AsicBoost: Scaling Debate Turns into Investigation

The Bitcoin scaling debate is one that has been going on for years and has been constantly evolving as new Bitcoin Improvement Proposals emerge. Most recently, Bitcoin Unlimited and SegWit have been competing for miner approval in order to activate their respective protocol changes.

With these two main options on the table, Bitcoin has been split in two factions. Those in support of Bitcoin Unlimited and its emergent consensus protocol and those in favour of SegWti and its soft-fork to increase block capacity and fix other issues like transaction malleability.

Several companies and individuals that hold influence in the Bitcoin community have aligned with either one or the other option (with exceptions). Although, Bitcoin Unlimited currently has an advantage in hashing power, a look at CoinDance’s political analysis reveals that most companies are in favour of SegWit and oppose BU. Among the supporters of Bitcoin Unlimited is Bitmain, one of the biggest mining pool and hardware providers in the industry.

While both sides of the debate are riddled with controversy, the latest theory regarding the actions of Bitmain towards BU and SegWit have caused outrage throughout the community.

CTO at Blockstream, Greg Maxwell made a proposal on the Bitcoin mailing list, claiming that someone successfully reverse engineered a particular mining chip and accused a mining hardware company of using AsicBost covertly. AsicBoost is an exploit that can provide the miner with a ~20% advantage by reducing the frequency of computing one part of the SHA-256 calculation. The post suggested a change

“Reverse engineering of a mining ASIC from a major manufacturer has revealed that it contains an undocumented, undisclosed ability to make use of this attack.”

However, this isn’t the most serious allegation, as miners are expected to be competitive. Although the company claims to have never used it on the Bitcoin network, they hold the Chinese patent for AsicBoost and they can legally use it.

The theory now is that Bitmain has aligned with Bitcoin Unlimited in order to block the activation of SegWit since the upgrade would be incompatible with the AsicBoost exploit. Maxwell wrote:

“An incompatibility would go a long way to explain some of the more inexplicable behavior from some parties in the mining ecosystem so I began looking for supporting evidence.”

Recently, Bitmain responded to the allegations via blog posts, claiming to have never used AsicBoost and that the “conspiracy theories do not add up”. Bitmain reminded the community that it has been in favour of the Hong Kong agreement which supported bigger blocks along with the activation of SegWit but that the chances of this happening looked slim and as so Bitmain started supporting BU. However, some have noted that the introduction of SegWit along with bigger blocks would allow Bitmain to keep their alleged secret advantage:

However, Bitmain also noted that it has always been in favor of bigger blocks, something that would reduce the advantage provided by the AsicBoost technology.

Since Bitmain’s response, others have weighed in on the recent rumours. Sam Cole, founder of KnCMiner, a Sweden-based hardware and mining company that is no longer active. Back in 2016, Sam Cole mentioned a secret advantage that the “Chinese” were possibly using.

However, in his recent blog post regarding the recent allegations, Sam Cole dismisses the theories and explains why they don’t make sense. He wrote:

“I also hear people claim to have reverse-engineered the chip not the device to look for the hidden laptop but the chip. This claim is not one that anyone should take as likely to be true. It’s nearly impossible to reverse engineer any 16nm ASIC chip without a huge lab. In one of those chips there are billions of transistors 16nm in size. The microscope needed to even see they exist isn’t exactly bought at Walmart. Without having access to the code of the chip it would be futile.”

Most recently, a member of the Bitcoin Unlimited team, Rhett Creighton, has decided to resign and made a blog post in which he claims that the only purpose of Bitcoin Unlimited is in fact to stop the implementation of any other upgrade. Creighton wrote in his blog post:

“I believe Bitcoin Unlimited was likely set up not to succeed, but simply to block any other progress from happening with Bitcoin.”

It is unclear if any of the allegations towards Bitmain are true. For now, we will have to wait and see.