Zip file password recovery in Linux

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
PASSWORD FOUND!!!!: pw == 987654321
real 5m8.981s
user 5m8.963s
sys 0m0.028s

$ time fcrackzip -l 6-9 -c a --use-unzip
PASSWORD FOUND!!!!: pw == pippolo
real 10m14.291s
user 10m14.242s
sys 0m0.008s 

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):

$ cd

extract the source code:

$ tar zxvf fcrackzip-1.0.tar.gz

move to the code directory

$ cd fcrackzip-1.0

configure the makefile

$ ./configure

build the executables

$ make

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:

  1. 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)
  2. I search for password contained in a dictionary (you can find a lot of dictionary on the internet)
  3. 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).


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