Requirement for the user to sign some aspx forms with his (local) certificate

Hi,

Asp.net 2 or 4.0

WE have a controlled list of the users (It s an Extranet solutions for our collaborators)

We need to develop some new web pages (not all) some of which require the user accessing the web page to fill out some form and sign it using his digital signature/certificate. Each customer has their own certificate which he has on his computer (either as a local desktop file or the certificate may be probably integrated into the browser certificates via browser advanced options).

In other words:

1- Allow a client visiting some of the web pages to digitally sign the form before submitting it to our web server (the signature is his specific certificate)

2- Send either the form and the certificate or the html encrypted with his certificate to the web server

3- Read and identify the certificate on the web server (C# code)

Does anything already exist for that perpose or Any alternative solution

Thank you