Hades: Practical Decentralized Identity with Full Accountability and Fine-grained Sybil-resistance

Abstract

Decentralized identity (DID), the idea of giving users complete control over their identity-related data, is being used to solve the privacy tension in the identity management of decentralized applications (Dapps). While existing approaches do an excellent job of solving the privacy tension, they have not adequately addressed the accountability and Sybil-resistance issues. Moreover, these approaches have a considerable gas overhead, making them impractical for Dapps. We presented Hades, a novel practical DID system supporting full accountability and fine-grained Sybil-resistance while providing strong privacy properties. Hades supports three aspects of accountability, i.e., auditability, traceability, and revocation. Hades is the first DID system that supports accountability in all these three aspects. Hades is also the first DID system that supports fine-grained Sybil-resistance, enabling Dapps to customize personalized Sybil resistance strategies based on users' identity attributes. Hades can run efficiently on the Ethereum Virtual Machine (EVM). We implemented and evaluated Hades. The benchmarks showed that Hades has the lowest gas cost incurred on EVM as far as we know. Also, we presented a case study on attribute-associated fair NFT distribution ("airdrops") where all previous works failed, whereas we gave a solution leveraging Hades.