Auto-configuration provides convenience in implementing a mobile ad hoc network. However, it may sacrifice network security if there is not a reliable authentication mechanism, e.g., an attacker may spoof other nodes and hijack their traffic. In this paper, we propose a secure address auto-configuration scheme for MANET. It binds each IP address with a public key, allows a node to self-authenticate itself, and thus thwarts address spoofing and other attacks associated with auto-con?guration.