Which of the following statements about private key cryptography is true?

In private key cryptography, also known as symmetric cryptography, the fundamental principle is that both the sender and the receiver utilize the same key for both the encryption and decryption processes. This shared key must be kept secret from anyone other than the two communicating parties, as it is crucial for maintaining the confidentiality of the messages exchanged.

The correctness of this statement is rooted in the mechanics of how symmetric encryption operates. The sender encrypts the plaintext message using this shared key, turning it into ciphertext, which can then be transmitted securely. Upon receipt, the receiver uses the same key to decrypt the ciphertext back into plaintext. The reliance on a single, shared key is what differentiates private key cryptography from public key cryptography, where different keys (a public key and a private key) are utilized.

This clear reliance on a single key highlights the importance of key management in private key systems, as both parties must securely exchange and store the key to ensure effective communication. Such an approach differs from the other choices, which misrepresent the nature of symmetric encryption: the second option incorrectly suggests the use of two different keys, and the third option states that a shared key does not need to be agreed upon in advance, which is not true for private key crypt