This paper presents a new scheme for online payment systems based on a mobile personal device and existing debit/credit card electronic payment protocols. The model focuses on trust to enhance the feeling of security in the use of debit/credit cards for online payment systems. A mobile personal device is used to control the payment process of customers in a transaction so as to give them the feeling of being in control of the payment process. The new model provides a way in which customer trust in controlling e-payment systems can be established, so that customers can trustfully participate in electronic commerce. We provide guidelines on how the trust of mobile devices can be applied to achieve mutual improvements between security and trust. Moreover, the model requirements are identified, and an analysis of these requirements against trust and security requirements in transactions is discussed.