Question

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

This question was addressed to me during an interview.

The origin of the question is Blowfish Algorithm in portion Pseudorandom Number Generation and Stream Ciphers and More Block Ciphers of Cryptograph & Network Security

Answer 1

Correct answer is (c) 4168

Easy 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.