You need to know so many bytes of compressed file as equal to password length. ZIP Yes , passwords of any length, you need to know at least 13 bytes of compressed file. Yes, passwords of any length, you need to know 3-4 bytes of compressed file. Currently no methods are known to do it. My favorite archiver Please give me an info Note that all these methods demand the knowledge of compressed file.
Some programs understand self-extracting archives.
If your program does not, just remove self-extracting header and you will get the normal archive. To do this you need to read technical description of archive format, find the signature archive begins with and remove all bytes lying between the beginning of file and this signature. You could also find this signature by looking at first bytes of normal archive. Passwords of any length can be cracked instantly. But because of US export regulations Office 97 uses 40-bit key.