ABSTRACT:
In this paper proposes Searchable Public-Key Ciphertexts with Hidden Structures (SPCHS) for keyword search as fast as possible without sacrificing semantic security of the encrypted keywords. In SPCHS, all keyword-searchable ciphertexts are structured by hidden relations, and with the search trapdoor corresponding to a keyword, the minimum information of the relations is disclosed to a search algorithm as the guidance to find all matching ciphertexts efficiently.
We construct a SPCHS scheme from scratch in which the ciphertexts have a hidden star-like structure. We prove our scheme to be semantically secure in the Random Oracle (RO) model. The search complexity of our scheme is dependent on the actual number of the ciphertexts containing the queried keyword, rather than the number of all ciphertexts.
Finally, we present a generic SPCHS construction from anonymous identity-based encryption and collision-free full-identity malleable Identity-Based Key Encapsulation Mechanism (IBKEM) with anonymity. We illustrate two collision-free full-identity malleable IBKEM instances, which are semantically secure and anonymous, respectively, in the RO and standard models. The latter instance enables us to construct an SPCHS scheme with semantic security in the standard model.
INTRODUCTION:
We start by formally defining the concept of Searchable Public-key Ciphertexts with Hidden Structures (SPCHS) and its semantic security. In this new concept, keywordsearchable ciphertexts with their hidden structures can be generated in the public key setting; with a keyword search trapdoor, partial relations can be disclosed to guide the discovery of all matching ciphertexts. Semantic security is defined for both the keywords and the hidden structures. It is worth noting that this new concept and its semantic security are suitable for keyword-searchable ciphertexts with any kind of hidden structures. In contrast, the concept of traditional PEKS does not contain any hidden structure among the PEKS ciphertexts; correspondingly, its semantic security is only defined for the keywords. Following the SPCHS definition, we construct a simple SPCHS from scratch in the random oracle (RO) model. The scheme generates keyword-searchable ciphertexts with a hidden star-like structure. The search performance mainly depends on the actual number of the ciphertexts containing the queried keyword. For security, the scheme is proven semantically secure based on the Decisional Bilinear DiffieHellman (DBDH) assumption in the RO model.
We build a generic SPCHS construction with IdentityBased Encryption (IBE) and collision-free full-identity malleable IBKEM. The resulting SPCHS can generate keyword-searchable ciphertexts with a hidden star-like structure. Moreover, if both the underlying IBKEM and IBE have semantic security and anonymity (i.e. the privacy of receivers’ identities), the resulting SPCHS is semantically secure. As there are known IBE schemes [4], [5], [6], [7] in both the RO model and the standard model, an SPCHS construction is reduced to collision-free full-identity malleable IBKEM with anonymity. We proposed several IBKEM schemes to construct Verifiable Random Functions2 (VRF). We show that one of these IBKEM schemes is anonymous and collision-free fullidentity malleable in the RO model. We transform this IBE scheme into a collision-free full-identity malleable IBKEM scheme with semantic security and anonymity in the standard model. Hence, this new IBKEM scheme allows us to build SPCHS schemes secure in the standard model with the same search performance as the previous SPCHS construction from scratch in the RO model.
LITRATURE SURVEY
TITLE: FUZZY KEYWORD SEARCH OVER ENCRYPTED DATA IN CLOUD COMPUTING
AUTOHR: Li J., Wang Q., Wang C., Cao N., Ren K., Lou W
PUBLISH: IEEE INFOCOM 2010, pp. 1-5. (2010)
EXPLANATION:
As Cloud Computing becomes prevalent, more and more sensitive information are being centralized into the cloud. For the protection of data privacy, sensitive data usually have to be encrypted before outsourcing, which makes effective data utilization a very challenging task. Although traditional searchable encryption schemes allow a user to securely search over encrypted data through keywords and selectively retrieve files of interest, these techniques support only exact keyword search. That is, there is no tolerance of minor typos and format inconsistencies which, on the other hand, are typical user searching behavior and happen very frequently. This significant drawback makes existing techniques unsuitable in Cloud Computing as it greatly affects system usability, rendering user searching experiences very frustrating and system efficacy very low. In this paper, for the first time we formalize and solve the problem of effective fuzzy keyword search over encrypted cloud data while maintaining keyword privacy. Fuzzy keyword search greatly enhances system usability by returning the matching files when users’ searching inputs exactly match the predefined keywords or the closest possible matching files based on keyword similarity semantics, when exact match fails. In our solution, we exploit edit distance to quantify keywords similarity and develop an advanced technique on constructing fuzzy keyword sets, which greatly reduces the storage and representation overheads. Through rigorous security analysis, we show that our proposed solution is secure and privacy-preserving, while correctly realizing the goal of fuzzy keyword search.
TITLE: ANONYMOUS FUZZY IDENTITY-BASED ENCRYPTION FOR SIMILARITY SEARCH
AUTOHR: Cheung D. W., Mamoulis N., Wong W. K., Yiu S. M., Zhang
PUBLISH: ISAAC 2010. LNCS, vol. 6505, pp. 61-72. Springer, Heidelberg (2010)
EXPLANATION:
The predicate that was studied in the very beginning is “exact keyword matching”. That is, whether the value hidden by the token is equal to the attribute value hidden in the ciphertext. Schemes that only provide data item security are basically “Identity-Based Encryption”. Schemes protecting both the data item and the attributes were initiated in the private-key setting public-key setting. Relationship between and “Anonymous Identity-Based Encryption” was revisited in range query as the predicate was also considered. Boneh et al. devised an Augmented Broadcast Encryption which allows checking if the attribute value falls within a range on encrypted data. Their scheme also provides attribute protection. Then, Boneh and Waters extended it to multi-dimensional range query.
However, there is no practical scheme supporting this predicate with attribute protection in public-key settings investigated this problem in the private-key setting and is IND2-CKA secure. His scheme is in a public-key setting. However, the scheme requires the threshold value t to be fixed in the setup time. Our work is using as a framework provided schemes for handling predicates represented as inner products. Their formulation of using inner products with bounded disjunction is powerful. We show how to reduce inner products to hamming distance similarity comparison predicate, and then derive a slightly different encryption scheme for better performance when considering the inequality case. In our work, we consider the problem of attribute protection in public-key setting. In some applications, people may also want to provide protection to predicate (“the token”), which is inherently unachievable in public-key setting. Note that a predicate encryption supporting inner product in private-key setting has been devised in which can provide predicate privacy
TITLE: TRAPDOOR PRIVACY IN ASYMMETRIC SEARCHABLE ENCRYPTION SCHEMES
AUTOHR: Arriaga A., Tang Q., Ryan P
PUBLISH: AFRICACRYPT 2014. LNCS, vol. 8469, pp. 31-50. Springer, Heidelberg (2014)
EXPLANATION:
Asymmetric searchable encryption allows searches to be carried over ciphertexts, through delegation, and by means of trapdoors issued by the owner of the data. Public Key Encryption with Keyword Search (PEKS) is a primitive with such functionality that provides delegation of exact-match searches. As it is important that ciphertexts preserve data privacy, it is also important that trapdoors do not expose the user’s search criteria. The difficulty of formalizing a security model for trapdoor privacy lies in the verification functionality, which gives the adversary the power of verifying if a trapdoor encodes a particular keyword. In this paper, we provide a broader view on what can be achieved regarding trapdoor privacy in asymmetric searchable encryption schemes, and bridge the gap between previous definitions, which give limited privacy guarantees in practice against search patterns. We propose the notion of Strong Search Pattern Privacy for PEKS and construct a scheme that achieves this security notion.
SYSTEM ANALYSIS
EXISTING SYSTEM:
Existing semantically secure PEKS schemes take search time linear with the total number of all ciphertexts. This makes retrieval from large-scale databases prohibitive. Therefore, more efficient search performance is crucial for practically deploying PEKS schemes. One of the prominent works to accelerate the search over encrypted keywords in the public-key setting enabling search over encrypted keywords to be as effi- cient as the search for unencrypted keywords, such that a ciphertext containing a given keyword can be retrieved in time complexity logarithmic in the total number of all ciphertexts.
This is reasonable because the encrypted keywords can form a tree-like structure when stored according to their binary values. However, deterministic encryption has two inherent limitations. First, keyword privacy can be guaranteed only for keywords that are a priori hardto-guess by the adversary (i.e., keywords with high minentropy to the adversary); second, certain information of a message leaks inevitably via the ciphertext of the keywords since the encryption is deterministic. Hence, deterministic encryption is only applicable in special scenarios.
Observe that a keyword space is usually of no high minentropy in many scenarios. Semantic security is crucial to guarantee keyword privacy in such applications. Thus the linear search complexity of existing schemes is the major obstacle to their adoption. Unfortunately, the linear complexity seems to be inevitable because the server has to scan and test each ciphertext, due to the fact that these ciphertexts (corresponding to the same keyword or not) are indistinguishable to the server.
DISADVANTAGES:
Each sender should be able to generate the keyword-searchable ciphertexts with the hidden star-like structure by the receiver’s public-key; the server having a keyword search trapdoor should be able to disclose partial relations, which is related to all matching ciphertexts. Semantic security is preserved 1) if no keyword search trapdoor is known, all ciphertexts are indistinguishable, and no information is leaked about the structure, and 2) given a keyword search trapdoor, only the corresponding relations can be disclosed, and the matching ciphertexts leak no information about the rest of ciphertexts, except the fact that the rest do not contain the queried keyword.
PROPOSED SYSTEM:
We propose methods of searchable Public-key Ciphertexts with Hidden Structures (SPCHS) and its semantic security. In this new concept, keywordsearchable ciphertexts with their hidden structures can be generated in the public key setting; with a keyword search trapdoor, partial relations can be disclosed to guide the discovery of all matching ciphertexts. Semantic security is defined for both the keywords and the hidden structures. Following the SPCHS definition, we construct a simple SPCHS from scratch in the random oracle (RO) model. The scheme generates keyword-searchable ciphertexts with a hidden star-like structure. The search performance mainly depends on the actual number of the ciphertexts containing the queried keyword.
We are also interested in providing a generic SPCHS construction to generate keyword-searchable ciphertexts with a hidden star-like structure. Our generic SPCHS is inspired by several interesting observations on Identity-Based Key Encapsulation Mechanism (IBKEM). We build a generic SPCHS construction with IdentityBased Encryption (IBE) and collision-free full-identity malleable IBKEM. The resulting SPCHS can generate keyword-searchable ciphertexts with a hidden star-like structure. Moreover, if both the underlying IBKEM and IBE have semantic security and anonymity (i.e. the privacy of receivers’ identities), the resulting SPCHS is semantically secure. As there are known IBE schemes in both the RO model and the standard model, an SPCHS construction is reduced to collision-free full-identity malleable IBKEM.
ADVANTAGES:
IBKEM schemes to construct Verifiable Random Functions2 (VRF) [8]. We show that one of these IBKEM schemes is anonymous and collision-free fullidentity malleable in the RO model utilized the “approximation” of multilinear maps to construct a standard-model version of Boneh-and-Franklin (BF) IBE scheme.
We transform this IBE scheme into a collision-free full-identity malleable IBKEM scheme with semantic security and anonymity in the standard model. Hence, this new IBKEM scheme allows us to build SPCHS schemes secure in the standard model with the same search performance as the previous SPCHS construction from scratch in the RO model.
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