Question: Which of the following NAS signalling messages are accepted by the UE without integrity protection?
Option 1: Only IDENTITY REQUEST and AUTHENTICATION REQUEST
Option 2: Only REGISTRATION REJECT and DEREGISTRATION ACCEPT
Option 3: Only SERVICE REJECT and AUTHENTICATION RESULT
Option 4: All of the following: IDENTITY REQUEST, AUTHENTICATION REQUEST, AUTHENTICATION RESULT, AUTHENTICATION REJECT, REGISTRATION REJECT (if the 5GMM cause is not #76, #78, #81 or #82), DEREGISTRATION ACCEPT (for non switch off), and SERVICE REJECT (if the 5GMM cause is not #76 or #78)
Explanation: According to the 3GPP specification, these messages are accepted by the UE without integrity protection as they may be sent by the network before security can be activated.