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Collaboration, Voice & AV · Intermediate

SIP Digest Authentication

SIP's challenge-response authentication in which a server responds 401 or 407 with a nonce and the client returns a hashed credential.

Definition

Based on HTTP digest authentication, the client hashes the username, realm, password, nonce and request details so the password is not sent in clear text. MD5 was the original algorithm, and RFC 8760 adds SHA-256 and SHA-512/256. ITSPs commonly require digest authentication for trunk registration and outbound calls from CUBE.

Example

CUBE receives 407 Proxy Authentication Required from the ITSP and resends the INVITE with an Authorization header.

Exam tip

401 comes from a registrar or UAS; 407 comes from a proxy.

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