Which of the following algorithms provides better protection against brute force attacks by using a 160-bit message digest?

MD5 produces only a 128-bit message digest, which is smaller than SHA-1's 160-bit output and therefore less resistant to brute force and collision attacks.

SHA-1 (Secure Hash Algorithm 1) generates a 160-bit message digest, which provides a significantly larger output space than 128-bit algorithms. The larger digest size means an attacker must search a much larger space to find a collision or preimage, increasing brute force resistance. It was designed by NIST as an improvement over MD5 specifically for stronger cryptographic integrity.

RC4 is a symmetric stream cipher used for encryption, not a hashing algorithm, so it does not produce a message digest of any bit length.

MD4 is the predecessor to MD5 and also produces a 128-bit message digest, making it weaker than SHA-1 and not the correct answer.