CompTIA Security+ Question A-23

Which of the following is the MOST likely cause of users being unable to verify a single user’s email signature and that user being unable to decrypt sent messages?

A. Unmatched key pairs
B. Corrupt key escrow
C. Weak public key
D. Weak private key

Answer: A

In a PKI the sender encrypts the data using the receiver’s public key. The receiver decrypts the data using his own private key. The sender and receiver must have a matching key in order for the receiver to decrypt the data.