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Thread: Finding the algorithm to an encrypted file

  1. #1
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    Default Finding the algorithm to an encrypted file

    I've been asked to try and decrypt a file (in the hope that it can't be done so they can prove their code is sound), but I've tried some stuff and the only thing I can think of, is trying to find their algorithm that they used for encryption from the file that was created.
    Can anyone point me in the right direction or is willing to undertake the test for me!
    TIA

  2. #2
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    Firstly, how is the file encrypted?
    It sounds like you've got some serious research ahead of you

    Secondly, don't ask around here for volunteers to help crack encrypted files for you.

  3. #3
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    Thank you very much for your reply. And sorry about asking as well - that was a throw away comment really.

    I believe that they are coding in XML, but on examining the file through notepad all I'm getting is a bunch of squares with no other real characters in it.

    Quite a nice file considering they want to keep their info safe, but they just wanted to know if the file was crackable so they could tighten it up.

    Any ideas on any tools that might let me see something else in there?

  4. #4
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    Its not going to be easy at all.

    But if its an XML file then look at the header of the XML that holds the version as XML usually has a header which you can match against.

    e.g. <?xml version="1.0"?>

  5. #5
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    Can't
    The file is unopenable of sorts. That's just my knowledge of them as a company. It's either that or a C created file.

  6. #6
    Senior Member Thorn's Avatar
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    Quote Originally Posted by samsam View Post
    I believe that they are coding in XML, but on examining the file through notepad all I'm getting is a bunch of squares with no other real characters in it.
    Notepad is NOT the right tool.

    Quote Originally Posted by samsam View Post
    Any ideas on any tools that might let me see something else in there?
    A hex editor is your best bet to start. However, if you're asking this in the first place, it's probably "uncrackable" as far as you are concerned, simply because you don't have the tools and lack the experience.

    The real question with any encryption algorithm is this: Knowing the class/operation of encryption that was used, can someone knowledgeable in decryption files derive the contents? Secondly, what is the least amount of time that a brute force attack can determine the contents?

    For what it's worth, most "home grown" encryption schemes have severe flaws because the programmers don't have the right math skills to do it right. Sometimes, even if it's done right, flaws will still creep into the code.
    Thorn
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  7. #7
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    Quote Originally Posted by Thorn View Post
    A hex editor is your best bet to start.
    Thank you for that - but I went straight into debug and did it the old fashioned way before that.

    But lack of experience I will take as a fair comment.

    But still the file is pretty good on a basic level then because the content is still not easily read.

  8. #8
    Senior Member ShadowKill's Avatar
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    Just for shits and giggles, is the file you've been tasked to crack proprietary in any way or are you able to post say....a snippet of the hex data?



    "The goal of every man should be to continue living even after he can no longer draw breath."

    ~ShadowKill

  9. #9

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    I for one don't see the reason for them not using widely known encryption standards. And as far as you're concerned, just confess to your "employers" that you are NOT the one to test the encryption of their files, because you don't know what encryption means, trying to decrypt a file by opening it with notepad? Debug? The way you should be doing that is opening it in hex, and trying to understand the sequence of data, eventually finding any algorithm in it etc... Reading a book or 2 on steganography will help I guess.

  10. #10
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    How about getting a let up from the file producers? As in get a basic structure or a few key words to try and decrypt?

    I know its half cheating but would would prive its stronger if you cant break in already kinda knowing whats in there.
    &#119;&#116;&#102;&#63;

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