3D-Secure authentication is an interactive process between the bank that has issued the card and yourself. In essence, the bank asks you to create a special security code (something like a new, different, more complex PIN) that only you know and which you need to enter with each online transaction to verify that you are the legitimate cardholder. This way, even if someone learns your card details, they will not be able to make online purchases since they won’t know this code. If the security code is correct, your transaction will be completed. If the security code is incorrect and 3D-Secure authentication is unsuccessful, the transaction will not be completed, even if all other card details are correct. You should be aware that if several successive failures occur, it is possible that the 3D Secure process will lock down and you will need to contact your bank.