{{Short description|Attack applicable to block and stream ciphers}}
{{no footnotes|date=August 2017}}
In [[cryptography]], '''mod ''{{Mvar|n''}} cryptanalysis''' is an [[cryptanalysis|attack]] applicable to [[block cipher|block]] and [[stream cipher]]s. It is a form of [[partitioning cryptanalysis]] that exploits unevenness in how the [[cipher]] operates over [[equivalence class]]es (congruence classes) [[modular arithmetic|modulo ''{{Mvar|n''}}]]. The method was first suggested in 1999 by [[John Kelsey (cryptanalyst)|John Kelsey]], [[Bruce Schneier]], and [[David A. Wagner|David Wagner]] and applied to RC5P (a variant of [[RC5]]) and [[M6 (cipher)|M6]] (a family of block ciphers used in the [[FireWire]] standard). These attacks used the properties of binary addition and bit rotation modulo a [[Fermat prime]].
