To earn Silver Keys, complete each level with a team score of 1000 or more Rupees, then beat Vaati for ending #1. To earn Gold Keys, complete each level with a team score of 3000 or more Rupees, then beat Vaati for ending #2. To earn Hero Keys, complete each level with a team score of 5000 or more Rupees, then beat Vaati for ending #3.