Question#1
Which type of encryption requires both communicating entities to share a single secret key for both encryption and decryption?
a) Public-key encryption
b) Symmetric encryption ✅ - Answer
c) Asymmetric encryption
d) Message authentication

Question#2
Which of the following is an example of a block cipher algorithm used in symmetric encryption?
a) RSA
b) Diffie-Hellman
c) AES (Advanced Encryption Standard) ✅ - Answer
d) RC4 (Rivest Cipher 4)

Question#3
Which cipher is known as a stream cipher among the major symmetric encryption algorithms listed?
a) RC4 (Rivest Cipher 4) ✅ - Answer
b) AES
c) DES
d) Blowfish

Question#4
What is true about the keys used in asymmetric encryption?
a) Only a private key is required
b) Both sender and receiver use the same key
c) A public key is shared and a private key is kept secret ✅ - Answer
d) A password is exchanged as the key

Question#5
Which advantage is specifically provided by asymmetric encryption over symmetric encryption?
a) It is recommended for bulk data transfer
b) It enables authentication and non-repudiation ✅ - Answer
c) It minimizes ciphertext size
d) It ensures very fast encryption speeds

Question#6
Which algorithm is NOT used as an example of symmetric key encryption?
a) RSA ✅ - Answer
b) AES
c) Blowfish
d) RC5

Question#7
What is the main difference in how data is handled between block and stream algorithms in symmetric encryption?
a) Block algorithms use two keys; streams use one key
b) Block algorithms encrypt data in fixed-size chunks; streams encrypt as data flows ✅ - Answer
c) Streams encrypt in fixed blocks; blocks encrypt streams
d) Block algorithms are used only for short messages

Question#8
How does the Caesar cipher encrypt letters?
a) Letters are paired in a matrix
b) Letters are replaced using two separate keys
c) Each letter is replaced by one three positions ahead in the alphabet ✅ - Answer
d) Each letter is shifted by a random number

Question#9
Which describes the operation of the Playfair cipher?
a) It shifts every letter by three positions
b) It generates a private and public key pair
c) It substitutes pairs of letters based on a 5x5 matrix from a keyword ✅ - Answer
d) It substitutes each letter with a numeric code

Question#10
In the Caesar cipher, if decryption calculation results in a negative value, what step is taken?
a) Take the absolute value of the result
b) Subtract 3 from the value
c) Add 26 to the negative value before modulo division ✅ - Answer
d) Use the original negative value in the formula

Question#11
Which asymmetric encryption technique can be used for digital signatures?
a) RSA ✅ - Answer
b) DES
c) RC6
d) Blowfish

Question#12
Which property is characteristic of symmetric encryption?
a) It is efficient and recommended for large amounts of text ✅ - Answer
b) It provides non-repudiation by default
c) It uses two unrelated keys
d) It does not require any key exchange

Question#13
What is a key feature of the shift cipher technique?
a) It pairs letters into digraphs
b) It uses a matrix for encryption
c) The key is always fixed at three
d) It allows the key value to range from 0 to 25 ✅ - Answer

Question#14
When would you use asymmetric encryption rather than symmetric encryption?
a) When secure key distribution and authentication are needed ✅ - Answer
b) For fast encryption of large files
c) To minimize implementation complexity
d) When both sides share a single key

Question#15
What must be done in the Playfair cipher if the plaintext has an odd number of letters?
a) Add a filler letter such as 'x' to the last letter ✅ - Answer
b) Duplicate the last letter
c) Shift the last letter by three positions
d) Leave the last letter as is

Question#16
Which property is unique to asymmetric encryption compared to symmetric encryption?
a) Only one key is required for encryption and decryption
b) It allows public keys to be shared openly while keeping private keys secret ✅ - Answer
c) Plaintext and ciphertext sizes are always identical
d) The ciphertext is always shorter than the plaintext

Question#17
If a block cipher waits in memory to fill with data before encryption, what kind of algorithm is this?
a) A stream cipher
b) A polyalphabetic cipher
c) A block algorithm ✅ - Answer
d) A digraph cipher

Question#18
What approach does the Playfair cipher use to handle repeating letters in a pair?
a) Encodes as a single letter
b) Shifts both letters by a fixed value
c) Removes one letter from the pair
d) It separates repeated letters with a filler such as 'x' ✅ - Answer

Question#19
Which set of algorithms is ONLY associated with asymmetric encryption?
a) Vigenere, Hill, Caesar, Playfair
b) RC5, RC6, IDEA, RC4
c) RSA, DSA, Diffie-Hellman, ECC ✅ - Answer
d) DES, AES, RC4, Blowfish

Question#20
Which is a recognized limitation of the Caesar cipher?
a) It encrypts pairs of letters
b) It requires a keyword matrix
c) It offers weak security ✅ - Answer
d) It needs two separate keys