Which of the following statements is true for a public key cryptosystem?

In a public key cryptosystem, the correct procedure involves using the receiver's public key to encrypt a message, which can then only be decrypted by the receiver's private key. This mechanism ensures that only the intended recipient can read the message, maintaining confidentiality.

The statement that is true describes that a secret message should be encrypted using the public key of the recipient and decrypted using the private key of that same recipient. The intent behind this process is to ensure that even if the encrypted message is intercepted, it cannot be decrypted by anyone lacking access to the private key.

In terms of secured communication, the public key is freely distributed and can be used by anyone to send secure messages to the key holder, while the private key remains confidential and secure with the key owner. This is the fundamental principle behind asymmetric encryption used widely in digital communications and transactions today.