Which of the following keys are used by the public key infrastructure (PKI)? Each correct answer represents a complete solution. Choose all that apply.

A.
Private Key

B.
Pairwise Transient Key

C.
Group Temporal Key

D.
Public Key

Explanation:
Public and private keys are used by the public key infrastructure (PKI).
What is a Public Key?
A Public Key is known commonly to everybody. It is used to encrypt data. Only specific users can decrypt it. Data encryption is used to encrypt data so that it can only be decrypted with the corresponding private key owned by the public key owner. The public key is also used to verify digital signatures. This signature is created by the associated private key.
What is private key?
In cryptography, a private or secret key is an encryption/decryption key known only to the party or parties that exchange secret messages. In traditional secret key cryptography, a key would be shared by the communicators so that each could encrypt and decrypt messages. Answer option B is incorrect. Pairwise Transient Key (PTK) is a 64-byte key that comprises the following:
16 bytes of EAPOL-Key Confirmation Key (KCK): This key is used to compute MIC on WPA EAPOL Key message. 16 bytes of EAPOL-Key Encryption Key (KEK): AP uses this key to encrypt additional data sent (in the ‘Key Data’ field) to the client. 16 bytes of Temporal Key (TK): This key is used to encrypt/decrypt unicast data packets. 8 bytes of Michael MIC Authenticator Tx Key: This key is used to compute MIC on unicast data packets transmitted by the AP. 8 bytes of Michael MIC Authenticator Rx Key: This key is used to compute MIC on unicast data packets transmitted by the station.Pairwise Transient Key is derived from the pairwise master key (PMK), Authenticator address (AA), Supplicant address (SPA), Authenticator nonce (A Nonce), and Supplicant nonce (S Nonce) using pseudo-random function (PRF). Answer option C is incorrect. Group Temporal Key (GTK) is a random value that is assigned by the broadcast/multicast source. It is used to protect broadcast/multicast medium access control (MAC) protocol data units. It is derived from a group master key (GMK).
What is a public key infrastructure?
A PKI (public key infrastructure) enables users of a basically unsecured public network such as the Internet to securely and privately exchange data and money through the use of a public and a private cryptographic key pair that is obtained and shared through a trusted authority. The public key infrastructure assumes the use of public key cryptography, which is the most common method on the Internet for authenticating a message sender or encrypting a message.