree at MIT, and his master's at Harvard, both in physics. www.wikipedia.org /wiki/Horst_Feistel   (295 words)

 Symmetric block cipher using multiple stages with modified type-1 and type-3 feistel networks - Patent 6189095 A Type-2 Feistel Network consists of dividing the data to be encrypted into two halves, and then performing some number of rounds, where each round consists of transforming the left half of the data based on the right half of the data, and then transforming the right half based on the modified left half. Feistel Networks are not limited to this case of dividing the data into two equal halves. In typical Feistel networks that use an expansion function, the function inside the expansion box is independent of the function outside the box (that is, the main cipher processing). www.freepatentsonline.com /6189095.html   (10983 words)

 FEAL article - FEAL 1987 1990 Block size(s) size Feistel network cryptanalysis Linear - What-Means.com   (Site not responding. Last check: 2007-10-21) The cipher is susceptible to various forms of cryptanalysis, and has acted as a catalyst in the discovery of differential and linear cryptanalysis. There have been several different revisions of FEAL, though all are Feistel ciphers, and make use of the same basic round function and operate on a 64-bit block. One of the earliest designs is now termed FEAL-4, which has four rounds and a 64-bit key. www.what-means.com /encyclopedia/FEAL   (512 words)

 Horst Feistel He lends his name to the Feistel network construction — a common method for constructing encryption algorithms — and his work at IBM led to the development of the pioneering Lucifer and Data Encryption Standard (DES) ciphers. During World War II, he was placed under house arrest, but at the end of the war he soon became a US citizen on 31 January 1944. Horst Feistel, H, W. Notz, J. Lynn Smith. www.starrepublic.org /encyclopedia/wikipedia/h/ho/horst_feistel.html   (276 words)

 Feistel cipher -- Facts, Info, and Encyclopedia article   (Site not responding. Last check: 2007-10-21) Feistel networks were first seen commercially in IBM's (Lighter consisting of a thin piece of wood or cardboard tipped with combustible chemical; ignites with friction) Lucifer cipher, designed by Feistel and (Click link for more info and facts about Don Coppersmith) Don Coppersmith. Feistel networks and similar constructions are (Click link for more info and facts about product cipher) product ciphers, and so combine multiple rounds of repeated operations, such as: Many modern symmetric block ciphers are based on Feistel networks, and the structure and properties of Feistel ciphers have been extensively explored by (Decoder skilled in the analysis of codes and cryptograms) cryptographers. www.absoluteastronomy.com /encyclopedia/F/Fe/Feistel_cipher.htm   (689 words)

 MacGuffin (cipher) It was intended as a catalyst for analysis of a new cipher structure, known as Generalized Unbalanced Feistel Networks (GUFNs) — "MacGuffin" refers to a plot device that holds no meaning or purpose of its own except to motivate the characters and advance the story. Schneier and Blaze based MacGuffin on DES, their main change being that the data block is not split into equal halves in the Feistel network. Since MacGuffin is a Feistel network, decryption is easy - simply run the encryption algorithm in reverse. www.starrepublic.org /encyclopedia/wikipedia/m/ma/macguffin__cipher_.html   (484 words)

 LOKI97 - Open Encyclopedia   (Site not responding. Last check: 2007-10-21) Like DES, LOKI97 is a 16-round Feistel cipher, and like other AES candidates, has a 128-bit block size and a choice of a 128-, 192- or 256-bit key length. It uses 16 rounds of a balanced feistel network to process the input data blocks (see diagram right). The complex round function f incorporates two substitution-permutation layers in each round.The key schedule is also a Feistel structure — an unbalanced one unlike the main network — but using the same F-function. open-encyclopedia.com /LOKI97   (387 words)

 Data Encryption Standard article - Data Encryption Standard (disambiguation) 1975 1977 Lucifer (cipher) Triple G-DES ...   (Site not responding. Last check: 2007-10-21) This time, IBM submitted a candidate which was deemed acceptable, a cipher developed during the period 1973–1974 based on an earlier algorithm, Horst Feistel's Lucifer cipher. Before the main rounds, the block is divided into two 32-bit halves and processed alternately; this criss-crossing is known as the Feistel scheme. The Feistel structure ensures that decryption and encryption are very similar processes — the only difference is that the subkeys are applied in the reverse order when decrypting. www.what-means.com /encyclopedia/DES   (3592 words)

 Exclusive disjunction - Encyclopedia.WorldSearch   (Site not responding. Last check: 2007-10-21) The xor operation is sometimes used as a simple mixing function in cryptography, for example, with one-time pad or Feistel network systems. In digital logic design, a two-input xor logic gate is often thought of as a programmable inverter, in that if one input is held at a logic '1', the output will be the inverse of the other input. Neural networks require an extra processing layer to handle the added complexity. encyclopedia.worldsearch.com /exclusive_disjunction.htm   (606 words)

 SSH : Support : Cryptography A-Z : Algorithms : Secret Key Cryptosystems Feistel networks: a Feistel network is a general way of constructing block ciphers from simple functions. The security of the Feistel structure is not obvious, but analysis of DES has shown that it is a good way to construct ciphers. This is an interesting new design (using a special type of a Feistel network), which depends heavily on the instruction sets available on modern 32-bit processors. www.ssh.com /support/cryptography/algorithms/symmetric.html   (3577 words)

 Lucifer (cipher) In cryptography, Lucifer was the name given to several of the earliest civilian block ciphers, developed by Horst Feistel and his colleagues at IBM. The cipher is a Substitution-permutation network and uses two 4-bit S-boxes. A later Lucifer was a 16-round Feistel network, also on 128-bit blocks and 128-bit keys, described in (Sorkin, 1984). www.mcfly.org /wik/Lucifer_(cipher)   (427 words)

 Blowfish Paper   (Site not responding. Last check: 2007-10-21) Almost all block ciphers since Lucifer [5,21] are Feistel ciphers, and all have a flat keyspace (with the possible exception of a few weak keys). The Feistel network that makes up the body of Blowfish is designed to be as simple as possible, while still retaining the desirable cryptographic properties of the structure. Figure 3 is round i of a general Feistel network: Rn,i are reversible functions of text and key, and Ni is a non-reversible function of text and key. www.tropsoft.com /strongenc/bfsverlag.htm   (4054 words)

 Design of Mercy Balanced Feistel networks are certainly the best studied frameworks from which to build a block cipher, although I know of no prior work applying them to such large block sizes. Balanced networks seem better suited to large block ciphers than unbalanced networks, since an unbalanced network is likely to have to do work proportional to the larger of the input and output data width. This suggests a distinction between perfect avalanche, and avalanche sufficient to defeat cryptanalysis; this distinction is useful since mechanisms for providing perfect avalanche, such as networks based on Fourier transforms (used in SAFER [12] and proposed by [16] for large block ciphers), can carry a heavy performance penalty on large blocks. www.ciphergoth.org /crypto/mercy/html/design_of_mercy.html   (1559 words)

 Security Forums Dot Com :: View topic - Principles of operation of symmetric cryptosystems Predominantly, as previously mentioned, they are based on the surrounding theory of Feistel networks and Substitution-Permutation Networks, iterated and/or product; along with them come many variations, such as unbalanced Feistel networks or modified Substitution-Permutation Networks, for example. In a Feistel network, we generally have a "round function" that is iterated for n rounds; in a Substitution-Permutation Network, we generally have layers of routines that perform substitutions and permutations, in a round transformation, obviously, iterated for n rounds. As for formulas that demonstrate the mathematical constructions of these design strategies, refer to the NIST's FIPS publications for DES [FIPS 46-3], a Feistel network, and AES [FIPS 197], a Substitution-Permutation Network. www.security-forums.com /forum/viewtopic.php?t=19889   (664 words)

 Station Information - Feistel cipher A Feistel cipher is a block cipher with a particular structure (known as a Feistel network). As cryptographers have performed much analysis of this structure and the strengths and weaknesses it produces, many--but by no means all--modern block ciphers are Feistel ciphers. DES is one of the earliest and best known such cipher. www.stationinformation.com /encyclopedia/f/fe/feistel_cipher.html   (136 words)

 Encyclopedia: SP-network   (Site not responding. Last check: 2007-10-21) In cryptography, an SP-network, or substitution-permutation network (SPN), is a series of linked mathematical operations used in block cipher algorithms such as AES. These networks consist of S-boxes and P-boxes that transform blocks of input bits into output bits. It is common for these transformations to be operations that are efficient to perform in hardware, such as exclusive or (XOR). www.nationmaster.com /encyclopedia/SP_network   (190 words)

 F-functions for Feistel block ciphers It's meant to be the F-function for each round in a Feistel network. It's not meant to stand against chosen-ciphertext differential attacks on its own (it has too few rounds); it's meant to stand against differential attacks when used as the F-function for a Feistel cipher with 8 to 16 rounds (in any case the avalanche is supposed to be one-way). Skipjack uses something almost exactly like this, and MISTY uses a recursive Feistel structure (although at this level the sboxes are 7-bit and 9-bit rather than 8-bit). www.totalblowhole.com /new-6236402-4287.html   (1743 words)

 Concepts of Cryptography Using the Feistel network gives the cipher two very desirable properties: decryption using the same f function (even if it is non-invertible) and the ability to iterate the function multiple times. There is currently research into generalized unbalanced Feistel networks (GUFNs), which divide the block into two parts of different lengths. MacGuffin (described in the Algorithms section) is an example of a GUFN cipher. www.baltsoft.com /files/ee/Concepts_of_Cryptography.htm   (702 words)

 Directv Dish Network Vs   (Site not responding. Last check: 2007-10-21) Such a "code" is called an error-correcting code, directv dish network vs and works by including carefully crafted redundancy with the stored (or transmitted) data. Still it is somewhat presumptous for one person to say that the elected government of Canada is wrong in its cultural policy and to directv dish network vs present that opinion as the opinion of all Canadians. Major social or political movements often have directv dish network vs one or more centres or headquarters around which they are focussed and from where they are directed. directv.webeve.com /directv-dish-network-vs.html   (918 words)

 Exam-april-01   (Site not responding. Last check: 2007-10-21) The general design of DES is called a Feistel network (named after one of the major contributors to the design of DES). Also show that two rounds in a Feistel network is clearly insufficient for the case of known or guessed plaintext, unless you regard the f-function as strong enough to be a cipher on its own! Please note that knowledge of what is a "Feistel network" has not been stated as a requirement for the course, but from knowledge of the structure of DES as a whole and the text above, you should be able to distinguish what is the DES specific parts and reconstruct the principles of a Feistel network. www.it.isy.liu.se /studentinfo/TSIT70/Examd0april-01.html   (1888 words)

 95040303.HTM   (Site not responding. Last check: 2007-10-21) Newsgroups: sci.crypt Subject: Re: Generalized Feistel Networks Date: 3 Apr 1995 15:23:07 GMT Organization: Just me and my PC.... , schneier@klondike.winternet.com (Bruce Schneier) wrote: }The key idea of a Feistel network is it turns a non-invertable one-way }function into an invertable block cipher. A Feistel }network is really: } } A' = B } B' = A XOR f(B) } }That function f does not have to be invertable at all; the Feistel structure }takes care of the invertability. www.ciphersbyritter.com /NEWS2/95040303.HTM   (178 words)

 MARS encryption algorithm - Project Report   (Site not responding. Last check: 2007-10-21) The algorithm is a type-3 Feistel network which is word (32 bit) oriented. Then it goes to the cryptographic core (a type-3 Feistel network) where eight rounds of keyed forward transformation and eight rounds of keyed backwards transformation are performed and at the end is another backward mixing stage, which contains eight rounds of unkeyed backwards mixing and a key subtraction. It is a 16 round Feistel cipher that works with key dependent 8x8 bit look-up tables, 4 by 4 matrices over the Galois field GF(128), a pseudo-Hadamard transform, permutations and rotations. security.ece.orst.edu /koc/ece575/00Project/Galli/MARSReport.html   (2310 words)

 The Ultimate SEED Dog Breeds Information Guide and Reference   (Site not responding. Last check: 2007-10-21) It is a 16-round Feistel network with 128-bit blocks and a 128-bit key. It also has some resemblance to MISTY1 in the recursiveness of its structure: the 128 bit full cipher is a Feistel network with an F-function operating on 64 bit halves, while the F-function itself is a Feistel network composed of a G-function operating on 32 bit halves. In the G-function, the 32 bit word is considered as four 8-bit bytes, each of which is passed through one or the other of the S-boxes, then combined in a moderately complex set of boolean functions such that each output bit depends on 3 of the 4 input bytes. www.dogluvers.com /dog_breeds/SEED_%28cipher%29   (228 words)

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