Question

For an n-bit tag and a k-bit key, the level of effort required for brute force attack on a MAC algorithm is

(a) 2^k

(b) 2^n

(c) min(2^k,2^n)

(d) 2^k/2^n

The question was asked in a national level competition.

I'd like to ask this question from Message Authentication Codes (MACs) topic in section Message Authentication Codes, Whirlpool Algorithm and Key Management and Distribution of Cryptograph & Network Security

Answer 1

Correct answer is (c) min(2^k,2^n)

For explanation: The level of effort required for brute force attack on a MAC algorithm is min(2^k,2^n).