Those software that claim can crack the password, I really doubt. I think they are using some hash calculation method which is some sort of brute-force. It will take years to crack if you have a well protected password like 8 characters long, using combination of small big alphabet and special characters.

If you don't want people to even see the contents of your rar file. Just double compress it. That means compress once without password. Then you will get a file called, eg filename.rar. Next, you compress that filename.rar with password protection and you will get another rar file maybe called filename-again.rar. So, when people open filename-again.rar, all they can see is filename.rar.