Location based services(LBS) pose risks to user’s privacy, as they have access to user’s identity, location and usage profile. Many approaches have been made up to deal with the privacy problems. But few of them meet the requirement of full privacy. In this paper, we propose a protocol that does not require a trusted third party and provides full privacy. We use group anonymous authentication to fulfill identity privacy, while using program obfuscation to satisfy the privacy requirement of usage profile. And we assume that there exist some geography or geometry methods to form a cloaking region to meet location privacy.