The strength of a hash function against brute-force attacks depends solely on which of the following?

• A. The length of the hash code produced
• B. The complexity of the algorithm
• C. The type of input data
• D. The hashing technique used

Answer: (A)

The strength of a hash function against brute-force attacks primarily hinges on the length of the hash code it produces. A longer hash code yields a larger number of possible combinations that an attacker must try to guess the original input. For example, if a hash produces a 256-bit output, that results in 2^256 possible hash values, which makes brute-force attacks computationally impractical, given current technology. In contrast, if the hash output were shorter—say 128 bits—the possible combinations would be significantly fewer (2^128), making it easier for an attacker to successfully run a brute-force attack.

While the complexity of the algorithm, the type of input data, and the specific hashing technique used can contribute to the overall security and robustness of the hashing process, they do not directly influence the number of potential combinations available for an attacker to exploit through brute force which primarily is determined by the hash code length. Therefore, focusing on the output length is crucial for estimating the resistance of a hash function to brute-force attacks.