Bitcoin Scalability Workshops

Scaling Bitcoin 2015 Phase I - September 12th-13th Montreal, Canada


Workshop Sponsorship

Sponsorship is now closed.

Travel Subsidy

Travel subsidy is no longer available.

If you have applied for travel subsidy, you will be notified before undefined.

Call for Proposals

The current Scaling Bitcoin Workshop will take place September 12th -13th  at the Centre Mont-Royal (Salon Mont-Royal I, 4 th floor) 2200 rue Mansfield Montréal Québec, H3A 3R8 . We are accepting technical proposals for improving Bitcoin performance including designs, experimental results, and comparisons against other proposals. The goals are twofold: 1) to present potential solutions to scalability challenges while identifying key areas for further research and 2) to provide a venue where researchers, developers, and miners can communicate about Bitcoin development.

We are accepting two types of proposals: one in which accepted authors will have an opportunity to give a 20-30 minute presentation at the workshop, and another where accepted authors can run an hour-long interactive workshop.

Topics of interest include:

  • Improving Bitcoin throughput
  • Layer 2 ideas (i.e. payment channels, etc.)
  • Security and privacy
  • Incentives and fee structures
  • Testing, simulation, and modeling
  • Network resilience
  • Anti-spam measures
  • Block size proposals
  • Mining concerns
  • Community coordination

All as related to the scalability of Bitcoin.

Important Dates

  • undefined - Last day for submission
  • undefined - Last day for notification of acceptance and feedback


We are doing rolling acceptance, so submit your proposal as soon as you can. Proposals may be submitted as a BIP or as a 1-2 page extended abstract describing ideas, designs, and expected experimental results. Indicate in the proposal whether you are interested in speaking, running an interactive workshop, or both. If you are interested in running an interactive workshop, please include an agenda.

Proposals should be submitted to by undefined.

All talks will be livestreamed and published online, including slide decks.


In recent months the Bitcoin development community has faced difficult discussions of how to safely improve the scalability and decentralized nature of the Bitcoin network. To aid the technical consensus building process we are organizing a pair of workshops to collect technical criteria, present proposals and evaluate technical materials and data with academic discipline and analysis that fully considers the complex tradeoffs between decentralization, utility, security and operational realities. This may be considered as similar in intent and process to the NIST-SHA3 design process where performance and security were in a tradeoff for a security critical application.

Since Bitcoin is a P2P currency with many stakeholders, it is important to collect requirements as broadly as possible, and through the process enhance everyone’s understanding of the technical properties of Bitcoin to help foster an inclusive, transparent, and informed process.

Those with technical interest are invited to participate in this pair of workshops with the following intent:

Phase 1

Scene setting, evaluation criteria and tradeoff analysis.

Montreal, Canada: September 12th-13th, 2015

Scalability is not a single parameter; there are many opportunities to make the Bitcoin protocol more efficient and better able to service the needs of its growing userbase. Each approach to further scaling the Bitcoin blockchain involves implicit trade offs of desired properties of the whole system. As a community we need to raise awareness of the complex and subtle issues involved, facilitate deeper research and testing of existing proposals, and motivate future work in this area.

The purpose of this workshop is to discuss the general tradeoffs and requirements of any proposal to scale Bitcoin beyond its present limits. Session topics are to include the presentation of experimental data relating to known bottlenecks of Bitcoin’s continued growth and analysis of implicit tradeoffs involved in general strategies for enabling future growth.

This event will not host sessions on the topic of any specific proposals involving changes to the Bitcoin protocol. Such proposals would be the topic of a 2nd, follow-on Phase 2 workshop described below; this event is intended to “set the stage” for work on and evaluation of specific proposals in the time between the workshops.

Phase 2 will be planned out further as part of Phase 1 with input from the participants.

Phase 2

Presentation and review of technical proposals, with simulation, benchmark results.

Hong Kong, SAR, China: December 6th-7th, 2015

Hopefully to be easier for the Chinese miners to attend, the second workshop pertaining to actual block size proposals is to be planned for Hong Kong roughly in the late November to December timeframe.

The purpose of this workshop is to present and review actual proposals for scaling Bitcoin against the requirements gathered in Phase 1. Multiple competing proposals will be presented, with experimental data, and compared against each other. The goal is to raise awareness of scalability issues and build a pathway toward consensus for increasing Bitcoin’s transaction processing capacity or, barring that, identify key areas of further required research and next steps for moving forward.

Preliminarily, phase 2 will be a time to share results from experiments performed as a result of phase 1 and an opportunity to discuss new developments.

How do the Workshops work?

  • Both events will be live-streamed with remote participation facilitated via IRC for parallel online discussion and passing questions to the event.
  • These workshops aim to facilitate the existing Bitcoin Improvement Proposals process. Most work will be done outside of the workshops in the intervening months. The workshops serve to be additive to the design and review process by raising awareness of diverse points of view, studies, simulations and proposals.
  • Travel, venue details, accommodation recommendation are available below. You can register at an early bird ticket price of $150 USD until September 3rd.
  • Please see the FAQ section below, it should answer most other questions.



September 11th
Opening party

September 12th


(5 min)
Introduction to Event and Format Overview
Jeremy Rubin
(30 min)
Review of Historical Context
Bryan Bishop

Implementated Work

(15 min)
Bitcoin Relay Network
Matt Corallo
(15 min)
Reworking Bitcoin Core's P2P Code to be More Robust and Event-Driven
Cory Fields
(10 min)
Block Upload Data and IBLT
Rusty Russell
(20 min)
Coffee Break

Security and Privacy

(20 min)
Overview of Security Concerns
Peter Todd
(20 min)
Scaling Bitcoin to Support Privacy-Preserving Smart Contracts
Ranjit Kumaresan

Testing, Simulation, and Modeling

(20 min)
A Testbed for Bitcoin Scaling
Ittay Eyal, Emin Gün Sirer
(15 min)
Stochastic Modeling of Bitcoin with Dynamic Block Sizes
Conner Fromknecht, Nathan Wilcox
(15 min)
Coinscope & Shadow-Bitcoin
Andrew Miller
(10 min)

Economics and Incentives

(15 min)
How Wallets Can Handle Real Transaction Fees
Bram Cohen
(15 min)
A Transaction Fee Market Exists without a Block Size Limit
Peter R
(15 min)
Mind the Gap: Security Implications of the Evolution of Bitcoin Mining
Miles Carlsten, Harry Kalodner, Arvind Narayanan
(60 min)
(2 min)
Workshop Primer
(60 min)
Roundtable Discussion A
Future of SPV Technology
LEADERS: Bryan Bishop
Network Propagation
LEADERS: Matt Corallo, Rusty Russell
Involving Academia
LEADERS: Joseph Bonneau, Olaoluwa "Laolu" Osuntokun
Trustless UX and Human-Crypto Interaction
LEADERS: Paige Peterson and Dan Elitzer
Threat Models and Boogeymen
LEADERS: Peter Todd, Andrew Poelstra
Testing and Simulation Methods
LEADERS: Andrew Miller, Ittay Eyal, Emin Gün Sirer
(60 min)
Roundtable Discussion B
Mathematical Modeling and Spherical Cows
LEADERS: Bram Cohen, Patrick Strateman
Miner-Developer Relations
LEADERS: Alex Petrov, Matt Corallo, Luke Dashjr
Scalability and Hosted Infrastructure
LEADERS: Ryan Charles, Ryan Smith, Charlie Lee
Pathway to Adopting Better Cryptography
LEADERS: Andrew Poelstra
Privacy and Scalability
LEADERS: Zooko Wilcox-OHearn, Ranjit Kumaresan, Andrew Miller
Potential for SHA3-like Contest Processes for Bitcoin
LEADERS: Shin'Ichiro Matsuo
(10 min)
(80 min)
Roundtable Discussion Summary Session
(30 min)
Invited Talk: Gabriella Coleman

September 13th

Community Communication Channels

(20 min)
Lessons learnt from the NIST SHA-3 Competition for scaling Bitcoin
Shin'ichiro Matsuo
(15 min)
Objective Functions in Bitcoin Development
Paul Sztorc

Payment Channels & Layer 2

(20 min)
Bitcoin failure modes and the role of the Lightning Network
Joseph Poon, Thaddeus Dryja
(10 min)
Experiences Working on Layer 2 Scalability Solutions
C.J. Plooy
(10 min)
Stroem - A Protocol for Microtransactions
Jarl Fransson
(20 min)
Coffee Break

Mining & Network Costs

(10 min)
How to Mine Bitcoin Profitably
Sveinn Valfells
(10 min)
Mining True Cost
Marshall Long
(5 min)
Initial Block Synchronization is Quadratic Time Complexity
Patrick Strateman
(20 min)
Validation Costs and Incentives
Eric Lombrozo
(10 min)

Block Size Research

(15 min)
Sharding the Blockchain
Vlad Zamfir
(15 min)
Alternatives to a Block Size Limit as a Rate-Limiter for Validator Resource Consumption for Consideration
Mark Friedenbach
(20 min)
Issues Impacting Block Size Proposals
Jeff Garzik
(15 min)
Mathematical Formalism for Voting Process
Alex Petrov
(20 min)
How Will Bitcoin's Block Size Affect Non-Currency Applications?
Harry Kalodner, Arvind Narayanan
(60 min)
(30 min)
Invited Talk: Nicholas Negroponte
(60 min)
Roundtable Discussion C
Communicating Without Official Structures
LEADERS: Elizabeth Stark
Payment Channels
LEADERS: Joseph Poon, CJ Plooy, Jarl Fransson
Interfacing with the IETF, W3C, and ISPs
LEADERS: Pindar Wong
Perspectives and Challenges on Interfacing with China
LEADERS: Marshall Long, Jinglan Wang
Systematizing Knowledge
LEADERS: Andrew Miller, SJ Klein, Arvind Narayanan
Non Currency Applications
LEADERS: Harry Kalodner, Devon Gundry
(60 min)
Roundtable Discussion D
Moving Forward: Pathways to Requirement Setting
LEADERS: Eric Lombrozo
Actionable Network Events and Planned Responses
LEADERS: Gregory Maxwell, Alex Chernyakhovsky
Challenges for Major Protocol Changes and their Benefits
LEADERS: Wladimir van der Laan, Vlad Zamfir
Education and Resources: How can we get 10x the number of "core" contributors?
LEADERS: Suhas Daftuar, Alex Morcos, Eric Martindale
Sustainable Financing for Bitcoin's Future
LEADERS: Micah Winkelspecht, Patrick Murck
Scalability of Wallet Technology
LEADERS: Greg Sanders, Lawrence Nahum
(10 min)
(80 min)
Roundtable Discussion Summary Session
(20 min)
Closing Session
Pindar Wong

Remote Participation

Live recording of the event is available on:
  • YouTube: :


The Centre Mont Royal Salon I can host up to 250 attendees in an academic-style conference facility with wifi internet and desks at each seat. The intent is for attendees to be able to take notes and engage in parallel online discussions during the scheduled presentations. The presentations will be lived streamed so the global community can follow and join in on online discussions.
Centre Mont-Royal
(Salon Mont-Royal I, 4th floor)
2200 rue Mansfield
Montréal Québec, H3A 3R8


We are sorry, but the event has been sold out.
You will still be able to participate via the live stream, IRC, and Twitter.
Due to space limitations, we will not be able to admit anyone at the door.


  • What does it cost?

    The early-bird ticket price is $150 USD until September 3rd 00:00 UTC when it becomes $200 USD. From September 9th tickets become $300 USD to accommodate a limited quantity of last-minute registrations.

  • I need some sort of document for a travel visa

    (Info: You are responsible for figuring out your own personal visa requirements to enter Canada. Let the logistics people at CryptoMechanics know if they can help with required documentation for you to enter the country.

  • I can’t go but I want to participate!

    The event will be livestreamed, and you will be able to participate via IRC. Although it is naturally easier to participate in person, everyone at the event will have a desk in front of them and will be encouraged to join in online discussions with global participants who are viewing the live stream. It is also important to understand that no decisions are to be made at the workshop. (read more below)

  • How do I give a presentation?

    You can submit your proposal to (see CfP below). If you’ve worked on research, we recommend that you post the results, including papers, simulation results, and source code, to the bitcoin-dev discussion list. Depending on the quantity of accepted presentations, the workshop will allot a fair amount of time to each presenter. If people have substantially overlapping plans, they may be suggested to merge. Publishing a paper is NOT required—if you have a good presentation plan, you can propose a detailed summary.

  • My company wants to sponsor!

    Sponsorship is currently available at the $1,000+ to get your company’s logo added to this website. Contact Anton at CryptoMechanics to make arrangements. Ticket prices cover only a portion of the event cost, and the four underwriters are on the hook for an undefined quantity of expenses for the travel subsidies of qualified presenters, so additional corporate sponsors would be very helpful. The four underwriters of the event are currently the MIT Digital Currency Initiative, Chaincode Labs, Blockstream and

  • Why Montreal?

    It was considered neutral territory, convenient to travel for Europeans and Americans, and some expressed a desire to not enter the U.S.

  • Why Hong Kong?

    The second workshop is being planned for Hong Kong to make it easier for the Chinese miners to attend.

  • Are any decisions made at the workshop?

    Absolutely no decisions are made at workshops, as this would run the risk of being rushed and unfair to the global community unable to attend in person. The workshop is about raising awareness of issues and proposals, finding common ground, and encouraging public discussion within the existing mechanism of technical progress through the Bitcoin Improvement Proposal process.

  • Will there be a debate?

    There will probably be no debate, and the workshop organizers and participants will be operating with the goal of making the event low-stress and non-confrontational. The intent of the workshops are to showcase diverse points of view and promote open-mindedness in order to improve our collective understanding of how to improve Bitcoin’s scalability. In-person debates could too easily do a disservice to the future of Bitcoin in being about solidifying simplified positions for the purpose of winning political points. It would be unreasonable to entrust the safety and security of the future of Bitcoin to smooth talking at a one-time event rather than deliberate technical study with time for the global community to weigh in.

  • Can we discuss governance of the Bitcoin projects at this workshop?

    These first two workshops in Montreal and Hong Kong are focused on raising technical awareness of scalability issues, simulations and proposals to improve scalability. For now the participants want this to be entirely focused on the science and engineering, which is how Open Source Software development has proven to deliver excellence.

  • Future Workshops? Workshop BIP?

    Some have proposed the workshops become regular events for working on technical issues, after the second currently in planning for Hong Kong. For example, a third workshop has been proposed to be held at MIT’s campus or in New York City. Some have also proposed that we write a BIP on how to organize workshops. These workshops are a work in progress; we will make some mistakes and learn how to do it better the next time. For now, let’s make the first two workshops a success, as that will inform how to define their organization in a written BIP and how to conduct further productive workshops. If you’re interested in discussing future workshops, please join the bitcoin-workshops discussion list.

Online Resources

Call for Proposals/Papers/Presentations

If you have any research relevant to issues surrounding Bitcoin scalability, we’d welcome your proposal for a presentation at the Montreal workshop. Please email your proposal to The deadline for submission is September 1st.


Scaling Bitcoin Planning Committee

  • Anton Yemelyanov, ASPECTRON Inc.
  • Nelly Milanova, ASPECTRON Inc.
  • Pindar Wong, VeriFi (Hong Kong) Ltd.
  • Alex Morcos, Chaincode Labs
  • Jeremy Rubin, MIT Digital Currency Initiative
  • Warren Togami, Blockstream
  • Elizabeth Stark, Lightning
  • Victoria van Eyk, Changetip
  • Dan Elitzer, IDEO Futures
  • Shawn O’Connor, Kraken
  • Adam Ludwin,
  • Marshall Long, FinalHash