Network - Encrypt messages with secret

[magroader]

There should be an encryption setup for server messages. This should apply to everything but the initial version checking messages, as that message needs to be sent so clients know whether they're allowed to connect in the first place.

The secret should be salted in some way. I don't know the precise proper way to do this.

There should not be a way to get around the encryption by the client - for example, you should not be able to just send a message that says whether it is encrypted or not. The server (and client, for that matter) should EXPECT that all messages are encrypted (except that version checking one).