Abstract: The general composition of IC arc prepayment product systems is briefly introduced. Three topics are investigated: the password security of the IC card, encrypting and checking the data on the IC card, and a novel comprehensive data security design scheme is proposed, so that damages by passive and active attacks are avoided. The product system adopts the technique of encrypting lock and the encryption mechanism of multi-hierarchy encryption key, which provide a new idea for the data encryption of IC card prepayment product systems.