User authentication is an important security mechanism for recognizing legal roaming users. In 2006, Lee, Hwang, and Liao proposed an enhanced authentication scheme with user anonymity for roaming environments. This article shows that Lee?Hwang?Liao?s scheme cannot provide anonymity under the forgery attack. Moreover, the heavy computation cost may consume battery power expeditiously for mobile devices. Therefore, we propose a novel authentication scheme to overcome these weaknesses that is efficient, secure, and suitable for battery-powered mobile devices in global mobility networks.