Which one of the following is used to provide authentication and confidentiality for e-mail messages?

A.
Digital signature

B.
PGP

C.
IPSEC AH

D.
MD4

Explanation:
PGP is often used for signing, encrypting, and decrypting texts, e-mails, files, directories, and whole disk
partitions and to increase the security of e-mail communications.
Incorrect Answers:
A: Digital signature is used only to ensure the origin, but cannot do any authentication.
C: IPSec can provide encryption and authentication, but work on packets not on email messages.
D: MD4 is an algorithm used to verify data integrity, but it cannot be used to provide authentication.

Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, New York, 2013, pp. 850-851