One round of des i-1 R KeyH-1 32 32 Shift Shift 56 Expansion Permutation Compression Permutation 48 Feistel 48 Network S-Box Substitution 32 P-Box Permutation 32 32 56 R i Keyi 1414 One Round of DES Expansion Permutation 48 P-Box Permutation S-Box Substitution 32 Shift Shift 48 Compression Permutation Feistel Network 56 32 32 Li-1 Ri-1 Keyi-1 Li Ri Keyi 32 32 56