Cryptography and Network Security Principles and Practice, 8th Edition - Pearson

APPENDIX C

Data Encryption Standard

The overall scheme for DES encryption is illustrated in Figure C.1, which repeats Figure 4.5. As with any encryption scheme, there are two inputs to the encryption function: the plaintext to be encrypted and the key. In this case, the plaintext must be 64 bits in length and the key is 56 bits in length.¹

Figure C.1 General Depiction of DES Encryption Algorithm

Looking at the left-hand side of the figure, we can see that the processing of the plaintext proceeds in three phases. First, the 64-bit plaintext passes through an initial permutation (IP) that rearranges the bits to produce the permuted input. This ...