With the advent of the Internet of Things，more and more objects are connected via various communication protocols like Bluetooth，Z-wave，WiFi , ZigBee etc. Among those protocols ZigBee accounts for the largest market share，it has been adapted to various applications like WSN（Wireless Sensor Network），Smart Home . Over the last few years, large amount of research has been conducted on the security of ZigBee. In this presentation we will introduce a new technique to beat the security of ZigBee, we found the “signature” of the location of the security key . We will go through a specific example and share the thinking process along the way. The techniques used throughout this example can be generalized and used by other hardware reverse engineers.