CompTIA Exam Questions

Which of the following is true about PKI?

Which of the following is true about PKI? (Choose two.)

A.
When encrypting a message with the public key, only the public key can decrypt it.

B.
When encrypting a message with the private key, only the private key can decrypt it.

C.
When encrypting a message with the public key, only the CA can decrypt it.

D.
When encrypting a message with the public key, only the private key can decrypt it.

E.
When encrypting a message with the private key, only the public key can decrypt it.

Explanation:
E: You encrypt data with the private key and decrypt with the public key, though the opposite is much more
frequent.
Public-key cryptography, also known as asymmetric cryptography, is a class of cryptographic protocols based
on algorithms that require two separate keys, one of which is secret (or private) and one of which is public.
Although different, the two parts of this key pair are mathematically linked.
D: 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.