Grayscale Investments, the company behind the Grayscale Bitcoin Trust and Grayscale Ethereum Trust, has expressed concerns that the SEC's proposed new rules around safeguarding custody of clients' crypto funds could prevent it from using Coinbase as the sole holder of its $5.4 billion of crypto assets. The proposed rule would make it illegal for centralized exchanges like Coinbase to hold customer funds in commingled accounts and credit customers for their value, rather than providing an individual wallet for each customer. Grayscale currently stores its funds with Coinbase via the Coinbase Custody Trust Company, which holds Grayscale's assets in offline cold storage, via unique onchain addresses, and are never commingled with other clients' funds. Coinbase has also complained about the proposed rule, which would ban registered investment advisers from trading on non-qualified custodian crypto exchanges.