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Is there a chance that we have a similar md5 hashes with a different value when it is converted? If yes How possible?And have you tried guys to decrypt before an MD5?

spicykimchi
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    Why would you need to decode an md5? – mellamokb Apr 29 '11 at 03:11
  • To compare the value with the existing one. – spicykimchi Apr 29 '11 at 03:15
  • to compare the value with the original, compare it after you hash the original. – Sufendy Apr 29 '11 at 03:21
  • @phelios The md5 already exist before they turn over it to me. – spicykimchi Apr 29 '11 at 03:23
  • To compare a raw value to a hash, hash the raw value and compare that hash to the one you already have. Refer to the [PHP manual](http://ca2.php.net/manual/en/function.md5.php) for an example of this. – zneak Apr 29 '11 at 03:24
  • possible duplicate of [How to output MD5 hashed password in plain text?](http://stackoverflow.com/questions/3126255/how-to-output-md5-hashed-password-in-plain-text) – Frank Farmer Apr 29 '11 at 03:25
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    probably you should explain your situation on your question. – Sufendy Apr 29 '11 at 03:27
  • @Phelios Have you tried before to convert an md5 hashes?Or make ways to convert an md5 hashes in to a readable value?There's no need to explain further I know what you really tried to say.To process first the un-md5 values.But I just need to know the possibility of converting. – spicykimchi Apr 29 '11 at 03:47

4 Answers4

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Forget md5 for a second. Instead imagine that your hashing function was really dumb and it just added up the value of each byte in the source data.

Now let's say that your source data is just two bytes: 0x01 and 0x02, in that order. For these inputs the hashed value is 3.

Problem is, you can get the same answer of 3 from lots of other byte sequences:

0x01 0x01 0x01
0x00 0x03
0x03
0x02 0x01

...you get the idea, and hopefully you also see that it's impossible to know with any certainty which of those possibilities could have been the original input when all you have is the hashed value, 3.

With md5, the algorithm is far more complex and way better at avoiding collisions, but the principle is the same. It's called a "one-way hash" for this very reason.

Brian Kelly
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A hash is just that: a one-way, condensed value of your input. Many inputs can produce the same output.

Yes, different source data can produce the same hash (a collision).

No, you cannot retrieve the original data from a hash.

Mitch Wheat
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If the MD5 is a salted MD5, there is a good chance it'll never be the same as a normal MD5 hash..

Jasdeep Singh
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    To put it another way: You can look up weak passwords hashed without a salt in a rainbow table. But assuming either a strong password, or passwords hashed with an unknown salt, using a rainbow table is impractical. – Frank Farmer Apr 29 '11 at 03:29
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Yes, it's possible to produce 1 same hash with different input. This is called collision. Such collision is possible because the input size is greater than the output size. Read about birthday attack to know why is this a bad things in hashing.

here is a article about MD5 has been broken because of the collision.

Sufendy
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