For my game I'm currently developing I have been considering implmenting some form of security for the data transmission between all the clients and the server, preferably not using any high security DES3 or RSA tricks . I came up with a couple of possible ideas, and was wondering if anybody has any knowledge that i could add to the list

First one is simple shoddy ASCII encryption using a key, ok, not the best in the world, but the principle is..
1. Server sends clients encrypted encryption key
2. Client decrypts encryption key using hard coded decryption key
3. Server & Client use the decrypted encryption key for data transfer
This is more obfuscation than encryption, but would keep most casual hackers at bay

The second method uses a key which changes every 4 frames(1 second) of the game, this would produce a changing encryption/decryption key and would prevent players being able to send packets through a packet sniffer without lots of added effort in working out the changing key and synching correctly with the server and client.

I had ideas about message CRC and frame counters encrypted inside the network message, but haven't tested this for speed yet