In this paper, we have proposed a secure, efficient, and
privacy-preserving LBS query scheme in the outsourced cloud,
which is called EPQ, for smartphones. Based on an improved
homomorphic encryption technique over a composite order
group, the proposed EPQ can achieve location privacy preservation
and confidentiality of LBS data. Specifically, for an LBS
query request from a registered user, the LBS query execution is
directly performed over ciphertext on the cloud server without
decryption, and the result of LBS query can only be decrypted
by the registered user. Thus, the user can get accurate LBS
query result without divulging his/her location information.Detailed
security analysis shows its security strength and privacypreserving
ability, and extensive experiments are conducted to
demonstrate its efficiency. In future work, we will take into
consideration the collusion attack and lower the trust level in
the cloud server from honest-but-curious model.