A company has decided to implement an electronic signature scheme based on public key infrastructure. The
user’s private key will be stored on the computer’s hard drive and protected by a password. The MOST
significant risk of this approach is:

A.
use of the user’s electronic signature by another person if the password is compromised.

B.
forgery by using another user’s private key to sign a message with an electronic signature.

C.
impersonation of a user by substitution of the user’s public key with another person’s public key.

D.
forgery by substitution of another person’s private key on the computer.

Explanation:
The user’s digital signature is only protected by a password. Compromise of the password would enable access
to the signature. This is the most significant risk. Choice B would require subversion of the public key
infrastructure mechanism, which is very difficult and least likely. Choice C would require that the message
appear to have come from a different person and therefore the true user’s credentials would not be forged.
Choice D has the same consequence as choice C.