Yamamoto, H., Ishida, K and Ohta, T.,
E-commerce faces a problem due to the risks inherent in C2C online trading. The most common worry is how to ensure that the buyer pays for the goods and the seller sends the goods to the buyer. Online trading has the features of anonymity and facility in participation or leaving. Therefore, a system for managing risk in the e-commerce market would very desirable. In this paper, we focus on online trading among consumers. In a traditional market, a law or a third-party service manages risk, but in this case, the traditional systems have limits. Ease of participation, low cost, and time lag when exchanging goods for money are characteristics typical of online trading. In these transactions, one has to worry about "free riders" within a community and lack of cooperation. We propose that the method of addressing these problems is explicit reputation circulation.