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Abstract
Data deduplication is a technique for eliminating duplicate copies of data, and has been widely used in cloud storage to reduce storage space and upload bandwidth. Promising as it is, an arising challenge is to perform secure deduplication in cloud storage. Although convergent encryption has been extensively adopted for secure deduplication, a critical issue of making convergent encryption practical is to efficiently and reliably manage a huge number of convergent keys. This paper makes the first attempt to formally address the problem of achieving efficient and reliable key management in secure deduplication. The project first introduces a baseline approach in which each user holds an independent master key for encrypting the convergent keys and outsourcing them to the cloud. However, such a baseline key management scheme generates an enormous number of keys with the increasing number of users and requires users to dedicatedly protect the master keys. To this end, this project proposes Dekey, a new construction in which users do not need to manage any keys on their own but instead securely distribute the convergent key shares across multiple servers.
In addition, the paper focuses on trade-offs between storage cost and rekeying cost for secure multicast based on hierarchical tree structure. Membership in secure multicast groups is dynamic and requires multiple updates in single time frame. The project presents a family of algorithms that provide a trade-off between the number of keys maintained by users and the time required for rekeying due to revocation of multiple users. It is shown that some well-known algorithms in the literature are members of this family. The project shows that algorithms in this family can be used to reduce the cost of rekeying when compared with previous solutions while keeping the number of keys manageable. It also describes a scheme to reduce the number of secrets further when revocations are periodic.