Protocol Encryption Methods

Question

Encryption

Prompt methods of enciphering of messages for communication of the client and the server through a socket.
I have all commands and responses implemented using json + security key.

Here's an example:
{"event":{"1":{"type":"balance","method":"update","data":-20619.42}},"timestamp":1319203322}#83423475abc6572

We need a lightweight method that won't heavily load either the server or the clients. Strong protection is also not required.