So far most mobile payment solutions have focused on payments between businesses and customers (B2C) but there is still no solution that provides an easy way to conduct customer-to-customer (C2C) payments. The majority of payment systems on the market require an active internet connection to carryout a transaction. Unfortunately, cell phone coverage is not available everywhere, especially in rural and abandoned areas. When going abroad, mobile internet may result in high roaming costs which limit the usefulness of online apps. Therefore, a protocol focusing on offline C2C transactions is proposed which solves the described problems. This work analyses established online and mobile payment systems, investigates pros and cons, and draws conclusions for a novel mobile payment system. The existing solutions and their protocols are analysed and evaluated with a simple framework that is also presented in this work. The proposed payment system and its protocol are designed for high security and availability. Moreover, it works without an active internet connection. Therefore, the payment service is always available to the user as long as both transaction parties are carrying their phones. Additionally, Near Field Communication is used to make transactions easier and more seamless for the user. A prototype which implements the proposed protocol shows how it works.