The upstart stock exchange Second Market has made a name for itself allowing investors to buy shares of hot private companies such as Twitter. Now that those companies are going public, Second Market is turning its attention to the next new thing — bitcoin.

On Thursday, Second Market is expected to begin raising money for an investment fund — the first of its kind in the United States — that will hold only bitcoins, giving wealthy investors exposure to the trendy but controversial virtual currency.

The fund, the Bitcoin Investment Trust, aims to provide a reliable and easy way to bet on the future price of bitcoin, a currency generally traded on unregulated, online exchanges based overseas.

"If you speak with people who have tried to purchase bitcoin in the past — you'll hear, 'it's a difficult process,' 'it's a confusing process,' 'it's a scary process,' " said Barry Silbert, the chief executive of Second Market, based in New York. "We want to make it an accessible asset class."

Second Market's venture into bitcoin represents the latest effort to bring the virtual currency into the mainstream. But it is also likely to fuel the debate around the legitimacy and legality of a form of money that exists outside the conventional banking system, and has already attracted scrutiny for being used in illicit transactions.

Created in 2009 by a still unknown individual, or group, known as Satoshi Nakamoto, bitcoins exist only in digital form and can be bought with traditional money through the Internet. New bitcoins are "mined" by programmers solving complex math problems. The original programmers determined that only a finite number of bitcoins would be created.

While bitcoin is accepted as a form of payment by a growing, but still small number of businesses, it is mostly the domain of speculators.

NEW YORK TIMES