I'm using a third party web service. In order for my users to be able to access their third party account, they need to log in. I provide the interface for them to log in to the third party site from my site. My question is, do I need a `SSL certificate` if the webservice already provides one? The webservice has a special Login method, which uses the `https` protocol. Does this mean that I don't need one for my site, or will I have to purchase a SSL certificate for my site?

Thanks