A Light Weight Enhancement to RC4 Based Security for Resource Constrained Wireless Devices

The Wired Equivalent Privacy (WEP) uses the 64 bit RC4 secret key stream cipher as its layer 2 security protocol. Although the underlying RC4 cipher is secure, the potential reuse of the same key stream by different frames is a weakness in the WEP. One enhancement to WEP is the Temporal Key Integrity Protocol (TKIP), which acts as a wrapper to the WEP protocol and uses a 128 bit RC4 encryption to eliminate the possibility of key reuse within a given session. However, TKIP cannot be gainfully employed in devices where the 64 bit RC4 encryption is hardwired. Also, with 128 bit encryption TKIP can secure 10 frames per session. Comparing this to the typical number of frames per session (500-1000), it is easy to see that the use of a 128 bit key causes unnecessary drain of power. The Wifi Protected Access (WPA), uses a 128 bit Advanced Encryption Standard (AES) cipher in the Counter-Mode-CBC-MAC Protocol (CCMP). This protocol requires higher computational power than the TKIP and is only intended for devices which possess higher computational power and memory. In this paper, we propose a light weight enhancement to the 64 bit WEP, which provides significant improvement in security (measured as the number of frames securely transmitted before base key change) with small energy and memory overhead. Moreover, our technique can be tailored to the specific needs of resource constrained environments to provide just the necessary level of security. We use the Intrinsyc CerfCube [2] as a resource constrained wireless device and measure the resource consumed by various wireless security protocols on this device. From the experimental results we see that proposed LWE consumes about 62% less power compared to TKIP and 99% less power compared CCMP (AES), while providing a security enhancement of 2 over the WEP protocol. These results demonstrate the utility of LWE as a good security protocol for wireless networks with battery power constrained devices and systems where 64 bit WEP is hardwired.