Principles and Performance of Cryptographic Algorithms

By Bart Preneel, Vincent Rijmen, and Antoon Bosselaers

Dr. Dobb's Journal December 1998

Figure 2: Two rounds of the DES, the most famous block cipher. It has the Feistel structure. E denotes the linear expansion of the 32 input bits to 48 input bits, denotes the bitwise XOR with the round key, S is the nonlinear substitution, and P is the bit permutation.

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