Find a bug and give a suggestion

[huangbaoliu]

1. When you want to split a key into m parts, you need to choose m rand as x. So these x should be different to each other, you shoud check then rand number choosen by you. Your code doesn't do this check !
2. Because x is an one-byte value, you only need to malloc 256 bytes to store the invert table . In your code you use 64k byes to store the invert table.