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cfb Ciphertext feeback mode c[i] = f1(K, c[i-1]) ^ p[i] p[i] = f1(K, c[i-1]) ^ c[i]

Suppose instead of c[i-1] you use c[i-N] where N is say 10.

Wouldn't the size of your IV have to grow as N grows? Jim Russell SynData Technologies