The present invention relates to a web trading system and method for performing financial transactions securely over a public data network, such as the Internet, using a web browser as the user interface. The financial transactions are offered, for example, by a financial institution to its customers at the institution's web site. They include transactions such as foreign currency exchange, currency and money market trades, and warrant trades. The web trading system and method provide secure communication protocol between the Internet user interface and a virtual private network (VPN) of a financial institution to enable implementation of trading applications by the financial institution's application servers across the VPN. Security for the financial transactions is provided by the web trading systems and software downloaded to the customer's personal computer (PC) and includes encryption, authentication, authorization, message and transaction integrity capabilities, registration authority, handshake protocol, and firewalls.