Healthcare is experiencing a rapid increase in medical records, requiring confidentiality and data integrity. Privacy plays a significant role in healthcare security. In general, users used to share data through insecure channels, and attacks may occur. Therefore, the healthcare system should ensure a secure authentication process. The proposed model uses blockchain technology to share and store patient data securely. For secure data access, the authentication process is to be performed between users and the blockchain using cryptographic algorithms. The proposed protocol uses the zero-knowledge proof (ZKP) embedded with the post-quantum cryptography technique NTRUEncrypt for the authenticating process, which is resistant to all attacks. The security analysis of the proposed protocol is performed through formal security verification using the Scyther tool and informal security analysis. The security analysis proves that the proposed protocol is resistant to well-known attacks. In addition, the proposed protocol provides better performance than existing models.