In Figure 31.9, we have two straight permutation operations: initial permutation and final permutation. Experts believe these operations are useless and do not help to make the cipher stronger. Can you find the reason for this statement?

Figure 31.9

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64-bit plaintext DES 32 bits 32 bits Initial permutation K1 Round I 48-bit f( R1. K; ) K; Round i 56-bit 48-bit cipher key K16 Round 16 48-bit Final permutation 32 bits 32 bits Each round 64-bit ciphertext