if there is none for MD5 is there some other?
Is there a program that can build a file from a MD5 sum? This would make a lot of sense to use in back up because the check sum is only a kilo big. I can understand if it would me very slow but stil I would help me alot.
if there is none for MD5 is there some other?
MD5 is only a checksum used to verify the integrity of file(s). It would be black magic if you can turn a MD5 number back to what it is calculated from.
bzip2 is the best you can get now.
yea I figured that it wasn't possible(for now)
But couldn't hurt to ask.

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