The present document specifies a system to make Mobile Operator services@ based on USAT functionality and USIM based security functionality@ available to an internet environment. This is achieved by specifying the necessary components and protocols for a secure narrow band channel between the internet application and an USAT Interpreter on the USIM. The actual application could be developed using the application language of choice. Two types of applications interfaces are used as examples@ i.e.@ mark-up language based on WML and Remote Procedure Call (RPC). The interpreter and the secure narrow band channel form a core platform to enable services like: - Advanced security functionality@ e.g.@ digital signatures in m-commerce applications - Value added services based on position and roaming - Controlled activation and management of other applications@ e.g. multimedia and payment type of applications. The secure narrow band channel is achieved by specifying the following: - specific application and content related functionalities of the interface between the application system and the USAT Gateway; - specific functionalities and protocols of the interface between the USAT Gateway and the USAT Interpreter associated with a USIM@ achieved by defining a low level command set for interpretation by the USAT Interpreter; - defined level of functionality available to the application server for the implementation of USIM based services such as PKI@ location services@ push and broadcast services@ event based services@ etc.. The present document does not specify any elements of the protocol stack between the application server and the USAT Gateway@ the mark-up language definition@ and the transport protocols between the USAT Gateway and the USAT Interpreter.