How to resolve to resolve - Error: SecureChannelFailure (The authentication or decryption has failed

Hi Guys,
I am facing an issue Error: SecureChannelFailure (The authentication or decryption has failed while consuming Secured https
I even using modernclient.

I referred
https://forums.xamarin.com/discussion/10405/the-authentication-or-decryption-has-failed-in-the-web-request
https://forums.xamarin.com/discussion/2653/authentication-or-decryption-has-failed-for-webservice-over-https
http://stackoverflow.com/questions/4926676/mono-webrequest-fails-with-https/21291774#21291774

It suggest to add handler, but i don't know where should i add the call back handler.
Please share idea or sample code.