A lot of smart context-aware services would be adopting location information as context information. However, the location information is also very important information to be protected for users’ privacy, security, and safety. In this paper, we propose One Time Password (OTP) in the communication between users’ devices and network devices such as APs. By using this approach, APs does not keep user specific information but OTP values, so that attackers cannot get user information even though they access to the log files in APs. We also introduce context-aware service scenario and context information for the service.