Já nevím proč, zeptej se někde u Elcomsoftu :)
Našel jsem třeba toto (dotaz na zjištění hesla 7z):

You can use 7zrecover, it is easy to use and if you know what words could be in your password you will get it back pretty fast.

7z encryption is a pain ass, it is specially made to slow brute force attacks. Good luck!