Abstract: Public key infrastructure (PKI) system provides very important security services for the implementation of e-commerce, e-government and office automation. This paper builds a certificate authority (CA) based on blockchain and smart contract and proposes a dual blockchain-based distributed PKI model. As used in medical application scenarios, the PKI model can manage certificates and patient information with blockchain and smart contract technology, realize the privacy protection and access control of patient information, and solve the problems of single point of failure, multi-CA mutual trust, insecure certificate issuance, certificate transparency and rapid verification in traditional PKI. Security analysis and experiments show that the proposed model can solve a variety of problems existing in traditional and existing single-chain PKI models, effectively protect patient privacy, and significantly improve the efficiency of certificate issuance and validation.

Key words: public key infrastructure (PKI), certificate authority (CA), blockchain, smart contract