The Design & Realization Based On WiFi Offline Payment System

Offline Payment is usually used for small payments, also known as off-line payment, transaction speed requirements, the completion of the transaction within half a second or even a short time, this fast and convenient features, loved by the people.In recent years, Alipay and Wechat payment, as the representative of the online payments have developed rapidly. However, the applications of offline payments have developed rather slowly. The emergence of technology NFC(Near Field Communication) will possibly combine these two payment methods. NFC payment is very potential in the offline payment field. But ten years later, the application of NFC has not yet spread. While many cities have tried hard to promote the application of NFC, it enables the business of online issuing cards and recharging service. Yet, the applications of NFC for offline payment are still fewer. According to the users’ views, the applications of NFC don’t give users more benefits. Therefore, the promotion is not so ideal. Why the development of offline payments is less successful than the online ones? The reasons are various. It is difficult to guarantee the security for the offline payment. Besides, The NFC industry chain is very complicated. It is difficult to integrate the terminal hardware manufacturers, telecom operators, card companies etc.This paper, as another attempt beyond the NFC technology, it achieves the offline payment by Wi Fi communication technology. Since the Wifi communication distance is further than the NFC technology, the security of transactions has become a more important issue. The solution is to follow the physical IC card transaction standard process. The transaction process adopts a new password each time and checks the transaction authentication code(MAC1, MAC2). Based on the physical IC card transaction process, it increases in the asymmetric encryption. The asymmetric encryption is generally considered to be less efficient, but it is proved by the practice that the computing ability of the modern mobile phone is sufficient to support the asymmetric encryption. It completes a transaction between 200 and 400 milliseconds. It entirely meets the requirements of the offline transactions within 500 milliseconds.This paper dissertates the analysis and comparison of two kinds of the asymmetric encryption algorithms, RSA and ECC(Elliptic Curves Cryptography). Apparently, ECC is much more efficient than RSA. And the encryption is stronger. Therefore, this system selects ECC encryption algorithm.The main work for this system includes: 1. The security analysis for Wifi payment is based on the modern encryption algorithms, including symmetric and asymmetric encryption. They are applied to different stages of the transaction according to their own features. 2. It achieves the consuming transactions by virtual card and APDU instruction with Wifi communication.