Smartphone's are becoming a major part in everybody's daily life. All kinds of activities, including banking or financial m-commerce transactions (e.g. online shopping), are nowadays performed online via Smartphone's. In this paper, the authors propose a location based authentication and authorization scheme for mobile transactions using smart phones. Location-based authentication is a new direction in development of authentication techniques. Authentication and authorization are two of the most important security features for mobile transaction systems. They uses space time authentication technique that uses GPS system for a position determination of the person.