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L Input .KÖÝLWDÑRKRDÛQYÔ L 1 =Ro Ro + F + F + F ³DÝRNKÖÝLWDÑRKRÛDQYÔ 2XWSXW Lo R 1 = Lo + F(R 1 ,K 1 ) L 15 = R 14 R 2 = L 1 + F(R 1 ,K 2 )L 2 = R 1 R 15 = L 14 + F(R 14 ,K 15 ) + F R 16 = L 15 + F(R 15 ,K 16 ) L 16 = R 15 1,2,3, . 64 1,2,3, . 64 1,2,3, . 32 K 1 K 2 Kn K 16 Hình 1: Encryption computation 1,2,3, . 32 &KRÑQKRÛDQYÔ /HIW6KLIW /HIW6KLIW /HIW6KLIW/HIW6KLIW /HIW6KLIW /HIW6KLIW &KRÑQKRÛDQYÔ &KRÑQKRDÛQYÔ &KRÑQKRDÛQYÔ 1,2,3, . 64 1,2,3, . 28 1,2,3, . 28 K 1 Kn K 16 +ÎQK Key Schedule Calculation Key Key Key C 1 D 1 Cn Dn C 16 D 16 S 1 S 2 S 3 S 6 S 5 S 7 S 4 S 8 P 32 bits + E 48 bits K ( 48 bits ) 5 ELWV Hình 3 : Calculation of f(R,K) 6 4 %DÝQJD%DÝQJKRDÛQYÔÓDÂXWLHÄQ,3  %DÝQJE%DÝQJKRDÛQYÔFXRÃLFXÚQJ,3   %DÝQJ%DÝQJFKRÑQEÏW( %DÝQJ%DÝQJKRDÛQYÔ3 %DÝQJ%DÝQJKRDÛQYÔNKRÛD3& %DÝQJ%DÝQJKRDÛQYÔNKRÛD3&     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