Section: 5.4.1 Secure messaging between the USIM and the network
Content: USIM Application Toolkit, as specified in TS 31.111[ Universal Subscriber Identity Module (USIM) Application Toolkit (USAT) ]  [15], provides the capability for operators or third party providers to create applications which are resident on the USIM (similar to SIM Application Toolkit in GSM). There exists a need to secure messages which are transferred over the network to applications on the USIM, with the level of security chosen by the network operator or the application provider. Security features for USIM Application Toolkit are implemented by means of the mechanisms described in TS 23.048[ Security mechanisms for the (U)SIM application toolkit; Stage 2 ]  [7]. These mechanisms address the security requirements identified in TS 22.048[ Security mechanisms for the (U)SIM application toolkit; Stage 1 ]  [16].