Final answer:
SIP-message authentication is achieved using a challenge-response mechanism where a nonce value and a hash including the username and password are used. The server matches the hashed response with its expected hash to authenticate the device. Additional security can be provided through encrypted channels like TLS.
Step-by-step explanation:
To ensure that a SIP-message can only be sent by an authenticated device, the Session Initiation Protocol (SIP) uses various security mechanisms. Authentication in SIP typically involves using a combination of a username and password, similar to many other internet protocols. The process works as follows:
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- A device attempting to initiate a SIP communication will send a REGISTER request to a SIP server.
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- The server then challenges the request by sending a 401 Unauthorized response that contains a nonce value, which is a one-time token.
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- The device responds with an ACK request that includes an authorization header. This header contains a response based on the hashed combination of the nonce, the username, the password, and the SIP request.
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- The server computes the expected hash on its end using the stored credentials for the username and compares it to the hash received from the device. If they match, the device is authenticated.
This authentication process, which uses a challenge-response mechanism, helps prevent unauthorized devices from sending SIP messages because only those with the correct credentials can generate the proper hash. Further security can be added by using encrypted channels like TLS (Transport Layer Security) for SIP message exchanges.