What is the purpose of a session key in encryption?

• A. To encrypt data permanently
• B. To provide temporary encryption between two principals
• C. To store user passwords securely
• D. To facilitate digital signatures

Answer: (B)

A session key serves as a temporary encryption key used for securing communication between two parties during a single session. Its primary purpose is to protect data exchanges over a specific session or connection, ensuring that the information remains confidential and secure from unauthorized access during that time.

The use of a session key is particularly advantageous because it limits the exposure of the key to only the duration of the session. After the session ends, the key is discarded, which enhances security by reducing the risk of key compromise. Each session can use a different key, helping to ensure that even if one session's key is compromised, it does not affect others.

This concept is fundamental in symmetric encryption protocols, where both parties share the same session key for encryption and decryption of messages. Overall, the use of a session key facilitates secure and efficient communication by providing an additional layer of protection and ensuring data integrity during the exchange.