Sometimes, you could need to recover a password for an old encrypted zip file. To do this you can use fcrackzip. fcrackzip is a CPU bound software, so you shall take in mind that to obtain a result in a reasonable time you shall use a strong CPU, otherwise you could wait for a large amount of hours. However I have used it on my netbook (ATOM 270) and I have obtained good results. I tried fcrackzip on two encrypted zip files, the first one was encrypted with a 9 numbers password, the second one was encrypted with a 7 chars password that wasn’t in the dictionary, these are the results:
$ time fcrackzip -l 4-9 -c 1 --use-unzip inkey.zip
PASSWORD FOUND!!!!: pw == 987654321
$ time fcrackzip -l 6-9 -c a --use-unzip inkey.zip
PASSWORD FOUND!!!!: pw == pippolo
In Ubuntu you can install fcrackzip by typing the following command:
$ sudo apt-get install frcrackzip
for others linux distributions you can download the source code from this link, then you shall perform the following step:
Move to the directory where you have downloaded the tarball (for me is my home directory):
extract the source code:
$ tar zxvf fcrackzip-1.0.tar.gz
move to the code directory
$ cd fcrackzip-1.0
configure the makefile
build the executables
Install the software
$ sudo make install
If you want to use Windows operating systems you can download the precompiled binaries from this link.
To obtain good results in a small amount of time I use fcrackzip as shown in the following sequence:
- I search for password composed only of numbers (is very easy for a computer to check all combinations of numbers because these combinations are few)
- I search for password contained in a dictionary (you can find a lot of dictionary on the internet)
- Last I use fcrackzip as brute forcer cracking tool.
80% of password can be retrived with the first two steps in a very small amount of time, the third step is a very CPU bound process (but with this method you are sure to retrieve the password).