Mock Paper B

📝 Mock Examination B

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Question 1: Authentication

(a) Compare Hashing vs. Encryption.

1. Which one is reversible?
2. Which one is used for storing passwords?
3. Which one is used for ensuring data confidentiality during transit? [5 marks]

(b) Explain the “Downgrade Dance” in the context of the POODLE attack on SSL v3.0. How does an attacker force a modern browser to use an insecure protocol? [5 marks]

(c) In a Phishing attack, list three common “Indicators of Compromise” (red flags) that a user might spot in a malicious email. [5 marks]

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Question 2: Public Key Infrastructure (PKI)

(a) Alice wants to digitally sign a document to prove it came from her.

1. Which key does she use to sign the hash?
2. Which key does Bob use to verify the signature?
3. If Bob successfully verifies the signature, what two security properties have been achieved? (e.g., Confidentiality, Integrity, Non-repudiation). [6 marks]

(b) A Root Certificate Authority (CA) is compromised.

1. What is the impact on the “Chain of Trust” for all certificates signed by this CA?
2. What mechanism (acronym: CRL or OCSP) allows browsers to reject these now-invalid certificates? [4 marks]

(c) RSA Calculation: Given $p=3$ and $q=5$.

1. Calculate the modulus $n$.
2. Calculate Euler’s Totient $\varphi (n)$.
3. If we choose public exponent $e=3$, find the private exponent $d$ such that $d\times e\equiv 1(\mathrm{mod}\varphi (n))$. [10 marks]

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Question 3: Network Security

(a) Analyze the diagram below (Text Description):

• Zone A: Contains the Database Server and Employee Workstations.
• Zone B: Contains the Public Web Server and Email Relay.
• Zone C: The Internet.

1. Which Zone represents the DMZ?
2. Where should the Firewalls be placed? (Between which zones?)
3. If the Web Server in Zone B is compromised, what prevents the attacker from immediately accessing the Database in Zone A? [8 marks]

(b) Compare IDS (Intrusion Detection System) and IPS (Intrusion Prevention System).

• Which one is “Passive” and which is “Active”?
• Which one introduces a risk of blocking legitimate traffic (False Positives) that causes a denial of service? [7 marks]

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Question 4: Attacks & Defense

(a) A user is logged into their banking website. They open a new tab and visit a malicious site which contains a hidden form that submits a “Transfer Money” request to the bank.

1. Name this attack.
2. Explain why the bank accepts the request (Hint: Cookies).
3. What specific token can the bank implement to prevent this? [8 marks]

(b) Block Cipher Modes:

1. Why is ECB (Electronic Codebook) mode considered insecure for encrypting images or large files?
2. What is the purpose of the IV (Initialization Vector) in CBC mode? [7 marks]