SaTC: CORE: Small: Collaborative: A Broad Treatment of Privacy in Blockchains

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Blockchains provide a new perspective on secure, decentralized information sharing and are projected to be the technology of the future. Blockchains were first introduced as the underlying mechanism of cryptocurrencies and are used to secure financial transactions without the need for a central trusted party. Today, blockchains are also recognized for their potential advantages in various contexts ranging from identity management to health data records. However, despite being such a promising tool, the data posted on a blockchain is public and immortally captured and thus the privacy of the users can be massively violated if privacy concerns are not taken into consideration. The goals of this project are to develop a formal model for privacy in blockchains and privacy-preserving tools.This project develops a framework that captures privacy requirements for transactions, data blocks and the mining process under a threat model that reflects the adversarial capabilities over the Internet (i.e., composable security). Building on this framework, the researchers investigate new privacy-preserving mechanisms for existing blockchain payment systems and the design of new blockchain-based payment systems with built-in privacy properties that do not require a trusted setup. Next, the researchers investigate new privacy requirements like hiding the identity of the miner which is relevant in scenarios where mining a block might signify the endorsement of the information included in the block. Finally, the researchers develop techniques to guarantee accountability even in a privacy-preserving setting where privacy should be preserved only so long as a pre-specified bad behavior is not detected.