The way that everyone is talking about BlockChain, you might think it is a brand new idea. It is actually a rather old idea but one that nobody could really make use of because it was patented and the owner of the patent really didn't understand how to make use of it or make money from it.
NB: All the information provided here is at your own risk, no warranty is given or implied as to the status of these patents or the claims made therein. One of the features of US patent law is that patents that are continuations in part may introduce new claims under certain circumstances. Also, the mere fact that there is prior art invalidating a patent does not prevent someone bringing a lawsuit claiming infringement that is designed to be ruinously expensive to defend.