Which security measure BEST provides non-repudiation in electronic mail?

A.
Digital signature

B.
Double length Key Encrypting Key (KEK)

C.
Message authentication

D.
Triple Data Encryption Standard (DES)

Explanation:
A tool used to provide the authentication of the sender of a message. It can verify the origin of the
message along with the identity of the sender. IT is unique for every transaction and created with a
private key. – Shon Harris All-in-one CISSP Certification Guide pg 930 “Secure Multipurpose Internet
Mail Extensions (S/MIME) offers authentication and privacy to email through secured attachments.
Authentication is provided through X.509 digital certificates. Privacy is provided through the use of
Public Key Cryptography Standard (PKCS) Enryption. Two types of messages can be formed using
S/MIME: signed messages and enveloped messages. A signed message provides integrity and sender
authentication. An enveloped message provides ntegrity, sender authentication, and
confidentiality.” Pg 123 Tittle: CISSP Study Guide