Adding concurrency to smart contracts

Thomas Dickerson, Paul Gazzillo, Maurice Herlihy, Eric Koskinen

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

112 Scopus citations

Abstract

Modern cryptocurrency systems, such as Ethereum, permit complex financial transactions through scripts called smart contracts. These smart contracts are executed many, many times, always without real concurrency. First, all smart contracts are serially executed by miners before appending them to the blockchain. Later, those contracts are serially re-executed by validators to verify that the smart contracts were executed correctly by miners. Serial execution limits system throughput and fails to exploit today's concurrent multicore and cluster architectures. Nevertheless, serial execution appears to be required: contracts share state, and contract programming languages have a serial semantics. This paper presents a novel way to permit miners and validators to execute smart contracts in parallel, based on techniques adapted from software transactional memory. Miners execute smart contracts speculatively in parallel, allowing non-conflicting contracts to proceed concurrently, and "discovering" a serializable concurrent schedule for a block's transactions, This schedule is captured and encoded as a deterministic fork-join program used by validators to re-execute the miner's parallel schedule deterministically but concurrently. Smart contract benchmarks run on a JVM with ScalaSTM show that a speedup of 1.33x can be obtained for miners and 1.69x for validators with just three concurrent threads.

Original languageEnglish
Title of host publicationPODC 2017 - Proceedings of the ACM Symposium on Principles of Distributed Computing
Pages303-312
Number of pages10
ISBN (Electronic)9781450349925
DOIs
StatePublished - 26 Jul 2017
Event36th ACM Symposium on Principles of Distributed Computing, PODC 2017 - Washington, United States
Duration: 25 Jul 201727 Jul 2017

Publication series

NameProceedings of the Annual ACM Symposium on Principles of Distributed Computing
VolumePart F129314

Conference

Conference36th ACM Symposium on Principles of Distributed Computing, PODC 2017
Country/TerritoryUnited States
CityWashington
Period25/07/1727/07/17

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