Blockchain-based Privacy-Preserving Group Data Auditing with Secure User Revocation

Progress in cloud computing makes group data sharing in outsourced storage a reality. People join in group and share data with each other, making team work more convenient. This new application scenario also faces data security threats, even more complex. When a user quit its group, remaining data block sig-natures must be re-signed to ensure security. Some researchers noticed this problem and proposed a few works to relieve computing overhead on user side. However, considering the privacy and security need of group auditing, there still lacks a comprehensive solution to implement secure group user revocation, sup-porting identity privacy preserving and collusion attack resistance. Aiming at this target, we construct a concrete scheme based on ring signature and smart con-tracts. We introduce linkable ring signature to build a kind of novel meta data for integrity proof enabling anonymous verification. And the new meta data sup-ports secure revocation. Meanwhile, smart contracts are using for resisting possible collusion attack and malicious re-signing computation. Under the combined effectiveness of both signature method and blockchain smart contracts, our proposal supports reliable user revocation and signature re-signing, without revealing any user identity in the whole process. Security and performance analysis com-pared with previous works prove that the proposed scheme is feasible and efficient.