Digipass for SIM, a SIM based token applet, enables strong authentication and digital signature functionality from a GSM phone. The combination of the World Wide Web and wireless communication will bring the most explosive technology of the new economy. It represents a huge new market for m-Commerce where the number of users is no longer constrained to PCs connected to the Internet, which itself is a massive market. Digipass for SIM adds another functionality to the GSM mobile phone: it turns the GSM into a personal hardware security device. It provides a comprehensive solution to enable strong authentication for financial transactions such as on-line banking and share trading over mobile devices.