AES + WinRar = Oil + Water

Discussion related to AES Crypt, the file encryption software for Windows, Linux, Mac, and Java.
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OxiCln
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Joined: Sun Mar 04, 2018 4:09 am

AES + WinRar = Oil + Water

Post by OxiCln » Sun Mar 04, 2018 4:23 am

So I encrypted quite a few sensitive files with AES Crypt and it worked flawlessly, however I was attempting to transport them after that so I compressed them using WinRar and password protected that as well. (is this overkill?) Later upon trying to revisit the files I entered the correct password and was still met with an error message saying either the password was wrong or the file had been modified.

Questions:

If there's a solve, what is it?

(provided your answer to the first was no continue)

Is there anyway to isolate and reverse whatever it is WinRar changed?

Is there anyway to recover the files outside of AES Crypt?

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paulej
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Re: AES + WinRar = Oil + Water

Post by paulej » Sun Mar 04, 2018 3:16 pm

It sounds as if WinRAR is altering the files in some way.

I'd be happy to look at it if you would send me a sample. The easiest thing to do is create a file using notepad with just the word "test" or something inside. Encrypt that file. Then copy the encrypted file so we have a "before and after" version. Create a RAR file with WinRAR holding the encrypted file. Delete the encrypted file (but not the copy). Extract the RAR file. Try to decrypt the encrypted file.

If you can reproduce it with non-secret information, email the encrypted file and the one altered by WinRAR. I can tell you exactly what changed.

I do have a hacked up version of AES Crypt that removes all the error checking. That might help in recovering files, but you might also end up with garbage, depending on what WinRAR is doing.

Honestly, I'm surprised WinRAR would damage file contents, so I'm very curious to see what is going on.

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