Secure boot of GDP on Raspberry Pi3

This request from ACCESS

"We have ported ACCESS NetFront Browser (NF) BE (Blink Edition) onto GDP on Raspberry Pi 3. We are planning to integrate DRM as part of the media player for NFBE on GDP+RPi3.
We know that RPi3 has security features stemming from ARMv7/v8, like Secure State, Secure Physical Address space, that are configurable via NS and NSTable bits.

However, we are not sure whether GDP itself has any infrastructure for secure boot that is the key point for any DRM.

Could you please provide more info about the secure boot of GDP on RPi?"