Prepaid System Based On Chaotic AES

At present,prepaid credit card terminal is widely used in the field of public service charge,however,the prepaid terminal witch uses GPRS wireless data transmission mainly adopts Plaintext Transmit Mode.There is a security and reliability problem with data transmission.The embedded technology and an improved algorithm of AES based on chaos(Chaos_LAES)mentioned in this thesis,which was used to design a set of cheap,safe and reliable prepaid system.The system communicates with the server through GPRS module.It had read-write card,voice broadcast,screen display and other human-computer interaction.There are two difficulties in building a prepaid system:one is construction and programming of prepaid terminal,the other is How to ensure the security and reliability of message transmission between the upper computer(multithreaded Socket)and the lower computer(prepaid terminal).IC card reading and writing module was designed based on STM32 which was used as MCU,M6311 was used as GPRS communication module and 24C02 was used as storage module,the connection port and communication mode of each module with STM32 were determined,the communication program between STM32 based on library function and other modules was designed in the system.The thesis designed the transmission message between the upper computer and the lower computer,and adopt CRC message caching technology to ensure the reliability of message transmission in poor communication environment and the integrity of the recharge business under the condition of GPRS module failure.At the same time,the system used the logistic model to generate the pseudo random sequences to disperse the key and replace the AES’wheel key generation algorithm,which effectively solved the problem that AES was vulnerable to Square attack and power consumption analysis threat.And through the simplification of AES wheel operation to form a new improved algorithm of AES encryption based on Chaos(Chaos LAES),this algorithm was used to encrypt the transmission packets to guarantee the terminal speed and the security of message transmission between the upper computer(multithreaded Socket)and the lower computer(prepaid terminal).Through the system test and online running in Inner Mongolia tongliao shows:the prepayment system based on chaos AES has good human-computer interaction experience,the data transmission is safe and reliable,and the recharge can be completed accurately.