An Improved Privacy Protocol in Location Based Service

Several protocols of secure processing of user's information in Location Based Service (LBS) have been raised up. Kohlweiss et al constructed a secure framework protecting for both the user's location information and user's usage profiles using oblivious transfer and homomorphic encryption. However, an intermediate proxy was introduced in the protocol to interact between the server and the user, which makes the privacy security partly depending on the proxy's honesty. Moreover, the usages of homomorphic encryptions and zero knowledge proves in the protocol make the efficiency not so satisfying. Based on Kohlweiss et al's protocol, we propose an improved one using two oblivious transfers. In our improved protocol, no trusted third party is needed and user's location information and usage information can be protected by using oblivious transfer twice. We show that this improved protocol is easily constructed and with higher privacy security and more satisfying efficiency.