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Author Topic: Is there a free non-Adobe PDF-reader which can decrypt 256-bit encrypted PDFs ?  (Read 13491 times)

Offline RD

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Is there free PDF-reader software, other than Adobe reader, which can decrypt 256-bit encrypted PDFs ?

Free Non-Adobe PDF readers can deal with 128-bit encryption, but here doesn't seem to be a free one which can decrypt a PDF which has been encrypted using the latest 256-bit AES.
« Last Edit: 27/03/2013 22:09:50 by RD »


 

Offline syhprum

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I have Adobe acrobat 9 pro will that do it ? I have never tried it is not free but trial versions can be downloaded , put up an encrypted one plus key to make a test.
« Last Edit: 28/03/2013 01:18:13 by syhprum »
 

Offline RD

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I have Adobe acrobat 9 pro will that do it ?

I was looking for something other than Adobe products, (something more lightweight, and preferably multi-platform).

... put up an encrypted one plus key to make a test.

Currently I don't have the ability to produce a 256-bit test PDF,

and I don't fancy posting the genuine encrypted document in question on the internet with the password (key).
 

Offline CliffordK

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I'm seeing several commercial packages that claim to create or decode the 256 bit encryption.

Did you try Lizzard Secure PDF viewer?

http://www.locklizard.com/pdf_security_viewer.htm

I'm not sure of all of its capabilities, but it would be worth trying.
 

Offline RD

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I'm seeing several commercial packages that claim to create or decode the 256 bit encryption.

Currently I don't need to create 256-bit encrypted PDFs , I'm just interested in reading them using a free PDF reader, other than Adobe reader.

Did you try Lizzard Secure PDF viewer?

The locklizard PDF software seems to use their own unique encryption methods ...

Quote from: locklizard.com
If you seek unprecedented PDF protection for your valuable information, want total control over how it is used, wish to scale up from password protecting documents, which is neither comprehensive nor fool-proof, then Safeguard PDF Security is for you.
http://www.locklizard.com/pdf_security.htm

[ and locklizard is not free ]

I think I have it : the latest version of FireFox browser [#19] has a PDF reader built-in which can read encrypted PDFs ... http://support.mozilla.org/en-US/kb/view-pdf-files-firefox-without-downloading-them
« Last Edit: 28/03/2013 09:38:07 by RD »
 

Offline syhprum

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I have produced an encrypted file for test with Adobe Acrobat X but I cannot post it as an attachment but will email it to any interested parties.
It will not decrypt with Lizard secure but I will try Firefox and post results.
I have loaded Firefox/Thunderbird but I cannot se anyway that they help with encrypted files
 
« Last Edit: 28/03/2013 11:43:16 by syhprum »
 

Offline RD

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I have produced an encrypted file for test with Adobe Acrobat X but I cannot post it as an attachment

PDFs can be attached to posts if they are less than 128kB in size,
one is attached to this post, the password is "thenakedscientists" (don't include the quotes).
 

Offline syhprum

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There is a simple Adobe Acrobat reader 11.1 that will open both 128 and 256 encrypted files, free download only it foists Chrome on you.
 

Offline RD

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There is a simple Adobe Acrobat reader 11.1 that will open both 128 and 256 encrypted files, free download only it foists Chrome on you.

But the brief is ...
Quote
Topic: Is there a free non-Adobe PDF-reader which can decrypt 256-bit encrypted PDFs

 

Offline syhprum

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There may or may not be a non adobe PDF reader but I am not going to hunt for it when there is a small ,Free adobe program to do the job
Here is a test file encrypted with 256 bit encryption to test the highly original password is password
 

Offline CliffordK

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Ok,
Both Okular & "Document Viewer" in Linux can open both "Test Card 2" &  "* 128-bit encryption, key is ''thenakedscientists'' (no quotes).pdf"

So far I am unable to open the doc sent by PM from Syhprum using the PW specified.
 

Offline syhprum

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I made a check the 361Kb encrypted file opens with both Acrobat reader and Acrobat X pro no problem with the key "openme"
 

Offline CliffordK

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I wonder...
Do we truly need 256 bit encryption?

2128 = 3 x 1038

Most of the current PCs run on the order of a giga operations per second, or a billion ops per second.
Multiply that by a thousand, and one gets teraflops, or a trillion ops per second, or 1012 ops per second.

So, at a teraflop, a brute force decryption would still take about 1026 seconds.
And one still has a good number of years to do the calculation.

On the other hand, if one uses a lower case alpha password that is 10 characters long, one ends up with 2610 = 1 x 1014, or so possibilities.  At 1 teraflop, it would take about a minute to decode.

Use, say a 100 character set for a 10 letter password, and one gets 10010 possibilities, or about 1 x 1020.  And, it takes about a year to decode at 1 teraflop.  A few teraflops and it would decode much quicker. 

However, If one restricted the search to, say 7 lower case characters, and 3 "other" characters, it would again reduce the possibilities greatly.

If you restrict the search to words in a dictionary, various tenses, abbreviations, and names.   One comes up with less than a million or so possibilities.  Even a rather mediocre computer should be able to crack the password rather quickly.

The key, of course, is good heuristics, and the ability to guess the PW.
 

Offline RD

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... Here is a test file encrypted with 256 bit encryption ... Test Card 2.pdf (72.75 kB

Your "Test Card 2.pdf" has 128-bit encryption, not 256-bit  ...

 

Offline RD

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I wonder...
Do we truly need 256 bit encryption?

2128 = 3 x 1038

Most of the current PCs run on the order of a giga operations per second, or a billion ops per second.
Multiply that by a thousand, and one gets teraflops, or a trillion ops per second, or 1012 ops per second.

So, at a teraflop, a brute force decryption would still take about 1026 seconds.
And one still has a good number of years to do the calculation.

I think the 256-bit is overkill at the moment , an attempt to future-proof ... http://en.wikipedia.org/wiki/Moore%27s_law

... If you restrict the search to words in a dictionary, various tenses, abbreviations, and names.   One comes up with less than a million or so possibilities.  Even a rather mediocre computer should be able to crack the password rather quickly.

The password is the weakest link. Some password encryption methods apply PBKDF with thousands of iterations to delay dictionary-type cracking.
« Last Edit: 28/03/2013 22:34:31 by RD »
 

Offline syhprum

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Indeed I may have accidentally created some with only 128 bit encryption I took care with this one it should definitely be 256 key "openme".
 

Offline RD

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... I took care with this one it should definitely be 256 key "openme"...  P Marchese 2007.pdf (27.16 kB

No joy with Adobe reader 9 ...


Nor with FireFox 19 ...


FireFox 19 CAN read 128-bit ...
« Last Edit: 28/03/2013 23:06:23 by RD »
 

Offline syhprum

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there is an AES 256 bit encryption system available but it does not seem to be compatible with the Adobe Acrobat system.

http://www.integralmemory.com/faq/what-aes-256-bit-hardware-based-encryption
 

Offline RD

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there is an AES 256 bit encryption system available but it does not seem to be compatible with the Adobe Acrobat system.

256-bit AES is not a proprietary (patented) encryption, it's used widely, and is just an extension of the 128-bit AES encryption that the non-Adobe PDF readers can currently cope with ... http://en.wikipedia.org/wiki/Advanced_Encryption_Standard#Description_of_the_cipher

Unless Adobe have added a secret tweak to their implementation of 256-bit AES, then I don't see why Non-Adobe PDF readers could not be modified to decrypt 256-bit PDFs.
 

Offline syhprum

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It seems a bit of a pointless exorcise hunting for a non adobe decrypter when a free adobe one is available, so far I have tried four but none work !!, if you have one please publish it.
 

Offline CliffordK

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What is "Free" isn't always "Free".

Read about Adobe & Gnash development.
http://en.wikipedia.org/wiki/Gnash#Adobe_Flash_Player_End-User_License_Agreement

Earlier I was having problems with finding a good 64 Bit Linux Flash or Acrobat, although that may be resolved for now.

Also, when I want to view a PDF, I just want to view it.  Perhaps rotate a few pages or something.  The last time I used Adobe Acrobat, I was getting annoyed with all the "Extras" that Adobe was adding.  I think there was also "nag-ware" to try to get people to buy the commercial version.
 

Offline RD

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It seems a bit of a pointless exorcise hunting for a non adobe decrypter when a free adobe one is available

You described Adobe as "small", but it expands to about the same size as my Linux operating system.
I was looking for something more lightweight, less bloated, and possibly with more features and better security against malware, (like Foxit Reader)

... if you have one please publish it.

If I find one I will.
« Last Edit: 02/04/2013 02:28:20 by RD »
 

Offline syhprum

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FoxitRead seems to be the answer it opens files produced by Adobe Acrobat 256 bit encryption no problem.
 

Offline imatfaal

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None of the first 4 choices of pdf reader that I tried on Debian Linux could open the Marchese document.  Adobe did seem to be having problems with the implementation of standardised 256 bit encryption
 

Offline yor_on

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RD, if you're using Linux http://en.wikipedia.org/wiki/Xpdf might work for you. STDU viewer does not support encryption it seems, although it recognizes it? And that one is window btw :)
=

And ask for a password too???
Either it supports encryption and then the Adobe is non standard, or someone might have planned to support it?? Awwhhhhh..
« Last Edit: 21/08/2013 22:16:48 by yor_on »
 

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