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CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Autumn Examinations 2011/
School: Computing & Mathematics
Programme Title: MSc in Networking and Security
Programme Code: KNSEC_9_Y
Module Title: Cryptography
Module Code: COMP
External Examiner(s): Mr. M. Deegan Internal Examiner(s): Mr. V. Ryan
Instructions: Answer any 4 questions Each Question is worth 25 Marks.
Duration: 2 Hours
Sitting: Autumn 2012
Requirements for this examination:
Note to Candidates: Please check the Programme Title and the Module Title to ensure that you are attempting the correct examination. If in doubt please contact an Invigilator.
a) Explain what is meant by Kerchoff's Principle, and its implication for modern day cryptography. [5 Marks]
b) Outline the Feistel Cipher as it is used for encryption and decryption. Deduce a mathematical equation to represent a round of the Feistel. [7 Marks]
c) What do you understand by version rollback attack as it applies to SSL? Give details. [7 Marks]
d) Discuss issues that have surfaced regarding SSL in the last 18 months. Refer especially to the Comodo and Diginotar events. [6 Marks]
Question 2 a) Overview AES/Rijndael as it is used for encryption and decryption in the 128-bit key version. Explain why the decryption works. [8 Marks]
b) Describe the CTR (counter) mode of operation. [7 Marks]
c) Explain in detail how padding oracle attack works.
a) What do you understand by the zero point of an elliptic curve, and explain why it is needed. [5 Marks]
b) On the elliptic curve E 23 (1,4), if x= 14 is on the curve, find the corresponding y-values, if any. Show all workings clearly. [7 Marks]
c) Let E be an elliptic curve, defined over the binary field F 24
with the irreducible polynomial f(x) = x^4 + x + 1. Explain how the points on the curve can be found. [7 Marks]
d) Evaluate why ECC needs smaller key sizes than RSA. [6 Marks]
Question 6 a) Discuss the one-time pad encryption scheme. [6 Marks]
b) Detail the mathematics behind the reason why RSA encryption/decryption works. [9 Marks]
c) In the following field, F^2 4 , with irreducible polynomial f(x) = x^4 + x + 1, perform the following operation: 0111 * 1101. Show all workings clearly.
