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Cork Institute of Technology
Bachelor of Science (Honours) in Software Development – Award
(KSDEV_8_Y4)
Summer 2008
Security and Cryptography
(Time: 3 Hours)
Answer any four questions. Examiners : Mr. V. Ryan Dr. M. O Cinneide M. M. Donnelly
Question 1 a) Explain how the AES works for both encryption and decryption. Outline what happens in each round of the encryption algorithm. How many subkeys need to be generated from the key and why? [6 Marks]
b) When seeking a cipher to become the AES, what factors were considered? Explain why each of these factors is significant. [7 Marks]
c) Outline the COUNTER mode of operation, as used for encryption and decryption. [6 Marks]
d) Explain 4 advantages that this mode of operation exhibits. [6 Marks]
Question 2 a) Outline how public and private keys are generated in RSA, and how encryption and decryption are performed in RSA. [5 Marks]
b) Explain why the security of RSA depends on the factoring problem being difficult. [6 Marks]
c) Outline the progress that has been made in addressing the factoring problem. [5 Marks]
d) If in the RSA key generation process, the two prime numbers have been chosen as 89 and 197 and the exponent e has been chosen as 449. Find the private key exponent d. In your answer, demonstrate clearly that you have used the Euclidean Algorithm. [9 Marks]
Question 3 a) Outline the design of a typical hash function. [6 Marks]
b) Explain what is meant by a birthday attack on a hash function. Give an example of how a birthday attack might be mounted in practice. [7 Marks]
c) Compare the security of the hash functions MD5, SHA-1 and SHA-2. [6 Marks]
d) Compare the use of hash functions with the use of Message Authentication Codes. [6 Marks]
Question 4. a) Explain the purpose of each of the following SSL protocols: Record Protocol Alert Protocol Change Cipher Spec Protocol [6 Marks]
b) Explain in outline the steps that are followed by SSL when a user uses HTTPS to connect to a bank using an SSL session. [7 Marks]
c) Describe how man-in-the-middle attack against SSL might work. [6 Marks]
d) Outline the X.509 protocol. [6 Marks]
