CompTIA Security Plus Mock Test Q1108

Which of the following explains the difference between a public key and a private key?

A. The public key is only used by the client while the private key is available to all.
Both keys are mathematically related.
B. The private key only decrypts the data while the public key only encrypts the data.
Both keys are mathematically related.
C. The private key is commonly used in symmetric key decryption while the public key is used in asymmetric key decryption.
D. The private key is only used by the client and kept secret while the public key is available to all.


Correct Answer: D
Section: Cryptography

Explanation:
The private key must be kept secret at all time. The private key is only by the client.
The public key is available to anybody.

Incorrect Answers:
A: The private key is only by the client, while the public key is used by all.
B: You can use the private key to encrypt data. Then you would need to use the public key to decrypt it.
C: The key pair, consisting of a private key and a public key, is used in asymmetric encryption and asymmetric decryption.

References:
Dulaney, Emmett and Chuck Eastton, CompTIA Security+ Study Guide, 6th Edition, Sybex, Indianapolis, 2014, pp. 279-285