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{{Infobox block cipher
| name          = 3-Way
| image         = 
| caption       = 
| designers     = [[Joan Daemen]]
| publish date  = 1994
| derived from  = 
| derived to    = [[NOEKEON]]
| related to    = [[BaseKing]]
| key size      = 96 bits
| block size    = 96 bits
| structure     = [[Substitution-permutation network]]
| rounds        = 11
| cryptanalysis = [[related-key attack]]
}}

In [[cryptography]], '''3-Way''' is a [[block cipher]] designed in 1994 by [[Joan Daemen]]. It is closely related to [[BaseKing]]; indeed, the two are variants of the same general cipher technique.

3-Way has a [[block size (cryptography)|block size]] of 96 [[bit]]s, notably not a [[power of two]] such as the more common 64 or 128 bits. The [[key length]] is also 96 bits. The figure 96 arises from the use of three 32 bit [[word (computer architecture)|word]]s in the algorithm, from which also is derived the [[cipher]]'s name. When 3-Way was invented, 96-bit keys and blocks were quite strong, but more recent ciphers have a 128-bit block, and few now have keys shorter than 128 bits. 3-Way is an 11-round [[substitution-permutation network]].

3-Way is designed to be very efficient in a wide range of platforms from 8-bit processors to specialized [[Computer hardware|hardware]], and has some elegant mathematical features which enable nearly all the decryption to be done in exactly the same circuits as did the encryption. 

3-Way, just as its counterpart BaseKing, is vulnerable to [[Related-key attack|related key]] [[cryptanalysis]]. [[John Kelsey (cryptanalyst)|John Kelsey]], [[Bruce Schneier]], and [[David A. Wagner|David Wagner]] showed how it can be broken with one related key query and about <math>2^{22}</math> [[chosen-plaintext attack|chosen plaintexts]].

==References==
* {{ cite conference
   | author = [[Joan Daemen|J. Daemen]], R. Govaerts, [[Joos Vandewalle|J. Vandewalle]]
   | url = http://citeseer.ist.psu.edu/73063.html <!-- A different version, but the same paper. -->
   | title = A New Approach to Block Cipher Design
   | booktitle = [[Fast Software Encryption]] (FSE) 1993
   | pages = 18–32
   | publisher = [[Springer-Verlag]]
   | date = 1993 }}   
* {{ cite conference
   | author = J. Kelsey, B. Schneier, and D. Wagner
   | title = Related-Key Cryptanalysis of 3-WAY, Biham-DES, CAST, DES-X, NewDES, RC2, and TEA
   | booktitle = ICICS '97 Proceedings
   | pages = 233–246
   | publisher = Springer-Verlag
   | date = November 1997
   | url = http://www.schneier.com/paper-relatedkey.html
   | format = [[PDF]]/[[PostScript]]
   | accessdate = 2007-02-14 }}

==External links==
* [http://www.users.zetnet.co.uk/hopwood/crypto/scan/cs.html#3-Way SCAN's entry for 3-Way]
* [http://www.esat.kuleuven.ac.be/~cosicart/ps/JD-9500/ Chapter 7 of Daemen's thesis] ([[gzip]]ped Postscript)
<!-- * [http://home.ecn.ab.ca/~jsavard/crypto/co040307.htm John Savard's description of 3-Way] -->

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