in reply to Reverse MD5

You mean, given an MD5 hash, retrieve the original text?

The short answer is: you can't - that's the point of an MD5 hash.

The longer answer is that it's unknown whether it can be done in any reasonable amount of time (even with reasonable being tens of years). You could of course generate all possible text, and eventually stumble upon a text that gives the given MD5 hash, but even then it's not sure whether you got the right one.

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Re^2: Reverse MD5
by mscharrer (Hermit) on Dec 02, 2008 at 12:19 UTC
    Digest::MD5::Reverse uses online DBs which seem to store large amounts of texts and the corresponding MD5 sums. That is probably the only reasonable way to do this. However, simply appending a random text/date on every text makes this pretty unusable.
[reply]
      The summer 2008 edition of 2600 has an interesting extension of this: using Google (etc.) to search for the hash and find an original text (password). Apparently a lot of people or systems post this information intentionally or inadvertently. In some limited sense, you don't need the reverse function if Google is mapping the forward function.

      -QM
      --
      Quantum Mechanics: The dreams stuff is made of

[reply]
Re^2: Reverse MD5
by Anonymous Monk on Feb 04, 2009 at 07:34 UTC
    How did they get the reverse value for md5? http://md5.rednoize.com/
[reply]
      They didn't.
[reply]

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