Which kind of user's information I can use for create unique user's key?
<p>I've next problem:
I need create unique user key based on user's information what I can receive from user's request to my web-page (ASP.NET).</p>

<p>I'll use this key for auto-login functionality (I know about cookie ^^)</p>

<p>What kind of information I can use?
Can anybody help me?</p>
