I have a coldfusion webservice that returns an XML file. I want to secure it so that the user needs to authenticate inorder to consume the service. I have to be able to pass the users credentials to the webservice via VB6. I haven't done anything with webservices or SOAP until now and i am unsure how to structure it. I have also heard about REST but i am not sure what the differences are. Can anyone help? Below is what i think it should look like but i am not sure. Any help is appreciated!

<?xml version="1.0" encoding="iso-8859-1"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">