----- Original Message -----
From: "zerof" <[EMAIL PROTECTED]>
To: <php-general@lists.php.net>
Sent: Tuesday, October 24, 2006 6:00 PM
Subject: [PHP] Re: Is there a function can decrypt md5 ??
Brad Chow escreveu:
Dear all:
Is there a function can decrypt md5 ??
I don't have any bad ideas.
I just want to know whether md5 can be decrypted or not.
--
Brad
------------------
The md5 hash is not a codification, but, yes, a validation key.
In this way, it cannot be decoded!
It only can be used to validate data, like a signature.
-----
zerof
I don't think this explains why it cannot be decodified, one thing does not
result from the other.
An analogy of why it cannot be decodified is thinking of the MD5 as the
remainder of a division. Even if you know the divisor and the remainder,
there are many numbers that could have produced that result. The remainder
or modulo operation loses information thus the original cannot be
reconstructed. It is a one way operation, while the same number will always
produce the same MD5, many numbers can be the origin of that result and
which one was it cannot be guessed. While dividing by 2 will only give you
reminders of 0 and 1 for every number, the result of Md5 produces a very
good variety of results with a good spread of values over the whole range of
possible results.
Satyam
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