Unidirectional Identity-Based Proxy Re-Signature with Key Insulation in EHR Sharing System

The introduction of the electronic medical record (EHR) sharing system has made a great contribution to the management and sharing of healthcare data. Considering referral treatment for patients, the original signature needs to be converted into a re-signature that can be verified by the new organization. Proxy re-signature (PRS) can be applied to this scenario so that authenticity and nonrepudiation can still be insured for data. Unfortunately, the existing PRS schemes cannot realize forward and backward security. Therefore, this paper proposes the first PRS scheme that can provide key-insulated property, which can guarantee both the forward and backward security of the key. Although the leakage of the private key occurs at a certain moment, the forward and backward key will not be attacked. Thus, the purpose of key insulation is implemented. What's more, it can update different corresponding private keys in infinite time periods without changing the identity information of the user as the public key. Besides, the unforgeability of our scheme is proved based on the extended Computational Diffie-Hellman assumption in the random oracle model. Finally, the experimental simulation demonstrates that our scheme is feasible and in possession of promising properties.