Interesting reports in the news recently about using optical fibres to produce a system that is 'uncrackable'. A reaonable summary can be found here - quantum , and no doubt elsewhere as well.
Probably be a few years before it is commercially viable, but from a scientific point of view it would seem to have a lot of merit. In many ways a bit like Heisenburg's uncertainy principle - which basically means that, for a single particle, the better you know its position the worse you know its velocity - or vice-versa.