Dynamic Searchable Symmetric Encryption Scheme Research Articles

SEDCPT: A secure and efficient Dynamic Searchable Encryption scheme with cluster padding assisted by TEE

Dynamic Searchable Symmetric Encryption (DSSE), which enables users to search and update encrypted data on an untrusted server without decryption, is a proven method when dealing with availability issues for outsourced data. However, the existing DSSE schemes suffer from forward and backward privacy problems. Although forward and backward privacy DSSE schemes can prevent these attacks, they still suffer from other challenges, such as count attacks, high communication overhead, and low computing efficiency. To solve the above problems simultaneously, we propose a secure and efficient dynamic searchable encryption scheme, which integrates a clustering algorithm, padding strategy, and trusted execution environments (TEE). The purpose of the scheme is to prevent count attacks while ensuring forward and backward privacy security. Our scheme also reduces the computing overhead and storage cost of the client by using TEE (e.g. Intel Software Guard Extension, Intel SGX) while maximizing the protection of client privacy. Furthermore, the scheme provides a secure hardware isolation environment for the cluster padding and search/update process to prevent malicious attacks from external software or super administrators. Finally, we provide corresponding security proofs and experimental evaluation which demonstrate both the security and efficiency of our scheme, respectively.

CoD-DSSE: A practical efficient dynamic searchable symmetric encryption with lightweight clients

Dynamic searchable symmetric encryption(DSSE) combines dynamic update with searchable encryption, allowing users to not only achieve keyword retrieval, but also dynamically update encrypted data stored on semi-trusted cloud server, effectively protecting user’s privacy. However, the majority of existing DSSE schemes exhibit inefficiencies in practical applications because of their complex structure. In addition, to store the status of keywords, the storage requirements of the client increase proportionally with the number of keyword/document pairs. Therefore, the client storage will be overwhelmed when confronted with a substantial increase in the volume of keyword/document pairs. To solve these issues, we propose a practical efficient dynamic searchable symmetric encryption scheme with lightweight clients—CoD-DSSE. A novel index structure similar to a chest of drawers is proposed in CoD-DSSE, which allows users to efficiently search all document indexes through XOR operations and keeps the keyword status on the server to lightweight clients. Furthermore, we use a random number generator to construct new search tokens for forward security and achieve backward security by using a Bloom filter to store the deleted document index, which can significantly reduce communication costs. The experimental and security analyses show that CoD-DSSE is efficient and secure in practice.

A provably lightweight and secure DSSE scheme, with a constant storage cost for a smart device client.

Outsourcing data to remote cloud providers is becoming increasingly popular amongst organizations and individuals. A semi-trusted server uses Searchable Symmetric Encryption (SSE) to keep the search information under acceptable leakage levels whilst searching an encrypted database. A dynamic SSE (DSSE) scheme enables the adding and removing of documents by performing update queries, where some information is leaked to the server each time a record is added or removed. The complexity of structures and cryptographic primitives in most existing DSSE schemes makes them inefficient, in terms of storage, and query requests generate overhead costs on the Smart Device Client (SDC) side. Achieving constant storage cost for SDCs enhances the viability, efficiency, and easy user experience of smart devices, promoting their widespread adoption in various applications while upholding robust privacy and security standards. DSSE schemes must address two important privacy requirements: forward and backward privacy. Due to the increasing number of keywords, the cost of storage on the client side is also increasing at a linear rate. This article introduces an innovative, secure, and lightweight Dynamic Searchable Symmetric Encryption (DSSE) scheme, ensuring Type-II backward and forward privacy without incurring ongoing storage costs and high-cost query generation for the SDC. The proposed scheme, based on an inverted index structure, merges the hash table with linked nodes, linking encrypted keywords in all hash tables. Achieving a one-time O(1) storage cost without keyword counters on the SDC side, the scheme enhances security by generating a fresh key for each update. Experimental results show low-cost query generation on the SDC side (6,460 nanoseconds), making it compatible with resource-limited devices. The scheme outperforms existing ones, reducing server-side search costs significantly.

Exploiting Hidden Information Leakages in Backward Privacy for Dynamic Searchable Symmetric Encryption

Dynamic searchable symmetric encryption (DSSE) enables searches over encrypted data as well as data dynamics such as flexible data addition and deletion operations. A major security concern in DSSE is how to preserve forward and backward privacy, which are typically achieved by removing the linkability between the newly added data and previous queries, and between the deleted data and future queries, respectively. After information leakage types were formally defined for different levels of backward privacy (i.e., Type-I, II, III), many backward private DSSE schemes have been constructed under the definitions. However, we observed that the backward privacy can be violated by leveraging additional secondary leakage, which is typically leaked in specific constructions of schemes in spite of their theoretical guarantees. In this paper, in order to understand the security gap between the theoretical definitions and practical constructions, we conduct an in-depth analysis of the root cause for the secondary leakage, and demonstrate how it can be abused to violate Type-II backward privacy (e.g., the exposure of the deletion history) of DSSE constructions in practice. We then propose a novel Type-II backward private DSSE scheme based on Intel SGX, which is resilient to the secondary leakage abuse attack. According to the comparative analysis of our scheme with the state-of-the-art SGX-based DSSE schemes, Bunker-B (EuroSec’19) and SGX-SE1 (ACNS’20), our scheme shows higher efficiency in terms of the search latency with a negligible utility loss under the same security level (cf. Bunker-B) while showing similar efficiency with a higher security level (cf. SGX-SE1). Finally, we formally prove that our scheme guarantees Type-II backward privacy.

Toward Forward and Backward Private Dynamic Searchable Symmetric Encryption Supporting Data Deduplication and Conjunctive Queries

In Internet of Things (IoT) application scenarios such as intelligent logistics, secure data access control and sharing based on dynamic searchable symmetric encryption (DSSE) has become a research hotspot in recent years. DSSE is an encryption technology which gratifies the above requirements, while protecting the sensitive data during the operation. The existing DSSE schemes do not achieve data deduplication and conjunctive queries concurrently, and exist problems such as complex update process, inflexible query method and privacy disclosure, etc. For this purpose, the paper proposes dynamic searchable symmetric encryption for data deduplication and conjunctive queries (DSSE-DC), and constructs a concrete DSSE-DC scheme. Our scheme uses symmetric encryption with homomorphic addition and bitmap index to develop a secure and reliable search architecture, and updates through modular addition. Meanwhile, we add a deduplication mechanism to realize data deduplication which avoids the waste of cloud storage resources. Furthermore, we introduce the idea of inner product matching to achieve efficient conjunctive queries. The adaptive security of DSSE-DC scheme is proved in the random oracle model. Whilst our scheme satisfies forward and backward privacy. In comparison to the existing DSSE schemes for conjunctive queries, our scheme has advantage in update and search performances, which is applicable to IoT applications like intelligent logistics.

A dynamic conjunctive keywords searchable symmetric encryption scheme for multiple users in cloud computing

With the continuous advancement of cloud computing technology, massive amounts of heterogeneous data are being outsourced to cloud servers. Dynamic searchable symmetric encryption (DSSE) is widely used for dynamically updating and searching ciphertext. Although many DSSE schemes have been developed in recent years, few can satisfy the requirement for multi-keyword search. To address this problem, we proposed a novel Dynamic Searchable Symmetric Encryption scheme supporting Multiple users and Multiple keywords (MMDSSE) in this paper, specifically designed for the multi-keyword cloud computing paradigm, while also enabling multi-user search capability. To achieve multi-keyword search, a tag is computed using an iso-or operation that records the relationship between the keyword and identifier. In addition, a unique key is assigned by the data owner to each user with different file access rights. This allows users to gain fine-grained control over the ciphertext, and the essential security properties, including forward and backward privacy, can be achieved accordingly. Furthermore, this scheme is resistant to collusion attacks. Finally, the experiment was simulated on the IDEA platform using the Java language. The experimental results demonstrate that this scheme performs well.

Efficient Strong Privacy-Preserving Conjunctive Keyword Search Over Encrypted Cloud Data

Searchable symmetric encryption (SSE) supports keyword search over outsourced symmetrically encrypted data. Dynamic searchable symmetric encryption (DSSE), a variant of SSE, further enables data updating. Most DSSE works with conjunctive keyword search primarily consider forward and backward privacy. Ideally, the server should only learn the result sets involving all keywords in the conjunction. However, existing schemes suffer from keyword pair result pattern (KPRP) leakage, revealing the partial result sets containing two of query keywords. We propose the first DSSE scheme to address aforementioned concerns that achieves strong privacy-preserving conjunctive keyword search. Specifically, our scheme can maintain forward and backward privacy and eliminate KPRP leakage, offering a higher level of security. The search complexity scales with the number of documents stored in the database in several existing schemes. However, the complexity of our scheme scales with the update frequency of the least frequent keyword in the conjunction, which is much smaller than the size of the entire database. Besides, we devise a least frequent keyword acquisition protocol to reduce frequent interactions between clients. Finally, we analyze the security of our scheme and evaluate its performance theoretically and experimentally. The results show that our scheme has strong privacy preservation and efficiency.

Result-pattern-hiding Conjunctive Searchable Symmetric Encryption with Forward and Backward Privacy

Dynamic searchable symmetric encryption (DSSE) enables the data owner to outsource its database (document sets) to an untrusted server and make searches and updates securely and efficiently. Conjunctive DSSE can process conjunctive queries that return the documents containing multiple keywords. However, a conjunctive search could leak the keyword pair result pattern (KPRP), where attackers can learn which documents contain any two keywords involved in the query. File-injection attack shows that KPRP can be utilized to recover searched keywords. To protect data effectively, DSSE should also achieve forward privacy, i.e., hides the link between updates to previous searches, and backward privacy, i.e., prevents deleted entries being accessed by subsequent searches. Otherwise, the attacker could recover updated/searched keywords and records. However, no conjunctive DSSE scheme in the literature can hide KPRP in sub-linear search efficiency while guaranteeing forward and backward privacy. In this work, we propose the first sub-linear KPRP-hiding conjunctive DSSE scheme (named HDXT) with both forward and backward privacy guarantees. To achieve these three security properties, we introduce a new cryptographic primitive: Attribute-updatable Hidden Map Encryption (AUHME). AUHME enables HDXT to efficiently and securely perform conjunctive queries and update the database in an oblivious way. In comparison with previous work that has weaker security guarantees, HDXT shows comparable, and in some cases, even better performance.

Towards Multi-Client Forward Private Searchable Symmetric Encryption in Cloud Computing

As a useful cryptographic primitive, searchable symmetric encryption (SSE) has been intensively studied to achieve the secure and efficient retrieval of encrypted data. In order to process update operations, dynamic SSE schemes have been proposed. But recently, file-injection attack has threatened the security of traditional dynamic SSE protocols. Therefore, designing dynamic SSE schemes with forward privacy becomes a new demand to resist the above attack. Meanwhile, multi-client setting is another requirement in SSE techniques where multiple clients can be delegated and have access to the database. However, most of previous forward private schemes were constructed for single-client setting and cannot directly extended to multi-client environment efficiently. To solve the problem, we propose a forward private SSE scheme with support for multi-client in cloud computing. The proposed scheme is based on XOR-homomorphic function and involves two new data structures as private link and public search tree. Security proof demonstrates the proposed scheme can meet the desired secure features. We then conduct experimental evaluation of the proposed scheme and make comparison with related schemes. The result shows that the proposed scheme tends to have high efficiency.

Verifiable dynamic search over encrypted data in cloud‐assisted intelligent systems

The cloud-assisted intelligent systems have attracted extensive attention due to their powerful data analysis and computation capabilities. However, how to handle encrypted data remains a challenging problem in intelligent systems. A promising solution is searchable symmetric encryption (SSE), which enables a client to privately outsource their data to the cloud while preserving keyword search functionality. In practice, dynamic SSE is more practical and supports efficient data addition and deletion. Unfortunately, data update will leak some additional information which can be exploited to break data privacy. To address this issue, forward and backward secure SSE schemes are proposed to reduce the leakage of data update. That is, forward security guarantees that the newly updated documents cannot reveal the previously searched keywords, while backward security guarantees that the server cannot recover the deleted documents. However, the existing forward and backward secure SSE schemes mainly consider curious-but-honest server. How to verify the soundness and completeness of search results is still a challenge. In this paper, we propose a noninteractive verifiable dynamic SSE scheme with forward and backward security from two universal accumulators. Specifically, the server in our scheme only needs one roundtrip to return the nondeleted search results to the client, which saves the communication overhead dramatically. Besides, our scheme can achieve public verification that anyone can verify the search results but not only the client who has the private key. Finally, we give a formal security analysis and compare the proposed scheme with other related work, the results show that our scheme can achieve the desired security properties with practical efficiency.

Verifiable Conjunctive Dynamic Searchable Symmetric Encryption With Forward and Backward Privacy

Abstract Dynamic searchable symmetric encryption (DSSE) with forward and backward privacy makes it possible to perform search on the outsourced encrypted database efficiently while still allowing updates under acceptable leakage. Current forward and backward private DSSE (FB-DSSE) scheme proposed by Zuo et al. cannot support conjunctive keyword query and the cloud server needs to be honest-but-curious. Recent FB-DSSE scheme supporting conjunctive keyword query proposed by Patranabis et al. cannot verify search results. On the other hand, searchable symmetric encryption scheme proposed by Wang et al. that supports conjunctive keyword query and the verification of search results cannot achieve forward and backward privacy. The problem of constructing a verifiable conjunctive FB-DSSE scheme is still open. In this paper, we propose a verifiable conjunctive dynamic searchable symmetric encryption scheme (VCDSSE). VCDSSE is a FB-DSSE scheme that additionally supports the verification of search results and conjunctive keyword query. We revisit homomorphic MAC to enable efficient verification of search results, adopt the technique of oblivious cross-tags to achieve conjunctive keyword query and utilize state chain to ensure forward and backward privacy. The formal security analysis and performance evaluation demonstrate that VCDSSE is secure and practical as compared with Mitra scheme in terms of search time.

Achieving Secure and Efficient Dynamic Searchable Symmetric Encryption over Medical Cloud Data

In medical cloud computing, a patient can send her medical data to a cloud server from afar. Because medical data is highly sensitive, only authorized doctors are allowed to access it in this case. A frequent solution is to encrypt data before outsourcing it, with the patient simply sending the corresponding encryption key to the authorized doctors. However, due to the difficulties of digging through the encrypted data, the usability of outsourced medical data is severely limited. Over medical cloud data, we propose Secure and Efficient Dynamic Searchable Symmetric Encryption (SEDSSE) schemes. To begin, we propose a dynamic searchable symmetric encryption scheme that uses the secure k-Nearest Neighbor (kNN) and Attribute-Based Encryption (ABE) techniques to achieve two important security features: forward privacy and backward privacy, both of which are difficult to achieve in the field of dynamic searchable symmetric encryption. Then, to address the key sharing problem that plagues the kNN-based searchable encryption strategy, we suggest an improved technique. In terms of storage, search, and update complexity, our solutions outperform prior proposals. Extensive tests show that our approaches are efficient in terms of storage overhead, index building, trapdoor generation, and query.

Achieving Privacy-Preserving DSSE for Intelligent IoT Healthcare System

As the product of combining Internet of Things (IoT), cloud computing, and traditional healthcare, Intelligent IoT Healthcare (IIoTH) brings us a lot of convenience, meanwhile security and privacy issues have attracted great attention. Dynamic searchable symmetric encryption (DSSE) technique can make the user search the dynamic healthcare information from IIoTH system under the condition that the privacy is protected. In this article, a novel privacy-preserving DSSE scheme for IIoTH system is proposed. It is the first DSSE scheme designed for personal health record (PHR) files database with forward security. We construct the secure index based on hash chain and realize trapdoor updates for resisting file injection attacks. In addition, we realize fine-grained search over encrypted PHR files database of attribute-value type. When the user executes search operations, he/she gets only a matched attribute value instead of the whole file. As a result, the communication cost is reduced and the disclosure of patient's privacy is minimized. The proposed scheme also achieves attribute access control, which allows users have different access authorities to attribute values. The specific security analysis and experiments show the security and the efficiency of the proposed scheme.

ROSE: Robust Searchable Encryption With Forward and Backward Security

Dynamic searchable symmetric encryption (DSSE) has been widely recognized as a promising technique to delegate <monospace xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">update</monospace> and <monospace xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">search</monospace> queries over an outsourced database to an untrusted server while guaranteeing the privacy of data. Many efforts on DSSE have been devoted to obtaining a good tradeoff between security and performance. However, it appears that all existing DSSE works miss studying on what will happen if the DSSE client issues irrational <monospace xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">update</monospace> queries carelessly, such as duplicate <monospace xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">update</monospace> queries and <monospace xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">delete</monospace> queries to remove non-existent entries (that have been considered by many popular database system in the setting of plaintext). In this scenario, we find that (1) most prior works lose their claimed correctness or security, and (2) no single approach can achieve correctness, forward and backward security, and practical performance at the same time. To address this problem, we study for the first time the notion of robustness of DSSE. Generally, we say that a DSSE scheme is robust if it can keep the same correctness and security even in the case of misoperations. Then, we introduce a new cryptographic primitive named key-updatable pseudo-random function and apply this primitive to constructing ROSE, a robust DSSE scheme with forward and backward security. Finally, we demonstrate the efficiency of ROSE and give the experimental comparisons.

A forward and backward secure conjunctive keywords dynamic searchable encryption scheme

Dynamic searchable symmetric encryption (DSSE) allows a user to carryout search and update operations on the outsourced encrypted data on cloud. The recent research work in DSSE exposed many flaws in existing strategies by introducing leakage abuse attacks. To protect DSSE schemes from leakage, forward and backward privacy notions were introduced. In this paper, we propose a forward and backward secure chained dictionary-based indexing mechanism with support for conjunctive keyword queries. The proposed scheme uses a minimal leakage index design, requiring compact storage at client, easier update operations at server and removes entries of deleted files from index to ensure backward privacy resulting in reduced index size. It ensures that the searches followed by update operation do not violate query privacy. Rigorous security analysis and experimental evaluations show that our scheme achieves sub-linear search time and supports efficient update operations ensuring forward and backward privacy.

Database Padding for Dynamic Symmetric Searchable Encryption

Dynamic symmetric searchable encryption (DSSE) that enables the search and update of encrypted databases outsourced to cloud servers has recently received widespread attention for leakage-abuse attacks against DSSE. In this paper, we propose a dynamic database padding method to mitigate the threat of data leakage during the update operation of outsourcing data. First, we introduce an outlier detection technology where bogus files are generated for padding according to the outlier factors, hiding the document information currently matching search keywords. Furthermore, we design a new index structure suitable for the padded database using the bitmap index to simplify the update operation of the encrypted index. Finally, we present an application scenario of the padding method and realize a forward and backward privacy DSSE scheme (named PDB-DSSE). The security analysis and simulation results show that our dynamic padding algorithm is suitable for DSSE scheme and PDB-DSSE scheme maintains the security and efficiency of the retrieval and update of the DSSE scheme.

Backward Private Searchable Symmetric Encryption with Improved Locality

Searchable symmetric encryption (SSE) enables clients to outsource their encrypted documents into a remote server and allows them to search the outsourced data efficiently without violating the privacy of the documents and search queries. Dynamic SSE schemes (DSSE) include performing update queries, where documents can be added or removed at the expense of leaking more information to the server. Two important privacy notions are addressed in DSSE schemes: forward and backward privacy. The first one prevents associating the newly added documents with previously issued search queries. While the second one ensures that the deleted documents cannot be linked with subsequent search queries. Backward has three formal types of leakage ordered from strong to weak security: Type-I, Type-II, and Type-III. In this paper, we propose a new DSSE scheme that achieves Type-II backward and forward privacy by generating fresh keys for each search query and preventing the server from learning the underlying operation (del or add) included in update query. Our scheme improves I/O performance and search cost. We implement our scheme and compare its efficiency against the most efficient backward privacy DSSE schemes in the literature of the same leakage: MITRA and MITRA*. Results show that our scheme outperforms the previous schemes in terms of efficiency in dynamic environments. In our experiments, the server takes 699ms to search and return (100,000) results.

A blockchain-based dynamic searchable symmetric encryption scheme under multiple clouds

A blockchain-based dynamic searchable symmetric encryption scheme under multiple clouds

Forward and backward secure keyword search with flexible keyword shielding

Dynamic Searchable Symmetric Encryption (DSSE) has gained increasing popularity as it enables users to perform both file updates and ciphertext retrieval over encrypted data. However, existing DSSE schemes still lead to privacy leakage (e.g., forward and backward privacy) in the dynamic setting. Some forward and backward secure DSSE schemes have been proposed, but still cannot support the keyword shielding flexibly. To solve this challenging issue, we propose a Forward and Backward Authorized Keyword Search (FB-AKS) scheme with recoverable keyword shielding by using trapdoor permutations and puncturable encryption in this paper. Compared with existing forward and backward private schemes, FB-AKS achieves keyword authorization flexibly (e.g., keyword shielding, keyword un-shielding). The formal security analysis proves that FB-AKS achieves forward and backward security. And extensive experiments demonstrate that FB-AKS has less computation and storage overheads.

Eurus: Towards an Efficient Searchable Symmetric Encryption With Size Pattern Protection

To achieve efficiently search and update on outsourced encrypted data, dynamic searchable symmetric encryption (DSSE) was proposed by just leaking some well-defined leakages. Though small, many recent works show that an attacker can exploit these leakages to undermine the security of existing DSSE schemes. In particular, an attacker can exploit even seemingly harmless size pattern to perform severe attacks. Many exiting schemes resort to oblivious RAM (ORAM) to hide search/access pattern; however, even such powerful cryptographic primitive cannot protect size pattern leakage. In this article, we first show that size pattern can lead to more information leakages, which is not well studied or protected by existing schemes. We then extend the existing privacy notion for DSSE to capture the size pattern leakage, achieving a strong forward and backward privacy definition. Following the definition, we propose a new DSSE scheme Eurus. Eurus can eliminate search/access pattern by relying on a multi-server ORAM scheme, meanwhile reducing size pattern with reasonable efficiency. We show that Eurus can reduce leakage significantly with better efficiency, compared with state-of-the-art leakage reduction schemes.