Decrypting MD5 encryption

H

Hughng

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Jun 24, 2003
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How do I decrypt an encrypted MD5 string. My program allow password to be encrypted using MD5 encrypting. Currently the only way I can checkk for valid password is encrypt the password and compare it with the original password. They match then I allow access otherwise don't. My question is how do I decrypt the original password so I can compare with the input from user instead of the current method which encrypt user input and verify with encrypted original password.

Thank you.
 
MD5 isn't an encryption algorithm it's a hash - designed to be one way. Not being able to decrypt them is more secure anyway.
Is there any reason why comparing hashes is a problem?
 
Not a big problem but I want to keep track with some information from user system.

Ex: The hash is generate from MAC address and HD serial number + user name + private key. I just want them to send me the Hash value then and I retrieve all other information from the hash key instead require them to send out those information. Basically, I just want to build a database of who is using my software.


Thank you.
 
Why do you want to keep track of that info?
Isn't having it in hashed form enough for you to maybe implement a security system for your app, or whatever you want to do?
 
This software is using internal to about 10 - 20 users. I want to build a database so they can query what version software other machines have, their license number and who register it. This information is required to setup a tracking system that recording the exact location of each machine. To make the long story short, I need this information to be able to service any machine using my software and be able to know I should to go (we have 2 buildings and I don't want to go to the wrong one). And I don't want them to have to do anything beside send the hash key at registration time.

Currently they have to send me the MAC Address + User Name + Hash key which is already stored the MAC Address + User name + HD serial number.
 
The only thing MD5 is good for is storing things like passwords or other information, and then you can check the MD5 hash of the input against the stored hash. For example:
Visual Basic: 
If CalculateMD5(password) = storedMd5 Then
  CorrectPassword()
End If
If you want to store it so it can be retreived, use some other kind of encoding or encryption.
 
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