In this work we propose a new blockchain model that ensure the GDPR compliance by handling references to the sensitive data and using metadata instead of manipulate private data directly within the blockchain. We accomplish this by defining a modular architecture that relies on strong cryptographic assumptions that provide the means to guarantee that the right to be forgotten is being well enforced.

We propose a new healthcare data exchange platform for research centers, hospitals and healthcare institutions. Our model is based on a federated blockchain network that interconnect the healthcare institutions and orchestrate the data life cycle from the data publication to the data consumption. The blockchain is responsabible to keep the traceability of the whole process and we use a specially designed smart contract to control the data sharing process. Moreover, we provide the means to enforce GDPR and thus achieve a GDPR compliant model. CCS CONCEPTS• Computer systems organization → Distributed architectures; • General and reference → Design; • Software and its engineering → Peer-to-peer architectures; • Theory of computation → Cryptographic protocols.

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With the immutability property and decentralized architecture, Blockchain technology is considered as a revolution for several topics. For electronic voting, it can be used to ensure voter privacy, the integrity of votes, and the verifiability of vote results. More precisely permissioned Blockchains could be the solution for many of the e-voting issues. In this paper, we start by evaluating some of the existing Blockchain-based e-voting systems and analyze their drawbacks. We then propose a fully-decentralized e-voting system based on permissioned Blockchain. Called DABSTERS, our protocol uses a blinded signature consensus algorithm to preserve voters privacy. This ensures several security properties and aims at achieving a balance between voter privacy and election transparency. Furthermore, we formally prove the security of our protocol by using the automated verification tool, ProVerif, with the Applied Pi-Calculus modeling language.

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Creating an online electronic voting system that meets all legal requirements of election organizers and voters has constituted a real challenge for a long period of time. Permissioned Blockchains (also called Private Blockchains) are a cutting-edge invention, introduced as a security breakthrough for many existing and emerging technologies. One potential application of private Blockchain concerns e-voting systems. We propose a fully-decentralized e-voting system based on permissioned Blockchain, called DABSTERS in e-voting. Our system uses a blinded signature consensus algorithm, which is a modified version of Practical Byzantine Fault Tolerance (PBFT), to preserve voter's privacy. Our protocol ensures several security properties: voter's eligibility, vote integrity, vote secrecy, fairness, receipt freeness, individual and universal verifiability.

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