Cryptanalysis of Lee and Lin's innovative electronic group-buying system

With the rapid development of network systems, many of our daily life activities can be performed via the Internet. Online shopping is one of the most common of these activities, which include group buying behavior. Group buying is a trading way, which is a mutually agreeable process. Buyers hope that they can buy their favorite goods or services through trading, and merchants hope that they can obtain a reasonable profit. In 2013, Lee et al. proposed an online group buying system for mobile commerce, they claimed that their proposed scheme achieves several important security requirements, for example: mutual authentication, integrity of transaction data, and non-repudiation. However, we found that there are still some defects in their proposed scheme. Thus, we made an analysis and discussion about these defects, like lack of negotiation description, cash flow issue, main shopper trust issue, limited payment method, not achieve non-repudiation, and arbitration issue.