String scrambling/unscrambling alogo help

I have a question how it would be best to do this, and if anyone knows of any examples.

I want to scramble strings inside some arrays in my game client because I don’t want players to see what secret items there are by decompiling. All data is stored and controlled server-side, however the client does have the lists of items stored in arrays.

My current idea would be to pass a key to the client to unscramble the game data on login. It could still be decoded by a programmer… But at least it would delay players finding out about certain new secret items.

I am not interested in loading any of this data out of mysql, even with memcached the increase in server load would be unacceptable.