Data Sharing with Fine-Grained Access Control for Multi-tenancy Cloud Storage System

Data sharing is one of the most significant applications of cloud computing. For security and privacy concerns, clients generally encrypt their data before upload them to the cloud. The existing data sharing schemes either entirely rely on the cloud to enforce access control or inevitably involve a trusted third party (TTP) to perform secret key distribution. This thesis proposes a secure data sharing scheme without TTP involved. Our scheme allows users to classify their data and achieves a fine-gained access authorization. The key-distribution is integrated with the user authorization and data sharing procedure. In terms of security, except for semi-honest cloud service provider and external adversary, we also take internal adversary into consideration and analysis security in this strong model.