The applications on handheld devices are involved in some critical information exchange. This thesis report investigates which concepts exist to shelter software from modification and how the communication of these applications running on a handheld device over public mobile network can be made more secured. This report highlights how a smart card can facilitate to enhance the security of the software running on it particularly for handheld devices. It also discusses the issues and threats to smart cards. Furthermore it proposes a solution based on the specified scenario. The security of the software comprises on two layers; one layer is for the analysis prevention which makes hard to understand the behaviour of the program both at static and dynamic levels. The other layer is responsible to verify the integrity of the software to ensure that it is not modified. Furthermore, the software is installed on smart card which acts as an extra security layer. The communication relies over the security features of the public mobile network with some enhancement. The border based VPN is deployed between the public mobile network and the remote server.