This note is written for RarCrack 0.2.

RarCrack brute forces password for encrypted zip, rar, 7z files.

rarcrack FILE_NAME --threads 4

Note that if --threads is omitted, RarCrack will use 2 threads, no matter how many cores your CPU has.

You can cancel the brute forcing (e.g. via Ctrl-c) at any time, and RarCrack will resume cracking at next startup. This is because RarCrack uses a status file FILE_NAME.xml at the same directory to record progress.

And this mechanism can be used to speed up cracking. For example, if you remember that the password is 6 digits:

<?xml version="1.0" encoding="UTF-8"?>

For zip and 7z files, an alternative to RarCrack is fcrackzip. And it has more features, e.g. specifying password range and using a dictionary. However, last time I tried to fcrackzip a zip file, it reported that the zip file is corrupt. And RarCrack successfully cracks the very zip file.