Synopsis
The simplified DES algorithm found in this book makes analysis easy. Everything takes place from the top of the page to the bottom of the page. There is no permutation of bits, no rotation of bits, no permuted choices. DES problems where the number of iterations are small are discussed in detail. Several problems, where the task is to recover the initial key, are provided. Moreover, the problems show the reader why 16 iterations or rounds contribute to the system's security. The author looks at the security afforded by the S-boxes, especially at the S-4 box, and with a computer program an attempt is made to find the four bits that exit from the S-box using only a limited number of entering bits. Text contains BASIC computer programs.
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