$ ./mkimxboot -i bootloader-fuzeplus.sansa -b sandisk-firmware.sb -o recovery.sb -t recovery
[INFO] mkimxboot models:
[INFO]   Fuze+: idx=0 rb_model=fuz+ rb_num=72
[INFO] mkimxboot mapping:
[INFO]   md5sum=c3e27620a877dc6b200b97dcb3e0ecc7 -> idx=0
[INFO] MD5 sum of the file: B7 C8 A7 A4 0D 10 1F B2 82 63 92 2F 00 56 86 88 
[ERR] MD5 sum doesn't match any known file
Result: -4