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Product’ = permutation + substitution. • Iterated cipher = many rounds – Key schedule– schedule: • Key K is used to construct Nr round keys (subkeys) K1, …, KNr. – Round function g: • stater = g(stater-1, Kr). • state0 = x.
Block ciphers Product ciphers ¢ ‘Product’ = permutation + substitution ¢ Iterated cipher = many rounds — Key schedule: ¢ Key K 1s used to construct Nr round keys (subkeys) K;, , Ky — Round function g: ¢ state, = g(state,,, K,) ¢ state, = x The Encryption and Decryption Encryption Decryption - — g(w®, K') wt! c g © g lề KT) to” — g(te`, K?) wprt-! g(wht-2, A Nt1) Tàn Sài yw, tD ~1/ (to xì 772 tơ”