The working principle of electric card: Because there is a chip called RFID, when we hold the card containing the RFID chip through the card reader, the electromagnetic wave emitted by the card reader will begin to read the information inside the card, the information in this can not only be read, but also can be written, modify, so the chip card is not only a key it is an electronic identity card.
Because as long as you write your personal data in the chip, you can know who is in and out of the card reader. The same technology is used in anti-theft chips in shopping malls and so on.