Citra looks for aes_keys.txt in specific directories relative to the operating system:
To make the file "portable" alongside the emulator executable (rather than in the user profile), "Portable Mode" builds of Citra check the sysdata folder relative to the executable path.
To keep your Citra AES keys.txt portable build working across different PCs: citra aes keystxt portable
"Citra still says keys are missing!"
Double-check that you are editing the correct user folder. If you see a user folder inside the Citra installation directory, that is the one used for portable mode. Do not place the file in your Windows Documents or AppData folders.
"Where do I get the keys?"
We cannot provide links to download these files. This is a legal grey area that risks copyright infringement. The only supported method is dumping them from hardware you own using tools like nimds or similar homebrew dumping scripts. Citra looks for aes_keys
Navigate to the folder where your Citra executable is located.
This is the hardest part, but it is necessary.
You will need a hacked 3DS with Custom Firmware (CFW) installed. The standard tool for this is boot9strap and various dumping utilities available on the homebrew scene. Once you have generated the aes_keys.txt file from your console, transfer it to your PC. To make the file "portable" alongside the emulator
AES (Advanced Encryption Standard) is the symmetric encryption algorithm used by the 3DS. Every 3DS game is encrypted with a unique key, but those keys are derived from a set of common master keys stored in the console’s hardware.
For Citra to decrypt a game on-the-fly, it needs access to a set of these AES keys. Without them, you will encounter the infamous black screen or the error: "Could not decrypt ROM (Missing AES keys)."
Now we arrive at the core of the keyword: "citra aes keystxt portable" – combining the decryption keys with the portable structure.