A change to the mechanics of BlackRock's proposed spot bitcoin(BTC)ETF opens the door for Wall Street banks, which face restrictions holding cryptocurrencies, to play a key role.

BlackRockrecently made itso authorized participants – a vital part of the ETF ecosystem – will be able to create new fund shares with cash, rather than only with cryptocurrency.

As highly regulated U.S. banks are unable to hold bitcoin themselves, this set-up would enable the likes of JPMorgan or Goldman Sachs – firms with some of the largest balance sheets in the world – to act as APs to BlackRock's ETF. (Whether they want to is another matter.)

The cash APs use in this process can then be exchanged into bitcoin by an intermediary and warehoused by the ETF's custody provider,as per a memo filingrelating to a Nov. 28 meeting involving the U.S. Securities and Exchange Commission, BlackRock and Nasdaq.

Optimism has grown that spot bitcoin ETFs will soon be approved by the SEC, which would be a game-changer for the digital assets industry if it lures in a flood of money from retail investors. A commonly held view up until now was that APs would be large market-making firms with experience in crypto, such asJane Street, Jump Trading and Virtu– not banks. But the change means banks could get a cut of the action, and broaden the ranks of liquidity providers.

"If the SEC accepts this revised, dual model of create and redeem with cash and physical, that means the liquidity that supports the ETF shares when they trade would be increased, because obviously, you have more potential APs as part of the process," CF Benchmarks CEO Sui Chung said in an interview. (CF Benchmarks is the Kraken-owned benchmarks administrator for several existing spot bitcoin ETF applications, including BlackRock's.) "And although trading firms like Jane Street, etc. are large and are experts, they fundamentally don't have the trillion-dollar plus balance sheets that large American banks have."