How can i decrypt data with MD5 algorith in C?
Start by figuring out that MD5 isn't a decryption algorithm but a hashing algorithm.
That should tell you how likely you are of decrypting anything with MD5 algorithm - C, assembler or any programming language you can think of.
the md5 hash is to make the key for het decryption. so?
So if you use MD5 on something to create a crypto key there are two rules.
MD5 is still not an encryption algorithm so it isn't used to decrypt either.
And the value of that key isn't worth more than the quality of the input data. If your input data for the MD5 is only worth 30 bits of secrecy, then it is easy to figure out what secret values that was used to create the MD5, so it is easy to recreate the same MD5.
Besides that, MD5 isn't cryptographically strong which means that it is possible to find alternative input data that gives same hash.