  As a fundraising method, Initial Coin Offering (ICO) has raised billions of
dollars for thousands of startups in the past two years. Existing ICO
mechanisms place more emphasis on the short-term benefits of maximal
fundraising while ignoring the problem of unbalanced token allocation, which
negatively impacts subsequent fundraising and has bad effects on introducing
new investors and resources. We propose a new ICO mechanism which uses the
concept of Gini index for the very first time as a mechanism design constraint
to control allocation inequality. Our mechanism maintains an elegant and
straightforward structure. It allows the agents to modify their bids as a price
discovery process, while limiting the bids of whales. We analyze the agents'
equilibrium behaviors under our mechanism. Under natural technical assumptions,
we show that most agents have simple dominant strategies and the equilibrium
revenue approaches the optimal revenue asymptotically in the number of agents.
We verify our mechanism using real ICO dataset we collected, and confirm that
our mechanism performs well in terms of both allocation fairness and revenue.
