What size is an MD5 message digest (hash)?

A.
128 bits

B.
160 bits

C.
256 bits

D.
128 bytes

Explanation:
“MD4
MD4 is a one-way hash function designed by Ron Rivest. It produces 128-bit hash, or message
digest, values. It is used for high-speed computation in software implementations and is optimized
for microprocessors.
MD5
MD5 is the newer version of MD4. It still produces a 128-bit hash, but the algorithm is more
complex, which makes it harder to break. MD5 added a fourth round of operations to be performed
during the hashing functions and makes several of it mathematical operations carry out more
steps or more complexity to provide a higher level of security.
MD2
MD2 is also a 128-bit one-way hash designed by Ron Rivest. It is not necessarily any weaker than
the previously mentioned hash functions, but is much slower.

SHA
SHA was designed by NIST and NSA to be used with DSS. The SHA was designed to be used
with digital signatures and was developed when a more secure hashing algorithm was required for
federal application.
SHA produces a 160-bit hash value, or message digest. This is then inputted into the DSA, which
computes the signature for a message. The message digest is signed instead of the whole
message because it is a much quicker process. The sender computes a 160-bit hash value,
encrypts it with his private key (signs it), appends it to the message, and sends it. The receiver
decrypts the value with the sender’s public key, runs the same hashing function, and compares
the two values. If the values are the same, the receiver can be sure that the message has not
been tampered with in transit.
SHA is similar to MD4. It has some extra mathematical functions and produces a 160-bit hash
instead of 128-bit, which makes it more resistant to brute force attacks, including birthday attacks.
HAVAL
HAVAL is a variable-length one-way hash function and is the modification of MD5. It processes
message blocks twice the size of those used in MD5; thus it processes blocks of 1,024 bits.
Pg. 508-509 Shon Harris CISSP Certification All-In-One Exam Guide