The former head of the SEC's Internet Enforcement Administration, John Reed Stark, suggested that bitcoin could be an unregistered security. John Reed Stark made this statement in response to a tweet by analyst Evan Van Ness, who wrote that 855 of the last 1,000 blocks created in the Bitcoin blockchain were mined by only five organizations: Antpool, Foundry, F2Pool, ViaBTC and Binance. This means