Most of the security proposals in m-commerce scenarios have been based on a classical payment model, which basically establishes relationships across domains among customers and merchants by means of business and banking domains. Nevertheless, these security solutions are not sufficiently robust when new components intend to participate in the m-commerce process. From our research, we can identify three emerging factors that could subordinate the design of current and future m-commerce scenarios: enhanced payment cards with networking functionalities, a plethora of infrastructures with constrained connectivity and intermediary entities with multiparty payment functionalities. Consequently, this paper identifies the need for review of the model being used so far in order to guarantee security robustness, and proposes an extended payment model that, among other advantages, allows the study of more effective security solutions.