Tyler and Cameron Winklevoss, impossibly strong-jawed and broad-shouldered rowers, tech entrepreneurs, and famous litigators of Mark Zuckerberg, are now two of the biggest and most famous players in Bitcoin, the cryptographic, digital currency whose wild price gyrations and security issues captivated the business press for a few weeks in March and April of this year. In April, the twins revealed to The New York Times that they owned some $11 million worth of Bitcoin.

Today, the twins filed an S-1 with the Securities and Exchange Commission, which is a first step to register shares with the SEC, so they can be offered to the public. The document describes a company, the Winklevoss Bitcoin Trust, which would issue and sell shares. The trust would own Bitcoins and shares of the trust would reflect the price of Bitcoin. The form describes the trust as "a cost-effective and convenient means to access exposure to Bitcoins." The trust plans to sell about $20 million in shares.

The document also says that "the investment objective of the Trust is for the Shares to reflect the performance of the Blended Bitcoin Price of Bitcoins less the expenses of the Trust's operations." The document also claims that the trust is the "first exchange-traded product that seeks to track the price" of Bitcoin. The form describes the "Blended Bitcoin Price" as "based on the daily average of high and low trading prices" on different Bitcoin exchanges. The form lists those exchanges for the price on June 27 as Mt. Gox K.K., Bitstamp, and BTC-e.

One major concern bedeviling the further use and interest in Bitcoin outside of enthusiasts has been security of Bitcoin exchanges and the Bitcoins themselves. The S-1 says that the fund's sponsor "has developed a proprietary security protocol for storing and safekeeping the Trust's Bitcoins."

Risk factors listed in the S-1 include the "relatively small use of Bitcoins in the retail and commercial marketplace in comparison to the large use by speculators, thus contributing to price volatility" as well as the possible loss or the "private key" that's necessary to access any given Bitcoin.

Unlike a typical S-1, which companies file before initial public offerings, this one does not list a bank that would manage the listing and selling of shares. The S-1 does not list an exchange that shares would be traded on or a ticker symbol.

The only listed expense of the trust is a "sponsor's fee" which is payment made in Bitcoin from the fund to the fund's sponsor.

The trust is sponsored by a Delaware-based company that was formed on May 9, Math-Based Asset Services LLC which is owned by Winklevoss Capital Management, which has the same New York City address as the trust. Cameron Winklevoss is listed as the chief executive officer and Tyler Winklevoss as the chief financial officer of Math-Based Asset Services. A call to Winklevoss Capital Management was not returned.

Cameron Winklevoss told the Times in April, "People say it's a Ponzi scheme, it's a bubble. People really don't want to take it seriously. At some point that narrative will shift to 'virtual currencies are here to stay.' We're in the early days."