SIP Security 2

Question 1

Which SIP header field is used to carry authentication credentials from a client to a server?

Accepted Answer

Authorization

Answer

The Authorization header carries the client's credentials in response to a WWW-Authenticate challenge from a UAS.

Question 2

What does the 'nonce' parameter in SIP Digest Authentication prevent?

Accepted Answer

Replay attacks

Answer

The nonce is a server-generated unique value that prevents replay attacks by ensuring each authentication exchange is unique.

Question 3

Which protocol provides end-to-end encryption of SIP message bodies but NOT the SIP headers?

Accepted Answer

S/MIME

Answer

S/MIME encrypts the SIP message body end-to-end, but SIP headers remain visible to intermediaries.

Question 4

A SIP 'registration hijacking' attack occurs when an attacker:

Accepted Answer

Registers a fake binding for a legitimate user's AOR

Answer

Registration hijacking involves an attacker registering their own contact URI under a victim's Address of Record, redirecting calls to the attacker.

Question 5

Which SIP security mechanism uses the 'Identity' header to provide cryptographic proof of caller identity?

Accepted Answer

RFC 8224 (STIR)

Answer

RFC 8224 (STIR - Secure Telephone Identity Revisited) uses the Identity header containing a JWT token to cryptographically assert caller identity.

(SIP) Session Initiation Protocol Practice Test