Privacy-preserving location-based service protocols with flexible access

We propose an efficient privacy-preserving, content-protecting location-based service (LBS) scheme. Our proposal gives refined data classification and uses generalised ElGamal to support flexible access to different data classes. We also make use of pseudo-random function (PRF) to protect users' position query. Since PRF is light-weight primitive, our proposal enables the cloud server to locate position efficiently while preserving the privacy of the queried position.