Cloud Data Sharing System with Enhanced Effectiveness for Flexible User Revocation

Attribute revocation is a secure data-sharing system that allows user revocation of shared data. The most effective attribute revocation scheme is still less effective in the revocation process. When revoking a user's access rights to a specified ciphertext, both that ciphertext and the keys of all other users must be updated. Similarly, when revoking a user from accessing all ciphertexts, all ciphertexts related to the revoked user and the keys of all non-revoked users must be updated, with computational cost linear to the number of attributes associated with the revoked user. In this work, to enhance the effectiveness of revocation, we design a cloud data-sharing system that supports flexible revocation. By introducing edge-server-assisted key puncturing techniques, our approach eliminates the need to update ciphertext and other users' keys when revoking a user's access rights to a specific ciphertext. Additionally, we leverage key splitting technology to divide data users' permissions between the data owner and the authority, ensuring that the update overhead for non-revoked users remains constant when revoking a user's access to all ciphertexts. On resource-constrained devices, when involving 50 attributes, non-revoked users only need approximately 0.02 milliseconds to update their keys, resulting in a 25x improvement in update speed.