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Review of Techniques for Privacy-Preserving Blockchain Systems

Privacy plays a central role in many application domains that utilize blockchain technology. It is central in Personal Data Management, Electronic Health records, or systems that interact with any public institution. However, blockchains are subject to potential privacy issues such as transaction linkability, compliance with data protection regulations, on-chain data privacy, and malicious smart contracts. To deal with these challenges, novel privacy-preserving solutions based on crypto-privacy techniques are emerging. The goal of this survey is to provide insights into the privacy-preserving techniques associated with blockchain. We analyse the existing privacy-preserving mechanisms for blockchain and propose a framework that categorizes the main techniques examined. Furthermore, we summarize some typical applications of blockchain where the privacy protection is the main requirement.