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Blockchain is one of the technology innovations for sharing data across organizations through a peer to peer overlay network. Many blockchain- based data sharing applications, such as sharing Electronic Health Records (EHRs) among different Care Delivery Organizations (CDOs), require privacy preserving verification services with dual capabilities. On one hand, the users want to verify the authenticity of EHR data as well as the identity of the signer. On the other hand, the signer wants to keep his real identity private such that others cannot trace and infer his identity information. However, typical blockchain systems that use pseudonyms as public keys, such as Bitcoin's blockchain, cannot support such privacy-preserving verification. In such systems, it is hard to verify the authenticity of signer's identity, and adversaries or curious parties can guess the real identity from the series of statements and actions taken with a specific pseudonym through inference attacks, such as by transaction graph analysis. In this paper, we propose a decentralized attribute- based signature scheme for healthcare blockchain, which provides efficient privacy-preserving verification of authenticity of EHR data and signer's identity. We also describe a holistic on-chain and off- chain collaborative storage system for efficient storage and verification EHR data. The analysis and experiments show that our scheme is effective and deployable.
Sun et al. (2018) studied this question.