Nearly all commercial 3DS software—whether on physical cartridges or digital eShop titles—was encrypted. This meant that if you ripped a game file (a ROM) from a cartridge you owned, the resulting file was scrambled. Without the specific decryption keys, the file was useless binary garbage to an emulator. The 3DS hardware had these keys burned into its processor; Citra, being software running on a PC, did not.
System Archive Decryption Failed.