SmartCast: An Incentive Compatible Consensus Protocol Using Smart Contracts

  • Abhiram KothapalliEmail author
  • Andrew Miller
  • Nikita Borisov
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 10323)


Motivated by the desire for high-throughput public databases (i.e., “blockchains”), we design incentive compatible protocols that run “off-chain”, but rely on an existing cryptocurrency to implement a reward and/or punishment mechanism. Our protocols are incentive compatible in the sense that behaving honestly is a weak Nash equilibrium, even in spite of potentially malicious behavior from a small fraction of the participants (i.e., the BAR model from Clement et al. [7]). To show the feasibility of our approach, we build a prototype implementation, called SmartCast, comprising an Ethereum smart contract, and an off-chain consensus protocol based on Dolev-Strong [10]. SmartCast also includes a “marketplace” smart contract that randomly assigns workers to protocol instances. We evaluate the communication costs of our system, as well as the “gas” transaction costs that are involved in running the Ethereum smart contract.


Atomic broadcast TRB Game theory Ethereum Smart contracts 


  1. 1.
    Bentov, I., Kumaresan, R.: How to use bitcoin to design fair protocols. In: Garay, J.A., Gennaro, R. (eds.) CRYPTO 2014. LNCS, vol. 8617, pp. 421–439. Springer, Heidelberg (2014). CrossRefGoogle Scholar
  2. 2.
    Bonneau, J.: Why buy when you can rent? Bribery attacks on Bitcoin consensus. In: Bitcoin Research Workshop (2016)Google Scholar
  3. 3.
    Bonneau, J., Clark, J., Goldfeder, S.: On bitcoin as a public randomness source. Cryptology ePrint Archive, Report 2015/1015 (2015).
  4. 4.
    Bonneau, J., Miller, A., Clark, J., Narayanan, A., Kroll, J.A., Felten, E.W.: Research perspectives and challenges for bitcoin and cryptocurrencies. In: IEEE Symposium on Security and Privacy (2015)Google Scholar
  5. 5.
    Castro, M., Liskov, B., et al.: Practical byzantine fault tolerance. In: OSDI, vol. 99, pp. 173–186 (1999)Google Scholar
  6. 6.
    Chase, M., Meiklejohn, S.: Transparency overlays and applications. In: Proceedings of the 2016 ACM SIGSAC Conference on Computer and Communications Security, pp. 168–179. ACM (2016)Google Scholar
  7. 7.
    Clement, A., Li, H., Napper, J., Martin, J.P., Alvisi, L., Dahlin, M.: BAR primer. In: 2008 IEEE International Conference on Dependable Systems and Networks With FTCS and DCC (DSN), pp. 287–296. IEEE (2008)Google Scholar
  8. 8.
    Delmolino, K., Arnett, M., Kosba, A.E., Miller, A., Shi, E.: Lessons and insights from a cryptocurrency lab. In: Bitcoin Research Workshop, Step by Step Towards Creating a Safe Smart Contract (2016)Google Scholar
  9. 9.
    Dingledine, R., Mathewson, N., Syverson, P.: Tor: the second-generation onion router. Technical report, DTIC Document (2004)Google Scholar
  10. 10.
    Dolev, D., Strong, H.R.: Authenticated algorithms for byzantine agreement. SIAM J. Comput. 12(4), 656–666 (1983)MathSciNetCrossRefzbMATHGoogle Scholar
  11. 11.
    Garay, J., Katz, J., Maurer, U., Tackmann, B., Zikas, V.: Rational protocol design: cryptography against incentive-driven adversaries. Cryptology ePrint Archive, Report 2013/496 (2013).
  12. 12.
    Kosba, A., Miller, A., Shi, E., Wen, Z., Papamanthou, C.: Hawk: the blockchain model of cryptography and privacy-preserving smart contracts. In: 2016 IEEE Symposium on Security and Privacy (SP), pp. 839–858 (May 2016)Google Scholar
  13. 13.
    Kumaresan, R.: Broadcast and Verifiable Secret Sharing: New Security Models and Round Optimal Constructions (2012)Google Scholar
  14. 14.
    Laurie, B., Langley, A., Kasper, E.: Certificate transparency. In: Network Working Group Internet-Draft, v12, work in progress (2013).
  15. 15.
    Luu, L., Chu, D.H., Olickel, H., Saxena, P., Hobor, A.: Making smart contracts smarter. In: Proceedings of the 2016 ACM SIGSAC Conference on Computer and Communications Security, pp. 254–269. ACM (2016)Google Scholar
  16. 16.
    Morris, D.Z.: Blockchain-based venture capital fund hacked for $60 million (June 2016).
  17. 17.
    Nakamoto, S.: Bitcoin: a peer-to-peer electronic cash system (2008).
  18. 18.
    Pierrot, C., Wesolowski, B.: Malleability of the blockchain’s entropy. Cryptology ePrint Archive, Report 2016/370 (2016).
  19. 19.
    Teutsch, J., Jain, S., Saxena, P.: When cryptocurrencies mine their own business. In: Bitcoin Research Workshop (2016)Google Scholar
  20. 20.
    Wood, G.: Ethereum: a secure decentralized transaction ledger (2014).

Copyright information

© International Financial Cryptography Association 2017

Authors and Affiliations

  • Abhiram Kothapalli
    • 1
    Email author
  • Andrew Miller
    • 1
  • Nikita Borisov
    • 1
  1. 1.University of Illinois at Urbana-ChampaignUrbanaUSA

Personalised recommendations