Linear Encryption with Keyword Search
Nowadays an increasing amount of data stored in the public cloud need to be searched remotely for fast accessing. For the sake of privacy, the remote files are usually encrypted, which makes them difficult to be searched by remote servers. It is also hard
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Abstract. Nowadays an increasing amount of data stored in the public cloud need to be searched remotely for fast accessing. For the sake of privacy, the remote files are usually encrypted, which makes them difficult to be searched by remote servers. It is also harder to efficiently share encrypted data in the cloud than those in plaintext. In this paper, we develop a searchable encryption framework called Linear Encryption with Keyword Search (LEKS) that can semi-generically convert some existing encryption schemes meeting our Linear Encryption Template (LET) to be searchable without re-encrypting all the data. For allowing easy data sharing, we convert a Key-Policy Attributed-Based Encryption (KP-ABE) scheme to a Key-Policy Attributed-Based Keyword Search (KP-ABKS) scheme as a concrete instance of our LEKS framework, making both the encrypted data and the search functionality under fine-grained access control. Notably, the resulting KP-ABKS is the first proven secure ABKS scheme with IND-sCKA security in the random oracle model, assuming the hardness of the -DCBDH problem derived from the (P, f )-DBDH problem family. Keywords: Searchable encryption
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· Keyword search · Cloud security
Introduction
Cloud computing [14] provides on-demand computing resources that are accessible via the Internet, including computing power and data storage. With the convenient cloud services, users can outsource their computing resources to the cloud, and access them through terminals with low computing capabilities, such as mobile devices. Usually, those terminals also have low network connectivity due to the transmission technology, access cost, and other factors. In terms of data storage, one important function is data search. Since all the user data are stored on the cloud server, users have to send search queries to the server to search for the data containing certain keywords. However, the normal search operation for plaintext is no longer working when data privacy is considered, since all the data are encrypted and cannot be read by the server. To perform search on encrypted data, it is impractical for the user to do the search locally with all the data downloaded from the server, due to the high c Springer International Publishing Switzerland 2016 J.K. Liu and R. Steinfeld (Eds.): ACISP 2016, Part II, LNCS 9723, pp. 187–203, 2016. DOI: 10.1007/978-3-319-40367-0 12
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demand on the bandwidth. It is also impractical to give the server the user secret key due to privacy concerns. Thus searchable encryption has been introduced such that the search operation is performed by the server, but the server cannot get any meaningful information from the search query or the encrypted data. In searchable encryption, all the data files and their associated keywords are encrypted. To search for the data with certain keyword, the user generates a trapdoor for the keyword and enquires the server with the trapdoor. The server searches the whole database to locate the data where the encrypted keyword matches the keyword embedd
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