You also need the (sometimes called otp or seed ). This is a console-specific key. Add this line at the top of your keys.txt :
Breath of the Wild key = 12345 (Wrong format, wrong length) wii u keystxt for cemu
The wii u keystxt for cemu file itself is a collection of numbers—copyright law varies on whether numbers can be copyrighted. However, You also need the (sometimes called otp or seed )
The Wii U console encrypts all its game files, updates, and DLC. When you rip a game disc (saving it as a WUD, WUX, or RPX file), the data is scrambled. Without the correct decryption key, your PC sees the file as gibberish. Cemu cannot execute code it cannot read. or RPX file)