One particular trend observed in healthcare is the progressive shift of data and services to the cloud, partly due to convenience (e.g. availability of complete patient medical history in real-time) and savings (e.g. economics of healthcare data management). There are, however, limitations to using conventional cryptographic primitives and access control models to address security and privacy concerns in an increasingly cloud-based environment. In this paper, we study the potential to use the Blockchain technology to protect healthcare data hosted within the cloud. We also describe the practical challenges of such a proposition and further research that is required.

Blockchain: A Panacea for Healthcare Cloud-Based Data Security and Privacy?

Blockchain based searchable encryption for electronic health record sharing

Blockchain technology has been deemed to be an ideal choice for strengthening existing computing systems in varied manners. As one of the network-enabled technologies, cloud computing has been broadly adopted in the industry through numerous cloud service models. Fusing blockchain technology with existing cloud systems has a great potential in both functionality/performance enhancement and security/privacy improvement. The question remains on how blockchain technology inserts into current deployed cloud solutions and enables the reengineering of cloud datacenter. This survey addresses this issue and investigates recent efforts in the technical fusion of blockchain and clouds. Three technical dimensions roughly are covered in this work. First, we concern the service model and review an emerging cloud-relevant blockchain service model, Blockchain-as-a-Service (BaaS); second, security is considered a key technical dimension in this work and both access control and searchable encryption schemes are assessed; finally, we examine the performance of cloud datacenter with supports/participance of blockchain from hardware and software perspectives. Main findings of this survey will be theoretical supports for future reference of blockchain-enabled reengineering of cloud datacenter.

Blockchain Meets Cloud Computing: A Survey

Recent booming growth of networking-based solutions have brought numerous challenges to security and privacy from both perspectives of insider and outsider threats. The encrypted data are relatively considered a safe storage status; however, the process of encrypting data is still facing adversarial actions and data process generally is inapplicable over ciphertexts. As a type of the encryption approach allowing computations over ciphertexts, a fully homomorphic encryption (FHE) can concurrently deal with the adversarial hazards and support computations on ciphertexts. This paper focuses on the issue of blend arithmetic operations over real numbers and proposes a novel tensor-based FHE solution. The proposed approach is called a FHE for blend operations model that uses tensor laws to carry the computations of blend arithmetic operations over real numbers. In our paper, we provide both theoretical proof and experimental evaluations in order to evince the adoptability of the proposed approach.

Blend Arithmetic Operations on Tensor-Based Fully Homomorphic Encryption Over Real Numbers

Currently, searchable encryption is a hot topic in the field of cloud computing The existing achievements are mainly focused on keyword-based search schemes, and almost all of them depend on predefined keywords extracted in the phases of index construction and query However, keyword-based search schemes ignore the semantic representation information of users’ retrieval and cannot completely match users’ search intention Therefore, how to design a content-based search scheme and make semantic search more effective and context-aware is a difficult challenge In this paper, for the first time, we define and solve the problems of semantic search based on conceptual graphs (CGs) over encrypted outsourced data in clouding computing (SSCG) We first employ the efficient measure of “sentence scoring” in text summarization and Tregex to extract the most important and simplified topic sentences from documents We then convert these simplified sentences into CGs To perform quantitative calculation of CGs, we design a new method that can map CGs to vectors Next, we rank the returned results based on “text summarization score” Furthermore, we propose a basic idea for SSCG and give a significantly improved scheme to satisfy the security guarantee of searchable symmetric encryption (SSE) Finally, we choose a real-world dataset, ie, the CNN dataset to test our scheme The results obtained from the experiment show the effectiveness of our proposed scheme

Enabling Semantic Search Based on Conceptual Graphs over Encrypted Outsourced Data

Searchable Symmetric Encryption (SSE) when deployed in the cloud allows one to query encrypted data without the risk of data leakage. Despite the widespread interest, existing surveys do not examine in detail how SSE’s underlying structures are designed and how these result in the many properties of a SSE scheme. This is the gap we seek to address, as well as presenting recent state-of-the-art advances on SSE. Specifically, we present a general framework and believe the discussions may lead to insights for potential new designs. We draw a few observations. First, most schemes use index table, where optimal index size and sublinear search can be achieved using an inverted index. Straightforward updating can only be achieved using direct index, but search time would be linear. A recent trend is the combinations of index table, and tree, deployed for efficient updating and storage. Secondly, mechanisms from related fields such as Oblivious RAM (ORAM) have been integrated to reduce leakages. However, using these mechanisms to minimise leakages in schemes with richer functionalities (e.g., ranked, range) is relatively unexplored. Thirdly, a new approach (e.g., multiple servers) is required to mitigate new and emerging attacks on leakage. Lastly, we observe that a proposed index may not be practically efficient when implemented, where I/O access must be taken into consideration.

Searchable Symmetric Encryption: Designs and Challenges

We investigate the problem of privately searching encrypted data that is structured in the form of knowledge. Our rationale in such an investigation lies on the potential emergence of knowledge-based search using natural language, which makes content searches more effective and is context-aware when compared with existing keyword searches. With knowledge-based search, indexes and databases will consist of data stored using knowledge representation techniques such as description logics and conceptual graphs. This leads naturally to the issue of how to privately search this data, especially when most existing searchable encryption schemes are keyword-based. We propose the first construction with CQA2-security for searching encrypted knowledge, where the knowledge is represented in a well-established formalism known as basic conceptual graphs. Our proposals are based on structured encryption schemes of Chase and Kamara [8].

Structured Encryption for Conceptual Graphs

Searchable Symmetric Encryption (SSE) allows a user to store encrypted documents on server(s) and later efficiently searches these documents in a private manner. So far most existing works have focused on a single storage server. Therefore in this paper we consider the natural extension of SSE to multiple servers. We believe it is of practical interest, given that a user may choose to distribute documents to various cloud storage that are now readily available. The main benefit compared to a single server scheme is that a server can be set to hold only subset of encrypted documents/blocks. A server learns only content of documents/blocks that it stores in the event of successful leakage attack or ciphertext cryptanalysis, provided servers do not collude. We define formally an extension of single server SSE to multiserver and instantiate provably secure schemes that provide the above feature. Our main scheme hides total number of documents and document size even after retrieval, achieving less leakages compared to prior work, while maintaining sublinear search time for each server. We further study leakages under the new setting of non-colluding and colluding servers.

Searchable symmetric encryption over multiple servers

Authenticated encryption (AE) is a cryptographic construction that simultaneously protects confidentiality and integrity. A considerable amount of research has been devoted to the area since its formal inception in 2000. Different lines of research have been proposed to enhance the available schemes in terms of security, efficiency, and design and to implement new ideas. However, a comprehensive systematic literature review (SLR) of the topic has not been provided to the best of the authors’ knowledge. This study fills this gap in the literature by proposing a framework for classifying AE schemes and highlighting past contributions to help researchers familiarize themselves with the current state and directions for future research in the area. This SLR covered AE schemes proposed from 2000 to 2020. A total of 217 articles, selected from eight sources, were categorized into independent schemes, CAESAR competition schemes, and NIST lightweight competition schemes. These schemes were then classified according to their design approaches, security-related properties, and functional features. Our analysis reveals that a significant outstanding challenge in AE is to balance security, efficiency, and the provision of desirable features.

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Authenticated Encryption Schemes: A Systematic Review

Structured encryption schemes generalise symmetric searchable encryption (SSE) schemes by allowing encrypted search on arbitrarily structured data, instead of keyword-based search only. Both structured encryption and SSE schemes mainly consider security against passive adversaries, until recently where SSE schemes secure against active adversaries were proposed. This means in addition of querying encrypted data, the adversaries can modify encrypted data in the storage. SSE schemes secure against such adversaries are termed verifiable SSE. In this paper, we examine verifiable SSE and propose an extension for structured encryption under the active adversary setting. We first define verifiable structured encryption and its security under the notion of reliability similar to verifiable SSE, but with difference on how a tag for verifiability is defined. This is mainly due to the notions of semi-private data that does not exist in a verifiable SSE scheme. We then present constructions secure under this model and prove security of the constructions.

Moesfa Soeheila Mohamad

Papers

Searchable Symmetric Encryption: Designs and Challenges

Structured Encryption for Conceptual Graphs

Searchable symmetric encryption over multiple servers

Authenticated Encryption Schemes: A Systematic Review

Verifiable Structured Encryption