Received February 5, 2021, accepted February 22, 2021, date of publication March 9, 2021, date of current version March 18, 2021. Digital Object Identifier 10.1109/ACCESS.2021.3064896 PETchain: A Blockchain-Based Privacy Enhancing Technology IBRAHIM TARIQ JAVED 1, FARES ALHARBI 2, TIZIANA MARGARIA 1, NOEL CRESPI 3, AND KASHIF NASEER QURESHI 4 1Lero—Science Foundation Ireland Research Centre for Software, University of Limerick, V94 T9PX Limerick, Ireland 2Computer Science Department, Shaqra University, Riyadh 11961, Saudi Arabia 3Institut Polytechnique de Paris, Telecom SudParis, 91011 Evry, France 4Department of Computer Science, Bahria University, Islamabad 44000, Pakistan Corresponding author: Ibrahim Tariq Javed (
[email protected]) This work is partly supported with the financial support of the Science Foundation Ireland grant 13/RC/2094_P2 and partly funded from the European Union's Horizon 2020 research and innovation programme under the Marie Skªodowska-Curie grant agreement No 754489. ABSTRACT With the increasing use of smart devices and sensors, enormous amounts of data are being generated continuously. The data is commonly stored in centralized cloud platforms and consumed by different services. The data is indeed a valuable resource for many service providers who provide advanced features and utilities to their subscribers. However, user data include personal and sensitive information which can be misused in many ways. There is no way for a subscriber to confirm that their service provider is compliant with data privacy regulations. The existing privacy enhancing techniques such as anonymization and differential privacy substantially reduce data usability while ensuring privacy. Therefore, it remains essential to provide a feasible solution that allows service providers to take advantage of user data while guaranteeing their privacy.