Blind and Anonymous Identity-Based Encryption and Authorised Private Searches on Public Key Encrypted Data

Public key encryption with keyword search (PKES) enables senders to send encrypted data to a Freceiver like traditional public key encryption (PKE) schemes. The difference between PKES and PKE is that the receiver in PKES can search on the encrypted data which is stored on the third-party server (like a cloud storage server). As far as we know, most of the existed PKES schemes are based on bilinear map, so they are costly in computation and hard to be used in practice. In this paper, we construct a PKES scheme based on factoring, it's computational efficient and secure. The public parameters in our scheme is also short, we just need a public modules and a random element of the set of integers.

Döttling and Garg (CRYPTO 2017) introduced a non-black-box approach to identity-based encryption (IBE). This paves the way for the first and still the only anonymous IBE (AIBE) scheme from the computational Diffie–Hellman (CDH) assumption of Brakerski et al. (EUROCRYPT 2018). This paper revisits the blinding technique of Brakerski et al. and introduces a suite of blind primitives, extending chameleon encryption, hash encryption, and one-time signature with encryption. Using them, we propose an AIBE scheme from CDH with improved efficiency compared to Brakerski et al., especially in the decryption time. We also propose the first anonymous hierarchical IBE (AHIBE) scheme from CDH and the first AIBE and AHIBE schemes from the $$\phi $$ -hiding assumption, with similar efficiency as their non-anonymous counterparts.

Outsourcing medical data and their search services to a third party cloud have been a popular trend for many medical practices, because using healthcare cloud services can help cut down the cost of Electronic Health Records (EHR) systems in terms of front-end ownership cost and IT maintenance burdens. Healthcare cloud applications need searchable encryption with the following two capabilities for protecting data privacy and access privacy: (1) the healthcare providers need to share the encrypted data with authorized users and enable querying over encrypted data, and (2) they also need to keep the query keywords and associated search operations private such that healthcare data hosting service providers cannot gain access to unauthorized content or trace and infer sensitive data stored in the healthcare cloud. This survey paper describes the notion of searchable encryption (SE) in the context of healthcare applications and characterize the SE use cases into four scenarios in healthcare. Then we provide a comprehensive overview of the four representative SE techniques: searchable symmetric encryption (SSE), public key encryption with keyword search (PEKS), attribute-based encryption with keyword search (ABKS), and proxy re-encryption with keyword search (PRES) according to different EHR retrieving scenarios and requirements. We categorize and compare the different SE schemes in terms of their security, efficiency, and functionality. The survey is designed to benefit both experienced researchers in the computer science (CS) field and non-specialists who are domain scientists or healthcare professionals with limited CS and information security background. Thus, we are in favor of technological overview of the state of art searchable encryption models and the underlying key techniques, instead of detailed proofs and constructions of the respective SE algorithms. We describe how the existing SE schemes relate to and differ from one another, and point out the connections between the SE techniques and the security and privacy requirements of healthcare applications and the open research problems.

Public-key encryption with keyword search (PEKS) is a versatile tool. It allows a third party knowing the search trapdoor of a keyword to search encrypted documents containing that keyword without decrypting the documents or knowing the keyword. However, it is shown that the keyword will be compromised by a malicious third party under a keyword guess attack (KGA) if the keyword space is in a polynomial size. We address this problem with a keyword privacy enhanced variant of PEKS referred to as public-key encryption with fuzzy keyword search (PEFKS). In PEFKS, each keyword corresponds to an exact keyword search trapdoor and a fuzzy keyword search trapdoor. Two or more keywords share the same fuzzy keyword trapdoor. To search encrypted documents containing a specific keyword, only the fuzzy keyword search trapdoor is provided to the third party, i.e., the searcher. Thus, in PEFKS, a malicious searcher can no longer learn the exact keyword to be searched even if the keyword space is small. We propose a universal transformation which converts any anonymous identity-based encryption (IBE) scheme into a secure PEFKS scheme. Following the generic construction, we instantiate the first PEFKS scheme proven to be secure under KGA in the case that the keyword space is in a polynomial size.

In this paper, we study the problem of secure integrating public key encryption with keyword search (PEKS) with public key data encryption (PKE). We argue the previous security model is not complete regarding keyword privacy and the previous constructions are secure only in the random oracle model. We solve these problems by first defining a new security model, then give a generic construction which is secure in the new security model without random oracles. Our construction is based on secure PEKS and tag-KEM/DEM schemes and achieves modular design. We also give some applications and extensions for our construction. For example, instantiate our construction with proper components, we have a concrete scheme without random oracles, whose performance is even competitive to the previous schemes with random oracles.

Driven by cloud computing technologies, public-key encryption with keyword search (PEKS) is becoming a common practice from aspects of the Industrial Internet of Things, smart healthcare, vehicular social networks, and so on. However, a dozen years of PEKS development is accompanied by some security and privacy issues in the encrypted data search and access processes. The keyword guessing attack is a typical user privacy threat model, that is, an adversary could guess the user’s retrieval keyword given a search trapdoor. On the other hand, the emergence of quantum computers make traditional PEKS schemes no longer secure. Although scholars put forward some postquantum secure PEKS schemes, these schemes are based on lattice cryptography with a larger key size. To the best of our knowledge, there is no quantum-resist PEKS scheme established on elliptic curve cryptography. This article utilizes PEKS with designated tester primitive and quantum resistance of isogeny. Then, we put forward a postquantum searchable encryption scheme named Isoga, which fights against keyword guessing attacks. We prove Isoga’s searchable ciphertext security and trapdoor indistinguishability under isogeny-related difficult assumptions. Performance evaluation indicates that the Isoga scheme is more practical in the quantum environment, considering seven schemes’ security properties, communication cost, and computing overload among.

Public-key encryption with keyword search (PEKS) enables users to search on encrypted data which is applicable to scenario of sharing data in the cloud storage. The existing PEKS schemes fail to verify the returned result from the tester, i.e. they cannot guarantee the correctness and completeness of the result. In this paper, we resolve this problem by constructing a verifiable PEKS scheme which can efficiently verify the completeness of the result and thus the correctness. We also consider the security of verifiable PEKS scheme against a kind of side-channel attacks called the continual memory attacks which allow the adversary to obtain some leakage information of the secret key used in the search trapdoor generation algorithm and can help it break the security of the scheme. We extend our scheme to an enhanced one which remains secure even when the adversary can obtain unbounded total leakage information during the whole lifetime. Moreover, to make it resist keyword guessing attacks, we extend our scheme to one with a designated tester.

Abdalla et al.[1, 6] proposed a transform of an anonymous IBE (A-IBE) scheme to a PEKS (Public key encryption with keyword search) scheme. Boneh et al. proposed a transform of a PEKS scheme to an A-IBE scheme for only one-bit message. A transform for constructing an A-IBE scheme for polynomially many-bit message by using a PEKS scheme has not been proposed yet. To construct a transform from any PEKS scheme to an A-IBE scheme for a polynomially many-bit message, we firstly define a multiple PEKS (mPEKS) scheme and show that a mPEKS scheme can be constructed from a PEKS scheme. We also prove that if a PEKS scheme is confidential, so is the resulting mPEKS scheme. We then provide a transform from a mPEKS scheme to an A-IBE scheme for a polynomially many-bit message.

As a very attractive cryptographic primitive, the public key encryption with keyword search (PEKS) enables users to search on encrypted data, and hence is applicable to the setting of cloud computing. Although the existing PEKS schems can allow a user to search encrypted data confidentially, most of them failed to verify the searched result and the system did not specify the users who can make a request for encrypted data files stored on the cloud server. Recently, a novel cryptographic solution, called verifiable attribute-based keyword search (VABKS) was proposed by Zheng. It allows a data user, whose credentials satisfy the data owner's access control policy, to search the encrypted data file and verify the searched result. However, the scheme exists an unrealistic assumption of secure as in the Boneh's scheme. In this paper, we propose a new scheme which removes secure channel and construct a novel method for verifying the searched result from the cloud server based on key policy attribute-based keyword search (KP-ABKS) of VABKS. It can be effectively to verify the correctness and integrity of the data file which the data user desired for. By our simulation for the verification, it proves that our scheme is more practical than VABKS.

The Snowden incident illustrates that an adversary may launch an algorithm substitution attack (ASA) by tampering with the algorithms of protocol participants to obtain users' secret information. A measure against ASA is to equip the protocol participants with cryptographic reverse firewalls (CRF). Public key encryption with keyword search (PEKS) as a cryptographic primitive allows users to search encrypted file in cloud servers while ensuring the security of the original file. The existing CRF constructions for PEKS does not consider the trust level of CRFs, leaving honest-but-curious CRF to deal with trapdoors that should be sent in the secure channels, which brings new security risks. This paper firstly introduces the notion of malleable designated tester public key encryption with keyword search (M-DPEKS). Based on M-DPEKS, we propose the generic construction of public key encryption with keyword search with cryptographic reverse firewalls to overcome the privacy leakage issue in cloud storage. Security proof indicates the generic construction is secure against ASA. Lastly, we instantiate the generic construction with a concrete M-DPEKS scheme and analyze the computation cost and communication overhead to evaluate the efficiency.

A more efficient public-key authenticated encryption scheme with keyword search

The emergence of public-key encryption with keyword search (PEKS) has provided an elegant approach to enable keyword search over encrypted content. Due to its high computational complexity proportional to the number of intended receivers, the trivial way of deploying PEKS for data sharing with multiple receivers is impractical, which motivates the development of a new PEKS framework for broadcast mode. However, existing works suffer from either the vulnerability to keyword guessing attacks (KGA) or high computation and communication complexity. In this work, a new primitive for keyword search in broadcast mode, named broadcast authenticated encryption with keyword search (BAEKS), is introduced, in which the sender not only encrypts the keyword but also authenticates it, eliminating the threats of KGA. Moreover, on top of keyword privacy, we formalize the notion of user anonymity (or key privacy) for BAEKS, which echoes the notion of key privacy for public-key encryption introduced by Bellare et al. (ASIACRYPT’01). We present a practical BAEKS construction that achieves all the desirable features, including keyword privacy of both searchable ciphertext and trapdoor, KGA-resistance, receiver anonymity of both searchable ciphertext and trapdoor, and universal keyword set scalability. Moreover, the trapdoor of our scheme achieves constant computation and communication cost, making it more suitable for broadcast mode where trapdoors are generated by multiple receivers in the search operations. The security of our scheme is proved under the standard DBDH assumption.

Privacy-preserving bidirectional keyword search over encrypted data for cloud-assisted IIoT

Anonymous identity-based encryption systems can be used to protect users' privacy and construct Public key Encryption with Keyword Search (PEKS) schemes where the ciphertext does not leak the identity of the recipient. Currently, there is no anonymous IBE scheme that is fully secure under simple assumptions without random oracles. In this paper, we propose an anonymous IBE scheme using the approach of Dual System Encryption. The scheme is fully secure without random oracles based on decisional bilinear Diffie-Hellman (BDH) and linear assumptions, and the security reduction is tight. These two assumptions are simple and our scheme is more secure than the previous anonymous IBE schemes.

Within modern internet infrastructure including networks that are ubiquitous, there is often a need for delegatable communication between nodes without compromising the confidentiality of information. In practice, this should be enforced while allowing some basic functionality for intermediate delegated nodes such as searching through encrypted content. This can be achieved using a Public key encryption with keyword search (PEKS) scheme, first proposed by Boneh et al., which enables to search publicly encrypted messages for keywords without revealing any information about the message. The issue of PEKS schemes being vulnerable to keyword guessing attacks (KGAs) was first shown by Byun et al., and two of the most recent PEKS schemes, i.e., due to Rhee et al. in (ASIACCS, pp 376–379, 2009; IEICE Electron Express 6(5):237–243, 2009) and (J Syst Softw 83(5):763–771, 2010), respectively, are designed with this security in mind. In this paper, we treat this KGA problem in detail and define new security models to capture KGAs against PEKS and designated PEKS schemes. These models are more security sufficient than the model considered by Rhee et al. (J Syst Softw 83(5):763–771, 2010); indeed the latter model does not afford sufficient adversarial capability in the sense that it is much weaker than the adversarial capability considered in the original IND-CKA model of Boneh et al. Our new models allow to capture KGAs on three recent designated PEKS schemes that cannot be captured in the weaker model of Rhee et al.