The credit card security code is a set of 3 or 4 digits on the credit card. It is used to prove that the payer has a credit card at the time of transaction, thus preventing credit card fraud.

Its generation method is that the bank extracts the account number, validity period and service code of the card, arranges them and then calculates them through a series of complicated algorithms. After this set of numbers is generated, only the issuing bank and the holder of the bank card know what this number is.

Extended data

The security code of UnionPay card is called CVN2, which has three digits and is printed on the back of the credit card after the last four digits of the card number.

The security code of MasterCard is called CVC2, which has three digits and is printed on the last four digits of the card number on the back of credit card.

The security code of Discover card is called Cardmember ID, which has 3 digits and is printed on the signature column on the back of the credit card.

The security code of JCB card (Japan Credit Bureau) is called CAV2 (card authentication value 2), which has 3 digits and is printed on the back of the credit card number.

The security code of American Express is called CID (Card Identification Number), which has 4 digits and is printed on the front of the credit card above the credit card number.

Baidu encyclopedia-credit card security code