A. A person sends a message that is encrypted by using their private key, and the receiver must also use that private key to decipher the message.

B. A person sends a message that is encrypted by the use of a public key, and the receiver can decipher the message using their private key.

C. Messages are encrypted into cipher text and then are deciphered upon receipt by using a pair of public keys.

D. Messages are encrypted into cipher text and then are deciphered upon receipt by using a pair of secure private keys.