Tutorial 1 – ICT 211

Question 1

a) Describe Active Attacks and Passive Attacks. Also describe three different types of passive attacks and four different types of active attacks. How would one counter an active attack?

b) Give examples of two possible scenarios when one cannot be absolutely certain that an adversary is launching a modification-of-message attack or denial-of-service attack, even when the proper security protections are in place. Explain your answer.

c) How could traffic analysis jeopardize security? Give an example to illustrate your answer.

Question 2

(a) Is it likely to achieve perfect security for a network (i.e. to have a network that will never fail in terms of security) in the real business world? Give three possible reasons to substantiate your answer.

(b) The computing speed is much faster these days compared to that some years back. On the other hand, old algorithms and systems are still in use. Give three reasons to explain this situation.

Question 3

a) (i) Explain Security Services and Security Mechanisms.

(ii) Suppose the main threat of a network is replay attack. Does the use of confidentiality services protect the network against such attack? Explain your answer.

(iii) Is it always the case that only one mechanism can be used to achieve the provision of a particular service? Give an example to illustrate and explain the answer.

(b) Explain how the following services ensure security of the systems or of data transfers and give possible example or scenario for each:

i) Message authentication ii) Non- repudiation iii) Confidentiality

Give a concrete application scenario that one may need authenticity of message but may not need confidentiality of message. Explain your answer clearly.