In paper-based prescribing in the United Kingdom's National Health Service (NHS), patients are responsible for protecting the privacy of their prescription information while it is in transit from the prescriber to the dispenser. The UK government has introduced a plan for future NHS reform that includes a change from paper-based prescribing to a national electronic transfer of prescriptions (ETP) system. This brings with it concerns for patient data privacy and questions about the burden of trust placed on professionals in the ETP system. As recently seen in the Emilio Calatayud case in the United States, systems that contain an aggregation of identifiable personal information can be abused. A similar case could result from malpractice in an ETP system. We have developed and implemented an ETP system for the UK NHS. We present our system for protecting the privacy of patient data, describe how we implemented it in Java, and discuss how others can use our system for other applications both inside and outside the healthcare sector.