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Author Topic: encrypting an already encrypted file  (Read 3492 times)

Armando

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encrypting an already encrypted file
« on: September 05, 2007, 02:51:20 AM »
Hello...
I haven't found much on that subject (encrypting -- mistakenly or not... -- an already encrypted file).
Is it something bad to avoid? I'm specifically thinking of encrypting an allready encrypted Word files with another "encrypter" (TrueCrypt, AxCrypt, whatever...).

Thanks!

f0dder

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Re: encrypting an already encrypted file
« Reply #1 on: September 05, 2007, 04:34:43 AM »
Shouldn't be any problems in doing this, but there shouldn't be much reason to do so anyway - use strong encryption in the first place. Some encryption apps support "chaining" of different ciphers, I guess the rationale is that if a specific attack is found against a cipher, it's hoped that this attack can't be used for other ciphers.
- carpe noctem

Armando

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Re: encrypting an already encrypted file
« Reply #2 on: September 05, 2007, 09:35:07 AM »
I see... Thank you f0dder.
(Even if I logically saw no reason why would some data corruption occur, I was more or less worried that it might happen...).

CWuestefeld

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Re: encrypting an already encrypted file
« Reply #3 on: September 05, 2007, 03:25:46 PM »
I can't imagine this causing any problems, but you're not going to buy yourself much security, either (I assume you're not trying to hide the plans to a nuclear warhead!).

As a matter of fact, TrueCrypt has a built-in feature that chains multiple layers of encryption, if that's what you want.

Armando

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Re: encrypting an already encrypted file
« Reply #4 on: September 05, 2007, 03:34:34 PM »
 ;D

I actually only got worried that using AxCrypt on a couple of already encrypted files (using one of MS Word's 2003 advanced encryption option) could potentially be harmful.... I'm not trying to hide any secret plans to hack into Mouser's computer and steel farr's source code...

cthorpe

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Re: encrypting an already encrypted file
« Reply #5 on: September 05, 2007, 03:53:47 PM »
I can't see how it would be an issue unless the second encryption program is known for making corrupt files.  But then that would be a problem even if you weren't layering or chaining encryption.  The encryption program won't care if the file it is working with is plain text, a regular word document, or an encrypted file.  Then when you decrypt, it will just put it back to however it was before you encrypted.



Carl

Armando

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Re: encrypting an already encrypted file
« Reply #6 on: September 05, 2007, 04:15:25 PM »
Yes. thanks Carl.
I've been encrypting already encrypted files for quite a while now and never had any corruption problems. But... As a good (pseudo) scientist, I've learned that when n=1, it's better to gather a bit more data before drawing any conclusions...
Ok. So now n=... what...4? We're getting there... :)

Lashiec

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Re: encrypting an already encrypted file
« Reply #7 on: September 05, 2007, 08:00:28 PM »
The only problem you would be facing using various ciphers is that you have to remember various passwords, and remember how to apply them in the correct order. About corruption, if the software is good enough there should be no problems, apart from that, if the disk corrupts itself... ;D

Chaining of cyphers was a good way to encrypt information if you used various weak algorithms (in a text file, you used ROT13, then you inverted the order of the characters and so on...), but if you use AES, you will be safe... until we get quantum computers (probably ;))

Armando

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Re: encrypting an already encrypted file
« Reply #8 on: September 06, 2007, 11:23:26 AM »
Thanks lashiec

until we get quantum computers (probably ;))

You are, off course, referring to TOOWILD's machine...