Question

1) to verify a digital CERTIFICATE, we need the ___
a) CA's private key
b) CA's public key
c) certificate owner's private key
d) certificate owner's public key

2) If the sender encrypts the message with the receiver's public key, it achieves the purpose of ___
a) confidentiality
b) authentication
c) confidentiality but not authentication
d) confidentiality and authentication

Answer 1

1. d) certificate owner's public key

We need the public key of certificate owner because only this will be able decrypt the certificate which is encrypted with private key of the owner.

2. c) confidentiality but not authentication

The public key is available to all, so anyone can encrypt the data therefore the message would not be authenticated because anyone can encrypt the message using that public key. But as the data is encrypted therefore it cannot be decrypted without private key therefore confidentiality is achieved.