In this talk we provide a high-level overview of our recent research activities
in the area of system security. The topics include security of wireless systems
and the physical layer authentication. We also talk about recent advances in
user authentication using physiological signals, such as eye-movement
biometrics, touchscreen gesture authentication, and pulse-reponse biometrics. We
discuss various tradeoffs between security designs and system performance, and
identify some interesting next steps in this research area.