The Hidden History of Bitcoin Unlimited

A deep dive into the history of Bitcoin Unlimited, a bitcoin implementation seeking to become the dominant software on the network.

AccessTimeIconApr 8, 2017 at 8:30 a.m. UTC
Updated Sep 11, 2021 at 1:13 p.m. UTC
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Paul Elliot-Ennis is a lecturer and assistant professor in management information systems in the College of Business, University College Dublin, while Rachel-Rose O'Leary is an artist and writer researching cryptographic systems. 

In this guest feature, Elliot-Ennis and O'Leary retrace the history of Bitcoin Unlimited, a bitcoin implementation seeking to become the dominant software on the network through a solution to the network's longstanding scaling debate.

In the midst of the scaling debate, it can be difficult to uncover the genealogical roots of the various competing projects.

The internet operates at a clip that renders analysis of how an open-source project emerged closer to detective work than it should be. Add into the mix rumors, innuendo and disinformation and one really has their work cut out for them.

In certain cases, personalities might transcend the murk and become quasi-official figures, as evident in the proselytizing of Andreas Antonopoulos, the 'let the code speak for itself' quietism of Pieter Wuille, or the informed whimsy of Samson Mow.

However, it is not always the case that important figures within the cryptocurrency ecosystem are visible at all, even when their actions have significant impact on the network. This is especially true with the case of Bitcoin Unlimited (BU) where, in contrast to the well-known developers associated with Bitcoin Classic (Gavin Andresen) and Bitcoin XT (Mike Hearn), the key developers of BU are not familiar names.

A little bit of history, then, would not be remiss in such an atmosphere  – if for nothing more than to make clear that, in the end, the two sides of the debate are populated by pretty normal folk who are just happy to disagree on a pretty arcane set of ideas, albeit ideas with expensive repercussions.

Early roots

Like most open-source projects, Bitcoin Unlimited is broadly a virtual community consisting of a motley crew of developers, writers, generalists and onlookers.

They are invariably people already involved with bitcoin for many years, and BU arose primarily from a single thread on Bitcoin Talk known as "Gold Collapsing Bitcoin Up". Like numerous such threads, debates were often heated, quite personalized, and partisan.

There are certain key figures at the time who seemed to have had a real impact on giving this new community a degree of confidence to expand beyond Core.

was clearly a significant voice and looks to have provided much of the intellectual weight behind BU's theoretical commitments, such as how transaction fees would occur within a network without a block size limit.

Rizun's ideas are effectively a response to the possibility of removing the current limit of 1MB as expressed in BIP 101 (an improvement proposal authored by Gavin Andresen) that proposed raising the block size limit to 8MB and implementing a biannual doubling thereafter in order to deal with the problem of full blocks and expensive transaction fees.

BIP 101 was never adopted, and has its own history within earlier scaling debates. However, it did inspire participants in the "Gold Collapsing Bitcoin Up" thread to seek out new solutions.

Gathering steam

The BU operation played out on that thread through the summer of 2015, gathering pace as the bitcoin blockchain began to feature ever higher fees.

According to Rizun, the four-week transactional average recorded on June 2015 had grown 376 times greater than was seen in September 2010. Bitcoin Magazine reported tens of thousands of unconfirmed transactions as the block size strained to accommodate network usage.

A little later, a post by Rizun in July 2015 noticed the average block size had bloated to 70% capacity and was continuing to surge. Discussion on Bitcoin Talk escalated, but the thread was soon locked in what the BU community read as a form of censorship.

The perceived villain of the piece here was Bitcoin Talk administrator Theymos and the same accusation from BU members would carry over to r/bitcoin, another online platform also administrated by Theymos.

Unlimited supporters turned to r/btc that, of course, Core supporters have tended to consider heavily censored, resulting in a kind of intellectual split that, whatever the technical details, is riven with what can appear to the outsider as quasi-conspiratorial paranoia.

The takeaway is that, once untethered from the perceived pro-Core climate of Theymos-dominated media, Bitcoin Unlimited set out on its own path, allowing for a period of off-grid development that would quietly emerge just as Core supporters assumed Segregated Witness (SegWit) would be implemented.

Grudge match

This essentially meant that when a form of competition did emerge, Bitcoin Core was blindsided and broadly unprepared.

This does not mean they were technically not ready, but rather they had overlooked two subtle developments: miners were not entirely convinced by SegWit, and not everybody completely accepted that it was the obvious solution.

This set up the scene for an ideological confrontation.

On the BU forums, the idea of a new bitcoin software did not occur immediately. Such a task requires a dedicated developer or development team, but it is not until Andrew Stone (theZerg) began to posit the idea an alternative client that there was real movement.

Here it is actually BIP 100 (authored by Jeff Garzik and others) that is most influential, since it explicitly puts the decision about removing the block size limit into the hands of the miners through a voting process.

Those who have been following the debate will know that a large amount of the current discussion centers on the role of miners, most often a core of Chinese pools, and to what extent that should be influencing the future direction of bitcoin.

Figures involved with these pools, such as Jihan Wu, have taken on almost a shadowy status, maligned agents looking to stall the adoption of SegWit in order to maintain their stranglehold on transaction fees.

No doubt there is some truth to the claims of self-interest; nobody is surely naive enough to think otherwise. However, the salient aspect for Bitcoin Unlimited is that having the miners on-side meant having a voice.

The kick-off

If bitcoin can be read, and no doubt many will have other interpretations, as a set of influential blocs, not always in competition, then the two most influential voices are surely those of the Core development team (technical credentials) and the large Chinese mining pools (hash rate credentials).

The current scaling debate only really kicks off when it becomes clear that, not only are many of the major pools not supporting SegWit, but they are actually signaling for Bitcoin Unlimited. This is thought by many as risking a hard fork of the network into rival blockchains, given how serious the divisions between Core and Unlimited are.

The undercurrent to all this are the socio-economic arguments underlying Bitcoin Unlimited. In Peter Rizun’s original BU white paper, we first encounter a now semi-familiar concept in emergent consensus (EC). EC maintains that, given the economic incentive of remaining on the same chain, miners will reconfigure their block size to match the majority of the network.

Notably, the white paper includes a section that is explicitly about values, not just technical themes, and they can be summarized as focused on speedy transactions (bitcoin as cash, not gold), on ensuring low fees and being censorship-resistant.

It is perhaps this approach that first caught the attention of noted bitcoin investor Roger Ver, who told us:

"I actually don’t recall where I first came across BU, but I suspect it was Reddit."

Ver almost certainly must have come across it browsing those subreddits sympathetic to Classic and XT, but one can easily see why he found BU appealing.

An outspoken investor, he has been consistently vocal about his vision of bitcoin as principally a payment system, and one that is, as he told us, "useful as money".

This economically minded vision, in the sense of insisting on bitcoin's core function as facilitating quick-and-easy transactions, is also evident with Bitcoin Unlimited’s lead developer, Andrew Stone.

He said:

"BU was conceived through discussions in the 'Gold Collapsing Bitcoin Up' thread on this forum. Someone (I forget who) observed that the block size should be a network layer, not a consensus layer constraint and I conceived of the emergent consensus mechanics to realize that thought. I then wrote the Articles of Federation with lots of help, drawing a lot of the first sections from a philosophy statement written by Peter Rizun, and other forum writings. I then released the first software version (with EC, although we didn't call it that then) around Christmas 2015, held elections and transitioned the project from a benevolent dictatorship :) to the framework described in the Articles in early 2016."

On motivations

In the current climate, it is almost impossible to simply relay the motivations behind such projects by retroactively viewing them through current debates.

However, even a cursory glance at the early inception of Bitcoin Unlimited mostly appears to be a sincere attempt to halt what that community views as a deviation from bitcoin's original vision, quite often expressed as 'Satoshi's vision'.

For BU, this can be broadly summarized as the primacy of wide-scale adoption, facilitated by transaction speed and the necessity for consensus rule across the network. If Emergent Consensus functions as anticipated, we will witness a synchronized adaptation of the network towards increased block size, in a movement that has been compared to a flock of birds working in harmony.

While criticism from Core suggests that this would further centralize the network, Andrew Stone anticipates that, if large mining pools choose to dominate the network with high difficulty blocks, smaller pools will simply switch to an alternate chain, effectively facilitating two economic niches.

The ideological split between what it means to be decentralized currency at the level of practice pivots around differing conceptions of control.

For BU, the block size limit is locus of an ideological game, where the system can only remain decentralized if this is distributed across nodes and miners. For them, the actions of Core enforce a hierarchical structure that contradict the promise of a decentralized cryptocurrency based entirely on technical adeptness.

Next steps

Whatever happens next will almost certainly confirm the suspicions of one side about the other.

If SegWit is adopted, adding a hitherto unforeseen degree of technical complexity to the network, then we enter a phase that confirms wide trust across the entire bitcoin community in the vision of the Core team.

If, however, the miners hold out and Unlimited results in a fork, whether now or later (once again possibly blindsiding Core), then we will have to face an ideological schism that asks us to speculate on what precisely we believe bitcoin to be.

What Bitcoin Unlimited has brought to light is precisely two competing conceptions over the essence of this entire project, and our worry is precisely this: because the debate has become so polarized, it has become increasingly difficult to communicate across the divide.

If bitcoin can be partially understood as a consensus protocol, we might soon have to get better at doing just that.

Hidden safe image via Shutterstock


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