New mobile payment protocol: Mobile pay center protocol 4 (MPCP4) by using new key agreement protocol: VAC2

Growing of wireless networks and popularity of mobile devices represents an incredible opportunity to empower them as a payment device. Unfortunately, some problems hindering the widespread acceptance of mobile payment for example: accountability properties, privacy protection, limitation of wireless networks and mobile devices. Recently, many public-key cryptography protocols have been presented for mobile payment. However, limited capabilities of mobile devices and wireless networks make these protocols unsuitable for mobile network. Moreover, these protocols were designed to preserve traditional flow of payment data, which is vulnerable to attack and increase the user's risk. In this paper, we propose a private mobile payment protocol which is based on client centric model and works by employing symmetric key operations. The proposed mobile payment protocol not only minimizes the computational operations and communications between the engaging parties, but also achieves a completely privacy protection for the payer, avoid repudiating transaction from each of them and decrease risk of replay attacks. In according to limitation of wireless networks and mobile devices, this paper recommends VAC2 key agreement protocol for generating shared session key between n parties that have fewer problems than Diffie-Hellman key agreement protocol. It is used instead of Diffie-Hellman key agreement protocol that works only for two parties.