Function to reverse md5()?

PHP
1

If I had encrypted (or hashed) a string using md5(), is there a function that I can use to decrypt to get back the original string?

2

Nope. MD5 is one way.

Try using the mcrypt library if you want two way encryption.

3

No sorry, impossible, which is why it is used to store password fields.

You can compare against it, ie. if(md5($password)) == $password_from_db) but I am pretty sure it cannot be deciphered.

Regards,
Jordan

Edit: Beaten :lol:

4

If that’s for user system “lost password” feature, you can generate a new password and send it to user.

5

Either that, or flag an option in the database that the next time the user logs on, they are presented with a screen to choose a new password.

Any system that can return my password to me in plain text after I have entered it, will be the last time I use that system.

Regards,
Jordan

6

Unless you get hold of the Chinese researcher who just broke SHA1, no.

7

Yep. saw it being slashdotted. But can we trust a chinese media is a different story altogether.

8

You can’t “break” md5. The algorithm throws information away, so there is no way you can reverse the process.

9

“To break” md5 (or another hash function) means “to invert” it, eg. given a hash value H, quickly find a string S so that H = md5(S). S doesn’t have to be orginal source string, but this usually doesn’t matter. For md5, such an algorithm has been indeed found.

10