how to send user ID across differnet application in ASP.Net?

Hello everyone,

I have two web applications all are developed by ASP.Net. Now I want to provide a feature which enables the user to click from one URL in application site (one virtual directory of IIS) A to the other URL in application site B (another virtual directory of IIS).

I have two ideas to implement them, but both of them have issues. I want to know what solution should be optimum solution?

Solution 1: using cookie, so from both application sites, we could retrieve user ID information from reading cookie, but I am afraid if cookie is disabled in browser, this "jump" feature never works.

Solution 2: When the user redirects to an URL in another site, I could append user ID after the URL, I could redirect to this URL in another site http://www.anotherapplicationsite.com/somesuburl?userID=foo, but I am afraird that in this way userID will be exposed easily which raise security issues.

Any advice?

thanks in advance,
George