decryption through md4 algorithm

how to decryption through md4 algorithm.
RuhelaAsked:
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pgnatyukCommented:
In the version I used few years ago, it was like here:
http://linux.die.net/man/3/md2

MD4_Init, MD4_Update, MD4_Final

Here is an example:
http://www.slavasoft.com/quickhash/help-online-frames/htmlpages/chmac__samplestring_md4.htm

Why MD4 and not MD5
http://userpages.umbc.edu/~mabzug1/cs/md5/md5.html
http://nepsin.com/mem/projects/md5.htm

CodeProject.MD5 File Creation and Verification
http://www.codeproject.com/KB/cpp/MD5.aspx?display=Print

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HappyCactusCommented:
MD4 and MD5 (like SHA) are not encryption function but hashing.
The base difference is that encryption is a reversible function, while an hashing function it is not (it's an injective function). This means that there can exists x1 and x2 with x1 <> x2, such that MD4(x1) = MD4(x2).
This implies that it is not simple to found x1 or x2 given MD4(x1) or MD4(x2).
But MD4 is a weak hashing algoritms, and here: http://www.infosec.sdu.edu.cn/uploadfile/papers/Collisions%20for%20Hash%20Functions%20MD4,%20MD5,%20HAVAL-128%20and%20RIPEMD.pdf you can find a very efficient algorithm that can find collisions also by hands...
But these are collisions, that means that you'll find x1 and x2, but you can't find the original value of the hash.
This is a very important distinction.

Hope that helps.

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HappyCactusCommented:
Also note that the previous article reports how to find two collision, so x2 when x1 is known.
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RuhelaAuthor Commented:
Solved
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