Making Decentralized Economic Policy

Bitcoin block size, a change in economic policy

The block size limit debate. This is the first major change in bitcoin economic policy since inception, Jan 2009. There is no perfect answer; as with most modern policy changes, any action ­ including inaction ­ generates winners and losers.

What is bitcoin? An existential question to answer.

Is bitcoin a commodity ownership transfer system? Is bitcoin a payment system? Is bitcoin a secure service for timestamping and notarizing documents? Is bitcoin a currency for 7 billion world citizens to personally use every day?

To make an informed decision on this change, one must first decide where you want to go, and how to best map the blockchain technology to that goal.

Does bitcoin natively provide an instant, secure, decentralized, trustless, egalitarian currency system? Is that a goal? Is that possible? If we can “turn a knob” and make a leap towards that goal, should we? What other uses are we aiming for? NASDAQ stock settlement, millions of trades per day on the blockchain, major non­currency applications competing for space with, and possibly crowding out, currency­based blockchain applications?

The future of blockchain tech is certainly bright ­ yet also unclear. The block size limit invites consideration of the best path forward.

High hurdle: Risky “hard fork” required to change policy

Economic policy in the bitcoin system is intentionally hard to change. According to the rules of the bitcoin consensus system, any deviation from the existing rules will cause immediate separation from the main network, as if an immune system attacking cancerous cells. Bitcoin users that fail to follow bitcoin’s protocol with 100.0% precision will find themselves banned from Bitcoin Island (until they return to 100.0% compliance).

Changing bitcoin’s rules requires a risky operation known as a hard fork, an abrupt global upgrade. There are many policy and engineering risks related to a hard fork. In many ways, it is akin to a Constitutional Convention in the US: Anything about the foundation of the bitcoin system may be changed in a hard fork. Nothing is sacred.

One of the largest risks is social: If two or more populations of users choose to follow different rules, one of bitcoin’s key axioms is broken: the same bitcoin may be spent twice (one in each user population). Each population has an enormous incentive to seek consensus and end this situation. If such a split occurs, bitcoin payment processors, exchanges and other businesses must either Pick A Side or simply shut down until the confusion is resolved, severely damaging confidence.

Censorship resistance: an engineering requirement

Preventing the double­spending of bitcoin tokens requires an underlying engineering system that cannot be altered by any party, ever, once transactions are published to the blockchain. This censorship resistance is required for reliable operation of the system, and enables a core principle also found in the Internet itself: permissionless innovation. Apps are more easily built upon top of open platforms such as bitcoin, or the Internet.

This is the core security service “backing” bitcoin. This irrevocable security service may be used to secure transfer currency tokens (BTC), physical assets (smart property), stocks, bonds, and more.

Eroding the censorship resistance of the system erodes bitcoin’s long term value. There can only be trust achieved in the system as a whole when bitcoin is viewed as a neutral actor.

What is the block size limit?

A hidden yet crucial metric in the bitcoin system is the $­cost to flood the system with garbage. Absent a speed limit, of sorts, attackers bog down the entire system. In the early days of bitcoin, when the dollar cost to flood the system was low, originator Satoshi added a limit on the total number of transactions validated every 10 minutes.

When the number of transactions in the past 10 minutes exceeds this speed limit, a bidding war occurs. Bitcoin transactions are prioritized based on the transaction fee attached. Higherfee paid by the user, the more likely their transaction will be prioritized before a lesser­paying user.

In short, with this limit, a block is an economically constrained resource for which bitcoin users bid space according to the laws of supply and demand. Your bitcoin transaction has very little security until it is validated and placed in a block. This system discourages garbage floods (spam) ­ it costs increasing amounts of money to do so. This system incentivizes conservation, efficiency,

Why change?

The primary reason is removing a roadblock to bitcoin growth. The theoretical limit with the current block size is 7 transactions/second. Any responsible business projecting capacity usage into the future sees the system reaching an absolute maximum capacity, with this speed limit in place. Increasing or removing this limit will encourage businesses to view bitcoin as scalable and capable of supporting millions of new users.

On a more practical level, as blocks get full and the bidding war ensues, the bitcoin user experience rapidly degrades to poor. In part due to bitcoin wallet software’s relative immaturity, and in part due to bitcoin’s settlement­based design, the end user experience of their transaction competing for block size results in erratic, and unpredictably extended validation times. The user is left waiting around for their payment, without knowing much why, or how to avoid this situation.

What are the consequences of inaction?

In a minority view, bitcoin is a commodity to which a silly little payment network is attached. These users view bitcoin as purely as a commodity whose storage cost is far less than the equivalent value of storage. To these users, increasing transaction volume on the network, scaling to support millions of users is simply folly. As the system approaches the speed limit, transaction fees rise. This userbase generates little transaction volume, and higher transaction fees are still offset by the value gained from the network’s protection of their commodity. These users likely feel inaction, keeping the speed limit intact, is the most rational step for their situation.

Conversely, a prevailing view is that this speed limit presents a severe constraint on growth and adoption. The speed limit, in the face of userbase growth, will lead to higher fees, ultimately reaching an equilibrium when the system capacity of 7 transactions/second isreached. This will cause a ripple effect where blockchain­centered business plans are shelved, or never started in the first place, for lack of perceived scalability.

Higher fees then drive a preference for centralized services which can aggregate those fees across multiple bitcoin users, or strike bulk rate deals. The use of bitcoin becomes a rather exclusive club.

What are the consequences of action?

Lower fees incentivize use of bitcoin at a key time in its young life. The cost to experiment with new and exciting bitcoin applications remains low. Noname and Big Name developers make plans to build atop bitcoin. Economic activity remains near frictionless. A virtuous cycle is created.

All very positive ­ yet there are costs.

This change creates some technical, policy, political and social fallout. This action is willfully ­ artificially? ­ keeping bitcoin transaction fees low. Thus, much like the US Federal Reserve’s goal of keeping inflation low, a more actively managed policy is being put into place. While true the consequences of inaction are painful, the parallels between Fed policy and the proposed solution are inescapable.

Keeping fees low (versus 1MB limit) has additional fallout. The natural economic state of a block is to be 100% full at all times. The only reason why this does not occur today is an anti­spam economic policy in the bitcoin software, which ignores extremely­low­value “dust” transactions which are accompanied by extremely low (or zero) fees. Lowering fees in the bitcoin system thus relies more heavily on the anti­spam system to filter out “junk” The definition of “junk” is subjective and not entirely technical.

Larger blocks push marginal actors off the network, having centralizing effects on the overall network. Techniques exist to mitigate this to some extent, but it remains true. Large blocks are more sensitive to network latency. Network bottlenecks, delays and cyberattacks, unintentional and malicious, are amplified at larger block sizes. The opportunities for bad actors to “push the system around” increases, as marginal actors leave, and decentralization leaves right along with it. 1MB is too small. How much is too much? Good answers remain elusive.

Overall system security may be impacted. Increased traffic on the bitcoin network will most likely exacerbate negative trends in metrics such as bitcoin network size (5,000 and falling), one key metric of network security health. As these metrics fall, increasing network load is shouldered by a decreasing number of actors.

Further, executing a hard fork to enact this change introduces the risks noted above.

If the number of validating actors in the system reaches an extreme minimum, bitcoin’s core value of censorship resistance, the core system security is easily eroded by government or private competition.

All depends on the degree of action. Proposal: Rather than simply removing the speed limit, a radical and overly risky move, raise the limit conservatively, simulate, field test and observe the results. Build a process that smooths future upgrades, to avoid the pain points of the current 1MB hard fork.

A concrete proposal: BIP 100

On balance, increasing block size limit above 1MB is needed.

It is clear that the current speed limit, 1,000,000 bytes, is too low and will retard growth and lead to user pain and expense if not increased. What is unclear and under­researched is the opposite side of the equation: How much is too much? Some Chinese pools and exchanges, for example, warn they will be at a disadvantage and ultimately pushed off the network at the originally proposed 20MB size.

Further, it is important to separate the hard fork risk away from the block size change events as much as possible. It is also important to plan ahead for change… yet not plan too far ahead. Be flexible and build a framework for rapid iteration as informed by field experience.

Protocol changes proposed:

  • 1. Hard fork to remove 1MB block size limit.
  • 2. Simultaneously,​addanewsoftforklimitof2MB.
  • 3. Schedule the hard fork on testnet for September 1, 2015.
  • 4. Schedule the hard fork on bitcoin main chain for December 11, 2015.
  • 5. Default miner block size becomes 1MB (easily changeable by miner at any time, as today).
  • 6. Changing the 2MB limit is accomplished in a manner similar to BIP 34, a one­way lock­in upgrade with a 12,000 block (3 month) threshold by 75% of the blocks.
  • 7. Limit increase may not exceed 2x in any one step.

This creates a framework whereby the network may increase the block size by consensus via soft fork, a lower and less politically risky hurdle than hard fork. Sizes beyond 2MB may be chosen without a flag­day network upgrade. A small size increment limits the potential forunexpected harm to bitcoin network security, and gives the network time to test, prepare and adjust overall behavior.

Other, more complex solutions such as extension blocks ­ a speed limit workaround ­ are rejected in favor of this one­time, highly simple change that greatly reduces the need for future hard forks in this area.

This BIP accomplishes several goals:

  • G1: Demonstrates change is possible; the bitcoin protocol can be upgraded.
  • G2: Eliminate 1MB limit as impediment to adoption.
  • G3: Get hard fork risk out of the way early.
  • G4: KISS solution, in terms of code changes.
  • G5: Upgrade path, yet constrained until problem & solution better understood.

This introduces friction into the block size increase process ­ making it changeable, yet giving participants in the system sufficient time to observe system behavior and change course. Ultimately moving towards a system where the market decides the best block size.

Discussion: Low signal, high noise

Major policy changes in an open source project are messy. What would, in a central bank, be a closed door policy discussion is instead held out in the open, with all parties airing their opinions in an open forum. Transparency wins, even if sometime a painful process.

Yet the amount of actual financial engineering involved in this debate has been disappointing. Simulations are practically non­existent. Data on the change has often lacked (or held constant) one or more key variables associated with today’s network. The proponents of a block size change have sometimes been poor debaters, exaggerating the arguments of opponents to a ludicrous degree.

In toto, this is a major change to bitcoin. Changing a $3B economic system ­ even if to keep it alive and growing and healthy ­ deserves more in­depth attention and research than has been given to date. The 1MB limit is a relic from an earlier time, always intended to be removed ­ yet paradoxically it forms the core of our economics today and cannot be changed lightly or without consequence.

Discussion: Accepting engineering reality

In the drive to “growth at any cost” in some bitcoin business models, some axioms tend to get glossed over.

Bitcoin is fundamentally a settlement based design. The nature of distributed consensus, known in database circles as eventual consistency, is that it takes time for the network to come to a consensus on the “right” historical timeline (blockchain). The blockchain takes time to bake.

Answering some the existential questions opened above, bitcoin as engineered today will not be the Star Trek ideal we all want: instant, secure, borderless, egalitarian, non­volatile currency directly accessible by 7 billion.

That should not be misinterpreted as the Star Trek ideal being impossible. Rather, systems will have economic and engineering incentives to use the bitcoin blockchain for its strength as ana​nchor,​therootchaininaforestofchains. Individualchains,thussecuredbythe“main” chain, will offer unique features such as Ethereum’s smart contract language, or serve specific user communities.

Putting all the world’s coffee transactions, and all the world’s stock trades, and all the world’s Internet­of­Things device samplings, on the bitcoin blockchain seems misguided. The block size limit does serve a useful function, discouraging wholesale dumping of multi­gigabyte files into the blockchain. Already “blockchain as my video dropbox” apps have been proposed, much to collective dismay.

A bitcoin transaction today is analogous to an irreversible, one­way message. In the world of computer networking, the lowest layers of networking are irreversible, one­way messages. Sometimes these messages, are lost, corrupted, need to be retransmitted or updated. IP, the Internet Protocol, requires additional, upper­layer protocols TCP and HTTP to be useful. Yet IP forms the foundational layer of the Internet.

Bitcoin protocol and network today is that foundational layer. It is value transfer network. Beyond that, it is a core, backbone security service securing contracts, physical and digital property, equities, bonds, robot A.I. and an enormous wave of applications which have not yet been conceived. Inventing bitcoin­the­currency, securing bitcoin­the­token, was the Minimum Viable Product, the necessary first step towards building a universe of secure, decentralized services.

Do not try to stuff every feature into the bitcoin protocol. Let it do what it does best. Build systems on top of bitcoin which use its strengths, the ultra­secure blockchain service & bitcoin ownership registration service (aka secure value transfer).

Open challenge: Decentralized governance

Many of these questions would seem to have answers if only one can “ask the users” This is easier said than done. Large bitcoin stakeholders may be offline for months, years. Quantifying users and enabling voting are a challenge. Secret cartels easily undermine public votes.

Open source projects are by their nature opt­in, join and contribute as your energy, funds and time permit. There is no natural constituency to handle marketing, governance, testing, as there is with a company building a software product. All those tasks must be collectively organized by the bitcoin community. Free riding is easy at multiple levels. The entire community must be proactive in contributing time and resources to upkeep of this “automaton”

How can we create a technical advisory board, potentially enshrining its members as a bitcoin priesthood, without the board becoming as corrupt and easy to manipulate as FIFA? Technical decisions have economic consequences in bitcoin. Imagine the economic impact of code changes at 10x, 100x+ scale.

Ultimately I have confidence that the free market, transparency and user choice will sort it all out. Bitcoin is as much about the humans that use the network, as it is about the technology. If the technology suddenly breaks, users have over $3B reasons to work towards fixing the problem.

Full Disclosure

The preceding text is my own personal, vendor neutral opinion. I have many formal and informal associations with bitcoin businesses, notably BitPay, most of whom support a block size increase. Those associations are held separate from this opinion.

Written by Jeff Garzik on June 12, 2015.