November 11 – 16 , 2018, Dagstuhl Seminar 18461

Blockchain Security at Scale


Rainer Böhme (Universität Innsbruck, AT)
Joseph Bonneau (New York University, US)
Ittay Eyal (Technion – Haifa, IL)

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Dagstuhl Report, Volume 8, Issue 11 Dagstuhl Report
Aims & Scope
List of Participants
Dagstuhl's Impact: Documents available
Dagstuhl Seminar Schedule [pdf]


The security of blockchain-based systems has attracted great interest in the research community following the initial financial success of Bitcoin. Several security notions for blockchain-based systems have been proposed, varying in degree of formality and applicability to real-world systems. However, a major blind spot remains about the environment surrounding blockchain-based systems. This environment is typically assumed to be static (irresponsive to activities of the blockchain system). This is a sound starting point for security analysis while the stakes involved are small compared to the environment (i. e., the global economic and political system). However, if blockchain-based systems truly offer compelling advantages over legacy systems, they may eventually become the dominant form of organizing certain social choice problems. This „scale change“ challenges the assumption that the blockchain-based system remains below the threshold of relevance for the parts of its environment that are vital for its security. One instance where this may already occur is the influence of mining puzzles on hardware design and electricity prices.

The purpose of the seminar was to bring together researchers with expertise in various subfields of blockchain-based systems to jointly revisit security foundations. The primary goal was to incorporate explicit consideration of reciprocity effects between properties of cryptocurrency protocols and their environment.

The primary intended outcome of this seminar was proposing a new design principle, viewing security as a key scalability property to consider in addition to performance and efficiency. Second, the seminar aimed to converge on standard terminology for security notions that are robust to scale. Third, we applied this new methodology to Bitcoin specifically as a test case, producing a sort-of "break glass in case of rampant runaway growth" security plan.

Specific questions were:

  1. From micro-level to macro-level incentives: Bitcoin's ecosystem remains small relative to large multinational corporations. What happens to incentives when a cryptocurrency reaches a scale similar to large national economies?
  2. Cryptographic agility: How does the ability to upgrade cryptographic algorithms might change in the future as cryptocurrency protocols become widely embedded in hardware and/or codified in the law?
  3. Reciprocity effects on hardware design: How will the hardware industry be affected by the increasing importance of superior hardware for mining, and possibly trusted execution environments (TEE) in the future?
  4. Mining economics at scale: How will mining economics change in the future, in particular, dynamics between miners at large-scale power consumption levels, with mass availability of cheap commodity mining hardware (including TEE-based), and with different incentives, e.g., in a high-valued fee-only revenue model.
  5. Reconsidering non-monetary incentives: Can cryptocurrencies be resilient to disruptive nation-level attacks that are not due to monetary incentives?
  6. Governance at scale: To date, cryptocurrencies largely rely on informal leadership from a small group of influential software developers. Can this be translated into a more democratic model? What does democratic control mean for a cryptocurrency when the demos is not clearly defined?

Summary text license
  Creative Commons BY 3.0 Unported license
  Rainer Böhme

Related Dagstuhl Seminar


  • Data Structures / Algorithms / Complexity
  • Modelling / Simulation
  • Security / Cryptology


  • Distributed consensus protocols
  • Authenticated data structures
  • Blockchain technology
  • Security foundations
  • Security economics


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