Castle Securities has entered the cryptocurrency market as a market maker. Citadel Group is a multi strategy hedge fund giant, and its subsidiary Citedal Securities is designated as a market maker by the New York Stock Exchange. The daily transaction volume accounts for over 30% of the daily trading volume of the New York Stock Exchange. The most well-known event of Citadel Securities back then was undoubtedly the Game Stop short squeeze, where retail investors joined forces to long and institutional investors short. Game Stop's stock price rose from 17 to 483, and Melvin Capital went bankrupt directly. But during the most intense battle between long and short positions, the largest retail trading platform, Rabinhood, imposed restrictions on buying Game Stop, or at worst, unplugged the network cable, only allowing sales and not buying. Later it was discovered that Citadel Securities had taken on most of Rabinhood's trading orders. But Citadel Group Fund is also a partner of Melvin Capital, giving Melvin 2 billion yuan in life-saving money. This is equivalent to being both a judge and an athlete. In the end, the SEC and the US Securities and Exchange Commission conducted a half day investigation and did not find any violations by Castle Securities. Moreover, Griffin admitted during the hearing that Castle Securities traded 7.4 billion shares in a single day during the days when the two sides were in a frenzy, making a huge profit from market making. The entry of such an institution can be said to be becoming increasingly standardized, but the difficulty will increase by another order of magnitude.