Private search over big data leveraging distributed file system and parallel processing

In this work, we identify the security and privacy problems associated with a certain Big Data application, namely secure keyword-based search over encrypted cloud data and emphasize the actual challenges and technical difficulties in the Big Data setting. More specifically, we provide definitions from which privacy requirements can be derived. In addition, we adapt an existing work on privacy-preserving keyword-based search method to the Big Data setting, in which, not only data is huge but also changing and accumulating very fast. Our proposal is scalable in the sense that it can leverage distributed file systems and parallel programming techniques such as the Hadoop Distributed File System (HDFS) and the MapReduce programming model, to work with very large data sets. We also propose a lazy idf-updating method that can efficiently handle the relevancy scores of the documents in a dynamically changing, large data set. We empirically show the efficiency and accuracy of the method through extensive set of experiments on real data

Efficient and secure ranked multi-keyword search on encrypted cloud data

Information search and document retrieval from a remote database (e.g. cloud server) requires submitting the search terms to the database holder. However, the search terms may contain sensitive information that must be kept secret from the database holder. Moreover, the privacy concerns apply to the relevant documents retrieved by the user in the later stage since they may also contain sensitive data and reveal information about sensitive search terms. A related protocol, Private Information Retrieval (PIR), provides useful cryptographic tools to hide the queried search terms and the data retrieved from the database while returning most relevant documents to the user. In this paper, we propose a practical privacy-preserving ranked keyword search scheme based on PIR that allows multi-keyword queries with ranking capability. The proposed scheme increases the security of the keyword search scheme while still satisfying efficient computation and communication requirements. To the best of our knowledge the majority of previous works are not efficient for assumed scenario where documents are large files. Our scheme outperforms the most efficient proposals in literature in terms of time complexity by several orders of magnitude

Distributed Searchable Symmetric Encryption

Searchable Symmetric Encryption (SSE) allows a client to store encrypted data on a storage provider in such a way, that the client is able to search and retrieve the data selectively without the storage provider learning the contents of the data or the words being searched for. Practical SSE schemes usually leak (sensitive) information during or after a query (e.g., the search pattern). Secure schemes on the other hand are not practical, namely they are neither efficient in the computational search complexity, nor scalable with large data sets. To achieve efficiency and security at the same time, we introduce the concept of distributed SSE (DSSE), which uses a query proxy in addition to the storage provider.\ud We give a construction that combines an inverted index approach (for efficiency) with scrambling functions used in private information retrieval (PIR) (for security). The proposed scheme, which is entirely based on XOR operations and pseudo-random functions, is efficient and does not leak the search pattern. For instance, a secure search in an index over one million documents and 500 keywords is executed in less than 1 second

An efficient scheme of common secure indices for conjunctive keyword-based retrieval on encrypted data

We consider the following problem: members in a dynamic group retrieve their encrypted data from an untrusted server based on keywords and without any loss of data confidentiality and member’s privacy. In this paper, we investigate common secure indices for conjunctive keyword-based retrieval over encrypted data, and construct an efficient scheme from Wang et al. dynamic accumulator, Nyberg combinatorial accumulator and Kiayias et al. public-key encryption system. The proposed scheme is trapdoorless and keyword-field free. The security is proved under the random oracle, decisional composite residuosity and extended strong RSA assumptions

Private search over big data leveraging distributed file system and parallel processing

As the new technologies recently became widespread, enormous amount of data started to be generated in very high speeds and stored in untrusted servers. The big data concept covers not only the exceptional size of the datasets, but also high data generation rate and large variety of data types. Although the Big Data provides very tempting benefits, the security issues are still an open problem. In this thesis, we identify security and privacy problems associated with a certain big data application, namely secure keyword-based search over encrypted cloud data and emphasize the actual challenges and technical difficulties in the big data setting. More specifically, we provide definitions from which privacy requirements can be derived. In addition, we adapt an existing work on privacy-preserving keyword-based search method, which is one of the fundamental operations that can be performed over encrypted data, to the big data setting, in which, not only data is huge but also changing and accumulating very fast. Therefore, in the big data setting, a secure index that allows search over encrypted data should be constructed and updated very fast in addition to an efficient and effective keyword-based search operation method. Our proposal is scalable in the sense that it can leverage distributed file systems and parallel programming techniques such as the Hadoop Distributed File System (HDFS) and the MapReduce programming model to work with very large datasets. We also propose a lazy idf-updating method that can efficiently handle the relevancy scores of the documents in dynamically changing and large datasets. We empirically show the efficiency and accuracy of the method through extensive set of experiments on real dat

Privacy-preserving targeted advertising scheme for IPTV using the cloud

Targeted advertising is an emerging business area that provides effective services for advertisers and end users. Advertising agencies need information about users to send them targeted advertisements. However, uncontrolled access to users' sensitive information for advertising purposes violates the privacy of individuals. Therefore, efficient techniques must be used to not only preserve users privacy but also enable advertisers to reach right users. In this thesis, we present a privacy-preserving scheme for targeted advertising via the Internet Protocol TV (IPTV). The scheme uses a communication model involving a collection of viewers/subscribers, a content provider (IPTV), an advertiser, and a cloud server. To provide high quality directed advertising service, the advertiser can utilize not only demographic information of subscribers, but also their watching habits. The latter includes watching history, preferences for IPTV content and watching time, which are published on the cloud server periodically along with anonymized demographics (e.g. weekly). Since the published data may leak sensitive information about subscribers, it is safeguarded using cryptographic techniques in addition to the anonymization of demographics. The techniques used by the advertiser, which can be manifested in its queries to the cloud, are considered (trade) secrets and therefore are protected as well. The cloud is oblivious to the published data, the queries of the advertiser as well as its own responses to these queries. Only a legitimate advertiser, endorsed with a so-called trapdoor by the IPTV, can query the cloud and utilize the query results. The performance of the proposed scheme is evaluated with experiments, which show that the scheme is suitable for practical usage