Revocable certificateless proxy re-signature with signature evolution for EHR sharing systems☆

Cloud computing has revolutionized in the healthcare industry, particularly in the management and accessibility of Electronic health records (EHR). However, maintaining the integrity and authenticity of EHR in cloud environments remains a crucial concern. To tackle this challenge, certificateless proxy re-signature is a promising cryptographic primitive for developing a practical EHR sharing system in the cloud. User revocation is a necessary issue in such system, but revocation introduces anew challenge, namely the continued validity of signatures from revoked users. A conventional method to solve this problem is to make the unrevoked users re-sign those valid EHR by using their current signing keys, which brings a lot of burden to the users. Therefore, we should establish an efficient mechanism to ensure that only signatures of valid data from non-revoked users can pass verification. In this paper, we propose a notion called revocable certificateless proxy re-signature with signature evolution (RCLPRS-SE), which allows for dynamic management of users and the ability to update signatures efficiently in accordance with evolving data requirements. We present a concrete construction of RCLPRS-SE and provide formal security proofs in the standard model. Compared with the existing related works, our scheme has a significant advantage in terms of signature updating efficiency.