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

MD5 produces a 128-bit message digest, which is shorter than SHA-1's 160-bit output and therefore offers less brute force resistance.

SHA-1 generates a fixed-length 160-bit (20-byte) hash output, which provides a significantly larger keyspace than MD4 or MD5 and therefore greater resistance to brute force and collision attacks. It was designed by the NSA and published by NIST as FIPS PUB 180-1, specifically improving upon MD4 with the larger digest size.

RC4 is a symmetric stream cipher used for encryption, not a hashing algorithm, and produces no message digest.

MD4 produces a 128-bit message digest, shorter than SHA-1, and has known cryptographic weaknesses making it even less suitable for protection against brute force.