platform_system_core/trusty/confirmationui

## Secure UI Architecture

To implement confirmationui a secure UI architecture is required. This entails a way
to display the confirmation dialog driven by a reduced trusted computing base, typically
a trusted execution environment (TEE), without having to rely on Linux and the Android
system for integrity and authenticity of input events. This implementation provides
neither. But it provides most of the functionlity required to run a full Android Protected
Confirmation feature when integrated into a secure UI architecture.

## Secure input (NotSoSecureInput)

This implementation does not provide any security guaranties.
The input method (NotSoSecureInput) runs a cryptographic protocols that is
sufficiently secure IFF the end point is implemented on a trustworthy
secure input device. But since the endpoint is currently in the HAL
service itself this implementation is not secure.

NOTE that a secure input device end point needs a good source of entropy
for generating nonces. The current implementation (NotSoSecureInput.cpp#generateNonce)
uses a constant nonce.