Google Code-in

This is our wiki. It is based on MediaWiki. We used to let users register on it by OpenID, but have disabled this mechanism, because of the hunderds of spam accounts being created by bots. Now users can't register and need to ask our staff to get an account. We would like to make a possibility of user's self-registration, but it needs to be secure and spam-resistant. Suggest us a working solution (in comment) and mark your task for review. Then you will have granted access to our server and you will have to apply the changes, later we will approve your task. Best luck!