Question: In a WebRTC IMS Client (WIC) using Solution 1.1 with SIP Digest credentials for IMS registration, what is the primary security concern related to the entities having access to the IMPI and SIP Digest password?
Option 1: Unauthorized access by external networks due to the use of 3GPP access networks.
Option 2: Compromise of the entire IMS subscription if the SIP Digest password is breached, due to shared credentials with regular IMS UEs.
Option 3: Insufficient encryption methods used for transmitting SIP Digest credentials between the WIC and IMS core network.
Option 4: Dependence on the security of the eP-CSCF for relaying authentication information without additional verification.
Explanation: The correct answer, Option 2, highlights a crucial security concern addressed in the text. To mitigate this risk, it is recommended to maintain a clear separation between WICs and regular IMS UEs by assigning a separate subscription with a unique IMPI and SIP Digest password for WIC access. This ensures that if the SIP Digest password is compromised, the impact is isolated to the WIC only. The other options either misrepresent the primary concern (Option 1), focus on an unrelated technical aspect (Option 3), or misunderstand the role of the eP-CSCF in this context (Option 4).