If a function decrypt(GHYFtg56) were possible crypt() would be useless for storing passwords as anyone else (including the attacker) could do the decyphering too. You would have won nothing by storing it as "GHYFtg56".

cryptographic hash function must have the property that it is easy to create the hash (i.e use crypt()) but impossible to do the inverse (i.e. decrypt()) in acceptable time.

In other words: Your script needs to know some password to do something. Whatever the script knows, everyone with access to the script can find out too. The only exception is if the script stores the information somewhere else. See my other post here for a possible method