To ensure the integrity of the application, TrustZone also provides a secure execution environment where only trusted applications can operate, safe from hacker/virus/malware style attacks, a Trusted Execution Environment (TEE).
TrustZone hardware provides the isolation for the TEE from software attack vectors. The hardware isolation extends to securing data input and output all the way to the physical peripheral, including for example, the keypad/touchscreen.
Armed with these key capabilities, chipsets equipped with TrustZone technology provide a wealth of opportunities to redefine the services users can access (more, better), how they access them (faster, easier), and where they can access them (anywhere, anytime).
For more detailed information on TrustZone technology click here
For information on efficiently designing and implementing secure systems go to the TrustZone Ready Program