Cenzic 232 Patent
Paid Advertising
sla.ckers.org is
ha.ckers sla.cking
Sla.ckers.org
This group should mostly be dealing with how web applications enable networking security issues that are otherwise not there. Everything is being tunneled over port 80 now so what does that enable and how do we fix it? 
Go to Topic: PreviousNext
Go to: Forum ListMessage ListNew TopicSearchLog In
PDF Password removal
Posted by: br0kan
Date: March 03, 2009 05:02PM

This topic didn't really fit anywhere and it is somewhat of a tangent. Regardless, I was wondering if anyone could explain how/why PDF password removal is possible in some cases. I know there are a multitude of tools out there to do it and understand that it is easy to do. What I am curious about is what exactly it is that those tools are doing.

Also I'm not interested in anything that has to do with Brute Force cracking of the passwords

Options: ReplyQuote
Re: PDF Password removal
Posted by: Spyware
Date: March 04, 2009 12:30AM

After reading through some fishy looking websites, my understanding is that those tools will decrypt the document (encryption happens when a user puts a password on it) and remove the segments of text which cause the authentication-process to happen at all.

This only works for "master" (open document) passwords and not "user passwords". Basically, "master" passwords merely limit the use of PDF files, for example the owner could disable selecting text, and you need to type in a password if you wanted to enable selecting text.

The "user" password is a password you need to type to open the document, this is the thing that people brute-force.

More here, but visit at your own risk: http://www.guapdf.com/

Options: ReplyQuote
Re: PDF Password removal
Posted by: br0kan
Date: March 04, 2009 12:46AM

Thanks...I'm still wondering exactly what that means when they say they "decyrpt" the document though. Does that mean that PDF encryption uses weak keys? Or does that mean when you put the PDF document into HEX there are a few areas that you need to tweak. I don't really want to mess with it too much though (isn't that what Dimitri went to jail for?) I'm just curious.

Thanks for the help though Spyware.

-Br0kan

Options: ReplyQuote
Re: PDF Password removal
Posted by: Spyware
Date: March 04, 2009 12:54AM

br0kan Wrote:
-------------------------------------------------------
> Thanks...I'm still wondering exactly what that
> means when they say they "decyrpt" the document
> though. Does that mean that PDF encryption uses
> weak keys? Or does that mean when you put the PDF
> document into HEX there are a few areas that you
> need to tweak.

I think you are right on the spot here, I'm guessing that these tools somehow "comment out" the auth process/security implementations. Regarding the decryption: Perhaps the decryption used when applying master passwords is reversible.

Options: ReplyQuote
Re: PDF Password removal
Posted by: tx
Date: September 18, 2009 02:12AM

S
P
A
M

-tx @ lowtech-labs.org



Edited 1 time(s). Last edit at 09/18/2009 02:14AM by tx.

Options: ReplyQuote
Re: PDF Password removal
Posted by: cynthiachen
Date: January 22, 2010 12:14AM

Spam cynthiachen (221.221.9.232) Spam cynthiachen (221.221.9.232) Spam cynthiachen (221.221.9.232) Spam cynthiachen (221.221.9.232) Spam cynthiachen (221.221.9.232) Spam cynthiachen (221.221.9.232)



Edited 1 time(s). Last edit at 01/22/2010 02:07AM by Gareth Heyes.

Options: ReplyQuote
Re: PDF Password removal
Posted by: pollostar
Date: March 13, 2012 07:26AM

For removing PDF password you need a software that is called PDF password remover.
This will help you for removing PDF password.
In this software you 1st import PDF files for this click on add files button then click on start button for removing PDF password.

Technical Support
HP Support

Options: ReplyQuote


Sorry, only registered users may post in this forum.