Alrite, so I'm ready to use the Capicom encryption component from microsoft to secure some messages between a client app and a server app. I plan on having them send certain messages back and forth that are often times identical, but their quantity is important. Anyways, here is the security hole i can't figure out a way to stop.

Client connects to server.

Client sends encrypted message to server.

Hacker sniffs this encrypted message, and although it still looks encryped to him, he then masquerades as the client and sends the same message to the server.

The server has no way of knowing that the message didn't come from the client, and things get all messed up!

Any ideas on how to stop this?

Thanks,
WeezelDS