Using a custom string to generate a key. (Or part of a key)

[Dylan Margoczi]

Hi there.

I want to use JCE for my encryption in my java program.

I was wondering if it's possible and how to use a custom string such as the hard drive serial number in my key. So that I that I can have a different key for each client that uses my program and so have my updates using a different key for each user. And so it may only be used on that machine and no other.

I haven't worked out how to get the hard drive serial number yet but I know that is a different subject all together using JNI.

I just need to know how to implement that string into the encryption. would I be able to make it part of the key, or am i going about it all wrong???

Thanks in advance.

[greg stark]

The usual way is to use the password-based encryption (PBE) ciphers. You would treat the serial number as a "password" for the purposes of understanding the parameters to PBE algorithms. Have a look at http://java.sun.com/javase/6/docs/technotes/guides/security/crypto/CryptoSpec.html#PBEEx for an example. Also look at http://java.sun.com/javase/6/docs/technotes/guides/security/SunProviders.html to see what PBE algorithms are supported by the Sun parameters. Other providers, e.g the bouncycastle provider, may support more or different algorithms.

[Dylan Margoczi]

thanks.
will have a look at it...

[Dylan Margoczi]

Thanks Greg. was just what I needed.

Only problem I'm getting now is with the Decryption. It Decrypts most the information fine but I see there are small sections here and there that are not decrypted properly. Is there a common reason for this that I can look for?
I'm very new to this stuff so forgive me if I seem to not know exactly what I'm doing.
Thanks again.

[greg stark]

Sorry, but without seeing your code I can only make guesses. Perhaps you are trying to use the Java String class as a container for the ciphertext? This is a common mistake.

[Dylan Margoczi]

Think that is what the problem was.
Got it sorted out now though.
Thanks for the help Greg.