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Overview

SIP Digest Authentication is a security mechanism that verifies access to your SIP endpoint using a username and password.
This method uses a secure challenge-response mechanism, meaning the password is not sent in plain text.
SIP Authentication

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Why It’s Needed

Digest Authentication protects your system from:
  • Unauthorized access
  • Fraudulent outbound calls
  • Unknown SIP connections
Only systems with valid credentials can connect.

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How It Works

SIP Digest Authentication uses a challenge-response mechanism to securely verify credentials.

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Step-by-step flow

  1. Client sends initial request (without authentication)
  2. Server responds with:
    • 401 Unauthorized
    • a nonce (challenge value)
  3. Client generates a secure response using:
    • SIP Username
    • SIP Password
    • Server-provided nonce
  4. Client sends the request again with the computed response
  5. Server validates the response:
    • If valid → access granted
    • If invalid → access denied

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Important

The password is never sent directly. Instead, a hashed value is calculated using the password and server challenge.
Each authentication request uses a unique nonce, which prevents replay attacks.

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Configuration

Provide the following credentials:
  • SIP Username — unique identifier for authentication
  • SIP Password — secure password used for verification
These credentials must match the configuration on your SIP provider or PBX.

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When to Use

Use SIP Digest Authentication when:
  • Your SIP provider requires credential-based authentication
  • IP Whitelisting is not available or sufficient
  • You need an additional layer of security

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Example

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Best Practices

Use strong, unique passwords and avoid sharing credentials publicly.
Incorrect credentials will result in failed call connections.
For maximum security, combine Digest Authentication with IP Whitelisting when possible.