Notion Of Public Key Encryption Research Articles

Efficient Public Key Encryption With Outsourced Equality Test for Cloud-Based IoT Environments

Cloud-based Internet of Things (IoT) system is becoming a promising architecture in our modern society. However, cloud-based IoT system brings a number of challenges in the security aspect while improving the efficiency of data analytics. Especially, searching on encrypted data is challenging given today’s technology. Thus searchable encryption has emerged as one of the important research fields. Public key encryption with equality test (PKEET) provides a simple but useful mechanism to cryptographically protect data while keeping it available for equality test on ciphertexts. However, PKEET schemes in the literature are not suitable for cloud-based IoT system with privacy protection enhancement since the untrustworthy cloud server may be interested in query results by itself and hence reveal the private information of data owner out of the expectation of data user. Even worse, it could launch offline message recovery attack (OMRA) based on the returned query results. In this paper, we introduce a new notion of public key encryption with outsourced equality test (PKE-OET) for adapting to cloud-based IoT environments as well as providing a flexible solution to resist against OMRA without taking any information about entrusted parties as input in encryption. We formally define the security model of PKE-OET against three types of adversary including IND-CCA-I, IND-CCA-II and IND-CCA-III. We present a generic PKE-OET construction using a new variant of smooth projective hash function (SPHF) with a novel Lin-Hom property, which is of independent interest. Then we provide an efficient PKE-OET instantiation from Symmetric eXternal Diffie-Helllman (SXDH) assumption and show its practicality for cloud-based IoT environments through a series of experiments on Cloud Server and Raspberry Pi.

Public-key authenticated encryption with keyword search achieving both multi-ciphertext and multi-trapdoor indistinguishability

The notion of Public-key Encryption with Keyword Search (PEKS) was first proposed by Boneh et al. in 2004. However, almost all PEKS schemes cannot resist offline Keyword Guessing Attacks (KGA). To address this issue, Huang and Li introduced the notion of Public-key Authenticated Encryption with Keyword Search (PAEKS) in 2017. Recently, Qin et al. put forward a new security model named Multi-Ciphertext Indistinguishability (MCI), in which an adversary aims to distinguish two tuples of ciphertexts. They found that Huang and Li’s scheme cannot achieve MCI-security, so they proposed a new scheme which is able to achieve MCI-security. Furthermore, Qin et al. referred to another security model named Multi-Trapdoor Indistinguishability (MTI). They stated that the future work direction is to design a scheme which can achieve both MCI-security and MTI-security. In this paper, we present a new PAEKS scheme and prove that it is capable of achieving MCI-security and MTI-security simultaneously with the help of random oracles. Finally, we compare our scheme with other four related schemes using PBC library and provide experimental results. It turns out that our scheme achieves a higher security level with a little more cost.

Public-key encryption with keyword search: a generic construction secure against online and offline keyword guessing attacks

In public-key setting, the problem of searching for keywords in encrypted data is handled by the notion of public-key encryption with keyword search (PEKS). An important challenge in designing secure PEKS schemes is providing resistance against variants of an attack known as the keyword guessing attack (KGA). Basically, by KGA, an adversary is able to determine the searched keyword through using the data communicated in the search process. Security against offline KGA performed by both inside/outside adversaries is well-studied in the literature. However, this is not true about the online version. In this paper, we employ a technique called ciphertext re-randomization to propose a generic construction for designing PEKS schemes which are secure against both online and offline KGAs performed by outsiders. We show that compared to existing literature, our construction is more efficient in terms of computational and communication costs.

Decentralized attribute-based conjunctive keyword search scheme with online/offline encryption and outsource decryption for cloud computing

In recent years, the increasing popularity of cloud computing has led to a trend that data owners prefer to outsource their data to the clouds for the enjoyment of the on-demand storage and computing services. For security and privacy concerns, fine-grained access control and secure data retrieval for the outsourced data is of critical importance. Attribute-based keyword search (ABKS) scheme, as a cryptographic primitive which explores the notion of public key encryption with keyword search (PEKS) into the context of attribute-based encryption (ABE), can enable the data owner to flexibly share his data to a specified group of users satisfying the access policy and meanwhile, maintain the confidentiality and searchable properties of the sensitive data. However, in most of the previous ABKS schemes, the decryption service is not provided, and a fully trusted central authority is required, which is not practical in the scenario that the access policy is written over attributes or credentials issued across different trust domains and organizations. Moreover, the efficiency of storage and computation is also the bottleneck of implementation of ABKS scheme. In this paper, for the first time, we propose a decentralized ABKS scheme with conjunctive keyword search for the cloud storage system. Besides the multi-keyword search in the decentralized setting, our scheme outsources the undesirable costly operations of decryption to the cloud without degrading the user’s privacy. Furthermore, the encryption phase is also divided into two phases, an offline pre-computation phase which is independent with the plaintext message, access policy, and keyword set, and can be performed at any time when the data owner’s device is otherwise not in use, and an online encryption phase which only incurs very little computation costs. Security analysis indicates that our scheme is provably secure in the random oracle model. The asymptotic complexity comparison and simulation results also show that our scheme achieves high computation efficiency.

An efficient public-key searchable encryption scheme secure against inside keyword guessing attacks

How to efficiently search over encrypted data is an important and interesting problem in the cloud era. To solve it, Boneh et al. introduced the notion of public key encryption with keyword search (PEKS), in 2004. However, in almost all the PEKS schemes an inside adversary may recover the keyword from a given trapdoor by exhaustively guessing the keywords offline. How to resist the inside keyword guessing attack in PEKS remains a hard problem.In this paper we propose introduce the notion of Public-key Authenticated Encryption with Keyword Search (PAEKS) to solve the problem, in which the data sender not only encrypts a keyword, but also authenticates it, so that a verifier would be convinced that the encrypted keyword can only be generated by the sender. We propose a concrete and efficient construction of PAEKS, and prove its security based on simple and static assumptions in the random oracle model under the given security models. Experimental results show that our scheme enjoys a comparable efficiency with Boneh et al.’s scheme.

New application of partitioning methodology: identity‐based dual receiver encryption

AbstractDual receiver encryption (DRE), a notion of public key encryption (PKE) introduced at CCS'04, allows two independent receivers to decrypt a ciphertext into a same plaintext. This crypto primitive is quite useful in designing denial of service attack‐resilient protocols. To our knowledge, prior DRE constructions are considered in the traditional PKE settings, which may face the difficulty of certificate management. This paper aiming at solving this dilemma of DRE in the traditional PKE settings, and gives an identity‐based variant version of DRE: identity‐based dual receiver encryption (ID‐DRE) that combines the notion of DRE and identity‐based encryption (IBE). Based on Waters' IBE (Crypto'05), two ID‐DRE schemes are constructed in the standard model and by partitioning methodology, provable security of our ID‐DRE schemes are obtained under the decisional bilinear Diffie‐Hellman. Furthermore, we achieve a tighter reduction by adopting a random walk‐like methodology of analysis on the lower bound of simulators' artificial abort, which also results in better security tightness for Waters IBE. This improved result for Waters' IBE, where n is the bitlength of messages and q is the number of adversarial key queries, is consistent with Hofheinz and Kiltz's result (Crypto'08). Copyright © 2017 John Wiley & Sons, Ltd.

Efficient privacy preserving predicate encryption with fine-grained searchable capability for Cloud storage

With the fast development in Cloud storage technologies and ever increasing use of Cloud data centres, data privacy and confidentiality has become a must. Indeed, Cloud data centres store each time more sensitive data such as personal data, organizational and enterprise data, transactional data, etc. However, achieving confidentiality with flexible searchable capability is a challenging issue. In this article, we show how to construct an efficient predicate encryption with fine-grained searchable capability. Predicate Encryption (PE) can achieve more sophisticated and flexible functionality compared with traditional public key encryption. We propose an efficient predicate encryption scheme by utilizing the dual system encryption technique, which can also be proved to be IND-AH-CPA (indistinguishable under chosen plain-text attack for attribute-hiding) secure without random oracle. We also carefully analyse the relationship between predicate encryption and searchable encryption. To that end, we introduce a new notion of Public-Key Encryption with Fine-grained Keyword Search (PEFKS). Our results show that an IND-AH-CPA secure PE scheme can be used to construct an IND-PEFKS-CPA (indistinguishable under chosen plain-text attack for public-key encryption with fine-grained keyword search) secure PEFKS scheme. A new transformation of PE-to-PEFKS is also proposed and used to construct an efficient PEFKS scheme based on the transformation from the proposed PE scheme. Finally, we design a new framework for supporting privacy preserving predicate encryption with fine-grained searchable capability for Cloud storage. Compared to most prominent frameworks, our framework satisfies more features altogether and can serve as a basis for developing such frameworks for Cloud data centres.

Efficient Public Key Encryption With Equality Test Supporting Flexible Authorization

We reformalize and recast the notion of public key encryption with equality test (PKEET), which was proposed in CT-RSA 2010 and supports to check whether two ciphertexts encrypted under different public keys contain the same message. PKEET has many interesting applications, for example, in constructing searchable encryption and partitioning encrypted data. However, the original PKEET scheme lacks an authorization mechanism for a user to control the comparison of its ciphertexts with others’. In this paper, we study the authorization mechanism for PKEET, and propose four types of authorization policies to enhance the privacy of users’ data. We give the definitions of the policies, propose a PKEET scheme supporting these four types of authorization at the same time, and prove its security based on the computational Diffie–Hellman assumption in the random oracle model. To the best of our knowledge, it is the only PKEET scheme supporting flexible authorization.

Public Key Encryption with Delegated Equality Test in a Multi-User Setting

Probabilistic public key encryption with equality test (PKEET), introduced by Yang et al. in CT-RSA 2010, is able to check whether two ciphertexts are encryptions of the same message under different public keys without leaking anything else about the message encrypted under either public key. PKEET schemes have many applications, for example, in constructing searchable encryption and partitioning encrypted data. Previous PKEET schemes lack a delegation mechanism for users to specify who can perform the equality test between their ciphertexts. In this paper, we propose the notion of public key encryption with delegated equality test (PKE-DET), which requires only the delegated party to deal with the work in a practical multi-user setting, and present a concrete construction in Type 2 pairing, which is provably secure under the newly introduced security notions.

Efficient public key encryption with revocable keyword search

ABSTRACTPublic key encryption with keyword search is a novel cryptographic primitive enabling one to search on the encrypted data directly. In the known schemes, once getting a trapdoor, the server can search associated data without any restrictions. However, in reality, it is sometimes essential to prevent the server from searching the data all the time because the server is not fully trusted. In this paper, we propose the notion of public key encryption with revocable keyword search to address the issue. We also develop a concrete construction by dividing the whole life of the system into distinct times to achieve our goals. The proposed scheme achieves the properties of the indistinguishability of ciphertexts against an adaptive chosen keywords attack security under the co‐decisional bilinear Diffie–Hellman assumption in our security model. Compared with two somewhat schemes, ours offers much better performance in terms of computational cost. Copyright © 2013 John Wiley & Sons, Ltd.

Public key encryption with keyword search secure against keyword guessing attacks without random oracle

The notion of public key encryption with keyword search (PEKS) was put forth by Boneh et al. to enable a server to search from a collection of encrypted emails given a “trapdoor” (i.e., an encrypted keyword) provided by the receiver. The nice property in this scheme allows the server to search for a keyword, given the trapdoor. Hence, the verifier can merely use an untrusted server, which makes this notion very practical. Following Boneh et al.’s work, there have been subsequent works that have been proposed to enhance this notion. Two important notions include the so-called keyword guessing attack and secure channel free, proposed by Byun et al. and Baek et al., respectively. The former realizes the fact that in practice, the space of the keywords used is very limited, while the latter considers the removal of secure channel between the receiver and the server to make PEKS practical. Unfortunately, the existing construction of PEKS secure against keyword guessing attack is only secure under the random oracle model, which does not reflect its security in the real world. Furthermore, there is no complete definition that captures secure channel free PEKS schemes that are secure against chosen keyword attack, chosen ciphertext attack, and against keyword guessing attacks, even though these notions seem to be the most practical application of PEKS primitives. In this paper, we make the following contributions. First, we define the strongest model of PEKS which is secure channel free and secure against chosen keyword attack, chosen ciphertext attack, and keyword guessing attack. In particular, we present two important security notions namely IND-SCF-CKCA and IND-KGA. The former is to capture an inside adversary, while the latter is to capture an outside adversary. Intuitively, it should be clear that IND-SCF-CKCA captures a more stringent attack compared to IND-KGA. Second, we present a secure channel free PEKS scheme secure without random oracle under the well known assumptions, namely DLP, DBDH, SXDH and truncated q-ABDHE assumption. Our contributions fill the gap in the literature and hence, making the notion of PEKS very practical. We shall highlight that our scheme is IND-SCF-CKCA secure.