Secure consistency verification for untrusted cloud storage by public blockchains

Kai Li, Yuzhe Tang, Beom Heyn Ben Kim, Jianliang Xu

Research output: Chapter in Book/Entry/PoemConference contribution

2 Scopus citations


This work presents ContractChecker, a Blockchain-based security protocol for verifying the storage consistency between mutually distrusting cloud provider and clients. Unlike existing protocols, the ContractChecker uniquely delegates log auditing to the Blockchain, and has the advantages in reducing client cost and lowering requirements on client availability, lending itself to modern scenarios with mobile and web clients. The ContractChecker collects the logs from both clients and cloud server, and verifies the consistency by cross-checking the logs. By this means, it does not only detect the attacks from malicious clients and server forging their logs, but also is able to mitigate those attacks and recover the system from them. In addition, we design new attacks against ContractChecker exploiting various limits in real Blockchain systems (e.g., write unavailability, Blockchain forks, contract race conditions). We analyze and harden the security of ContractChecker protocols under these proposed new attacks. We implement a functional prototype of the ContractChecker on Ethereum/Solidity. By experiments on private and public Ethereum testnets, we extensively evaluate the cost of the ContractChecker in comparison with that of existing client-based log auditing works. The result shows the ContractChecker can scale to hundreds of clients and save client costs by more than one order of magnitude. The evaluation result verifies our design motivation of delegating log auditing to the Blockchain in ContractChecker.

Original languageEnglish (US)
Title of host publicationSecurity and Privacy in Communication Networks - 15th EAI International Conference, SecureComm 2019, Proceedings
EditorsSongqing Chen, Kim-Kwang Raymond Choo, Xinwen Fu, Wenjing Lou, Aziz Mohaisen
Number of pages24
ISBN (Print)9783030372279
StatePublished - 2019
Event15th International Conference on Security and Privacy in Communication Networks, SecureComm 2019 - Orlando , United States
Duration: Oct 23 2019Oct 25 2019

Publication series

NameLecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering, LNICST
Volume304 LNICST
ISSN (Print)1867-8211


Conference15th International Conference on Security and Privacy in Communication Networks, SecureComm 2019
Country/TerritoryUnited States


  • Blockchain applications
  • Blockchain security
  • Cloud storage
  • Storage consistency

ASJC Scopus subject areas

  • Computer Networks and Communications


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