(a) Briefly describe what is meant by the word
cryptography.
(b) Briefly describe the Vigenere cipher,
including a discussion of the encryption and decryption
processes.
(c) Describe what is meant by a ‘Feistel
Cipher’.
(d) DES includes S-boxes as part of its
encryption and decryption steps. Each of eight S-boxes is a fixed 4
× 16 array, whose entries come from the integers 0, 1, . . . , 15.
Describe in detail how DES transforms a 48-bit string into...