Symmetric Ciphers Questions and Answers – Blowfish Algorithm – I

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This set of Cryptography Multiple Choice Questions & Answers (MCQs) focuses on “Blowfish Algorithm”.

1. What is the maximum size of the key in blowfish algorithm?
a) 256 bits
b) 512 bits
c) 56 bytes
d) 48 bytes

Explanation: The maximum size of the key in blowfish algorithm is 56 bytes or 448 bits.

2. Blowfish encrypts blocks of plaintext which have size
a) 256 bits
b) 64 bits
c) 72 bits
d) 128 bits

Explanation: The size of the blocks of the plaintext is 64 bits each.

3. The blowfish algorithm can be implemented on 16 bit processors.
a) True
b) False

Explanation: The statement is false as 32/64 bit processors are only capable of encrypting/decrypting the blowfish algorithm.
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4. What is the minimum size of the key in blowfish algorithm?
a) 64 bits
b) 32 bits
c) 56 bits
d) 48 bits

Explanation: The minimum size of the key in blowfish algorithm is 4 bytes or 32 bits.

5. The blowfish algorithm’s key expansion converts a key of at most 448 bits into several subkey arrays totaling ___________ bytes.
a) 4096
b) 4608
c) 4168
d) 4864

Explanation: Key expansion converts a key of at most 448 bits into several sub key arrays totaling 4168 bytes i.e. eighteen 32-bit sub keys + four 8×32-bit s boxes = 4168.

6. Blowfish algorithm uses the Feistel Structure.
a) True
b) False

Explanation: In the blowfish algorithm data encryption occurs via a 16-round Feistel network.

7. XOR and addition operations take place on bytes of size
a) 8 bits
b) 16 bits
c) 32 bits
d) 64 bits

Explanation: XOR and addition operations take place on bytes of size 32 bits.

8. How many S-boxes are present in the blowfish algorithm?
a) 2
b) 4
c) 6
d) 8

Explanation: There are 4 s-boxes in the blowfish algorithm.

9. How many entries are present in each of the S-boxes present in the blowfish algorithm?
a) 256
b) 512
c) 1024
d) 64

Explanation: There are 4 s-boxes with 256 entries each in the blowfish algorithm.