We present a covert side channel that uses the 802.11 MAC rate switching protocol. The covert channel provides a general method to hide communications in an 802.11 LAN. The technique uses a one-time password algorithm to ensure high-entropy randomness of the covert messages. We investigate how the covert side channel affects node throughput in mobile and non-mobile scenarios. We also investigate the covertness of the covert side channel using standardized entropy. The results show that the performance impact is minimal and increases slightly as the covert channel bandwidth increases. We further show that the channel has 100% accuracy with minimal impact on rate switching entropy. Finally, we present two applications for the covert channel: covert authentication and covert WiFi botnets.