cvc

[odedao]

How is the CVC number of your credit card calculated and whats its significance

[dzug]

How it's calculated will be a closely guarded secret of the banks. To all intents and purposes it's random.

It's there for card holder not present transactions - you quote it over the phone or on the internet to prove you have the card in your possession and don't just happen to know the account number and expiry date.