Problem: The biggest drawback with using symmetric key encryption is the lack of nonrepudiation. Anyone can gain access to the secret shared key and there is really no way of knowing who is utilizing it. In this method there isn't a way to verify the user or service, if you have the key then you are able to manipulate the data all you want. For the simple fact that, while it isn't 100% impossible, it is extremely hard and time consuming for authorities to track down where the money was sent. Where you aware that criminals typically ask for ransom to be in the form of cryptography?