Payment Gateway is a software interface between a web-basedshopping cart and a merchant account. It's an e-commerce application serviceprovider service that authorizes payments for e-businesses, online retailers, bricksand clicks, or traditional brick and mortar.

Security is most important Section for online gateways likePay pal & eBay.

For that in 2007, PayPal introduced an optional security keythat adds an additional layer of protection when logging into PayPal or eBayaccounts. A security Key is a may bejust like a physical device that an authorized user of computer servicesis given to aid in authentication. A user account tied to a security key has amodified login process; once the user enters their normal login ID andpassword, they are prompted to press a button on the security key, and thenenter the six-digit number generated by the key to complete the login process. Thistwo-factor authentication (T-FA) prevents an account from beingcompromised by a malicious third party without access to the physical securitykey. If a user loses their security key, they can authenticate by providingtheir credit card or bank account number listed on their account.

T-FA is an authentication factor is a segment of information and process used to substantiate or verify a person's identity for securitypurposes. Several products store passwords in plain text for either the tokenor smart card software or its associated management server. The option ofadding a security key to one's account is currently available only to usersregistered in the United States,Germany and Australia.