Decrypting PDF Password

[littlesmilinglady]

Hi guys 

I've had a look through all the tutorials on the site, and can't seem to find anything about decrypting PDF files.

The file has a user/open password, and has 128-bit encryption. One website said it would take 1.2 million years to decrypt! 

I've spent hours looking online for some way to decrypt it with no joy, and was wondering if any of you had any experience and could offer some hints or advice please?

Thank you so much! 

[Kulverstukas]

There's a reason why these encryptions were made, and you're going about it the wrong way - what you need to find is as password to decrypt it, otherwise it won't ever work... well I really doubt the PDF is worth such trouble anyway. You should look for password bruteforcers instead and apply it to the PDF, or ask the author for a password?

[littlesmilinglady]

Hey, Kulverstukas,

I know, I currently do have it running on the elcomsoft advanced pdf professional on a brute force attack- doubt it will ever work though. 

It is actually my college course's answer material pdf.... bad i know, but I'm on my last chance and desperate 

Thank you for your help

[white-knight]

It is actually my college course's answer material pdf.... bad i know, but I'm on my last chance and desperate 

It amazes me how many people come here and say that ..   

[chriskzn]

Funny you say that, I remember when one of Elcomsoft's developers were so good, they made available a decrypter tool that did precisely what you asking for, the only difference is I do not think we had 128 bit encryption in those days. I remember reading that the poor guy got arrested when he visited the U.S.A. for some conference. I just wish I could remember his name but the tool bypassed all passwords and decrypted the document no matter what. He was a genius and I am sure he still us today.

[Trevor]

Funny you say that, I remember when one of Elcomsoft's developers were so good, they made available a decrypter tool that did precisely what you asking for, the only difference is I do not think we had 128 bit encryption in those days. I remember reading that the poor guy got arrested when he visited the U.S.A. for some conference. I just wish I could remember his name but the tool bypassed all passwords and decrypted the document no matter what. He was a genius and I am sure he still us today.

It was the Russian Dmitry Sklyarov. Details on wiki

Answering the original question:
Sometimes decrypting passwords can be super easy due to a faulty implementation in encryption.
One such software is DRMsoft Pdf to EXE Encrypter where inspite of the password protection, it can be decrypted due to use of XOR encraption.