BISF 3201 CRYPTOGRAPHY.

UNIVERSITY EXAMINATIONS: 2021/2022
EXAMINATIONS FOR THE DEGREE OF BACHELOR OF SCIENCE IN
INFORMATION SECURITY AND FORENSICS
BISF 3201: CRYPTOGRAPHY
FULL TIME/PART TIME
DATE: DECEMBER, 2021 TIME: 2 HOURS
INSTRUCTIONS: Answer QUESTION ONE AND ANY OTHER TWO questions.

QUESTION ONE – COMPULSORY [20 MARKS]
a) Discuss the objectives of Cryptography. 4 Marks
b) Discuss the strengths and weaknesses of symmetric and asymmetric cryptographic
algorithms. 6 Marks
c) Discuss in detail the different ways of classifying classical cyphers and modern cyphers.
6 Marks
d) Discuss any four components of the Public Key Infrastructure (PKI) 4 Marks
QUESTION TWO [15 MARKS]
With the aid of relevant diagrams, discuss how the Data Encryption Standard (DES) algorithm
operates.
QUESTION THREE [15 MARKS]
a) Describe briefly five ways in which cryptographic algorithms are compromised.
5 Marks
b) Discuss how hashing is used in password protection. 3 Marks
c) Explain how encryption can help with message authentication, even if the encryption is
weak and easily broken. 3 Marks
d) Relations between encryption and signature methods became possible with the
“digitalization” of both and the introduction of the computational-complexity approach to
security.
(i) State the TWO requirements that a scheme for unforgeable signatures must
possess. 2 Marks
(ii) State the requirements for a scheme that would perform message authentication
2 Marks
QUESTION FOUR [15 MARKS]
a) Discuss any six cryptographic attacks. 6 Marks
b) Discuss how the following attacks are conducted:
(i) DUHK attack 3 Marks
(ii) Rainbow table attack 3 Marks
(iii) Hash Collision Attack 3 Marks

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