ABKS-SKGA: Attribute-based keyword search secure against keyword guessing attack

In order to guarantee security and privacy of sensitive data, attribute-based keyword search (ABKS) enables data owners to upload their encrypted data to cloud servers, and authorizes intended data users to retrieve it. Meanwhile, ABKS outsources heavy search work to cloud servers, which makes ABKS adaptive to mobile computing environment. However, as cloud servers can both generate keyword ciphertexts and run search algorithm, the existing most ABKS schemes are vulnerable to keyword guessing attack. In this paper, we show the fundamental cause that the existing ABKS schemes do not resist keyword guessing attack is any entity can generate keyword ciphertext. To solve the above problem, in the phase of keyword ciphertext generation, we use private key of data owner to sign keyword prior to generating keyword ciphertext. Therefore, any other entity does not forge keyword ciphertext, which can resist keyword guessing attack. We give the formal definition and security model of attributed-based keyword search secure against keyword guessing attack (ABKS-SKGA). Furthermore, we provide an ABKS-SKGA scheme. The ABKS-SKGA scheme is proved secure against chosen-plaintext attack (CPA). Performance analysis shows that the proposed scheme is practical.     

Privacy-preserving conjunctive keyword search on encrypted data with enhanced fine-grained access control

Cloud storage over the internet gives opportunities for easy data sharing. To preserve the privacy of sharing data, the outsourced data is usually encrypted. The searchable encryption technique provides a solution to find the target data in the encrypted form. And the public-key encryption with keyword search is regarded as a major approach for the searchable encryption technique. However, there are still several privacy leakage challenges for the further adoption of these major schemes. One is how to resist the keyword guessing attack which still leaks data user’s keywords privacy. Another is how to construct the access control policy to prevent illegal access of outsourced data sharing since illegal access always leak the privacy of user’s attribute. In our paper, we firstly try to design a novel secure keyword index to resist the keyword guessing attack from access pattern and search pattern. Second, we propose an attribute-based encryption scheme which supports an enhanced fine-grained access control search. This allows the authenticated users to access different data although their searching request contains the same queried keywords, and meanwhile unauthenticated users cannot get any attribute privacy information. Third, we give security proofs to show that the construction of keyword index is against keyword guessing attack from the access pattern and search pattern, and our scheme is proved to be IND-CPA secure (the indistinguishability under chosen plaintext attack) under the standard model. Finally, theoretical analyses and a series of experiments are conducted to demonstrate the efficiency of our scheme.

     

云环境下基于属性的多关键字可搜索加密方案

可搜索加密技术可在不解密数据密文的同时实现密文关键字的检索,很好地保护了数据存储方的隐私.针对目前大多数可搜索加密方案无法支持用户自定义搜索策略的问题,提出了一种安全、高效、可支持任意表达的基于属性可搜索加密方案.该方案首先基于LSSS搜索结构,支持任意合取、析取或单调布尔表达式的多关键字搜索策略,用户使用私钥为LSS...     

ABDKS: attribute-based encryption with dynamic keyword search in fog computing

Attribute-based encryption with keyword search (ABKS) achieves both fine-grained access control and keyword search. However, in the previous ABKS schemes, the search algorithm requires that each keyword to be identical between the target keyword set and the ciphertext keyword set, otherwise the algorithm does not output any search result, which is not conducive to use. Moreover, the previous ABKS schemes are vulnerable to what we call a peer-decryption attack, that is, the ciphertext may be eavesdropped and decrypted by an adversary who has sufficient authorities but no information about the ciphertext keywords.In this paper, we provide a new system in fog computing, the ciphertext-policy attribute-based encryption with dynamic keyword search (ABDKS). In ABDKS, the search algorithm requires only one keyword to be identical between the two keyword sets and outputs the corresponding correlation which reflects the number of the same keywords in those two sets. In addition, our ABDKS is resistant to peer-decryption attack, since the decryption requires not only sufficient authority but also at least one keyword of the ciphertext. Beyond that, the ABDKS shifts most computational overheads from resource constrained users to fog nodes. The security analysis shows that the ABDKS can resist Chosen-PlaintextAttack (CPA) and Chosen-Keyword Attack (CKA).     

云环境下基于属性策略隐藏的可搜索加密方案

基于属性的可搜索加密技术可以实现对数据的细粒度访问控制,但现有的可搜索加密方案,关键字的搜索、访问控制、文件加密基本上是分别执行的,导致攻击者可能跳过访问策略直接进行关键字索引匹配或文件解密;其次,现有方案中数据拥有者需将加密文件的密钥以安全通道传给用户,增加了数据拥有者的开销;此外,大多基于树型的访问控制策略是公开的...     

支持连接关键词搜索的属性加密方案研究

基于属性的加密机制能够实现细粒度的访问控制,支持多用户数据共享。针对大部分基于属性的可搜索加密方案存在效率低下、密钥易泄露以及仅支持单关键词搜索的问题,提出了一个支持连接关键词搜索的属性加密方案。该方案采用线性秘密共享矩阵实现访问控制,将秘密共享和恢复操作在一个与参与方属性关联的矩阵中进行,通过矩阵运算减少了计算量。在陷门生成阶段,避免直接将用户密钥提交给云服务器,保证了用户密钥的安全性。基于多项式方程实现了连接关键词搜索,缩小了搜索范围,提升了用户的搜索体验,严格的安全性分析证明方案能够达到抵抗关键字攻击安全。     

可验证的多用户云加密关键字搜索方案

针对云环境下多用户访问和大数据量存储的特点,提出了一种云环境下加密关键字搜索方案。与已有的大多数方案相比,该方案使用签名绑定关键字索引和其关联加密文件,实现了查询结果完备性和完整性的验证,使用重加密技术实现了多用户隐查询,并动态更新用户查询权限。此外,该方案在查询过程中使用哈希查询优化索引结构,实现了对云数据的快速访问。安全性分析表明,该方案是安全的;性能分析及仿真实验结果表明该方案和已有的一些算法相比有了较大的性能提升。     

Proxy re-encryption with keyword search

We introduce a new cryptographic primitive, called proxy re-encryption with keyword search, which is motivated by the following scenario in email systems: Charlie sends an encrypted email, which contains some keywords, such as “urgent”, to Alice under Alice’s public key, and Alice delegates her decryption rights to Bob via her mail server. The desired situations are: (1) Bob can decrypt mails delegated from Alice by using only his private key, (2) Bob’s mail gateway, with a trapdoor from Bob, can test whether the email delegated from Alice contains some keywords, such as “urgent”, (3) Alice and Bob do not wish to give the mail server or mail gateway the access to the content of emails.The function of proxy re-encryption with keyword search (PRES) is the combination of proxy re-encryption (PRE) and public key encryption with keyword search (PEKS). However, a PRES scheme cannot be obtained by directly combining those two schemes, since the resulting scheme is no longer proven secure in our security model. In this paper, a concrete construction is proposed, which is proven secure in the random oracle model, based on the modified Decisional Bilinear Diffie-Hellman assumption.     

一种安全的具有匿名性的可搜索加密方案

2004年,Boneh等利用匿名的基于身份加密方案构造了一个公钥可搜索加密方案（PEKS）,解决了特定环境下对加密数据进行检索的这一困难工作。已有的可搜索加密方案,都是实现对关键词信息的保护,其实一个真正安全的可搜索加密方案,在保证搜索能力的前提下,不仅要实现对关键词信息的保护,也要实现对消息查询方信息的保护。提出具有匿名性的基于身份可搜索方案（ANO-IBEKS）的构造算法,给出了方案在随机预言机模型下语义安全性的证明。该方案可以很好地解决大量数据交给第三方服务器存储（比如网络存储）的关键词密文查询问题,可以有效地保护查询关键词和查询者身份等敏感信息,无法追踪究竟是哪个用户查询了什么信息。     

抗关键词猜测攻击的可搜索属性基加密方案

可搜索属性基加密能够让属性满足访问控制策略(或用来加密关键词的属性满足用户私钥指定的访问控制策略)的用户搜索加密文件。但是,现有的方案不能抵抗关键词猜测攻击。外部攻击者可以生成若干关键词密文上传到云服务器,侦测云服务器将这些密文返回给哪些用户,进而获取这些用户的搜索信息。因此,提出一种可以抵抗关键词猜测攻击的可搜索属性基加密方案。基于DBDH困难问题,该方案在选择安全模型中被证明是选择明文攻击安全的。     

Integrity-verifiable conjunctive keyword searchable encryption in cloud storage

Conjunctive searchable encryption is an efficient way to perform multi-keyword search over encrypted data in cloud storage. However, most existing methods do not take into account the integrity verification of the search result. Moreover, existing integrity verification methods can only verify the integrity of single-keyword search results, which cannot meet the requirements of conjunctive search. To address this problem, we proposed a conjunctive keyword searchable encryption scheme with an authentication mechanism that can efficiently verify the integrity of search results. The proposed scheme is based on the dynamic searchable symmetric encryption and adopts the Merkle tree and bilinear map accumulator to prove the correctness of set operations. It supports conjunctive keyword as input for conjunctive search and gives the server the ability to prove the integrity of the search result to the user. Formal proofs and extensive experiments show that the proposed scheme is efficient, unforgeable and adaptive secure against chosen-keyword attacks.     

区块链上基于云辅助的属性基可搜索加密方案

可搜索加密技术在不解密的情况下搜索加密数据.针对现有的可搜索加密技术没有考虑数据用户细粒度搜索权限的问题,以及现有的可搜索加密方案中因云存储的集中化对数据安全和隐私保护带来的问题,提出了区块链上基于云辅助的属性基可搜索加密方案.该方案利用可搜索加密技术实现加密数据在区块链上的安全搜索,利用基于属性的加密技术实现数据的细粒度访问控制,利用区块链不可篡改的特性确保关键字密文的安全.在该方案中属性基加密技术用来加密关键字,区块链上存储关键字密文,云服务器上存储关键字密文和数据密文.基于困难问题假设,证明该方案能够保证关键字密文和陷门的安全性.数值实验结果表明:该方案在密钥生成阶段、陷门生成阶段、关键字搜索阶段具有较高的效率.     

高效无双线性对的带关键词搜索的基于证书加密方案

针对已有带关键词搜索的公钥加密方案中存在的复杂的证书管理、密钥托管以及密钥分发等问题,提出一种带关键词搜索的基于证书加密的方案。首先,给出带关键词搜索的基于证书加密方案及其安全模型的形式化定义;然后,基于椭圆曲线构造一个高效无双线性对的带关键词搜索的基于证书加密方案,并基于计算Diffie-Hellman问题（CDHP）证明了该方案满足适应性选择关键词攻击下的关键词密文不可区分性;最后,对所提出方案进行仿真模拟,并就方案特性和性能两个方面与已有的带关键词搜索的公钥加密方法进行对比。对比分析表明,所提出方案不仅具有隐认证、无密钥托管以及无密钥分发的优良特性,而且在计算效率和通信代价上要优于已有的带关键词搜索的无证书加密方案。     

结合公钥加密和关键字可搜索加密的加密方案

带关键字搜索的公钥加密(PEKS)是一种有用的加密原语，它允许用户将在加密数据上搜索的功能委托给不可信的第三方服务器，而不影响原始数据的安全性和隐私性。但是，由于缺乏对于数据的加密以及解密能力，PEKS方案不能单独进行使用，必须与标准的公钥加密方案(PKE)相结合。因此，Baek等人在2006年引入了一种新的加密原语，称为结合PKE和PEKS的加密方案(PKE+PEKS)，它同时提供了PKE和PEKS的功能。目前，已有文献提出了几种PKE+PEKS方案。然而，他们都没有考虑关键字猜测攻击的问题。本文提出一个新的高效且能够抵抗关键字猜测攻击的PKE+PEKS方案，与已有方案相比，该方案在性能上有很大的提升，并且在生成关键字和数据密文时，不需要使用双线性对，极大地降低了计算和存储成本。安全性分析表明，本文中所提出的方案能够满足密文隐私安全性、陷门不可区分性和抗关键字猜测攻击的安全性。效率分析表明，本分提出的方案更加高效。     

VCKSM: Verifiable conjunctive keyword search over mobile e-health cloud in shared multi-owner settings

Searchable encryption (SE) is a promising technique which enables cloud users to conduct search over encrypted cloud data in a privacy-preserving way, especially for the electronic health record (EHR) system that contains plenty of medical history, diagnosis, radiology images, etc. In this paper, we focus on a more practical scenario, also named as the shared multi-owner settings, where each e-health record is co-owned by a fixed number of parties. Although the existing SE schemes under the unshared multi-owner settings can be adapted to this shared scenario, these schemes have to build multiple indexes, which definitely incur higher computational overhead. To save bandwidth and computing resources in cloud servers and guarantee the correctness of search results, we present a secure cryptographic primitive, namely verifiable conjunctive keyword search over mobile e-health cloud scheme, in the shared multi-owner settings by utilizing multisignatures technique. Formal security analysis proves that our scheme is secure against the keyword guessing attacks in standard model. Empirical study using a real-world dataset justifies that our scheme is efficient and feasible in practical applications.     

基于区块链的多关键字属性基可搜索加密方案

云存储服务的出现可将文件上传至云服务器,节约了本地的信息存储空间以及管理开销。文件以明文的形式存储显然无法满足隐私保护和安全需求,但若将加密后的文件上传至云服务器,将失去搜索原文件的能力。因此,可搜索加密技术的出现解决了用户如何在文件不解密的情况下搜索加密数据。目前现有的单关键字可搜索加密方案会产生许多与检索内容不符合的信息,没有考虑数据用户细粒度搜索权限和搜索效率,以及因云存储的集中化带来的数据安全和隐私保护等问题。针对以上问题,该文提出了基于区块链的多关键字属性基可搜索加密方案。该方案使用多关键字可搜索加密技术实现了加密数据的有效搜索;利用基于属性的加密技术实现加密数据的细粒度访问控制;结合区块链的智能合约技术,经过多笔交易获得搜索结果。并且利用区块链的不可篡改性,满足了方案中相关性质的公平性,保证了在方案中三方的公平性和安全性并进行了相关分析。在随机预言机模型下,基于困难问题假设证明了方案的关键字安全及陷门安全,即所提方案满足在选择关键字攻击下的关键字密文不可区分性安全和陷门不可区分性安全。最后通过数值分析表明该方案在关键字密文生成阶段和关键字搜索阶段具有较高的效率。并展望了在未...     

VKSE-MO: verifiable keyword search over encrypted data in multi-owner settings

Searchable encryption (SE) techniques allow cloud clients to easily store data and search encrypted data in a privacy-preserving manner, where most of SE schemes treat the cloud server as honest-but-curious. However, in practice, the cloud server is a semi-honest-but-curious third-party, which only executes a fraction of search operations and returns a fraction of false search results to save its computational and bandwidth resources. Thus, it is important to provide a results verification method to guarantee the correctness of the search results. Existing SE schemes allow multiple data owners to upload different records to the cloud server, but these schemes have very high computational and storage overheads when applied in a different but more practical setting where each record is co-owned by multiple data owners. To address this problem, we develop a verifiable keyword search over encrypted data in multi-owner settings (VKSE-MO) scheme by exploiting the multisignatures technique. Thus, our scheme only requires a single index for each record and data users are assured of the correctness of the search results in challenging settings. Our formal security analysis proved that the VKSE-MO scheme is secure against a chosen-keyword attack under a random oracle model. In addition, our empirical study using a real-world dataset demonstrated the efficiency and feasibility of the proposed scheme in practice.     

Verifiable searchable symmetric encryption for conjunctive keyword queries in cloud storage

Searchable symmetric encryption (SSE) has been introduced for secure outsourcing the encrypted database to cloud storage, while maintaining searchable features. Of various SSE schemes, most of them assume the server is honest but curious, while the server may be trustless in the real world. Considering a malicious server not honestly performing the queries, verifiable SSE (VSSE) schemes are constructed to ensure the verifiability of the search results. However, existing VSSE constructions only focus on single-keyword search or incur heavy computational cost during verification. To address this challenge, we present an efficient VSSE scheme, built on OXT protocol (Cash et al., CRYPTO 2013), for conjunctive keyword queries with sublinear search overhead. The proposed VSSE scheme is based on a privacy-preserving hash-based accumulator, by leveraging a well-established cryptographic primitive, Symmetric Hidden Vector Encryption (SHVE). Our VSSE scheme enables both correctness and completeness verifiability for the result without pairing operations, thus greatly reducing the computational cost in the verification process. Besides, the proposed VSSE scheme can still provide a proof when the search result is empty. Finally, the security analysis and experimental evaluation are given to demonstrate the security and practicality of the proposed scheme.     

云存储中支持属性撤销的多关键词可搜索加密方案

云存储的便捷性和管理高效性使得越来越多的用户选择将数据存放在云端。为支持用户对云端加密数据进行检索,提出云存储中基于属性加密支持属性撤销的多关键词搜索方案。采用线性秘密共享矩阵来表示访问控制结构,实现密文细粒度访问控制,在属性撤销过程中不需要更新密钥,应对用户属性变更的情况,在此基础上构造基于多项式方程的搜索算法支持多关键词搜索,从而提高搜索精度。理论分析和实验结果表明,该方案具有陷门不可伪造性和关键词隐私性,能够保证用户数据的隐私和安全,相比CP-ABE方案,具有较高的存储性能和计算效率,功能性更强。     

An efficient PHR service system supporting fuzzy keyword search and fine-grained access control

Outsourcing of personal health record (PHR) has attracted considerable interest recently. It can not only bring much convenience to patients, it also allows efficient sharing of medical information among researchers. As the medical data in PHR is sensitive, it has to be encrypted before outsourcing. To achieve fine-grained access control over the encrypted PHR data becomes a challenging problem. In this paper, we provide an affirmative solution to this problem. We propose a novel PHR service system which supports efficient searching and fine-grained access control for PHR data in a hybrid cloud environment, where a private cloud is used to assist the user to interact with the public cloud for processing PHR data. In our proposed solution, we make use of attribute-based encryption (ABE) technique to obtain fine-grained access control for PHR data. In order to protect the privacy of PHR owners, our ABE is anonymous. That is, it can hide the access policy information in ciphertexts. Meanwhile, our solution can also allow efficient fuzzy search over PHR data, which can greatly improve the system usability. We also provide security analysis to show that the proposed solution is secure and privacy-preserving. The experimental results demonstrate the efficiency of the proposed scheme.