  In this paper, we propose a privacy-preserving medical treatment system using
nondeterministic finite automata (NFA), hereafter referred to as P-Med,
designed for the remote medical environment. P-Med makes use of the
nondeterministic transition characteristic of NFA to flexibly represent the
medical model, which includes illness states, treatment methods and state
transitions caused by exerting different treatment methods. A medical model is
encrypted and outsourced to the cloud to deliver telemedicine services. Using
P-Med, patient-centric diagnosis and treatment can be made on-the-fly while
protecting the confidentiality of a patient's illness states and treatment
recommendation results. Moreover, a new privacy-preserving NFA evaluation
method is given in P-Med to get a confidential match result for the evaluation
of an encrypted NFA and an encrypted data set, which avoids the cumbersome
inner state transition determination. We demonstrate that P-Med realizes
treatment procedure recommendation without privacy leakage to unauthorized
parties. We conduct extensive experiments and analyses to evaluate efficiency.
