View source for SHARK

{{Short description|Block cipher}}
{{other uses|Shark (disambiguation)}}
{{Infobox block cipher
| name = SHARK
| designers = [[Vincent Rijmen]], [[Joan Daemen]], [[Bart Preneel]], [[Antoon Bosselaers]], [[Erik De Win]]
| publish date = 1996
| derived from =
| derived to = [[KHAZAD]], [[Rijndael]]
| related to =
| key size = 128 bits
| block size = 64 bits
| structure = [[Substitution–permutation network]]
| rounds = 6
| cryptanalysis =
}}

In [[cryptography]], '''SHARK''' is a [[block cipher]] identified as one of the predecessors of [[Rijndael]] (the [[Advanced Encryption Standard]]).

SHARK has a 64-bit [[block size (cryptography)|block size]] and a 128-bit [[key size]]. It is a six-round [[substitution–permutation network|SP-network]] which alternates a [[key (cryptography)|key]] mixing stage with linear and non-linear transformation layers. The linear transformation uses an [[MDS matrix]] representing a [[Reed–Solomon error correction|Reed–Solomon]] [[error correcting code]] in order to guarantee good [[confusion and diffusion|diffusion]]. The nonlinear layer is composed of eight 8×8-bit [[S-box]]es based on the function ''F(x) = x<sup>−1</sup>'' over ''GF(2<sup>8</sup>)''.

Five rounds of a modified version of SHARK can be broken using an [[interpolation attack]] (Jakobsen and Knudsen, 1997).

==See also==
* [[KHAZAD]]
* [[Square (cipher)|Square]]

==References==
* {{ cite conference
 | author = [[Vincent Rijmen]], [[Joan Daemen]], [[Bart Preneel]], Anton Bosselaers, Erik De Win
 | title = The Cipher SHARK
 | conference = 3rd International Workshop on [[Fast Software Encryption]] (FSE '96)
 | pages = 99–111
 | publisher = [[Springer-Verlag]]
 | date = February 1996
 | location = [[Cambridge]]
 | url = http://citeseer.ist.psu.edu/rijmen96cipher.html
 | format = [[PDF]]/[[PostScript]]
 | access-date = 2007-03-06 }}
* {{ cite conference
 | author = [[Thomas Jakobsen|T. Jakobsen]], [[Lars Knudsen|L.R. Knudsen]]
 | title = The Interpolation Attack on Block Ciphers
 | conference = 4th International Workshop on [[Fast Software Encryption]] (FSE '97)
 | pages = 28–40
 | publisher = Springer-Verlag
 | date = January 1997
 | location = [[Haifa]]
 | url = http://citeseer.ist.psu.edu/jakobsen97interpolation.html
 | format = PDF/PostScript
 | access-date = 2007-01-23}}
* {{ cite book
 |author1=Joan Daemen |author2=Vincent Rijmen | title = The Design of Rijndael: AES—The Advanced Encryption Standard
 | publisher = Springer-Verlag
 | year = 2002
 | isbn = 3-540-42580-2 }}

==External links==
* [http://www.users.zetnet.co.uk/hopwood/crypto/scan/cs.html#SHARK-A SCAN's entry for SHARK]

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