How to check this is true password

[validator]

Hi, I want to develop a password cracker tool. For example I forgot a winrar password. I run this tool and How can I understand whether I have found password or not. I mean that where is the winrar password or hash in rar file. It is clear that I can not find winrar password as clear text so where is stored WinRAR password in rar file. I wonder this situation the other file types such as word, excel, power point ext.