Kill Switch Engage

Kill Switch Engage: Sia Cryptocurrency to Block Bitmain and Other Big Miners

After nearly a year of acrimonious debate, the Sia blockchain is moving to give big mining companies the boot.

David Vorick, founder and CEO of Nebulous – the for-profit company behind the $233 million distributed storage protocol – told CoinDesk that Sia will soon move to enact a software change meant to block certain types of specialized mining hardware from the platform, allowing hardware manufactured by Nebulous subsidiary Obelisk to remain one of the only ways to collect the blockchain's lucrative cryptocurrency rewards.

"Sia's decided to fork to obsolete or brick the Innosilicon and Bitmain hardware," Vorick said, referring to Obelisk's rival manufacturers of application-specific integrated circuit (ASIC) mining equipment for Siacoin.

In a draft statement on the decision acquired by CoinDesk, Vorick wrote that the company wants to embrace an "ASIC monopoly," arguing the system-wide upgrade, or hard fork – "is better than resisting ASICs altogether." That said, he added: "We don't believe that a cryptocurrency needs to embrace a parasitic or abusive ASIC monopoly."

Continuing, Vorick emphasized that the code change is optional, and is configured in such a way as to "enable a group of dissenters to easily split off and be on a separate blockchain where the hard fork was never implemented." According to the blog post, such a split will not impact the functionality of the Sia network.

Still, Vorick portrayed the code change as a near-unanimous decision taken by the community, and this Reddit thread – the closest thing to an official vote that was held in the community – appears to show broad support for the decision. The sentiments expressed represent a change from January, when another proposal to similarly fork Siacoin failed.

During those months of back-and-forth, some community members appeared just as concerned about Nebulous' consolidation of power as they were about Bitmain or Innosilicon (the latter, Vorick made clear, is the "monopoly" he has in mind).

Meanwhile, some in the community saw a fork as amounting to a bailout of Obelisk by Nebulous – a way to turn back the clock on production delays, political rifts and threats of legal action. The Reddit post containing the proposal argues, however, that it "seeks to protect the community members who invested in Obelisk ASIC units," not the company itself.

Bricking Innosilicon
In his statement and an interview with CoinDesk, Vorick described the motivation and method for bricking Innosilicon's ASIC miners.

Vorick said that Innosilicon controls 37.5 percent of the network's total mining power through its own mining operation. The company also sells ASICs to other miners. Since they "have the only rig capable of competing," Vorick wrote, Innosilicon is able to charge an estimated 100 percent markup on this hardware.

Speaking to CoinDesk, he described the method behind the so-called Sia kill switch, or the software change to disable hardware which the fork will activate:

"Basically blake2b Sia's hash algorithm is a circuit, and we added just a tiny extension in a clever place that you wouldn't just naively think to add that extension. So basically we made our circuit just very slightly more complex in a very sort of random way, and this is something that we do not expect anyone else to have anticipated."

As a result, as soon as the network's nodes adopt the upgrade, chips designed to run the unaltered blake2b algorithm will be useless for mining Siacoin.

"We believe that this will break tens of millions of dollars of hardware," said Vorick.

Notably, other networks have considered or followed through with similar forks aimed at disabling ASICs. For example, Monero did so in April, and momentum is building toward a similar change in the second largest blockchain by market capitalization, ethereum.