Substitution-Permutation networks: SPN Definition A substitution-permutation(SP)network is a product cipher composed of a number of stages each nvolving substitutions and permutations Substitution to;{01÷{01y Permutation Tp:{1,…,m}{1,…m The plaintext has Im bits X=XulI.. lIX Whe.0=(x/+1,…,X) The spn has Nr rounds, in which we perform on X m substitutionsπ s followed by one permutation兀p to get the ciphertext y.11 Substitution-Permutation Networks: SPN • Substitution pS : {0,1}l → {0,1}l • Permutation pP : {1, …,lm} → {1, …,lm} The plaintext has lm bits: x = x(1)|| . . . ||x(m) where: x(i)= (x(i-1)l+1 , . . . , xil ) The SPN has Nr rounds, in which we perform on x m substitutions pS followed by one permutation pP , to get the ciphertext y. Definition A substitution-permutation (SP) network is a product cipher composed of a number of stages each involving substitutions and permutations