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Author Topic: Question : Using CPU/GPU to crack a Locklizard protected PDF?  (Read 6961 times)
trumpetx
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June 24, 2011, 08:15:04 PM
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First of all, this is a hypothetical question.  My wife is a composer.  Her publisher uses Locklizard to send her PDFs, and I casually mentioned that it's silly that he bothers to password protect the PDFs as they can be cracked relatively easily (not to mention, who wants to steal what he's sending her anyway, but still - that's beside the point)

I'm not a hacker/cracker, just an ordinary programmer who thinks DRM is silly, and I wanted to show my wife "proof."

Lets say I am in possession of a locklizard protected PDF which is legally owned by me.  How would I go about brute force attacking it with a GPU/CPU?

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June 24, 2011, 08:50:28 PM
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I think you're posting this on the wrong website.  This is for bitcoins not hacking.

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June 24, 2011, 09:31:38 PM
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I think you're posting this on the wrong website.  This is for bitcoins not hacking.

And this is the offtopic forum.  I would imagine some who are involved with Bitcoins (specifically someone who's looked at the miner code) could also have similar knowledge when it comes to password cracking since some of the same principles apply.  I don't think it's much of a stretch.  Maybe that's just me though.

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June 24, 2011, 10:50:50 PM
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Not sure about Locklizard, but I use something called PDFunlocker to rip the PWs off most PDFs I work with so I can edit them.

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June 24, 2011, 11:13:57 PM
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Quote from:  trumpetx
And this is the offtopic forum.  I would imagine some who are involved with Bitcoins (specifically someone who's looked at the miner code) could also have similar knowledge when it comes to password cracking since some of the same principles apply.  I don't think it's much of a stretch.  Maybe that's just me though.
Ethically It's wrong, so even if I knew how to hack or even switch on a PC I would not help you Smiley maybe just watch your soon to be ex wife enter her password Smiley
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June 29, 2011, 02:10:51 AM
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Quote from:  trumpetx
And this is the offtopic forum.  I would imagine some who are involved with Bitcoins (specifically someone who's looked at the miner code) could also have similar knowledge when it comes to password cracking since some of the same principles apply.  I don't think it's much of a stretch.  Maybe that's just me though.
Ethically It's wrong, so even if I knew how to hack or even switch on a PC I would not help you Smiley maybe just watch your soon to be ex wife enter her password Smiley

Have you ever downloaded something? :x

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June 29, 2011, 03:11:48 AM
 #7

At most it would take 115,792,090,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 attempts to brute force one of their AES-256 keys. Given all the hardware on earth you'd be crunching until long after the heat death of the universe.

A better attack would be to OCR the pages, intercept the drawing routines as the pages are painted, or exploit the PDF client in some other way.
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