Improved blockchain-based user authentication protocol with ring signature for internet of medical things

In the field of e-healthcare, smart medical sensors are responsible for consistently collecting, transmitting, and communicating real-time data to support immediate decision-making, both within and between healthcare organizations. Privacy-preserving authentication is required, even when the sensors roam between different networks. Existing authentication protocols rely on centralized authentication servers and pose a number of challenges, including a single point of failure, performance bottlenecks, scalability challenges, and privacy concerns. Hence, a secure mutual authentication mechanism using Blockchain is essential in preventing attacks. In this paper, an Improved Chain Code Blockchain-based Key Agreement Authentication Mechanism (CCBKAAM) using the merits of SM9-based Secure Threshold Ring Signature (SM9-STRS) is proposed for achieving privacy and security. This proposed mechanism uses multiple key generation-based cipher identification algorithms for parameter maintenance. The integrated threshold ring signature prevents the limitations of the single key generation scheme. It uses Chain Codes over the Ethereum network for constructing the blocks during the process of mutual user authentication with trust equity score-based Improved PBFT Voting protocol for reaching consensus during authentication. This authentication protocol adopted blockchain for the objective of storing the identities and associated parameters to support the entities under communication during the process of authentication. The formal and informal verification of the proposed CCBKAAM confirmed its potentiality in resisting most of the possible attacks the IoMT is vulnerable to. The communication and computation overhead during the implementation are determined to be significantly lowered by 32.19% and 28.94%, better than the compared baseline blockchain-based mutual authentication. The performance analysis proved that this proposed CCBKAAM scheme is also potent in minimizing the storage overhead up to maximized level of 35.42%.