Web Service in 6.20 - SICF/Logon Information

Hello all. Hopefully I am putting this question into the correct area.

We are currently running on a WAS 6.20/SAP 4.7 environment. I have created an RFC and found the WSDL for this module.

In a 6.40 environment, I was able to generate the Proxy and call the Web Service successfully. I did get a prompt to login to the 6.20 system.

We need to be able to secure this web service because it is going to contain HR Data such as SSN#s and Credit Card Numbers. What is the best way to call this web service to avoid having to manually enter the user id and password?

Thanks,

Chris