Editing RC4 (section)

===Combinatorial problem===
A combinatorial problem related to the number of inputs and outputs of the RC4 cipher was first posed by [[Itsik Mantin]] and [[Adi Shamir]] in 2001, whereby, of the total 256 elements in the typical state of RC4, if ''x'' number of elements (''x'' ≤ 256) are ''only'' known (all other elements can be assumed empty), then the maximum number of elements that can be produced deterministically is also {{mvar|x}} in the next 256 rounds. This conjecture was put to rest in 2004 with a formal proof given by [[Souradyuti Paul]] and [[Bart Preneel]].<ref>[[Souradyuti Paul]] and [[Bart Preneel]], [http://www.cosic.esat.kuleuven.be/publications/article-40.pdf A New Weakness in the RC4 Keystream Generator and an Approach to Improve the Security of the Cipher]. [[Fast Software Encryption]] – FSE 2004, pp.&nbsp;245–259.</ref>