First Flight #2: Puppy Raffle

Summary

Raffle is vulnerable to Sybil attack

Vulnerability Details

A player can have multiple accounts, so assuming that all players are unique and checking duplicates doesn't help much. A player with a lot of money can enroll all their accounts with the entrance fee and since the winner is selected using modulo operation, the probability of winning can be simply increased by enrolling more accounts.

Impact

The player with the most money can increase their chances of winning.

Tools Used

Manual

Recommendations

• Don't assume players to be unique

• Add a refund fee that would decrease the motivation to enroll multiple accounts