Major Exam B · Term unknown
- Source: photos of a blank copy (pages 2, 3, 5, 6 and 7 of 7). The cover and page 4 (Question 2 B–D, 3.5 marks) weren't photographed, so the paper is marked out of 16.5.
- It shares several questions with Major Exam C, so the two are probably versions of the same exam.
كلية علوم الحاسب ونظم المعلومات
A) Choose the Correct Option. [2.5 Marks]
Given the nested DES encryption operation C = EKC(DKB(EKA(P))); what is the correct sequence of decryption operations?
The following message is encrypted using Caesar Cipher, find
its associated key assuming the space is replaced by the
letter “X”.
Message = THE IDES OF MARCH ARE COME
Plaintext =
THEXIDESXOFXMARCHXAREXCOME
Ciphertext =
AOLEPKLZEVMETHYJOEHYLEJVTL
Sarah, a financial analyst at a multinational company located in London, needs to share a confidential financial report with her manager, before a very important meeting in Riyadh as part of LEAP conference. She is considering different ways to send the file and wants to ensure that the data remains secure. Which of the following security controls should Sarah follow when storing, accessing, and transferring confidential data?
A hospital categorizes its data as Confidential, Internal Use, or Public. Which data classification is correct?
You have been tasked with crafting a fairly stable security plan. It also needs to define the security function and align it to the goals, mission, and objectives of the organization. What are you being asked to create?
كلية علوم الحاسب ونظم المعلومات
B) For each statement, choose the appropriate Term from the given table to fill the blank. [2.5 Marks]
| Utility | Authenticity | Brute-Force Attack |
| Cyber criminal | Tailgating | Confidentiality |
| Two factor authentication | Firewall | Phishing |
refers to the quality or state of preventing disclosure or exposure to unauthorized individuals.
a physical security breach where an unauthorized person gains access to a restricted area by following an authorized individual without proper authentication.
The main motivation of is to gain financial benefits and make money.
if information is available, but not in a format meaningful to the end user. For example if a doctor tries to access a patient’s file but receives the data in raw hexadecimal code instead of a readable medical report
can prevent unauthorized access even if a user’s password is compromised.
A)
- List down the STRIDE threats. (Column 1)
- For each threat, write the security property it violates (Column 2).
- For each STRIDE threat, write an appropriate Cyber security threat category (given below) (Column 3).
| Interruption |
| Interception |
| Modification |
| Fabrication |
| STRIDE THREAT [1.5 Marks] | PROPERTY VIOLATED [1.5 Marks] | CYBER SECURITY THREAT CATEGORY [1.5 Marks] |
|---|---|---|
| Threat | Property | Category |
|---|---|---|
| Spoofing | Authentication | Fabrication |
| Tampering | Integrity | Modification |
| Repudiation | Non-repudiation | Fabrication (Modification also accepted) |
| Information disclosure | Confidentiality | Interception |
| Denial of service | Availability | Interruption |
| Elevation of privilege | Authorization | Modification |
كلية علوم الحاسب ونظم المعلومات
E) You are presented with the following scenarios related to a company’s cybersecurity practices. For each scenario, classify it as either an example of due care or due diligence, and briefly explain your reasoning. [1 marks]
| Scenario A: A company in Riyadh implements a robust employee training program that includes regular workshops on phishing awareness and secure password practices to meet NCA requirements. |
|
Model answer · 0.25 marksDue
care: running the training to meet NCA requirements is the
reasonable protective action itself.
|
| Scenario B: The company conducts risk assessments every two months to identify potential security threats and vulnerabilities in its systems. |
|
Model answer · 0.25 marksDue
diligence: regular risk assessments are the ongoing
investigation that identifies what needs protecting.
|
A) Assuming the block size b=64 bits. The plaintext is “wewillattentandenjoyLEAPinKSA”.[1 mark]
How many Padded bits are needed to send the complete data? bits
How many blocks will be used?
B) Using the Playfair cipher, construct a Playfair matrix, and encrypt the message ” COMMITTEES ” with the keyword ” EFFECTIVENESS ” considering that (I/J) will be in the same cell. Show your answer. [1.5 mark]
Ciphertext:
| E | F | C | T | I/J |
| V | N | S | A | B |
| D | G | H | K | L |
| M | O | P | Q | R |
| U | W | X | Y | Z |
كلية علوم الحاسب ونظم المعلومات
C) Using Vigenère cipher, decrypt the Ciphertext: “CMRUVLERMYOLRX” with key “ RIYADH ”. [1 Marks]
| A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| A | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
| B | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | A |
| C | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | A | B |
| D | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | A | B | C |
| E | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | A | B | C | D |
| F | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | A | B | C | D | E |
| G | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | A | B | C | D | E | F |
| H | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | A | B | C | D | E | F | G |
| I | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | A | B | C | D | E | F | G | H |
| J | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | A | B | C | D | E | F | G | H | I |
| K | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | A | B | C | D | E | F | G | H | I | J |
| L | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | A | B | C | D | E | F | G | H | I | J | K |
| M | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | A | B | C | D | E | F | G | H | I | J | K | L |
| N | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | A | B | C | D | E | F | G | H | I | J | K | L | M |
| O | O | P | Q | R | S | T | U | V | W | X | Y | Z | A | B | C | D | E | F | G | H | I | J | K | L | M | N |
| P | P | Q | R | S | T | U | V | W | X | Y | Z | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O |
| Q | Q | R | S | T | U | V | W | X | Y | Z | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P |
| R | R | S | T | U | V | W | X | Y | Z | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q |
| S | S | T | U | V | W | X | Y | Z | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R |
| T | T | U | V | W | X | Y | Z | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S |
| U | U | V | W | X | Y | Z | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T |
| V | V | W | X | Y | Z | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U |
| W | W | X | Y | Z | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V |
| X | X | Y | Z | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W |
| Y | Y | Z | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X |
| Z | Z | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y |
Plaintext:
D) Given the following figure, answer the following questions. [2.5 Marks]
What is the encryption Mode? [1 Mark]
كلية علوم الحاسب ونظم المعلومات
Write the encryption function for C[2] / decryption function for P[2]. [1.5 Mark]
Encryption: C[2] = EK(P[2] ⊕ C[1])
Decryption: P[2] = DK(C[2]) ⊕ C[1]
General form: C[i] = EK(P[i] ⊕ C[i−1]) and P[i] = DK(C[i]) ⊕ C[i−1], with C[−1] = IV (the V in the figure).