The U.S. Securities and Exchange Commission (SEC) has issued guidance on how broker-dealers can legally custody crypto asset securities under existing customer protection rules. Released by the Division of Trading and Markets on December 17, the guidance clarifies Rule 15c3-3, emphasizing the importance of physical possession or control of these assets. The SEC's statement details conditions under which a broker-dealer can consider itself in possession of a crypto asset security, such as having direct blockchain access and transfer capabilities. It also highlights the need for documented assessments of blockchain characteristics, operational resilience, and controls to safeguard private keys and manage potential on-chain disruptions like 51% attacks or hard forks.