If you cannot obtain the proper system keys from your own 3DS hardware using tools like GodMode9 , the most reliable "fix" is to use game files (typically in .3ds or .cci format). Decrypted ROMs do not require an aes_keys.txt file to run in Citra.

Many users download the file and drop it in the main folder, but Citra still says keys are missing. This is usually because the file is in the User Directory , not the installation directory.

Instead of fixing keys, download .3DS or .CIA files (already unpacked). Citra runs these without any keys.txt . Check ROM sites for "decrypted" tags.

: If you cannot find or dump your own keys, many users prefer downloading Decrypted versions of 3DS games (usually .3ds or .cci files), which do not require an aes_keys.txt file to run.

: Legally, you should dump these from your own hacked 3DS using a script like GodMode9 .