In a secure electronic payment system, authentication data is sent from a payment
account issuer to user software operated by a purchaser. The user software sends
the authentication data to a merchant using hidden fields on the Web page of the
merchant. The merchant generates an authorization request message based upon the
authentication data. The authorization request message is sent to a payment organization
either directly from the merchant or via the merchant's acquirer. The payment organization
forwards the authorization request message to a payment account issuer which verifies
the authorization request message, thereby generating an authorization response
message which is sent to the payment organization. The payment organization forwards
the authorization response message to the merchant, either directly or via the acquirer.
