To get your platform key use this command in the tegra30-debrick directory.
sudo ./fusee-launcher/fusee-launcher.py –-tty ./fusee-launcher/dump-sbk-via-usb.bin
Add the -P parameter at the end to specify the product_id if "No TegraRCM device found" is the output. For the Surface RT 1 this is 7130.
This will output a lot of things. Look for the line with hello world, after that line something like this
should show up. Remove the b, the two ' and the last 8 remaining characters. This is your platform key. It is used to encrypt and decrypt the BCT and the firststage bootloader