Two programs used for encrypting and decrypting the R4 firmware (_DS_MENU.DAT) or main cheat database (CHEAT.DAT). The routines in these programs are faster than the ones in r4crypt by chishm. Thanks to party for the link when none were available.
I don't have a wii u anymore to test it myself, but if homebrews are not visible on the wii u menu I think you can press L + R + minus to open the plugin menu, there should be an option called "homebrews on wii u menu" or something similar