(a) Random numbers play an important role in the use of cryptography for various security application.

i. Briefly explain pseudorandom number generator (PRNG).

ii. How to apply PRNG in cryptography?

iii. Indicate THREE (3) difference between true random number generator (RNG) and pseudorandom number generator..

(b) Stream and block ciphers are both essential in modern symmetric cryptosystems.

Compare the differences between stream and block ciphers in terms of speed of transformation, error propagation, diffusion and susceptibility to malicious modification. Show your answer in a table.

(c) In cryptography, confusion and diffusion are two properties of the a secure cipher identified by Claude Shannon. Identify ONE (1) main difference between confusion and diffusion in Shannons original definitions.

(d) Briefly explain the TWO (2) purposes of S-boxes in DES.