A message M is divided into the following 5 message blocks, M1, ..., M5, each of whose size is 8 bits, i.e., the block size is 8 bits:

• M1 = 11010101

• M2 = 00111011

• M3 = 00010001

• M4 = 10001001

• M5 = 01111100

Problem 1

XOR Hash function takes M as an input. Compute the hash code C. You must show all the intermediate works (scratch works which are readable).

Problem 2

Give an example forgery of M that an adversary would create. You must show all the intermediate works (scratch works which are readable).

Problem 3

Suppose a recipient receives the forgery created in Problem 2. Explain why the recipient would not suspect any foul play on the received message. You must show all the intermediate works (scratch works which are readable).