After click on GRN Link following e - Payment Challan will open in pdf format.
(See the following Screen and go through Instructions)

e - Payment Challan



Right Click on digitally Signed symbol

Choose Validate Signature


Click on Signature Properties... Button


Signature Properties

Click on Show Cerificate Button
Certificate Viewer Popup will open


Certificate Viewer
Choose Trust tab

Click on Ok Button


See the above Signature Valid Mark.