behrouz a forouzan cryptography and network security

Applying the MixColumn transformation to P1 and P2, we get:. One advantage of CFB is that no padding is required because the size of the blocks, r, is normally chosen to fit the data unit to be encrypted. Note that there is one trans- formation for pre-round. The first routine multiplies two bytes; the second routine finds the quotient of dividing the first byte by the second. A substitution cipher replaces one char- acter with another character.

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