The mechanism of patch downloading based on USIM card is proposed in this paper. This mechanism adopts authentication technology to enable the co authentication between OTA (over the air) and dynamic linking library (DLL)

ensuring the mutual trust. In the paper

DLL is also suggested to practise the patch download mechanism. In this approach the application on USIM card can be updated by OTA through the control and management of patch downloading provided by the definition of lower level API.