Hummingbird key establishment protocol for low-power ZigBee

From the “Smart Grid” to smart buildings, the ZigBee communication standard for wireless personal area networks (WPAN) is being adopted by applications that deal with highly sensitive data. Because all traffic in these networks is broadcast, issues like eavesdropping and injection are serious concerns to security and privacy. ZigBee specifies the network and applications layers and is built on top of IEEE 802.15.4 which specifies the link and physical layers. ZigBee also provides a key establishment service that relies upon AES. AES, with block sizes of 128-bits or greater, was not designed for the resource-constrained devices that form ZigBee networks. Hummingbird, a rotor-based symmetric key algorithm, operates on 16-bit blocks and was designed specifically to work on devices with minimal memory and processing capabilities such as ZigBee devices. We present a mutually authenticated key establishment procedure named Hummingbird Key Establishment (HBKE) to secure key agreement between an initiator and a responder device. Hummingbird´s state-based cipher allows for highly efficient mutual authentication and privacy, with little communication overhead. The use of Hummingbird instead of AES provides high security with smaller hardware sizes, faster operation, and smaller power consumption.