SSCA Security in SIP 2

Question 1

Which SIP header field carries the Digest authentication credentials from a UAC to a UAS?

Accepted Answer

Authorization

Answer

The Authorization header carries the UAC's Digest credentials in response to a 401 challenge from a UAS.

Question 2

What does the 'nonce' parameter in SIP Digest authentication primarily prevent?

Accepted Answer

Replay attacks

Answer

The nonce is a server-generated, time-limited random value that prevents replay attacks by making each authentication exchange unique.

Question 3

Which transport protocol provides encryption and integrity protection for SIP signaling?

Accepted Answer

TLS

Answer

TLS (Transport Layer Security) encrypts and integrity-protects SIP signaling messages in transit.

Question 4

What URI scheme is used to indicate that a SIP connection must be established over TLS?

Accepted Answer

sips:

Answer

The 'sips:' URI scheme mandates that TLS must be used for the entire path to the destination.

Question 5

When a SIP proxy challenges a UAC for authentication, which response code does it return?

Accepted Answer

407

Answer

A SIP proxy uses 407 Proxy Authentication Required, while a UAS uses 401 Unauthorized to issue authentication challenges.

(SSCA) Sip School Certified Associate Practice Test