▁standard ▁headers ▁or ▁foot ers ▁which ▁can ▁be ▁guess ed ▁easily . ▁ ▁Given ▁the ▁intercept ed ▁ ▁and ▁our ▁known / gu essed ▁, ▁we ▁may ▁easily ▁find ▁ ▁for ▁ ▁by ▁X OR ing ▁the ▁two ▁together . ▁ ▁We ▁now ▁know ▁ 3 2 ▁consecutive ▁bits ▁of ▁the ▁generator ▁output . ▁ ▁Now ▁we ▁may ▁begin ▁a ▁br ute ▁force ▁search ▁of ▁the ▁space ▁of ▁possible ▁keys ▁( initial ▁values ) ▁for ▁L FS R - 3 ▁( ass uming ▁we ▁know ▁the ▁t apped ▁bits ▁of ▁L FS R - 3 , ▁an ▁assumption ▁which ▁is ▁in ▁line ▁with ▁Ker ck hoff s ' ▁principle ). ▁ ▁For ▁any ▁given ▁key ▁in ▁the ▁keys pace , ▁we ▁may ▁quickly ▁generate ▁the ▁first ▁ 3 2 ▁bits ▁of ▁L FS R - 3 ' s ▁output ▁and ▁compare ▁these ▁to ▁our ▁recovered ▁ 3 2 ▁bits ▁of ▁the ▁entire ▁generator ' s ▁output . ▁ ▁Because ▁we ▁have ▁established ▁earlier ▁that ▁there ▁is ▁a ▁ 7 5 % ▁correlation ▁between ▁the ▁output ▁of ▁L FS R - 3 ▁and ▁the ▁generator , ▁we ▁know ▁that ▁if ▁we ▁have ▁correctly ▁guess ed ▁the ▁key ▁for ▁L FS R - 3 , ▁approximately ▁ 2 4 ▁of ▁the ▁first ▁ 3 2 ▁bits ▁of ▁L FS R - 3 ▁output ▁will ▁match ▁up ▁with ▁the ▁corresponding ▁bits ▁of ▁generator ▁output . ▁ ▁If ▁we ▁have ▁guess ed ▁incorrectly , ▁we ▁should ▁expect ▁roughly ▁half , ▁or ▁ 1 6 , ▁of ▁the