The following BIF file sample shows the red key stored in BBRAM:
the_ROM_image: { [aeskeyfile] bbram.nky
[keysrc_encryption] bbram_red_key
[bootloader, encryption=aes, destination_cpu=a53-0] ZynqMP_Fsbl.elf
[destination_cpu = a53-0, encryption=aes] App_A53_0.elf
}