Android 4.4 introduced a number of security enhancements, most notably SELinux in enforcing mode. One security feature that initially got some press attention, because it was presumably aiming to 'end all custom firmware', but hasn't been described in much detail, is verified boot. This post will briefly explain how verified boot works and then show how to configure and enable it on a Nexus device.
more here.........http://nelenkov.blogspot.com/2014/05/using-kitkat-verified-boot.html
more here.........http://nelenkov.blogspot.com/2014/05/using-kitkat-verified-boot.html