From WikiTemp, the GBAtemp wiki
There are three partitions on the disk. Extractpartition is used to extract the partition with the proper information.
Mac OS X
Download the extractpartion to your home directory. Create an arbitrary file of exactly 516 byte (done with dd) and name it root-key. Then create a directory in your home folder called ".wii". The created file has to be moved into this directory with the common-key file.
./extractpartition inputfile.iso output.iso
Courtesy of searchforglory