Craftlocks

CraftLocks is a new Minecraft mod which adds keys to lock your doors from other players. You can lock any type of doors.
With CraftLocks you can be calm about your home and protect it from grief. Safe your items or hide in secret underground doors.
Any key is connected within a door. You can't use your key to open other players' doors.
Keys and locks are very cheap protection which doesn't need expensive resources like diamonds or a lot of gold. But it isn't so cheap that you can craft keys at any time or have unlimited keys. Every item is balanced.
This is the best solution to protect yourself!