Short Paper: Deploying PayWord on Ethereum

  • Muhammad Elsheikh
  • Jeremy ClarkEmail author
  • Amr M. Youssef
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 11599)


We revisit the 1997 PayWord credit-based micropayment scheme from Rivest and Shamir. We observe that smart contracts can be used to augment this system, apply to ‘claim or refund’ paradigm of cryptocurrencies to remove the counter-party risk inherent in PayWorld, and use a smart contract to ‘staple’ real value (in Ether) to payments in the system. Our implementation is more concise than any Ethereum payment channel we are aware of and the offline payments are very compact values (264 bits). It only uses hash functions and not digital signatures. EthWord becomes cheaper than standard Ethereum transfers when more than 16 payments between the same participants are made and appears to maintain its advantage for up to 1000+ transactions, at which point signature-based payments become cheapest. The main drawback of EthWord is the moderate gas price of using the system—despite dropping signatures, it is still priced out of the micropayments use-case. Like any payment channel, requires only two on-blockchain function calls to open and close the channel, while allowing the rest to be made off-blockchain.


  1. 1.
    Anderson, R., Bergadano, F., Crispo, B., Lee, J.-H., Manifavas, C., Needham, R.: A new family of authentication protocols. SIGOPS Oper. Syst. Rev. 32(4), 9–20 (1998)CrossRefGoogle Scholar
  2. 2.
    Bentov, I., Kumaresan, R.: How to use bitcoin to design fair protocols. In: CRYPTO (2014)Google Scholar
  3. 3.
    Chaum, D.: Blind signatures for untraceable payments. In: CRYPTO (1982)Google Scholar
  4. 4.
    Decker, C., Wattenhofer, R.: A fast and scalable payment network with bitcoin duplex micropayment channels. In: SSS (2015)Google Scholar
  5. 5.
    Di Ferrante, M.: Ethereum payment channel in 50 lines of code. Medium (2017)Google Scholar
  6. 6.
    Dziembowski, S., Eckey, L., Faust, S., Malinowski, D.: Perun: virtual payment channels over cryptographic currencies. IACR ePrint (2017)Google Scholar
  7. 7.
    Green, M., Miers, I.: Bolt: anonymous payment channels for decentralized currencies. In CCS (2017)Google Scholar
  8. 8.
    Heilman, E., Alshenibr, L., Baldimtsi, F., Scafuro, A., Goldberg, S.: Tumblebit: an untrusted bitcoin-compatible anonymous payment hub. In: NDSS (2017)Google Scholar
  9. 9.
    Jarecki, S., Odlyzko, A.: An efficient micropayment system based on probabilistic polling. In: Financial Cryptography (1997)Google Scholar
  10. 10.
    Khalil, R., Gervais, A.: Revive: rebalancing off-blockchain payment networks. In: CCS (2017)Google Scholar
  11. 11.
    Lamport, L.: Password authentication with insecure communication. CACM 24(11), 770–772 (1981)CrossRefGoogle Scholar
  12. 12.
    Malavolta, G., Moreno-Sanchez, P., Kate, A., Maffei, M., Ravi, S.: Concurrency and privacy with payment-channel networks. In: CCS (2017)Google Scholar
  13. 13.
    McCorry, P., Möser, M., Shahandasti, S.F., Hao, F.: Towards bitcoin payment networks. In: Information Security and Privacy (2016)Google Scholar
  14. 14.
    Miers, I., Garman, C., Green, M., Rubin, A.D.: Zerocoin: anonymous distributed e-cash from bitcoin. In: IEEE Symposium on Security and Privacy (2013)Google Scholar
  15. 15.
    Miller, A., Bentov, I., Kumaresan, R., McCorry, P.: Sprites: payment channels that go faster than lightning. CoRR, abs/1702.05812 (2017)Google Scholar
  16. 16.
    Nakamoto, S.: Bitcoin: a peer-to-peer electionic cash system. Unpublished (2008)Google Scholar
  17. 17.
    Narayanan, A., Bonneau, J., Felten, E.W., Miller, A., Goldfeder, S.: Bitcoin and Cryptocurrency Technologies. Princeton (2016)Google Scholar
  18. 18.
    Narayanan, A., Clark, J.: Bitcoin’s academic pedigree. CACM 60(12), 770–772 (2017)CrossRefGoogle Scholar
  19. 19.
    Pass, R., Shelat, A.: Micropayments for decentralized currencies. In: CCS (2015)Google Scholar
  20. 20.
    Poon, J., Dryja, T.: The bitcoin lightning network: scalable off-chain instant payments (2015)Google Scholar
  21. 21.
    Rivest, R.L.: Electronic lottery tickets as micropayments. In: FC (1997)Google Scholar
  22. 22.
    Rivest, R.L., Shamir, A.: PayWord and MicroMint: two simple micropayment schemes. In: Security Protocols (1996)Google Scholar
  23. 23.
    Roos, S., Moreno-Sanchez, P., Kate, A., Goldberg, I.: Settling payments fast and private: efficient decentralized routing for path-based transactions. In: NDSS (2018)Google Scholar
  24. 24.
    Sander, T., Ta-Shma, A.: Auditable, anonymous electronic cash. In: CRYPTO (1999)Google Scholar
  25. 25.
    Sasson, E.B., et al.: decentralized anonymous payments from bitcoin. In: IEEE Symposium on Security and Privacy (2014) Google Scholar
  26. 26.
    Wan, Z., Deng, R.H., Lee, D., et al.: MicroBTC: efficient, flexible and fair micropayment for bitcoin using hash chains. J. Comput. Sci. Technol. 34, 403–415 (2019). Scholar
  27. 27.
    Wheeler, D.: Transactions using bets. In: Security Protocols (1997)Google Scholar

Copyright information

© International Financial Cryptography Association 2020

Authors and Affiliations

  • Muhammad Elsheikh
    • 1
  • Jeremy Clark
    • 1
    Email author
  • Amr M. Youssef
    • 1
  1. 1.Concordia UniversityMontrealCanada

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