Cheat protection

[Trilarion]

This is rather low priority but just to summarize what we have:

• Stop players from trying to propose moves in the name of other players.
• Password protect access to a specific player in a game (if desired)

Overall, there should not be much cheat protection. It's too much work and anyway very difficult with an open source game. The overall idea should be that you should not play the game with someone who steals your milk and knows how to use a text editor.