Determine available protocols on client browser?

See more:

browser

SSL

TLS

We are eliminating SSL as a possibility in the very near future on our website. We are requiring TLS security - but we would like a grace period where we warn our users they need to upgrade to a browser that supports TLS.

Is there any way to determine what SSL protocols a person is connecting with?

I've tried to figure out how to use the SslProtocols enum under System.Security.Authentication - but can only seem to use it in the context of an SslStream - which I cannot seem to use in the context of a current request.

Here's what I tried initially - but I'm getting an invalid cast exception when trying to cast the InputStream to an SslStream:

protected void Page_Load(object sender, EventArgs e)
        {
            SslStream ssl;
            if (HttpContext.Current.Request.IsSecureConnection)
            {
                ssl = (SslStream) HttpContext.Current.Request.InputStream;
                switch (ssl.SslProtocol)
                {
                    case System.Security.Authentication.SslProtocols.Tls:
                        Response.Write("You are using TLS");
                        break;
                    case System.Security.Authentication.SslProtocols.Ssl2:
                        Response.Write("You are using SSL Version 2 - you need to upgrade to the current century.");
                        break;
                    case System.Security.Authentication.SslProtocols.Ssl3:
                        Response.Write("You are using SSL Version 3 - you need to upgrade to the current decade.");
                        break;
                    default:
                        Response.Write("You are using another version of Security we don't care about");
                        break;
                }
            }
            else
                Response.Write("It does not appear that you are connecting securely");
        }

Hopefully that gives you an idea of what I'm trying to do.

Is there an obvious method I'm missing?

Thanks!