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