What do the message digest algorithms MD2, MD4 and MD5 have in common?

A.
They are all used in the Secure Hash Algorithm (SHA).

B.
They all take a message of arbitrary length and produce a message digest of 128-bits.

C.
They all take a message of arbitrary length and produce a message digest of 160-bits.

D.
They are all optimized for 32-bit machines.

Explanation:
* Answer “They all take a message of arbitrary length and produce a message digest of 160-bits” is
obviously, then, incorrect. * Answer “They are all optimized for 32-bit machines” is incorrect since
MD2 (B.S. Kaliski, The MD2 Message Digest Algorithm, RFC 1319, April 1992) is targeted for 8-bit
machines. It is used in Privacy Enhanced Mail (PEM). MD4 (R.L. Rivest, The MD4 Message Digest
Algorithm, RFC 1186, Oct 1990) and MD5 (R.L. Rivest, The MD5 Message Digest Algorithm, RFC 1321,
April 1992) are designed for 32-bit machines. MD5 is considered more secure than MD4, and MD5 is
also used in PEM. Answer d is incorrect since the SHAis a separate algorithm from MD2, MD4, and
MD5, but is modeled after MD4. SHA produces a 160-bit message digest.