Company A sends a PGP encrypted file to company B. If company A used company B’s public key
to encrypt the file, which of the following should be used to decrypt data at company B?

A.
Registration

B.
Public key

C.
CRLs

D.
Private key

Explanation:
In a PKI the sender encrypts the data using the receiver’s public key. The receiver decrypts the
data using his own private key.

PKI is a two-key, asymmetric system with four main components: certificate authority (CA),
registration authority (RA), RSA (the encryption algorithm), and digital certificates. Messages are
encrypted with a public key and decrypted with a private key.
A PKI example:
You want to send an encrypted message to Jordan, so you request his public key.
Jordan responds by sending you that key.
You use the public key he sends you to encrypt the message.
You send the message to him.
Jordan uses his private key to decrypt the message.