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Under the assumption of honest-but-curious cloud service provider, various cryptographic techniques have been used to address the issues of data access control and confidentiality in public cloud storage. Among which, attribute-based encryption (ABE) has been shown to be an attractive scheme. Although the technique of ABE brings in various benefits, its onerous overhead should not be ignored. In this paper, based on an improved LSSS (linear secret sharing scheme) matrix expression integrated in CP-ABE (Ciphertext-Policy Attribute-Based Encryption) algorithm, we present an efficient and secure attribute-based access control scheme for the scenarios where multiple data are shared and encrypted with frequently used sub-policies. In the scheme, a user can store the parameters about a specific sub-policy in his/her first decryption, which can be reused in the subsequent data decryptions whose embedded access policies include the same sub-policy so as to significantly reduce the computation cost. Our proposed scheme is proved to be semantically secure under chosen plaintext attacks and can well preserve the confidentiality of the data sharing system. Our analysis and experimentation also show that our scheme does significantly reduce the decryption time and while trades in only very little storage overhead, and thus effectively promotes the efficiency.

F2C (fog-to-cloud) enables service providers to rent the low-cost cloud/fog resources to publish their services, and the fog nodes, which are deployed at the edge, can provide short-latency service to users. However, new security threats come along with this new computing paradigm, where the access control and trusted payment are concerned in this work. We propose a privacy-preserving authentication scheme. By integrating $k$ k -times anonymous authentication ( $k$ k -TAA) and attribute-based access control, in our proposed scheme, service providers can autonomously determine a fine-grained access policy and the maximal access times for authorized users. Thus, users who satisfy the access policy can receive benefits of this service for certain number of times without leaking any private information. Our authentication phase has a low latency because it is offloaded to the fog as what the service does. This paper presents a lightweight and trusted billing mechanism using Merkle Hash Tree (MHT), which can detect the cloud's service forgery with high probability, without costing too much of service provider's bandwidth and computation. Rigorous security analysis proves that the proposed scheme is secure against malicious users, fogs, and cloud, and the experimental results show the significant performance advantage on both the delay reduction and service providers’ cost saving.

More and more users are eager to obtain more comprehensive network services without revealing their private information. Traditionally, in order to access a network, a user is authorized with an identity and corresponding keys, which are generated and managed by the network operator. All users' personally identifying information are centralized stored by the network operator. However, this approach makes users lose the control of their personally identifying information. Users are concerned about who can access these sensitive data and whether they have been compromised. In this paper, we propose a blockchain-based identity management and authentication scheme for mobile networks, where users' identifying information are controlled by the users themselves. Our scheme let users generate their self-sovereign identities (SSIs) and corresponding public keys and private keys. The private key used to authenticate the user's identifying information is only known to the user. We use blockchain to record SSIs and public keys of legitimate user, and adopt chameleon hash to delete illegal users' information on the blockchain, while keeping the block head unchanged. Furthermore, other service providers can obtain the user's SSI and public key and authenticate users by querying the blockchain. Experimental results confirm that our scheme can greatly reduce the revocation overhead and communication overhead.

The new paradigm of outsourcing data to the cloud is a double-edged sword. On the one hand, it frees data owners from the technical management, and is easier for data owners to share their data with intended users. On the other hand, it poses new challenges on privacy and security protection. To protect data confidentiality against the honest-but-curious cloud service provider, numerous works have been proposed to support fine-grained data access control. However, till now, no schemes can support both fine-grained access control and time-sensitive data publishing. In this paper, by embedding timed-release encryption into Ciphertext-Policy Attribute-based Encryption (CP-ABE), we propose a new time and attribute factors combined access control on time-sensitive data for public cloud storage (named TAFC). Based on the proposed scheme, we further propose an efficient approach to design access policies faced with diverse access requirements for time-sensitive data. Extensive security and performance analysis shows that our proposed scheme is highly efficient and satisfies the security requirements for time-sensitive data storage in public cloud.

In public cloud storage services, data are outsourced to semi-trusted cloud servers which are outside of data owners' trusted domain. To prevent untrustworthy service providers from accessing data owners' sensitive data, outsourced data are often encrypted. In this scenario, conducting access control over these data becomes a challenging issue. Attribute-based encryption (ABE) has been proved to be a powerful cryptographic tool to express access policies over attributes, which can provide a fine-grained, flexible, and secure access control over outsourced data. However, the existing ABE-based access control schemes do not support users to gain access permission by collaboration. In this paper, we explore a special attribute-based access control scenario where multiple users having different attribute sets can collaborate to gain access permission if the data owner allows their collaboration in the access policy. Meanwhile, the collaboration that is not designated in the access policy should be regarded as a collusion and the access request will be denied. We propose an attribute-based controlled collaborative access control scheme through designating translation nodes in the access structure. Security analysis shows that our proposed scheme can guarantee data confidentiality and has many other critical security properties. Extensive performance analysis shows that our proposed scheme is efficient in terms of storage and computation overhead.

With the dramatically increasing deployment of the Internet of Things (IoT), remote monitoring of health data to achieve intelligent healthcare has received great attention recently. However, due to the limited computing power and storage capacity of IoT devices, users’ health data are generally stored in a centralized third party, such as the hospital database or cloud, and make users lose control of their health data, which can easily result in privacy leakage and single-point bottleneck. In this paper, we propose Healthchain, a large-scale health data privacy preserving scheme based on blockchain technology, where health data are encrypted to conduct fine-grained access control. Specifically, users can effectively revoke or add authorized doctors by leveraging user transactions for key management. Furthermore, by introducing Healthchain, both IoT data and doctor diagnosis cannot be deleted or tampered with so as to avoid medical disputes. Security analysis and experimental results show that the proposed Healthchain is applicable for smart healthcare system.

Standalone solar carbon dioxide conversion without the use of any external energy is a primary goal of solar carbon-based fuel production. So far, researchers have performed many staged studies, for example, on the independent oxygen evolution reaction and CO2 reduction reaction, to focus on these key steps and strengthen specific characteristics, including photoresponse, energy carrier separation, and transfer. Noteworthy performance has been obtained for almost every stage. However, recent pioneering works have demonstrated that staged research cannot always be easily pieced together. Here, recent advances in standalone systems are collected and reviewed. We focus on the critical assessment of the key components requiring improvement. In addition, the opportunities for hybrid systems of photocatalysts with photothermocatalysts and photovoltaics with electrocatalysts are assessed. This review aims to discuss the direction of standalone solar carbon fuel production and potential knowledge transfer to intersecting fields.

People endorse the great power of cloud computing, but cannot fully trust the cloud providers to host privacy-sensitive data, due to the absence of user-to-cloud controllability. To ensure confidentiality, data owners outsource encrypted data instead of plaintexts. To share the encrypted files with other users, ciphertext-policy attribute-based encryption (CP-ABE) can be utilized to conduct fine-grained and owner-centric access control. But this does not sufficiently become secure against other attacks. Many previous schemes did not grant the cloud provider the capability to verify whether a downloader can decrypt. Therefore, these files should be available to everyone accessible to the cloud storage. A malicious attacker can download thousands of files to launch economic denial of sustainability (EDoS) attacks, which will largely consume the cloud resource. The payer of the cloud service bears the expense. Besides, the cloud provider serves both as the accountant and the payee of resource consumption fee, lacking the transparency to data owners. These concerns should be resolved in real-world public cloud storage. In this paper, we propose a solution to secure encrypted cloud storages from EDoS attacks and provide resource consumption accountability. It uses CP-ABE schemes in a black-box manner and complies with arbitrary access policy of the CP-ABE. We present two protocols for different settings, followed by performance and security analysis.

VCC is an emerging computing paradigm developed for providing various services to vehicle drivers, and has attracted more and more attention from researchers and practitioners over the last few years. However, privacy preserving and secure data sharing has become a very challenging and important issue in VCC. Unfortunately, existing secure access control schemes consume too many computation resources, which prevents them from being performed on computing resource constrained vehicle onboard devices. Also, these cloud-based schemes suffer large latency and jitter due to their centralized resource management, and thus may not be suitable for real-time applications in VANETs. In this article, we thus propose a novel fog-to-cloud-based architecture for data sharing in VCC. Our scheme is a cryptography-based mechanism that conducts fine-grained access control. In our design, the complicated computation burden is securely outsourced to fog and cloud servers with confidentiality and privacy preservation. Meanwhile, with the prediction of a vehicle's mobility, pre-pushing data to specific fog servers can further reduce response latency with no need to consume more resources of the fog server. In addition, with the assumption of no collusion between different providers for the cloud and fog servers, our scheme can provide verifiable auditing of fog servers' reports. The scheme is proved secure against existing adversaries and newborn security threats. Experimental test shows significant performance improvement in edge devices' overhead saving and response delay reduction. Introduction

With the development of society, energy shortage and environmental problems have become more and more outstanding. Solar energy is a clean and sustainable energy resource, potentially driving energy conversion and environmental remediation reactions. Thus, solar‐driven chemistry is an attractive way to solve the two problems. Photothermal chemistry (PTC) is developed to achieve full‐spectral utilization of the solar radiation and drive chemical reactions more efficiently under relatively mild conditions. In this review, the mechanisms of PTC are summarized from the aspects of thermal and non‐thermal effects, and then the interaction and synergy between these two effects are sorted out. In this paper, distinguishing and quantifying these two effects is discussed to understand PTC processes better and to design PTC catalysts more methodically. However, PTC is still a little far away from practical. Herein, several key points, which must be considered when pushing ahead with the engineering application of PTC, are proposed, along with some workable suggestions on the practical application. This review provides a unique perspective on PTC, focusing on the synergistic effects and pointing out a possible direction for practical application., Solar‐driven chemistry is an attractive way to solve energy and environmental problems, among which photothermal chemistry (PTC) can realize full‐spectral utilization of solar radiation and driving chemical reactions more efficiently under relatively mild conditions. In order to push ahead with the engineering application of PTC, multisystem integration can be considered.

Attribute-based encryption (ABE) has opened up a popular research topic in cryptography over the past few years. It can be used in various circumstances, as it provides a flexible way to conduct fine-grained data access control. Despite its great advantages in data access control, current ABE based access control system cannot satisfy the requirement well when the system judges the access behavior according to attribute comparison, such as “greater than $x$ ” or “less than $x$ ”, which are called comparable attributes in this paper. In this paper, based on a set of well-designed sub-attributes representing each comparable attribute, we construct a comparable attribute-based encryption scheme (CABE for short) to address the aforementioned problem. The novelty lies in that we provide a more efficient construction based on the generation and management of the sub-attributes with the notion of 0-encoding and 1-encoding. Extensive analysis shows that: Compared with the existing schemes, our scheme drastically decreases the storage, communication and computation overheads, and thus is more efficient in dealing with the applications with comparable attributes.

Data access control is a challenging issue in public cloud storage systems. Ciphertext-policy attribute-based encryption (CP-ABE) has been adopted as a promising technique to provide flexible, fine-grained, and secure data access control for cloud storage with honest-but-curious cloud servers. However, in the existing CP-ABE schemes, the single attribute authority must execute the time-consuming user legitimacy verification and secret key distribution, and hence, it results in a single-point performance bottleneck when a CP-ABE scheme is adopted in a large-scale cloud storage system. Users may be stuck in the waiting queue for a long period to obtain their secret keys, thereby resulting in low efficiency of the system. Although multi-authority access control schemes have been proposed, these schemes still cannot overcome the drawbacks of single-point bottleneck and low efficiency, due to the fact that each of the authorities still independently manages a disjoint attribute set. In this paper, we propose a novel heterogeneous framework to remove the problem of single-point performance bottleneck and provide a more efficient access control scheme with an auditing mechanism. Our framework employs multiple attribute authorities to share the load of user legitimacy verification. Meanwhile, in our scheme, a central authority is introduced to generate secret keys for legitimacy verified users. Unlike other multi-authority access control schemes, each of the authorities in our scheme manages the whole attribute set individually. To enhance security, we also propose an auditing mechanism to detect which attribute authority has incorrectly or maliciously performed the legitimacy verification procedure. Analysis shows that our system not only guarantees the security requirements but also makes great performance improvement on key generation.

Objective: Numerous studies have proved the importance of Evidence-Based Medicine (EBM) in daily clinical practice, however, clinicians&rsquo, attitudes play an important role in determining its implementation. The objective of this study was to investigate Chinese clinical physicians&rsquo, perception of and attitude towards EBM and their Evidence-Based Practice (EBP) as well as the barriers towards EBP. Methods: Using a cross-sectional design, self-response questionnaires were distributed to clinical physicians (internal medicine and surgery departments) across three tertiary hospitals in Wuhan, China. Results: In total, 131 out of 195 (67.2%) physicians completed and returned the questionnaire. A total of 64.9% of the physicians either knew moderately or a lot about EBM. The mean score of physicians&rsquo, attitude toward EBM was 2.35 &plusmn, 0.35, and that of their EBP skill/ competency was 1.51 &plusmn, 0.56 (on 0&ndash, 3 Likert scale). In total, 76.0% of physicians often or sometimes applied EBM in routine daily practice. The largest barrier preventing implementation was the varying individual differences in diseases (61.0%), followed by a lack of investment from the hospital/department (39.8%), and a lack of patient cooperation (37.4%). Chinese physicians in tertiary hospitals possessed expressed positive attitudes towards EBM, however, they only retained a moderate level of clinical evidence competency. Both an individual factor (personal interest) and organizational factors (workload, hospital requirement) had an effect on physicians&rsquo, attitudes and their EBP skills. Management and organizational efforts, in addition to time dedicated for EBP projects could help reduce barriers that prevent EBP.

With an advancement of mobile communication technology, the space information network (SIN) has been proposed to meet the increasing demands of mobile communication due to its advantage of providing great expanding access services. In SIN, authentication is significant for the security to prevent the network resource from unauthorized access. However, the features of highly exposed links and extremely high propagation delay make it difficult to design a secure and fast authentication scheme for SIN. Although some existing researches have tried to design authentication protocols for SIN, they haven't taken the intolerable authentication delay and the risk of satellite compromising into consideration. Faced with these problems, we design a proxy signature-based authentication scheme for SIN, in which, the interaction process of authentication can be only implemented between the mobile user and the satellite node, thus reducing the long authentication implementation delay. Furthermore, we utilize the proxy signature to mitigate the risk of satellites being attacked. The results of security and performance analysis show that the proposed scheme can provide the required security and largely reduce the authentication latency.