Tools for Game Theoretic Models of Security for Cryptocurrencies - PowerPoint PPT Presentation

Tools for Game Theoretic Models of Security for Cryptocurrencies Sarah Azouvi Protocol Labs, University College London Alexander Hicks University College London CES’20 MIT March, 8th 2020

Blockchains Block1 Block2 Block3 = • Defends against Sybil attacks • Incentivizes consensus • Decentralised • More participation More secure

Blockchains’ Security • Traditional Distributed Systems and Cryptography do not consider incentives • Game Theory does not consider security notions • How to capture blockchains’ security? • Mix Game Theory and Security?

Game Theory (GT) and Security? • Has been studied a lot before Bitcoin • We reviewed a lot of papers • Non-exhaustive

Why mix GT and security? • Security Economics tells us that security is about more than technical constructions • “Incentives in Security Protocols” (SPW 2018) • GT/Mechanism Design (MD) serves to promote good outcomes

GT/MD primer Nash Equilibrium (NE)

NE Limitations Coalitions? Irrational Players Arbitrary Faults External Incentives Computing a NE is hard

Mechanism Design Desired outcome Game Israeli Nursery Study

Security Things “work” No Trusted third party

Why is combining security and GT is hard? • Mixing di ff erent framework: • Addition skills required • Increased Complexity • Di ff erent assumptions

Consensus

BAR Model Rational Players Byzantine (Malicious) Players Altruistic Players

Robustness Rational Players Altruistic Players Byzantine (Malicious) Players Coalitions Coalitions

Cryptography

Rational Cryptography Rational protocol design 𝛒 𝘉 Protocol can have vulnerabilities

Blockchains • Consensus • No model widely adapted • Decentralisation • Empirical work

Open problems • Utilities hard to compute in practice • Most of the research is theoretical • Empirical data on behaviour of players and coalitions (especially short term profit vs long term profit)

Questions? sarah.azouvi@protocol.ai @SarahAzouvi