Identity-Based Key Aggregate Cryptosystem from Multilinear Maps

The key-aggregate cryptosystem~(KAC) proposed by Chu et al. in 2014 offers a solution to the flexible access delegation problem in shared data environments such as the cloud. KAC allows a data owner, owning $N$ classes of encrypted data, to securely grant access to any subset $S$ of these data classes among a subset $\hat{S}$ of data users, via a single low overhead \emph{aggregate key} $K_{\mathcal{S}}$. Existing constructions for KAC are efficient in so far they achieve constant size ciphertexts and aggregate keys. But they resort to a public parameter that has size linear in the number of data classes $N$, and require $O(M\u27M)$ secure channels for distribution of aggregate keys in a system with $M\u27$ data owners and $M$ data users. In this paper, we propose three different multilinear-map based KAC constructions that have at most polylogarithmic overhead for both ciphertexts and public parameters, and generate constant size aggregate keys. We further demonstrate how the aggregate keys may be efficiently broadcast among any arbitrary size subset of $M$ data users using only $O(M\u27+M)$ secure channels, in a system with $M\u27$ data owners. Our constructions are secure in the generic multilinear group model and are fully collusion resistant against any number of colluding parties. In addition, they naturally give rise to \emph{identity based} secure access delegation schemes

Data Sharing and Access Using Aggregate Key Concept

Cloud Storage is a capacity of information online in the cloud, which is available from different and associated assets. Distributed storage can provide high availability and consistent quality, reliable assurance, debacle free restoration, and reduced expense. Distributed storage has imperative usefulness, i.e., safely, proficiently, adaptably offering information to others. Data privacy is essential in the cloud to ensure that the user’s identity is not leaked to unauthorized persons. Using the cloud, anyone can share and store the data, as much as they want. To share the data in a secure way, cryptography is very useful. By using different encryption techniques, a user can store data in the cloud. Encryption and decryption keys are created for unique data that the user provides. Only a particular set of decryption keys are shared so that the data can be decrypted. A public–key encryption system which is called a Key-Aggregate cryptosystem (KAC) is presented. This system produces constant size ciphertexts. Any arrangement of secret keys can be aggregated and make them into a single key, which has the same power of the keys that are being used. This total key can then be sent to the others for decoding of a ciphertext set and remaining encoded documents outside the set stays private. The project presented in this paper is an implementation of the proposed system