•Smart cross-domain data sharing. Patient’s medical records are encrypted using a cross-domain access policy, which can be access by the authorized users in the entire system.•Smart self-adaptive ...access control. The access control is self-adaptive to normal and emergency situations. A break-glass access method is designed for the emergency situation.•Smart deduplication. This system supports smart deduplication and provides a new access policies combination method, where no plaintext message is leaked.
In this paper, a privacy-preserving smart IoT-based healthcare big data storage system with self-adaptive access control is proposed. The aim is to ensure the security of patients’ healthcare data, realize access control for normal and emergency scenarios, and support smart deduplication to save the storage space in big data storage system. The medical files generated by the healthcare IoT network are encrypted and transferred to the storage system, which can be securely shared among the healthcare staff from different medical domains leveraging a cross-domain access control policy. The traditional access control technology allows the authorized data users to decrypt patient’s sensitive medical data, but also hampers the first-aid treatment when the patient’s life is threatened because the on-site first-aid personnel are not permitted to get patient’s historical medical data. To deal with this dilemma, we propose a secure system to devise a novel two-fold access control mechanism, which is self-adaptive for both normal and emergency situations. In normal application, the healthcare staff with proper attribute secret keys can have the data access privilege; in emergency application, patient’s historical medical data can be recovered using a password-based break-glass access mechanism. To save the storage overhead in the big data storage system, a secure deduplication method is designed to eliminate the duplicate medical files with identical data, which may be encrypted with different access policies. A highlight of this smart secure deduplication method is that the remaining medical file after the deduplication can be accessed by all the data users authorized by the different original access policies. This smart healthcare big data storage system is formally proved secure, and extensive comparison and simulations demonstrate its efficiency.
Metal‐organic frameworks (MOFs) are promising porous precursors for the construction of various functional materials for high‐performance electrochemical energy storage and conversion. Herein, a ...facile two‐step solution method to rational design of a novel electrode of hollow NiCo2O4 nanowall arrays on flexible carbon cloth substrate is reported. Uniform 2D cobalt‐based wall‐like MOFs are first synthesized via a solution reaction, and then the 2D solid nanowall arrays are converted into hollow and porous NiCo2O4 nanostructures through an ion‐exchange and etching process with an additional annealing treatment. The as‐obtained NiCo2O4 nanostructure arrays can provide rich reaction sites and short ion diffusion path. When evaluated as a flexible electrode material for supercapacitor, the as‐fabricated NiCo2O4 nanowall electrode shows remarkable electrochemical performance with excellent rate capability and long cycle life. In addition, the hollow NiCo2O4 nanowall electrode exhibits promising electrocatalytic activity for oxygen evolution reaction. This work provides an example of rational design of hollow nanostructured metal oxide arrays with high electrochemical performance and mechanical flexibility, holding great potential for future flexible multifunctional electronic devices.
A novel hollow and porous NiCo2O4 nanowall array on carbon cloth is fabricated and utilized as an efficient electrode for flexible supercapacitor and oxygen evolution reaction catalysis.
The Al effect on the electrochemical properties of layered double hydroxides (LDHs) is not properly probed, although it is demonstrated to notably promote the capacitive behavior of LDHs. Herein, ...ternary NiCo2Alx layered double hydroxides with varying levels of Al stoichiometry are purposely developed, grown directly on mechanically flexible and electrically conducting carbon cloth (CC@NiCo2Alx‐LDH). Al plays a significant role in determining the structure, morphology, and electrochemical behavior of NiCo2Alx‐LDHs. At an increasing level of Al in NiCo2Alx‐LDHs, there is a steady evolution from 1D nanowire to 2D nanosheets. The CC@NiCo2Al‐LDH at an appropriate level of Al and with the nanowire–nanosheet mixed morphology exhibits both significantly enhanced electrochemical performance and excellent structural stability, with about a 2.3‐fold capacitance of NiCo2‐OH. When applied as the anode in a flexible asymmetric supercapacitor (ASC), the CC@NiCo2Al‐LDH gives rise to a remarkable energy density of 44 Wh kg−1 at the power density of 462 W kg−1, together with remarkable cyclic stability with 91.2% capacitance retention over 15 000 charge–discharge cycles. The present study demonstrates a new pathway to significantly improve the electrochemical performance and stability of transition metal LDHs, which are otherwise unstable in structure and poorly performing in both rate and cycling capability.
A flexible asymmetric supercapacitor device is fabricated by using CC@NiCo2Al‐LDH with mixed morphologies of 1D nanowires and 2D nanosheets as the positive electrode. ZIF‐8 derived porous carbon (ZPC), PVA/KOH, and filter paper serve as the negative electrode, solid‐state electrolyte, and seperator, respectively. The device exhibits an energy density of 44 Wh kg−1 at 462 W kg−1.
Clinical decision support system, which uses advanced data mining techniques to help clinician make proper decisions, has received considerable attention recently. The advantages of clinical decision ...support system include not only improving diagnosis accuracy but also reducing diagnosis time. Specifically, with large amounts of clinical data generated everyday, naïve Bayesian classification can be utilized to excavate valuable information to improve a clinical decision support system. Although the clinical decision support system is quite promising, the flourish of the system still faces many challenges including information security and privacy concerns. In this paper, we propose a new privacy-preserving patient-centric clinical decision support system, which helps clinician complementary to diagnose the risk of patients' disease in a privacy-preserving way. In the proposed system, the past patients' historical data are stored in cloud and can be used to train the naïve Bayesian classifier without leaking any individual patient medical data, and then the trained classifier can be applied to compute the disease risk for new coming patients and also allow these patients to retrieve the top-k disease names according to their own preferences. Specifically, to protect the privacy of past patients' historical data, a new cryptographic tool called additive homomorphic proxy aggregation scheme is designed. Moreover, to leverage the leakage of naïve Bayesian classifier, we introduce a privacy-preserving top-k disease names retrieval protocol in our system. Detailed privacy analysis ensures that patient's information is private and will not be leaked out during the disease diagnosis phase. In addition, performance evaluation via extensive simulations also demonstrates that our system can efficiently calculate patient's disease risk with high accuracy in a privacy-preserving way.
As a milestone in the development of outsourcing services, cloud computing enables an increasing number of individuals and enterprises to enjoy the most advanced services from outsourcing service ...providers. Because online payment and data security issues are involved in outsourcing services, the mutual distrust between users and service providers may severely impede the wide adoption of cloud computing. Nevertheless, most existing solutions only consider a specific type of services and rely on a trusted third-party to realize fair payment. In this paper, to realize secure and fair payment of outsourcing services in general without relying on any third-party, trusted or not, we introduce BPay, an outsourcing service fair payment framework based on blockchain in cloud computing. We first propose the system architecture, adversary model and design goals of BPay, then describe the design details. Our security and compatibility analysis indicates that BPay achieves soundness and robust fairness and it is compatible with the Bitcoin blockchain and the Ethereum blockchain. The key to the robust fairness and compatibility lies in an all-or-nothing checking-proof protocol and a top-down checking method. In addition, our experimental results show that BPay is computationally efficient. Finally, we present the applications of BPay in outsourcing services.
Highly active and durable air cathodes to catalyze both the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are urgently required for rechargeable metal–air batteries. In this ...work, an efficient bifunctional oxygen catalyst comprising hollow Co3O4 nanospheres embedded in nitrogen‐doped carbon nanowall arrays on flexible carbon cloth (NC‐Co3O4/CC) is reported. The hierarchical structure is facilely derived from a metal–organic framework precursor. A carbon onion coating constrains the Kirkendall effect to promote the conversion of the Co nanoparticles into irregular hollow oxide nanospheres with a fine scale nanograin structure, which enables promising catalytic properties toward both OER and ORR. The integrated NC‐Co3O4/CC can be used as an additive‐free air cathode for flexible all‐solid‐state zinc–air batteries, which present high open circuit potential (1.44 V), high capacity (387.2 mAh g−1, based on the total mass of Zn and catalysts), excellent cycling stability and mechanical flexibility, significantly outperforming Pt‐ and Ir‐based zinc–air batteries.
An efficient bifunctional oxygen catalyst comprising hollow Co3O4 nanospheres embedded in N‐doped carbon nanowall arrays (NC‐Co3O4) is facilely fabricated from a metal–organic framework. The additive‐free NC‐Co3O4 electrode can be directly utilized as an efficient air cathode for a flexible solid‐state Zn–air battery, which demonstrates much improved cycling stability and mechanical flexibility over Pt‐ and Ir‐based zinc–air batteries.
In this paper, we propose a privacy-preserving e-health system, which is a fusion of Internet-of-things (IoT), big data and cloud storage. The medical IoT network monitors patient’s physiological ...data, which are aggregated to electronic health record (EHR). The medical big data that contains a large amount of EHRs are outsourced to cloud platform. In the proposed system, the patient distributes an IoT group key to the medical nodes in an authenticated way without interaction round. The IoT messages are encrypted using the IoT group key and transmitted to the patient, which can be batch authenticated by the patient. The encrypted EHRs are shared among patient and different data users in a fine-grained access control manner. A novel keyword match based policy update mechanism is designed to enable flexible access policy updating without privacy leakage. Extensive comparison and simulation results demonstrate that the algorithms in the proposed system are efficient. Comprehensive analysis is provided to prove its security.
•Anonymous identities are assigned to patients and medical nodes, and real identities can be traced.•Authenticated IoT key distribution.•IoT ciphertext are authenticated by the patient, and a batch authentication method is also provided.•Lightweight fine-grained access control.•Flexible subset keyword match based access policy update.
In this paper, we propose a toolkit for efficient and privacy-preserving outsourced calculation under multiple encrypted keys (EPOM). Using EPOM, a large scale of users can securely outsource their ...data to a cloud server for storage. Moreover, encrypted data belonging to multiple users can be processed without compromising on the security of the individual user's (original) data and the final computed results. To reduce the associated key management cost and private key exposure risk in EPOM, we present a distributed two-trapdoor public-key cryptosystem, the core cryptographic primitive. We also present the toolkit to ensure that the commonly used integer operations can be securely handled across different encrypted domains. We then prove that the proposed EPOM achieves the goal of secure integer number processing without resulting in privacy leakage of data to unauthorized parties. Last, we demonstrate the utility and the efficiency of EPOM using simulations.
MOFs are among the most popular precursors and templates for deriving various porous materials, where the derivatives can inherit a large surface area, abundant active sites for targeted ...functionalities and a high degree of porosity inherited from their parent MOFs. Those unique structural features make them promising candidates in multiple applications. More interestingly, the structure and properties of these MOF derivatives can be modulated by the choice of the parent MOFs and the design in the conversion process. In this overview, the transformation pathways from MOFs into their porous derivatives, the principles underlying these transformations, and the behavior of the MOF components in the transition process are discussed. Recently, there has been tremendous progress in preserving and enhancing the surface area, the amount of active sites and the level of porosity of the MOF-derived materials for targeted applications, from the perspectives of both customizing the parent MOFs and tailoring the transformation process. To develop the rationally designed MOF-derived materials and thus to elucidate the precursor-process-product correlations, some typical examples of the MOF derivatives applied in electrochemical energy storage and conversion, water treatment, gas sensing, and biomedicine are discussed to demonstrate the effectiveness of the key design strategies.
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•The pathways leading to, and precursor-process-product correlations in, MOF-derived porous materials are elucidated.•Design strategies for improving the structural features of MOF-derived materials are formulated from “nature” to “nurture”.•MOF-derived porous materials are discussed for different targeted applications.
Cyclic codes are a subclass of linear codes and have applications in consumer electronics, data storage systems and communication systems as they have efficient encoding and decoding algorithms. In ...this paper, by investigating the solutions of certain equations over finite fields, we make progress towards three conjectures about optimal ternary cyclic codes which were proposed by Ding and Helleseth.
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