Fine-Grained, Multi-key Search Control in Multi-user Searchable Encryption

Abstract

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Searchable encryption schemes support selective retrieval of encrypted data stored in the cloud storage. However, extending this scheme to support diverse set of users to selectively share and retrieve data from the cloud storage still remains as a challenge; it requires managing the access control policies of the users by a third party, the cloud provider. When multiple users are involved, the system needs to ensure that only controlled information is disclosed to a legitimate user and also a dishonest user colluding with the cloud provider cannot leak any thing beyond the granted privileges. The proposed model is designed to support fine grained search control on selected set of documents by authorized users. The system does not require shared keys or expensive trusted third parties. The search complexity is linear to the number of documents that can be accessed by an authorized user and is also secure against the possible leakage due to collusion attack. The security of the system is proved using rigorous security analysis.