Low-frequency RFID systems use ID cards, known as Identification Cards, as their electronic tags. ID card is a kind of induction card that can not be written, its internal only stored data is a fixed ID card number, its record content (card number) is written by chip manufacturers before sealing card factory, sealing card can not be changed, developers can only read card number to be used. ID card and we use magnetic card normally same, used only “the number of card” just, besides card number inside card, without any confidential function, its “card number” is open, bare.