INF4831 PAST EXAMS MULTIPLE CHOICE QUESTIONS MCQ AND ANSWERS

INF4831 - EXAM PACK 2025
150+ PAST EXAM MCQ AND ANSWERS

,Encryption Basics
1. What is the primary purpose of encryption?
A. Compress data
B. Hide data from unauthorized users
C. Increase data size
D. Improve network speed
2. Encryption converts plaintext into:
A. Hash
B. Key
C. Ciphertext
D. Algorithm
3. Decryption is the process of:
A. Scrambling data
B. Compressing files
C. Converting ciphertext back to plaintext
D. Creating keys
4. Which of the following best defines a cipher?
A. A password
B. A secret message
C. A method of encryption
D. A key generator
5. Which term refers to readable data before encryption?
A. Ciphertext
B. Plaintext
C. Hash
D. Token


Caesar Cipher
6. The Caesar Cipher is an example of:
A. Transposition cipher
B. Substitution cipher
C. Asymmetric encryption
D. Hashing
7. In a Caesar Cipher, what happens to letters?
A. They are rearranged
B. They are deleted
C. They are shifted by a fixed amount
D. They are replaced randomly

, 8. What is the key used in a Caesar Cipher?
A. Keyword
B. Public key
C. Shift value
D. Private key
9. Which shift value gives the strongest Caesar Cipher?
A. 1
B. 5
C. 13
D. None— all are equally weak
10. What is the main weakness of the Caesar Cipher?
A. Requires padding
B. Easy to brute force
C. Uses two keys
D. Changes letter frequency


Substitution Ciphers
11. A substitution cipher works by:
A. Rearranging letters
B. Replacing letters with other letters
C. Removing vowels
D. Adding random characters
12. Which cipher is a simple substitution cipher?
A. Columnar Transposition
B. Caesar Cipher
C. Rail Fence
D. Hashing
13. What stays the same in a substitution cipher?
A. Letter order
B. Letter frequency
C. Message length
D. Key size
14. Which is NOT a substitution cipher?
A. Caesar Cipher
B. Vigenère Cipher
C. Columnar Transposition
D. Monoalphabetic cipher
15. Substitution ciphers are vulnerable to:
A. Padding attacks