In: Advanced Math
(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 a 32-bit string using the S-boxes.
(e) Without giving details of the algorithm, briefly discuss some of the shortcomings of DES.
THIS QUESTIONS FOR CRYPTOGRAPHY