Answer: The answer is three-digit code.
In many cases the encryption or safeguard on an e-card comes in the form of a three-digit code on the back.
Explanation: An electronic card (e-card) is a card with greeting that is sent through the internet to a recipient in order to be viewed on the computer. An electronic card (e-card) is easy and fast to send and also include animation and personal message. E-cards have different backgrounds and text fonts. E-cards save paper.