Of course, one can do it with clandestine operation just as NK probably did with Cheonan.
I truly think the world needs to come to grips with the reality that it is just a matter of time before we are going to see a nuke detonation on our soil or the soil of a close ally.
Its a fact we need to all accept and prepare for. its coming, maybe tomorrow, maybe next year or in 10 years but it will happen.