A Proposed Architecture for Secure Two-Party Mobile Payment J. E. Rice and Y. Zhu Dept. of Math & Computer Science University of Lethbridge 4401 University Dr. W., Lethbridge, AB, Canada {j.rice, yunpu.zhu}@uleth.ca Abstract The evolution of wireless networks and mobile devices has resulted in increased concerns about performance and security of mobile payment systems. In this paper we pro- pose a new secured architecture for two-party mobile pay- ments, e.g. mobile banking. The proposed architecture em- ploys a lightweight cryptography system that combines pub- lic key and symmetric key cryptography systems (ECDSA and AES), as well as a multi-factor authentication mech- anism. These are coupled with a transaction log strategy to satisfy the properties of confidentiality, authentication, integrity and non-repudiation. Compared to some exist- ing mobile payment platforms the proposed architecture is a lightweight secured mechanism that is more suitable for two-party banking transactions over resource-limited mo- bile devices. 1. Introduction Wireless networks and mobile devices are becoming more and more widely used. At the same time, in part due to the prevalence of non-protected public transmissions over wireless systems, security issues are becoming more and more problematic. In this paper we propose a a new secured architecture for mobile banking/payments. We pro- pose use of a lightweight cryptography system along with a multi-factor authentication mechanism and a transaction log strategy to ensure all security requirements are fulfilled. We argue that compared to various architectures and models such as [7], [9], [18] and [1], the architecture we propose is simpler and better suited to two-party mobile payment transactions over resource-limited mobile devices. 2. Background Some background in this area may be of benefit in un- derstanding the proposed architecture. In our research, mobile devices are recognized as hand- held devices generally with internet browsing capability and other basic computational capabilities. A mobile device can be viewed as an identifier for a particular individual, in that each individual generally has one’s own mobile device which is not usually shared with others. Mobile payment can be defined as any payment trans- action which involves a mobile device [2]. According to Gao et al. existing mobile payment systems can be classi- fied into two types: mobile POS payment systems that en- able customers to purchase products on vending machines with their mobile devices, and account-based payment sys- tems which can be mobile phone-based, smart card or credit card-based [5]. It is on this latter type that we focus. The two-party payment model of mobile payments is the sim- plest type of mobile payment model. The two parties in- volved are assumed to be a customer and a financial service provider. There are two common channels that can be recog- nized as wireless networks: the wireless local area network (WLAN) and the mobile phone network [17]. The mobile phone network, on which our research focuses, is a radio network which consists of a number of cells, each of which is served by one or more fixed transmitters [16]. In order to provide security for two-party transactions an implementation is generally expected to reside either on the transport layer or on the application layer [7]. Our ar- chitecture is proposed on the application layer. The applica- tion layer’s security architecture is independent of the lower layers’ security protocols, and is designed such that the ap- plication handles all the security-related functions. Further- more, implementing an application layer security architec- ture does not require modifications to the current wireless network’s infrastructure and protocols. [11] details a number of concerns held by customers re- garding security in mobile payments. Table 1 summarizes the requirements resulting from these concerns, and tech- nologies recommended to address them. The third column of Table 1 describes the specific solutions proposed in this