skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Adding concurrency to smart contracts
Modern cryptocurrency systems, such as the Ethereum project, 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. We have proved that the validator’s execution is equivalent to miner’s execution. Smart contract benchmarks run on a JVM with ScalaSTM show that a speedup of 1.39× can be obtained for miners and 1.59× for validators with just three concurrent threads.  more » « less
Award ID(s):
1917990
PAR ID:
10206401
Author(s) / Creator(s):
Date Published:
Journal Name:
Distributed computing
Volume:
33
ISSN:
0178-2770
Page Range / eLocation ID:
209–225
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; (, 2021 IEEE 41st International Conference on Distributed Computing Systems (ICDCS))
    Public blockchains have spurred the growing popularity of decentralized transactions and smart contracts, especially on the financial market. However, public blockchains exhibit their limitations on the transaction throughput, storage availability, and compute capacity. To avoid transaction gridlock, public blockchains impose large fees and per-block resource limits, making it difficult to accommodate the ever-growing high transaction demand. Previous research endeavors to improve the scalability and performance of blockchain through various technologies, such as side-chaining, sharding, secured off-chain computation, communication network optimizations, and efficient consensus protocols. However, these approaches have not attained a widespread adoption due to their inability in delivering a cloud-like performance, in terms of the scalability in transaction throughput, storage, and compute capacity. In this work, we determine that the major obstacle to public blockchain scalability is their underlying unstructured P2P networks. We further show that a centralized network can support the deployment of decentralized smart contracts. We propose a novel approach for achieving scalable decentralization: instead of trying to make blockchain scalable, we deliver decentralization to already scalable cloud by using an Ethereum smart contract. We introduce Blockumulus, a framework that can deploy decentralized cloud smart contract environments using a novel technique called overlay consensus. Through experiments, we demonstrate that Blockumulus is scalable in all three dimensions: computation, data storage, and transaction throughput. Besides eliminating the current code execution and storage restrictions, Blockumulus delivers a transaction latency between 2 and 5 seconds under normal load. Moreover, the stress test of our prototype reveals the ability to execute 20,000 simultaneous transactions under 26 seconds, which is on par with the average throughput of worldwide credit card transactions. 
    more » « less
  2. (, International Conference on Blockchain)
    null (Ed.)
    Ethereum Smart Contracts, also known as Decentralized Applications (DApps), are small programs which orchestrate financial transactions. Though beneficial in many cases, such contracts can and have been exploited, leading to a history of financial losses in the millions of dollars for those who have invested in them. It is critical that users be able to trust the contract code they place their money into. One way for verifying a program’s integrity is Symbolic Execution. Unfortunately, while the information derived from symbolic execution is beneficial, performing it is often financially and technically infeasible for users to do. To address this problem, this paper describes the design and implementation of a registry of vulnerable Ethereum contracts. The registry compiles the results of exhaustive application of symbolic analysis to deployed contracts and makes it available to users seeking to understand the risks associated with contracts they are intending to utilize. 
    more » « less
  3. ; ; ; ; ; (, Proceedings of the USENIX Conference)
    Calciu, Irina; Kuenning, Geoff (Ed.)
    We present RAINBLOCK, a public blockchain that achieves high transaction throughput without modifying the proof-ofwork consensus. The chief insight behind RAINBLOCK is that while consensus controls the rate at which new blocks are added to the blockchain, the number of transactions in each block is limited by I/O bottlenecks. Public blockchains like Ethereum keep the number of transactions in each block low so that all participating servers (miners) have enough time to process a block before the next block is created. By removing the I/O bottlenecks in transaction processing, RAINBLOCK allows miners to process more transactions in the same amount of time. RAINBLOCK makes two novel contributions: the RAINBLOCK architecture that removes I/O from the critical path of processing transactions (txs), and the distributed, multiversioned DSM-TREE data structure that stores the system state efficiently. We evaluate RAINBLOCK using workloads based on public Ethereum traces (including smart contracts). We show that a single RAINBLOCK miner processes 27.4K txs per second (27× higher than a single Ethereum miner). In a geo-distributed setting with four regions spread across three continents, RAINBLOCK miners process 20K txs per second. 
    more » « less
  4. ; ; (, IEEE)
    As quantum computing continues to scale, the ability to execute quantum circuits across distributed quantum networks is becoming increasingly important. While prior work has largely focused on distributing a single circuit to optimize the number of entanglement pairs (EPs) used or the execution time, future applications will require the efficient scheduling and execution of multiple circuits on a shared quantum network. Therefore, we study the problem of efficiently distributing multiple quantum circuits across a shared quantum network under decoherence and network constraints and seek to minimize the execution time required to execute all circuits (makespan). Solving the above problem involves jointly determining when and where each circuit should be executed, and how to schedule concurrent EP generation required to execute remote gates. We propose several algorithmic approaches for this multi-circuit distribution problem and provide theoretical performance guarantees for special cases. To assess the practical effectiveness of our methods, we conduct extensive simulations using the NetSquid quantum network simulator. 
    more » « less
  5. ; ; (, Leveraging Applications of Formal Methods, Verification and Validation. Industrial Practice. ISoLA 2018. Lecture Notes in Computer Science, vol)
    Smart contracts are programs that run atop of a blockchain infrastructure. They have emerged as an important new programming model in cryptocurrencies like Ethereum, where they regulate flow of money and other digital assets according to user-defined rules. However, the most popular smart contract languages favor expressiveness rather than safety, and bugs in smart contracts have already lead to significant financial losses from accidents. Smart contracts are also appealing targets for hackers since they can be monetized. For these reasons, smart contracts are an appealing opportunity for systematic auditing and validation, and formal methods in particular. In this paper, we survey the existing smart-contract ecosystem and the existing tools for analyzing smart contracts. We then pose research challenges for formal-methods and program analysis applied to smart contracts. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email