Editing Stream cipher (section)

===Non-linear combining functions===
[[Image:Nonlinear-combo-generator.png|thumbnail|One approach is to use ''n'' LFSRs in parallel, their outputs combined using an ''n''-input binary Boolean function (''F'').]]
Because LFSRs are inherently linear, one technique for removing the linearity is to feed the outputs of several parallel LFSRs into a non-linear [[Boolean function]] to form a ''combination generator''. Various properties of such a ''combining function'' are critical for ensuring the security of the resultant scheme, for example, in order to avoid [[correlation attack]]s. 
{{Expand section|date=June 2008}}