Paper 2019/154

FastKitten: Practical Smart Contracts on Bitcoin

Poulami Das, Lisa Eckey, Tommaso Frassetto, David Gens, Kristina Hostáková, Patrick Jauernig, Sebastian Faust, and Ahmad-Reza Sadeghi


Smart contracts are envisioned to be one of the killer applications of decentralized cryptocurrencies. They enable self-enforcing payments between users depending on complex program logic. Unfortunately, Bitcoin – the largest and by far most widely used cryptocurrency – does not offer support for complex smart contracts. Moreover, simple contracts that can be executed on Bitcoin are often cumbersome to design and very costly to execute. In this work we present FastKitten, a practical framework for executing arbitrarily complex smart contracts at low costs over decentralized cryptocurrencies which are designed to only support simple transactions. To this end, FastKitten leverages the power of trusted computing environments (TEEs), in which contracts are run off-chain to enable efficient contract execution at low cost. We formally prove that FastKitten satisfies strong security properties when all but one party are malicious. Finally, we report on a prototype implementation which supports arbitrary contracts through a scripting engine, and evaluate performance through benchmarking a provably fair online poker game. Our implementation illustrates that FastKitten is practical for complex multi-round applications with a very small latency. Combining these features, FastKitten is the first truly practical framework for complex smart contract execution over Bitcoin.

Available format(s)
Cryptographic protocols
Publication info
Published elsewhere. Major revision. USENIX Security Symposium 2019
BlockchainBitcoinSmart ContractsSGX
Contact author(s)
patrick jauernig @ trust tu-darmstadt de
david gens @ trust tu-darmstadt de
tommaso frassetto @ trust tu-darmstadt de
ahmad sadeghi @ trust tu-darmstadt de
poulami das @ cs tu-darmstadt de
lisa eckey @ cs tu-darmstadt de
kristina hostakova @ cs tu-darmstadt de
sebastian faust @ cs tu-darmstadt de
2019-04-18: last of 2 revisions
2019-02-20: received
See all versions
Short URL
Creative Commons Attribution


      author = {Poulami Das and Lisa Eckey and Tommaso Frassetto and David Gens and Kristina Hostáková and Patrick Jauernig and Sebastian Faust and Ahmad-Reza Sadeghi},
      title = {FastKitten: Practical Smart Contracts on Bitcoin},
      howpublished = {Cryptology ePrint Archive, Paper 2019/154},
      year = {2019},
      note = {\url{}},
      url = {}
Note: In order to protect the privacy of readers, does not use cookies or embedded third party content.