Editing RC6 (section)

{{Short description|Block cipher}}
{{more footnotes|date=March 2009}}{{About||the Swedish locomotive|SJ Rc}}{{Infobox block cipher
| name          = RC6
| image         = [[Image:RC6 Cryptography Algorithm.JPG|300px|center]]
| caption       = The [[Feistel cipher|Feistel function]] of the RC6 algorithm.
| designers     = [[Ron Rivest]], [[Matt Robshaw]], [[Ray Sidney]], [[Yiqun Lisa Yin]]
| publish date  = 1998
| derived from  = [[RC5]]
| derived to    = 
| related to    =
| certification = [[AES finalist]]
| key size      = 128, 192, or 256 bits
| block size    = 128 bits
| structure     = [[Feistel cipher|Feistel network]] (Type 2)<ref>{{cite conference |title=On Generalized Feistel Networks |last1=Hoang |first1=Viet Tung |last2=Rogaway |first2=Phillip |date=2010 |publisher=Springer |book-title=LNCS 6223 |pages=613–630 |location=USA |conference=CRYPTO 2010|doi=10.1007/978-3-642-14623-7_33 |doi-access=free }}</ref>
| rounds        = 20
| cryptanalysis =
}}

In [[cryptography]], '''RC6''' ('''Rivest cipher 6''') is a [[symmetric key]] [[block cipher]] derived from [[RC5]]. It was designed by [[Ron Rivest]], [[Matt Robshaw]], Ray Sidney, and [[Yiqun Lisa Yin]] to meet the requirements of the [[Advanced Encryption Standard]] (AES) [[AES competition|competition]]. The algorithm was one of the five finalists, and also was submitted to the [[NESSIE]] and [[CRYPTREC]] projects. It was a proprietary algorithm, patented by [[RSA Security]].

RC6 proper has a [[block size (cryptography)|block size]] of 128 bits and supports [[key size]]s of 128, 192, and 256 bits up to 2040-bits, but, like RC5, it may be parameterised to support a wide variety of word-lengths, key sizes, and number of rounds. RC6 is very similar to RC5 in structure, using data-dependent rotations, [[modular arithmetic|modular]] addition, and [[XOR]] operations; in fact, RC6 could be viewed as interweaving two parallel RC5 encryption processes, although RC6 does use an extra multiplication operation not present in RC5 in order to  make the rotation dependent on every bit in a word, and not just the least significant few bits.