Which type of authentication does SIP use?

SIP (Session Initiation Protocol) primarily uses Digest Authentication to verify the identity of users and ensure the integrity of the authentication process. Digest Authentication enhances security by avoiding the transmission of passwords in clear text and instead, it employs a challenge-response mechanism. This method requires the client to use a hash function to create a response to a challenge from the server, which includes nonce values and user credentials.

This approach is more secure than Basic Authentication, which transmits usernames and passwords in plain text, making it susceptible to interception. While Token-Based Authentication and SSL are important security concepts, they are not the primary mechanisms utilized by SIP for user authentication. Token-Based Authentication is often used in different contexts like web applications and APIs, while SSL is a protocol for encrypting data in transit but does not serve as a direct authentication method within SIP. Thus, Digest Authentication stands out as the correct choice due to its specific design for secure user validation in SIP communications.