Due to the sensitive nature of the data many wireless sensor networks are tasked to collect security of this data is an important concern. The best way to secure this data is to encrypt it using a secure encryption algorithm before it is transmitted over the air ways. However due to the constrained nature of the resources available on sensor nodes the cost, both in terms of power consumption and speed, of any software based encryption procedure can often out weigh the risks of the transmission being intercepted. We present a solution to reduce this cost of employing encryption by taking advantage of a resource already available on many sensor nodes; this resource being the encryption module available on the Chipcon CC2420 transceiver chip. © 2007 IOP Publishing Ltd.