Fundamental of cyber security

Question 1
a) What is the difference between an unconditionally secure cipher and a computationally
secure cipher (10 marks)
b) Define confusion and diffusion within the context of cryptography principles and highlight
differences between them.
(15 marks)
(Total 25 marks)
Question 2
When not even the large number of keys in a monoalphabetic cipher provided sufficient
security, an approach to improving security was to encrypt multiple letters. The Playfair Cipher
is an example.
a) Describe the encryption process for the Playfair Cipher, including the rules for special cases.
(10 marks)
b) Describe the decryption process for the Playfair Cipher.
(10 marks)
c) Discuss and quantify the security of the Playfair Cipher.
(5 marks)
(Total 25 marks)
Question 3
d) Discuss the concept of digital signature, and the basic process of generating a digital
(10 marks)
e) Present an application of digital signature. In the context of the application, discuss how a
digital signature is applied and verified.
(15 marks)
(Total 25 marks)
Question 4
a) Explain the concept of RBAC, and its main features.
(10 marks)
b) Considering the Blackboard system, analyse how to use RBAC mechanism to restrict users’
resource access control based on their roles in the system (e.g. staffs and students).
Comparing with Access Control List (ACL) mechanism, discuss the advantages of using
RBAC to implement the authorization in such a system.
(15 marks)

Sample Solution