In this new post to her blog Lorna Mitchell looks at authentication in web services with a few questions for you to consider as you make your development plans.

Quite a lot of services don't require any authentication at all, similar to quite a lot of the web. In either setting, the information is there for users to consume when they want. However the difference comes when services start doing more than making data available. If changes can be effected by the service, then we need to identify who is requesting the change.

She notes that one popular method is the tried-and-true username and password combination. This simple (and familiar) technique can even make the load lighter on your application, reducing the complexity of the authorization process. She suggests using a token to identify your users once they've authenticated, providing a simple and secure method for user tracking.

With this information being independent and just used to verify the user, there is also the option of storing this in an alternative, faster, mechanism such as memcache.