Recently, the emergence of wireless and mobile networks has made possible the admission of electronic commerce to a new application and research subject: mobile commerce, defined as the exchange or buying and selling of commodities, services, or information on the Internet through the use of mobile handheld devices. In just a few years, mobile commerce has emerged from nowhere to become the hottest new trend in business transactions. However, the prosperity and popularity of mobile commerce will be brought to a higher level only if information is securely and safely exchanged among end...