If you are between 11.0.0 and 11.2.0, you must follow this guide to downgrade your NFIRM using one of the methods at the bottom of this page to directly dump and restore your NAND.
All of these are working implementation of the "FIRM partitions known-plaintext" exploit detailed [here](https://www.3dbrew.org/wiki/3DS_System_Flaws).