What is the principle of bathing white card?

There are two white card principles for bathing:

One is that the card contains actual amount data, and the machine will automatically modify the amount data in the card after swiping the card. The operation between the card reader and the card is encrypted. This is a general type of bus card.

The other is that there is no amount data in the card, only the serial number or card number. The credit card reader reads the data on your card, inquires the account balance of your card on the server through networking, and applies for deduction from the server. This is a bank card type with only magnetic stripe, and so is the access card used in general communities. In the past, our school also used hole cards, with some irregular holes punched in them, which were inserted into the machine when swiping the card. The machine knows the serial number of your card by detecting the location of the hole, and checks the account amount online ... Deduction ... This cracking is not to crack the card, but to connect the network of this card and attack the server or terminal to modify the account amount.