Multi-Key Searchable Encryption

We construct a searchable encryption scheme that enables keyword search over data encrypted with {\em different} keys. The scheme is practical and was designed to be included in a new system for protecting data confidentiality in client-server applications against attacks on the server

Multi-Key Searchable Encryption, Revisited

We consider a setting where users store their encrypted documents on a remote server and can selectively share documents with each other. A user should be able to perform keyword searches over all the documents she has access to, including the ones that others shared with her. The contents of the documents, and the search queries, should remain private from the server. This setting was considered by Popa et al. (NSDI \u2714) who developed a new cryptographic primitive called Multi-Key Searchable Encryption (MKSE), together with an instantiation and an implementation within a system called Mylar, to address this goal. Unfortunately, Grubbs et al. (CCS \u2716) showed that the proposed MKSE definition fails to provide basic security guarantees, and that the Mylar system is susceptible to simple attacks. Most notably, if a malicious Alice colludes with the server and shares a document with an honest Bob then the privacy of all of Bob\u27s search queries is lost. In this work we revisit the notion of MKSE and propose a new strengthened definition that rules out the above attacks. We then construct MKSE schemes meeting our definition. We first give a simple and efficient construction using only pseudorandom functions. This construction achieves our strong security definition at the cost of increasing the server storage overhead relative to Mylar, essentially replicating the document each time it is shared. We also show that high server storage overhead is not inherent, by giving an alternate (albeit impractical) construction that manages to avoid it using obfuscation

A SURVEY ON CRYPTOGRAPHIC CLOUD STORAGE WITH KEY AGGREGATE SEARCHABLE ENCRYPTION

Cloud is a new way to store large amount of data. In cloud computing, data owners host their data on cloud servers and users can access the data from cloud servers. By data outsourcing, users can be relieved from the burden of local data storage and maintenance. Cloud storage has emerged as a promising solution for providing ubiquitous, convenient, and on-demand accesses to large amounts of data shared over the Internet.Considering the practical problem of privacy preserving data sharing system based on public cloud storage which requires a data owner to distribute a large number of keys to users to enable them to access his/her documents, we for the first time propose the concept of key-aggregate searchable encryption (KASE) and construct a concrete KASE scheme. Both analysis and evaluation results confirm that our work can provide an effective solution to building practical data sharing system based on public cloud storage

Sharing of Data Using Key Aggregation and Searchable Encryption

Sharing data with different users is an important functionality of the cloud. However, while enjoying the convenience provided by the cloud storage, user’s main concern is regarding the data leakage present in cloud. A promising approach to prevent this is encryption of data before uploading onto cloud. The desire to selectively and securely share documents with any group of users demands different documents to have different encryption keys. This necessitates the distribution of a large number of keys to users for both encryption and search, those users will have to securely store these keys, and submit an equally large number of keyword trapdoors to the cloud in order to perform search. In this paper, we resolve this problem by extending the concept of Key Aggregate Searchable Encryption (KASE) scheme which employs a single aggregate key and a single trapdoor. Here, the data owner only needs to distribute a single key to a user for sharing a large number of documents, and the user only needs to submit a single trapdoor to the cloud for querying the documents. Also, we provide a functionality of selection of keyword based on their rank by the Data owner in such a way that the selected keywords describe the file. Thus, this scheme makes the management of the keys efficient and also makes the sharing of documents over the cloud more secure

Privacy-preserving data search with fine-grained dynamic search right management in fog-assisted Internet of Things

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.Fog computing, as an assisted method for cloud computing, collects Internet of Things (IoT) data to multiple fog nodes on the edge of IoT and outsources them to the cloud for data search, and it reduces the computation cost on IoT nodes and provides fine-grained search right management. However, to provide privacy-preserving IoT data search, the existing searchable encryptions are very inefficient as the computation cost is too high for the resource-constrained IoT ends. Moreover, to provide dynamic search right management, the users need to be online all the time in the existing schemes, which is impractical. In this paper, we first present a new fog-assisted privacy-preserving IoT data search framework, where the data from each IoT device is collected by a fog node, stored in a determined document and outsourced to the cloud, the users search the data through the fog nodes, and the fine-grained search right management is maintained at document level. Under this framework, two searchable encryption schemes are proposed, i.e., Credible Fog Nodes assisted Searchable Encryption (CFN-SE) and Semi-trusted Fog Nodes assisted Searchable Encryption (STFN-SE). In CFN-SE scheme, the indexes and trapdoors are generated by the fog nodes, which greatly reduce the computation costs at the IoT devices and user ends, and fog nodes are used to support offline users’ key update. In STFN-SE scheme, the semi-trusted fog nodes are used to provide storage of encrypted key update information to assist offline users’ search right update. In both schemes, no re-encryption of the keywords is needed in search right updates. The performance evaluations of our schemes demonstrate the feasibility and high efficiency of our system.National Key Research and Development ProgramNational Natural Science Foundation of ChinaSichuan Provincial Major Frontier IssuesState Key Laboratory of Integrated Services Networks, Xidian Universit

A SURVEY ON KEY-AGGREGATE SEARCHABLE ENCRYPTION FOR GROUP DATA SHARING IN CLOUD STORAGE

Security concerns over inadvertent data leaks in the cloud may greatly ease the capability of selectively sharing encrypted data with different users via public cloud storage. So designing such an encryption schemes is a key challenge which lies in the efficient management of encryption keys. When any group of selected documents need to share with any group of users a desired flexibility is required with demands different encryption keys, which are used for different documents. However this also indicates the need of securely sharing to users a large number of keys for encryption and search, and those users will have to safely save the received keys, and submit an equally large number of keywords trapdoors to the cloud in order to perform search over the shared data. The indicated purpose of safe communication, storage, and difficultly clearly renders the approach impractical. In this paper, we address this practical problem, which is greatly neglected in the literature, here we are proposing the new concept of key aggregate searchable encryption and instantiating the concept through a concrete KASE scheme. In this scheme, the documents are shared by just submitting a single trapdoor by the user to the cloud for querying and this single key is being received by the data owner for sharing large number of documents. Our proposed scheme can confirm prove both the safety as well as practically efficient channels by security analysis and performance evaluation. It can securely store and manage the users in their devices. In order to perform a keyword search over many files a large number of trapdoors must be generated by users and submitted to the cloud. Such a system with secure communication, storage and computational complexity may lead to inefficiency and impracticality

Aggregation of Key with Searchable Encryption for Group Data Sharing

Data sharing is an important functionality in cloud storage. In this article, we show how to securely, efficiently, and flexibly share data with others in cloud storage. We describe new public-key cryptosystems which produce constant-size ciphertexts such that efficient delegation of decryption rights for any set of ciphertexts are possible. The novelty is that one can aggregate any set of secret keys and make them as compact as a single key, but encompassing the power of all the keys being aggregated. In other words, the secret key holder can release a constant-size aggregate key for flexible choices of ciphertext set in cloud storage, but the other encrypted files outside the set remain confidential. This compact aggregate key can be conveniently sent to others or be stored in a smart card with very limited secure storage. We provide formal security analysis of our schemes in the standard model. We also describe other application of our schemes. In particular, our schemes give the first public-key patient-controlled encryption for flexible hierarchy, which was yet to be known