How to create "static" key / simple text exchange

Question

Hi
I am completely new to JCE and have a relatively simple licencing scenario.
A program licenced to a client should send information when it's called to a file on a remote-server via ftp. This text-information must be encrypted to that the client is unable to read it.
On the remote-machine that I host myself the encoded information must be decoded by another Java-program.
My first question is, how do I generate a "static" key, that I use in both programs?
Is it really necessary to use Diffie-Hellman Key Exchange to solve this?
Could you advise me a code example that solves this problem?
Thanks.
Marc

Answer 1

Thanks again for your input.
You suggest to use RSA. In the solution that I have figured out I use DES and generate a SecretKey. Would using RSA instead of DES bring me some significiant benefit?
Regards
Marc
From the customer's point of view, what you say
you're sending isn't important - because it's
encrypted, you might be sending ANYthing!
Would you be able to identify the hard-coded code(a
byte-array) from the Java byte-code?Yes. If pressed, and if there was enough at stake, I
could probably figure out how to beat the licensing
even if you wrote the whole app in C++ or native
assembler (although it would be more difficult).
People have been doing this kind of thing forever -
bytes aren't nearly as opaque as folk would like to
believe.
If you happen to have a better solution for licence
validation pls let me know.Licensing is hard. No matter what you do, there
will be a way to get around it. The best you
can do is make breaking your scheme hard enough that
the average user would rather pay for your license
than go through the hassle. How much work is enough
on your part depends on too many things I don't know
(e.g., how much are you charging, what class of
customer are you targetting, what's the risk to the
customer if they're caught violating your license,
etc.).
If your customer is willing to put up code that "calls
home" every time it's run, which sends an encrypted
packet each time it does so, and which will (I
assume?) refuse to work if it doesn't get a proper
answer from home - then go ahead and use RSA to
encrypt your data.
But please don't fool yourself into thinking that you
can absolutely guarantee that no-one will be able to
break your license system. Lots of smart people with
lots of money behind them have been trying for almost
as long as software has been sold - and to date,
they've failed. MS spends a huge amount on building
better license schemes every year, and so far all
they're really managed to do is irritate their
legitimate customers...
Good luck,
Grant