Question: What is the implication of using `0xFF` as the first octet for a Ua security protocol identifier in terms of registration and potential security risks?
Option 1: It requires mandatory registration with 3GPP to ensure global uniqueness, eliminating any risk of security breaches.
Option 2: It denotes a reserved space for future 3GPP specifications, and its use is temporarily allowed without registration until further notice.
Option 3: It allows for the definition of local/experimental protocols without needing registration, but may introduce risks of cross-protocol security breaches.
Option 4: It is exclusively used for protocols specified by GSMA, requiring coordination with them for any new identifier.
Explanation: Using `0xFF` as the first octet enables creating local or experimental Ua security protocol identifiers without formal 3GPP registration. However, this flexibility introduces potential security risks, as unmanaged identifiers might allow exploiting a vulnerability in one protocol to attack another within this private range, highlighting a trade-off between development ease and robust security measures.