A Verifiable and Fair Attribute-Based Proxy Re-Encryption Scheme for Data Sharing in Clouds

Cloud computing has been rapidly embraced in the healthcare industry, which has made it possible to store and share the processed Electronic Medical Records in large volumes. Nevertheless, due to the property of third-party cloud servers to store sensitive medical data, this installation may result in significant threats of security as per the data privacy, fine- grained access control, and trust. Even though the Attribute- Based Encryption (ABE) has the advantage of providing potent access-control capabilities, it does not have effective secure data-delegation measures. Attribute-based Proxy Re-encryption (ABPRE) can address this weakness by giving cloud providers the ability to re-encrypt ciphertexts on behalf of legitimate secondary reimbursees. However, the current ABPRE schemes have two significant weaknesses: verifiability, since users are not able to determine that the cloud has performed the transformation of the data appropriately, and fairness, since the cloud servers cannot prove their goodwill in the face of malicious claims by the users. This paper thus presents and compares a new scheme of Verifiable and Fair Attribute-based Proxy Re-Encryption (VF- ABPRE). The cryptographic architecture is a hybrid approach that leverage the power of computational capabilities of AES to provide efficient encapsulation of data as well as leverage the use of VF-ABPRE to provide a finer level of security on key encapsulation. A fairness system was integrated, which is based on cryptographic commitments, so that as a user and a cloud provider and can resolve a conflict in a mathematically provable way. The application is developed in Python and Flask and performance measurement proves that the system can be used as a practical implementation in the area of medical data sharing.