Since 1997, IBM has had a program called jStart (short for jump-start — see Resources) to help its customers and business partners work with new emerging technologies. The program’s goal is to help early adopters leverage new technologies to help make their businesses more successful. Last fall, the jStart program worked with a company who wanted to provide a business-to-business Web service using the Internet as a transport. They desired a strong level of security and interoperability, and they decided to use a WS-Security approach to secure the SOAP message traffic with their business partners. This paper discusses that project and its use of WS-Security.

Why WS-Security?
As the use cases for our customer’s application were being developed, a set of security-related, non-functional requirements were identified:

• The communication between our customer and his business partner should not be able to be viewed by a third party as it travels on the Internet.
• Our customer needed to be able to determine from whom the message was coming and be able to verify that the sender was who the sender claimed to be.
• Our customer needed to be able to ensure that the data being transmitted was not tampered with.

Non-functional requirement #1 will be addressed through the use of HTTPS/SSL transport security. Since this application will be a point-to-point application, with no third party service providers or intermediaries involved, the idea of using cryptography to encrypt all or part of the SOAP message was evaluated but not implemented at this time. Given no third parties were involved, the value gained from an additional encryption step that would encrypt a segment of the SOAP message was not enough to justify the additional development expense and complexity that would have been needed to implement a form of message-level encryption.

Non-functional requirements #2 and #3 will be addressed through the use of digital signatures and digital certificates. When using a digital certificate approach, the Web service requester must have a digital certificate which has been signed by a trusted certificate authority. The requester will use this certificate to assert their identity and will digitally sign the SOAP message so that the requester’s identity and the message’s integrity can be verified.

Once the message is received at our customer’s system, it will be time stamped and logged. At this point, the digital signature will be validated. The validation process will ensure that the message came from the sender as well as verify that the message contents have not been modified since it was signed at the sender’s site. The SOAP message log that our customer creates in DB2 will be used for non-repudiation purposes.

The Web service
Now that you understand the requirements and the technical approach, let’s take a look at what was implemented. The application that our customer chose to implement as a Web service was developed using WebSphere Studio Application Developer and some tools from the IBM alphaWorks Web site, namely, the XML Security Suite, and the Apache Axis run time that was part of the IBM Web Services Toolkit. Although the application is quite powerful as it drives our customer’s core business application, it is simple in that it only implements one method. It was deployed on WebSphere Application Server and interacts with the customer’s core business application through WebSphere MQ Series.

By using the TCP/IP monitor that is part of Application Developer, we’ve captured the SOAP message that is sent to the Web service for processing. Note that in order to maintain the confidentiality of our customer, we made the SOAP URLs generic, removed the application-specific SOAP payload, and lightly modified some of the calculated values: