Question: During a UTRAN Attach procedure with a mapped GUTI, if the UE has no current EPS NAS security context, how are the truncated NAS-token and KSI set in the P-TMSI signature IE of the Attach Request?
Option 1: Truncated NAS-token is set to a random value, and KSI is set to '000'.
Option 2: Truncated NAS-token is set to all zero, and KSI is set to a dynamically allocated value.
Option 3: Truncated NAS-token is set to a predefined non-zero value, and KSI is set to '111'.
Option 4: Truncated NAS-token is set to all zero, and KSI is set to '111'.
Explanation: According to the specified security procedures for UTRAN Attach with a mapped GUTI, if the UE lacks a current EPS NAS security context, it must indicate this by setting the truncated NAS-token to all zeros (to signify no valid security context) and the KSI to '111' (a predefined value indicating the absence of available keys). This setup triggers the appropriate security initialization processes in the network.