Paper 2021/805

Practical Settlement Bounds for Proof-of-Work Blockchains

Peter Gaži, Ling Ren, and Alexander Russell

Abstract

Nakamoto proof-of-work ledger consensus currently underlies the majority of deployed cryptocurrencies and smart-contract blockchains. While a long and fruitful line of work studying the provable security guarantees of this mechanism has succeeded to identify its exact security region---that is, the set of parametrizations under which it possesses asymptotic security---the existing theory does not provide concrete settlement time guarantees that are tight enough to inform practice. In this work we provide a new approach for obtaining concrete and practical settlement time guarantees suitable for reasoning about deployed systems. We give an efficient method for computing explicit upper bounds on settlement time as a function of primary system parameters: honest and adversarial computational power and a bound on network delays. We implement this computational method and provide a comprehensive sample of concrete bounds for several settings of interest. We also analyze a well-known attack strategy to provide lower bounds on the settlement times. For Bitcoin, for example, our upper and lower bounds are within 90 seconds of each other for 1-hour settlement assuming 10 second network delays and a 10% adversary. In comparison, the best prior result has a gap of 2 hours in the upper and lower bounds with the same parameters.

Metadata
Available format(s)
PDF
Category
Applications
Publication info
Published elsewhere. MINOR revision.ACM CCS 2022
Keywords
Bitcoinproof of work
Contact author(s)
peter gazi @ iohk io
renling @ illinois edu
alexander russell @ uconn edu
History
2022-04-26: last of 3 revisions
2021-06-16: received
See all versions
Short URL
https://ia.cr/2021/805
License
Creative Commons Attribution
CC BY

BibTeX

@misc{cryptoeprint:2021/805,
      author = {Peter Gaži and Ling Ren and Alexander Russell},
      title = {Practical Settlement Bounds for Proof-of-Work Blockchains},
      howpublished = {Cryptology ePrint Archive, Paper 2021/805},
      year = {2021},
      note = {\url{https://eprint.iacr.org/2021/805}},
      url = {https://eprint.iacr.org/2021/805}
}
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