The only way to prevent match-fixing would be to have a GM oversee every game played between players in a tournament. This is not going to happen. Triple Triad is a mini-game with a voluntary weekly "tournament" that's exists solely to reward prizes. You can't use the duty finder since so few people actually participate in the tournaments to begin w/. The most likely players to exploit the system are those who are most interested in playing triple triad anyhow.