Signature Panel Code / CVC / CVV2 / CVC2
All credit cards now have a security code (CVC, CVV or CSC) on them. This can be found on the signature line on the reverse side of most credit cards. The last 3 digits on the right hand side of the string of numbers are used.
If you are using an American Express credit card or your credit card does not have a security number on the signature strip, please use the 3 or 4 digit number on the front, right hand side of the credit card, slightly above the credit card number.
Mastercard sometimes calls the signature panel code CVC2, Visa calls it CVV2, American Express calls it CID. But "signature panel code" seems to be a well-established expression used by all credit card companies.
In our reference implementation we often simply refer to the CVC. But we mean the same: the Signature Panel Code.