UPDATE (24th October 10:02 BST): Chief executive Austin Hill originally told CoinDesk that Blockstream's SEC filing was an "incomplete and inaccurate notice". He has since clarified that the SEC filing is complete and accurate, but does not "portray the whole picture" at this point in the company's fundraising process. This article has been updated accordingly.

Blockstream has raised at least $15.18m toward a major funding round expected to close in the coming weeks, according to a recent Securities and Exchange Commission (SEC) filing.

The filing also shows that Reid Hoffman, a partner at venture firm Greylock Partners and co-founder of LinkedIn, will take a seat on the startup's board of directors.

Speaking to CoinDesk, Blockstream chief executive Austin Hill stressed that the funding round is still open and that it will close this week. He declined to provide more details until the fundraising round is complete.

The SEC filing is dated 1st October and signed by Blockstream's chief financial officer Hammie Hill, but the CEO implied that its contents may be deficient, saying:

Despite Hoffman's presence on Blockstream's board, he said Greylock is not participating in this fundraising round.

Hoffman currently sits on the boards of Airbnb, Swipely, Kiva and Mozilla Corporation. He has been a director at mobile gaming giant Zynga and payments pioneer PayPal.

Form D is a disclosure form used by companies that raise funds without receiving prior approval from the SEC. Businesses that do so are required to file a Form D within 15 days of their first security issuance.

After months of relative silence, the Canada-based company has entered into the industry conversation following the Wednesday release of a white paper that proposed a new way of transferring assets across multiple block chains. The much-hyped work was supported in part by Blockstream, a company founded by several of the paper's authors, though it builds on past proposals.

The executive team will also include Hill, former HashCash developer Adam Back, Osler and Hoskin & Harcourt LLP managing partner Shahir Guindi, and Zero-Knowledge Systems co-founder Hammie Hill, the document states.

Blocksteam has long been an anticipated project in the bitcoin community due to Austin Hill's background. The founder of anonymous networking and privacy technology Zero-Knowledge Systems, he raised more than $80m for the project in the late 1990s. Current Blockstream executives Hammie Hill and Guindi were also involved with the company.

Blockstream further boasts a team of veteran developers on its staff, including Bitcoin Core developers Gregory Maxwell, Jonathan Wilkins, Matt Corallo and Pieter Wuille, Freicoin project leader Jorge Timon, and former NASA engineer Mark Friedenbach.

Publicly, the company has been less visible, with Austin Hill notably pulling out of a speaking slot at The North American Bitcoin Conference in July, at the time, giving only a humorous response on Twitter to explain his absence.

Aside from the debate surrounding the sidechains white paper, Blockstream itself has also sparked conversation on Reddit regarding how block chain technologies should be funded and developed.

Some commentators, for example, have taken issue with the company's market strategy, which seemingly seeks to use a for-profit model to fund sidechain development. Bitcoin Core development, by contrast, is managed by both the Bitcoin Foundation and developers employed at major bitcoin companies like Blockchain and BitPay.

Detractors allege that Blockstream is a potential threat to bitcoin's decentralized nature, with others praising it as a necessary step given the concerns that bitcoin's core technology has suffered from a lack of well-funded developers.

At press time, representatives from Blockstream have not responded to further requests for comment.

Stan Higgins and Joon Ian Wong contributed reporting.

Images via Blockstream; Shutterstock