Efficient Privacy Preserving Key Management for Public Cloud Networks

Abstract: Most applications and documents are stored in a public cloud for storage and management purposes in a cloud computing environment. The major advantages of storing applications and documents in public cloud are lower cost through use of shared computing resources and no upfront infrastructure costs. However, in this case the management of data and other services is insecure. Therefore, security is a major problem in a public cloud as the cloud and the network are open to many other users. In order to provide security, it is necessary for data owners to store their data in the public cloud in a secure way and to use an appropriate access control scheme. Designing a computation and communication efficient key management scheme to selectively share documents based on fine-grained attribute-based access control policies in a public cloud is a challenging task. There are many existing approaches that encrypt documents prior to storage in the public cloud: These approaches use different keys and a public key cryptographic system to implement attribute-based encryption and/or proxy re-encryption. However, these approaches do not efficiently handle users joining and leaving the system when identity attributes and policies change. Moreover, these approaches require keeping multiple encrypted copies of the same documents, which has a high computational cost or incurs unnecessary storage costs. Therefore, this project focused on the design and development of an efficient key management scheme to allow the data owner to store data in a cloud service in a secure way. Additionally, the proposed approach enables cloud users to access the data stored in a cloud in a secure way. Many researchers have proposed key management schemes for wired and wireless networks. All of these existing key management schemes differ from the key management schemes proposed in this thesis. First, the key management scheme proposed in this thesis increases access level security. Second, the proposed key management scheme minimizes the computational complexity of the cloud users by performing only one mathematical operation to find the new group key that was computed earlier by the data owner. In addition, this proposed key management scheme is suitable for a cloud network. Third, the proposed key distribution and key management scheme utilizes privacy preserving methods, thus preserving the privacy of the user. Finally, a batch key updating algorithm (also called batch rekeying) has been proposed to reduce the number of rekeying operations required for performing batch leave or join operations. The key management scheme proposed in this thesis is designed to reduce the computation and communication complexity in all but a few cases, while increasing the security and privacy of the data.