Recently, the technologies for child care and safety have been developing rapidly, together with the various IT convergence services. In particular, several mobile operators (e.g., SKT, KTF, and LGT) in Korea and Gangnam province in Seoul provide their own child-care services. However, some problems such as incorrect location information, privacy violation, and difficulty of an end-user to control the child-care service still exist. In this paper, we derive the security requirements of a child-care and safety service and establish a conceptual model satisfying the requirements. Based on the system model, we propose a privacy-preserving location supporting protocol for a child-care and safety service using wireless sensor networks. While addressing the above problems, our protocol can be operated over various networks (e.g., Wi-Fi and UWB) providing an RSSI (received signal strength indication) without any modification. Through performance and security analysis of our protocol, we show that our protocol is efficient and secure. More precisely, our protocol reduces the computation and communication overhead of the existing infrastructures to support better scalability. (C) 2011 Elsevier Ltd. All rights reserved.