You can use an Active Directory web service to identify the user and there login details.
So if they have already authenticated you can piggy back on to it by linking their login to the form.
You can also use digital signatures with their login.
I would think once they have authenticated to get the form, which can also be dynamically secured and controlled via a database that the signature could be automatic. but it depends on your requirments.
You could maybe use code to also call the pin code app.