Posted by Erwin Moller on 09/30/05 11:19

NurAzije wrote:

> In PHP there is MD5 function it converts strings to MD5 encription, I
> use it very often but I want something to reverse the proccess, I want
> the encripted strings back..
> Can you help me please,
> Thank you ..

Hi NurAzije,

Well, you are in trouble then. :-(
MD5 is not ment as an encryption to be decrypted, but only as a signature.

YOU CANNOT GET THE ORIGINAL STRING BACK BASED ON THE MD5 HASHES.
I am sorry to bring you this bad news.


Read here:

DESCRIPTION
A message digest is a compact digital signature for an arbitrarily long
stream of binary data. An ideal message digest algorithm would never
generate the same signature for two different sets of input, but achieving
such theoretical perfection would require a message digest as long as the
input file. Practical message digest algorithms compromise in favour of a
digital signature of modest size created with an algorithm designed to make
preparation of input text with a given signature computationally
infeasible. Message digest algorithms have much in common with techniques
used in encryption, but to a different end; verification that data have not
been altered since the signature was published.

[source: http://www.fourmilab.ch/md5/]

Conclusion: You will NOT get the original strings back.
If however you think you have the original string, you can feed it to a MD5
algorithm to see if it was the original.
But there is no way you can find the original string....


Regards,
Erwin Moller

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