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Date: Thu, 4 Dec 2014 20:07:36 +0000
From: Rostislav Khlebnikov <>
Subject: Re: Recovering password given the unpacked data available

Thank you,

I will try that. Actually I already did - even had to compile the x64
version of pkcrack, but with no success. I will try to figure out what am I
doing wrong. For one of the files no matter what level of compression I use
(7-zip or WinZip) I can't get the compressed plaintext file to be smaller
than the extracted encrypted file, which is rather strange. My wife
remembers parts of the password, so I will try dict attack too... Eh.
Thanks for help anyway! :)


On Thu, Dec 4, 2014 at 7:51 PM, jfoug <> wrote:

> search for pkcrack   It is a plaintext attack against pkzip encryption.
> If this is the WinZip AES encryption, then I doubt having the plaintext
> will help you out at all.  pkcrack is simply an implementation of this
> known plaintext attack.  The attack only needs 13 bytes of original
> plaintext, which is the exact compressed data, but unencrypted.  The more
> data the better and faster the crack.  I have broken many zip files a
> decade or so ago using this technique.   There likely are other tools that
> are much more up to date than this (Elcomsoft ?)
> > From: Rostislav Khlebnikov
> > I have a rather unusual problem. I have the zip password-protected
> archive and I also have the extracted contents of the archive. Do you think
> there is a rather simple way to recover the password that the archive was
> created with?

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