Which of the following can be used to encrypt email messages, files, and disk drives? (Select the best answer.)

A.
L2TP

B.
PEM

C.
PGP

D.
S/MIME

Explanation:
Pretty Good Privacy (PGP) is software that can be used to encrypt email messages, files, and disk drives. PGP
can be used to provide confidentiality, integrity, and nonrepudiation. PGP uses an asymmetric encryption
method to encrypt information. To encrypt a file or a message by using PGP, you must use the recipient’s
public key. The recipient will then use his or her private key to decrypt the file or message. Many modern
operating systems (OSs) offer their own builtin support for file level and disk level encryption. Therefore, thirdparty software is often no longer necessary for encrypting files.
Privacy Enhanced Mail (PEM) and Secure/Multipurpose Internet Mail Extensions (S/MIME) can be used to
encrypt email messages, but they cannot be used to encrypt files or disk drives. PEM is defined in Requests for
Comments (RFCs) 1421 through 1424 but was never widely used. S/MIME, which was created by RSA Data
Security, is now an RFC standard defined in RFCs 3369, 3370, 3850, and 3851.
Although Layer 2 Tunneling Protocol (L2TP) can be used along with an encryption protocol to encrypt files and
email messages while they are sent over a virtual private network (VPN), L2TP is not used to encrypt disk
drives. L2TP does not offer any security on its own but provides the tunnel by which IP packets encapsulated in
User Datagram Protocol (UDP) packets can travel.

Search Security: Tech Target: Pretty Good Privacy (PGP)
Microsoft TechNet: Understanding S/MIME