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Main points of this exam paper are: RSA Cipher, Advantages, Binary Square, Euclidean Algorithm, Exponentiation Algorithm, Identification Protocols, Purpose, Protocol, Fiat-Shamir, Security
Typology: Exams
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(NFQ – Level 9)
Instructions: Answer any three questions. Each Question is worth 40 Marks. Note that the 120 Marks available equate to 100%.
Examiners: Mr. V. Ryan Mr. P. French Dr. S. McGrath Mr. A. Murphy
Q1. (a) Explain why public-key cryptography is needed. [6 Marks] (b) Outline the RSA Cipher. [5 Marks] (c) Explain why RSA works. [6 Marks] (d) Explain why RSA is secure. [6 Marks] (e) Explain, using an example, the advantages of using the binary square and multiply algorithm (fast exponentiation algorithm) in RSA calculations. [7 Marks] (f) Suppose that in choosing RSA keys, we had chosen p=157 , q=109 and e=. Using the Euclidean Algorithm, find the value of d. [10 Marks]
Q3. (a) Define what is meant by a firewall. [5 Marks] ( b) What are the advantages and disadvantages of packet filtering as a firewall technology? [7 Marks] (c) Outline some typical rules that might appear in a packet filtering firewall. [7 Marks] (d) Give an example of a ruleset that would differ significantly in a stateful packet filter from a stateless packet filter. [6 Marks] (e) What type of attacks prove difficult for packet filters, and why? [6 Marks] (f) What do you understand by the term application proxy gateway firewall? [9 Marks]
Q4. (a) Outline, using a diagram, how the OFB mode of operation works for both encryption and decryption. [7 Marks] (b) Explain what is meant by the short-cycle problem as it applies to OFB. [9 Marks] (c) Outline the AES as it is used for encryption. [6 Marks] (d) What is the role of each of the 4 steps that are used in every round? [9 Marks] (e) Explain the characteristics that the NIST were looking for in a cipher when they were choosing the AES. [9 Marks]
