64-bit inpul 56bit key Symmetric key permute crypto:DES 48-6i1K1 CL1,R1KID DES operation 2 R2 initial permutation 48-bit K2 2.R2,K2D 16 identical "rounds"of function application, [3 R3 each using different 48 bits of key final permutation 48-bit K16 L17R17 permute 64-bit output 8:Network Security 8-13 8: Network Security 8-13 Symmetric key crypto: DES initial permutation 16 identical “rounds” of function application, each using different 48 bits of key final permutation DES operation