IT-478-Network Security

College of Computing and Informatics

Assignment 1
Deadline: Wednesday 01/10/2025 @ 23:59
[Total Mark for this Assignment is 8]
Student Details:
Name: ###

ID: ###

CRN: ###
Instructions:

• You must submit two separate copies (one Word file and one PDF file) using the Assignment Template on
Blackboard via the allocated folder. These files must not be in compressed format.

• It is your responsibility to check and make sure that you have uploaded both the correct files.
• Zero mark will be given if you try to bypass the SafeAssign (e.g. misspell words, remove spaces between
words, hide characters, use different character sets, convert text into image or languages other than English
or any kind of manipulation).

• Email submission will not be accepted.
• You are advised to make your work clear and well-presented. This includes filling your information on the cover
page.

• You must use this template, failing which will result in zero mark.
• You MUST show all your work, and text must not be converted into an image, unless specified otherwise by
the question.

• Late submission will result in ZERO mark.
• The work should be your own, copying from students or other resources will result in ZERO mark.
• Use Times New Roman font for all your answers.

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Question One

Pg. 01
Learning
Outcome(s):
CLO1:
Explain the
concepts of
cryptography,

Question One

Transfer the plaintext “I love Network Security” to ciphertext by using the following
operations:
– Substitution (Atbash Cipher)
– Columnar Transposition (Key Word: Saeed)
In your words, what are the strengths and weaknesses of these operations?

encryption, hash
functions,
message
authentication,
digital signatures
and Network
Security.

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2 Marks

Answer:

Question Two

Pg. 02
Learning
Outcome(s):
CLO1:

Question Two

Why is unpredictability in random numbers more critical than simple randomness for
cryptography? Illustrate your answer with one example.

Explain the
concepts of
cryptography,
encryption, hash
functions,
message
authentication,
digital signatures
and Network
Security.

Restricted – ‫مقيد‬

2 Marks

Answer:

Question Three

Pg. 03
Learning
Outcome(s):

Question Three

2 Marks

CLO1:

What is the difference between symmetric and asymmetric encryption? Are hashing and
encryption the same? Please clarify.

Explain the

Answer:

concepts of
cryptography,
encryption, hash
functions,
message
authentication,
digital signatures
and Network
Security.

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Question Four

Pg. 04
Learning
Outcome(s):

Question Four

2 Marks

Answer the following questions based on the Kerberos protocol:

CLO1:
Explain the
concepts of
cryptography,
encryption, hash
functions,
message
authentication,
digital signatures
and Network
Security.
a) In Step 1, Alice’s request to the Authentication Server (AS) is sent in plaintext.
Why is it considered secure to send her identity without encryption at this step?
b) In Step 2: What is the major security advantage of discarding the key immediately
after initial authentication?
c) Explain how the combination of the ticket and the timestamp in Step 3 of the
protocol makes it difficult for an attacker to perform a replay attack. Why can’t
an attacker simply reuse a captured message from Step 3?
d) In Step 4. Why does TGS send a ticket specifically for Bob, encrypted with Bob’s
key, instead of just sending the session key to Alice?
Answer:

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