May 20, 2005

OAKBROOK TERRACE, Ill., and BRUSSELS, Belgium, May 18, 2005 - VASCO Data Security International, Inc. (Nasdaq: VDSI) ( www.vasco.com), the global number one vendor of strong user authentication products to the financial sector, today announced that it is cooperating with S1 Corporation (NASDAQ: SONE), a leading provider of integrated front-office financial services applications, to deliver enhanced user authentication to S1 customers as part of S1’s Internet banking offerings. Utilizing a flexible authentication framework built into the S1 Enterprise system at inception, S1’s strategy is designed to provide its customers with the flexibility to choose the right security solution for their specific needs and customer preferences.
“We take our responsibility of providing mission-critical software to financial institutions very seriously, and therefore security is in our DNA. It is paramount in everything we do, from the design of our applications and the framework on which they operate, to our world-class data center,” said Jaime Ellertson, chief executive officer of S1. “As the landscape of security and identity theft is ever-changing, we believe one size does not fit all and that banks need a wide range of options, as well as multiple solutions, to address the unique needs of their customer segments and lines of business.”
According to Jan Valcke, president and COO of VASCO, “VASCO gives financial institutions the opportunity to offer truly secure Internet banking to their end users without any hassle. S1 customers are able to add two-factor authentication to their systems without having to install a separate authentication server and complicated infrastructure. The joint solutions will protect the bank’s customers against the multitude of threats online banking faces nowadays.”

Several years ago, S1 and VASCO forged a strategic relationship that has paid off in enhanced security for their joint customers. A number of S1 customers are currently using VASCO’s Digipass strong authentication tokens in conjunction with S1 applications. The two companies are committed to deepening their relationship and continuing to align their technologies.
S1 is working with several different third-party software and device providers to give its customers security options. VASCO Data Security International is the leading provider of strong user authentication products to the financial services market with more than 2,000 customers and 15 million end-users around the world. VASCO’s Digipass two-factor authentication products enable financial institutions of all sizes to add strong user authentication, including One-Time Passwords (OTP), host authentication, and eSignatures
At Siam Commercial Bank, a large financial institution in Asia that currently uses S1 Corporate Banking on the S1 Enterprise Platform, VASCO’s Digipass enables the bank to offer nearly 8,000 of their more than 30,000 commercial customers two-factor authentication. “By offering our customers this added security while making internet-based payments, we are able to give our customers confidence in the integrity and security of their transactions,” said Charamporn Jotikasthira, executive vice president from Siam. “The capability of S1’s products to let us choose the right solution for our institution and our customers has been very important to us as we navigate the changing landscape of secure Internet transactions.”
S1 is able to leverage its years of experience and network of more than 4,000 financial institution customers around the world to develop best practices in application and transaction security services. An intense focus on security is in the Company’s heritage, dating back to the inception of the company with SecureWare and FivePaces joining forces to create Security First Technology and launch the world’s first Internet bank nearly 10 years ago. A great deal of attention has recently been placed on one technique of online banking identity theft called phishing. S1 continues to work closely with its customers to offer technology solutions and user-education information to combat all forms of identity theft. For more information on S1’s identity theft strategy and capabilities, visit www.s1.com.
About S1 Corporation

S1 Corporation is a leading global provider of integrated front-office applications for more than 4,000 banks and insurance providers around the world. Comprised of applications that address virtually every market segment and delivery channel, S1 solutions help integrate and optimize an institution's entire front office, resulting in increased operational efficiencies, revenue opportunities and overall customer satisfaction. S1 is the only provider with the proven experience, breadth of products and financial strength to empower financial services companies' enterprise strategies. Additional information about S1 is available at www.s1.com.
About VASCO Data Security
VASCO designs, develops, markets and supports patented user authentication products for the financial world, remote access, e-business and e-commerce. VASCO’s user authentication software is delivered via its Digipass hardware and software security products. With over 15 million Digipass products sold and delivered, VASCO has established itself as a world-leader for strong User Authentication with over 370 international financial institutions and approximately 1,700 blue-chip corporations and governments located in more than 80 countries.
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Forward Looking Statements
Statements made in this news release that relate to future plans, events or performances are forward-looking statements. Any statement containing words such as “believes,” “anticipates,” “plans,” “expects,” and similar words, is forward-looking, and these statements involve risks and uncertainties and are based on current expectations. Consequently, actual results could differ materially from the expectations expressed in these forward-looking statements.

Reference is made to the Company's public filings with the US Securities and Exchange Commission for further information regarding the Company and its operations.

For more information contact:
Jochem Binst, +32 2 456 9810, [email protected]