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    Usually, when sharing the key is a concern, the solution is using an asymmetric encryption algorithm. Commented Apr 8, 2013 at 7:51
  • @kinunt You are right, I could definitely use a RSA like approach but what I haven't told you is that the message in this case is not being sent over a traditionally channel that allows back and forth communication, it is strictly one way, sender to receiver. It is not necessarily the case than I can relay any information back to the original sender as the message might pass through several intermediates that I do not have any control over and I don't think it's possible to use asymmetric encryption without some back and forth. Commented Apr 8, 2013 at 7:58
  • @kinunt As the message is passed forward, it might travel through nodes that knows nothing about the encryption key used and they are supposed to simply forward the message further up the food chain. I guess it's less than ideal but that's why I'm bound to some sort of key identification rather than key exchange. Also, the symmetric key might have a rather long life-span. Commented Apr 8, 2013 at 8:02
  • @JohnLeidegren is it possible to have the sender know the recipients public key ahead of time? Then the sender can simply make up a key and encrypt it using the receiver's public key. This would allow you to use RSA or another established asymmetric encryption scheme rather than reinventing one. Commented Apr 8, 2013 at 10:04
  • @TomMarthenal that could work. Didn't think of it that way, was too caught up with idea of RSA being a handshake thing. Which clearly it does not have to be. Commented Apr 8, 2013 at 13:30