Abstract: Cloud computing, is an emerging computing paradigm, enabling users to remotely store their data in a server and provide services on-demand. In cloud computing cloud users and cloud service providers are almost certain to be from different trust domains. Data security and privacy are the critical issues for remote data storage. A secure user enforced data access control mechanism must be provided before cloud users have the liberty to outsource sensitive data to the cloud for storage. With the emergence of sharing confidential corporate data on cloud servers, it is important to adopt an efficient encryption system with a fine-grained access control to encrypt outsourced data. Attribute-based encryption is a public key based encryption that enables access control over encrypted data using access policies and specified attributes. Cipher text-Policy Attribute-based Encryption (CP-ABE) is regarded as one of the most suitable scheme for data access control in cloud storage, because it gives data owners more direct control on access policies. However, it is difficult to directly apply existing CP-ABE schemes to data access control for cloud storage systems because of the attribute revocation problem. The system proposed is, to design an efficient and revocable data access control scheme for multi-authority cloud storage systems, where there are multiple authorities co-exist and each authority is able to issue attributes independently. More specifically, itís a revocable multi-authority CP-ABE scheme, to ensure the data access control.

Keywords: Cloud Storage, Access Control, Attribute Revocation, Multi-authority.