With the widespread sharing of personal face images on the Internet, systems based on face recognition encounter the real threat of being breached by potential adversaries who are able to access individuals’ face images and use them to intrude the systems. In this article, we propose a novel privacy protection method in the sparsified multiscale feature subspaces to protect sensitive facial features, taking care of the influence or weight-ranked subspace coefficients on the privacy budget, named “ranked differential privacy (RDP).” After the multiscale subspaces’ decomposition, the lightweight Laplacian noise is added to the dimension-reduced sparsified subspaces’ coefficients according to the geometric superposition method. Then, we rigorously prove that the RDP satisfies$\varepsilon _{0}$-differential privacy. After that, the nonlinear Lagrange multiplier method (LM) is formulated for the constraint optimization problem of maximizing the utility of protected face images of high-visualization quality with sanitizing noise, under a given privacy budget$\varepsilon _{0}$. Then, two methods are proposed to solve the nonlinear Lagrangian multiplier method (LM) problem and obtain the optimal noise scale parameters: 1) the analytical normalization approximation (NA) method with identical average noise scale parameter for real-time online applications and 2) the LM optimization method via gradient descent (LMGD) to obtain the nonlinear solution through iterative updating for more accurate offline applications. Experimental results on two real-world datasets show that our proposed RDP outperforms other state-of-the-art methods: at a privacy budget of$\varepsilon _{0} = 0.2$, the peak signal-to-noise ratio (PSNR) of the optimized RDP is about ~10 dB higher than (10 times as high as) the highest PSNR of all state-of-the-art methods compared.

The deep integration of Internet of Things (IoT) and cloud computing promotes a wide deployment of body area networks (BANs) for smart health services. The data security raises new challenges when patients’ health records (HRs) are uploaded into the cloud server by BAN. The attribute-based encryption (ABE) primitive is a potential option to ensure HRs security, which provides the data confidentiality guarantee and fine-grained access control simultaneously via cryptographic means. However, most ABE schemes are unsuitable to be deployed in smart health application as access policies associated with encrypted HRs reveal patient’s privacies. Though the recently proposed ABE with partially hidden access policy based on composite order can alleviate the privacy leakage by only disclosing the attribute names and concealing the practical attribute values, the exposed attribute names still leak individual privacies. In this article, we put forward a privacy-enhanced and efficient ABE construction with fully hidden access policy over prime order group based on the prominent ABE construction due to Bethencourt et al.. Our scheme hides the sensitive attributes in the access structure by several nontrivial designs without compromising the correctness and security. Moreover, our scheme’s performance is far superior to the attribute partially hidden schemes. Extensive experiments demonstrate the conclusion.

With an increasing amount of data produced by pervasive and ubiquitous smart devices, many Internet of Things (IoT) applications adopt the cloud platform to store and process data. To protect data security and privacy, attribute-based encryption (ABE) has been widely used in cloud-assisted IoT systems. However, most ABE schemes usually require a central authority to distribute decryption keys for all users, which may raise security and efficiency concerns; in addition, the exposure of decryption keys would severely damage the data privacy. In this article, we introduce a novel notion of decentralized attribute-based puncturable encryption (DABPE). DABPE allows data owner to generate public and secret keys by himself, without relying on any central authority. When outsourcing data to the cloud, the data owner can encrypt data with an access policy; moreover, the data owner could issue particular keys for different data users and only those users whose keys satisfy the access policy can access the data. To achieve a flexible forward security, the data owner and data user can update their keys with some tags such that the data specified by the tags would not be revealed even if the keys are disclosed. We design a concrete DABPE scheme and prove its security in the standard model, and also conduct extensive experiments to show the efficiency of the proposed scheme.

Internet of Things (IoT) devices play essential roles in both industry and daily scenarios. However, unlike smartphones and computers, IoT devices typically lack conventional user interfaces (UIs) such as keyboards and touchscreens. It renders the traditional user authentication designs, e.g., PINs and patterns, inapplicable. In this article, we proposeTouchAccessthat enables users to unlock an arbitrary IoT device by applying a simple touch. Our design is motivated by the key observation that IoT devices unavoidably generate electromagnetic emanations (EMM) while they are functioning. When the user touches the device, it causes time-varying coupling between those two and generates unique EMMs. Our feasibility studies further reveal that thesehuman-induced EMMsare distinct and strongly correlated with the circuitry properties of the user and the device, but are susceptible to environmental EM noises, thus lowering the authentication accuracy. To address this challenge, we develop signal processing techniques with a Siamese network learning scheme that clears the ambient electromagnetic (EM) noises, extracts robust signal features, and builds noise-resistant classifiers, enabling users to be correctly recognized. A significant advantage ofTouchAccessis that it requires only a low-cost analog-to-digital converter (ADC) to sense the EM signal. We implementTouchAccesson commercial off-the-shelf (COTS) IoT devices, which vary significantly in terms of UIs, sizes, and hardware designs. The performance evaluations show thatTouchAccessachieves an average authentication accuracy as high as 97.85%.

Secure search techniques over encrypted cloud data allow an authorized user to query data files of interest by submitting encrypted query keywords to the cloud server in a privacy-preserving manner. However, in practice, the returned query results may be incorrect or incomplete in the dishonest cloud environment. For example, the cloud server may intentionally omit some qualified results to save computational resources and communication overhead. Thus, a well-functioning secure query system should provide a query results verification mechanism that allows the data user to verify results. In this paper, we design a secure, easily integrated, and fine-grained query results verification mechanism, by which, given an encrypted query results set, the query user not only can verify the correctness of each data file in the set but also can further check how many or which qualified data files are not returned if the set is incomplete before decryption. The verification scheme is loose-coupling to concrete secure search techniques and can be very easily integrated into any secure query scheme. We achieve the goal by constructing secure verification object for encrypted cloud data. Furthermore, a short signature technique with extremely small storage cost is proposed to guarantee the authenticity of verification object and a verification object request technique is presented to allow the query user to securely obtain the desired verification object. Performance evaluation shows that the proposed schemes are practical and efficient.

Decision tree classification has become a prevailing technique for online diagnosis services. By outsourcing computation intensive tasks to a cloud server, cloud-assisted online diagnosis services are better ways for cases that the storage and computation requirements exceed the capability of medical institutions. With privacy concerns as well as intellectual property protection issues, the valuable diagnosis classifier and the sensitive user data should be protected against the cloud server. In this paper, we identify a work-flow for cloud-assisted online diagnosis services. We propose an efficient and secure decision tree classification scheme in the proposed work-flow. Specifically, the medical institution transforms a locally pre-trained decision tree classifier to a decision table, and later uses searchable symmetric encryption to encrypt the decision table. Then, the encrypted table is outsourced to the cloud server, and a user can submit encrypted physiological features to the cloud server and obtain an encrypted diagnosis prediction back. We provide formal security proofs to demonstrate that our scheme protects the confidentiality of the decision tree classifier and the user's data. The performance analysis shows that our scheme achieves faster-than-linear classification speed. Experimental evaluations show that our scheme requires several micro-seconds to process a diagnosis request in the tested datasets.

Cross correlations are ubiquitous in time-series IoT data sets such as trajectories from smartphones and smart meters data in smart grids. Conventional privacy methods have difficulty to protect cross correlation privacy within such correlated data set. Here we propose a novel Correlated noise mechanism for Cross-correlated Data Privacy (CCDP). Because the Fourier coefficients of the cross correlation of two data records are the linear product of those of the two data records, the sanitizing Fourier coefficients noise is used for efficient optimization. Also, the noise is added via the Geometric sum method, which is proved to provide the required Laplace distribution. We perform rigorous mathematical analysis of the CCDP and prove that it satisfies ε-Pufferfish privacy. We also prove that the CCDP can achieve the optimal data utility for a given privacy budget ε. What's more important, we further derive the mathematical procedure to obtain the optimal Laplace noise scale parameter to achieve better data utility. Simulations show that the proposed CCDP outperforms the independent Fourier coefficients noise mechanism, as well as two other state-of-the-art time-domain privacy mechanisms in the literature, for three types of data sets: computer-generated data, real-world trajectory data, and smart meter data.

Embodied learning and the design of embodied learning platforms have gained popularity in recent years due to the increasing availability of sensing technologies. In our study, we made use of the Mathematical Imagery Trainer for Proportion (MIT-P) that uses a touchscreen tablet to help students explore the concept of mathematical proportion. The use of sensing technologies provides an unprecedented amount of high-frequency data on students' behaviors. We investigated a statistical model called mixture Regime-Switching Hidden Logistic Transition Process (mixRHLP) and fit it to the students' hand motion data. Simultaneously, the model finds characteristic regimes and assigns students to clusters of regime transitions. To understand the nature of these regimes and clusters, we explore some properties in students' and tutor's verbalization associated with these different phases.

New privacy implications are induced to individuals and families because of the time-series data classification problem in the Internet of Things such as appliance classifications in the smart grid. To prevent the adversary from inferring the household appliance classification used in the smart grid, a singular spectrum analysis (SSA) has been applied to the local differential privacy (SSA-LDP). First, the Fourier spectrum noise has been added via the geometric sum which has been proved to achieve the Laplace noise distribution. Furthermore, we have proved that the sanitized data through the SSA-LDP is ε -deferentially private for the adversary inference attack. In addition, to achieve a better data utility, a formula has been obtained for the optimal Fourier spectrum noise by decomposing it into the superposition of power spectra of the dominant SSA eigenfilters. Finally, experiments have been performed with a computer-generated data set and a real-world smart-meter data set. Comparisons to other privacy approaches show that the optimized SSA-LDP does achieve a better data utility for a given data privacy.

A mutual correlation between trajectories of two users is very helpful to real-life applications such as product recommendation and social media. While providing tremendous benefits, the releasing of correlated trajectories may leak sensitive social relations, due to potential links between mutual correlations and social relations. To the best of our knowledge, we take the first step to propose a mathematically rigorous n-body Laplace framework, satisfying "-differential privacy, which efficiently prevents a social relation inference through the mutual correlation between n-node trajectories of two users. The problem is mathematically formulated by defining a trajectory correlation score to measure the social relation between two users. Then, under the n-body Laplace framework, we propose two Lagrange Multiplier-based Differentially Private (LMDP) approaches to optimize the privacy budgets, for the data utility measured by location distances and the data utility measured by location correlations, i.e., UD-LMDP and UC-LMDP. Also, we present detailed analyses of privacy, data utility, adversary knowledge and the constrained optimizations. Finally, we perform experimental studies with real-life data. Our experimental results show that our proposed approaches achieve better privacy and data utility than the existing approaches.

Cloud computing has become an important and popular infrastructure for data storage and sharing. Typically, data owners outsource their massive data to a public cloud that will provide search services to authorized data users. With privacy concerns, the valuable outsourced data cannot be exposed directly, and should be encrypted before outsourcing to the public cloud. In this paper, we focus on k-Nearest Neighbor (k-NN) search over encrypted data. We propose efficient and secure k-NN search schemes based on matrix similarity to achieve efficient and secure query services in public cloud. In our basic scheme, we construct the traces of two diagonal multiplication matrices to denote the Euclidean distance of two data points, and perform secure k-NN search by comparing traces of corresponding similar matrices. In our enhanced scheme, we strengthen the security property by decomposing matrices based on our basic scheme. Security analysis shows that our schemes protect the data privacy and query privacy under attacking with different levels of background knowledge. Experimental evaluations show that both schemes are efficient in terms of computation complexity as well as computational cost.

Location-based services (LBSs) are increasingly popular in today’s society. People reveal their location information to LBS providers to obtain personalized services such as map directions, restaurant recommendations, and taxi reservations. Usually, LBS providers offer user privacy protection statement to assure users that their private location information would not be given away. However, many LBSs run on third-party cloud infrastructures. It is challenging to guarantee user location privacy against curious cloud operators while still permitting users to query their own location information data. In this paper, we propose an efficient privacy-preserving cloud-based LBS query scheme for the multiuser setting. We encrypt LBS data and LBS queries with a hybrid encryption mechanism, which can efficiently implement privacy-preserving search over encrypted LBS data and is very suitable for the multiuser setting with secure and effective user enrollment and user revocation. This paper contains security analysis and performance experiments to demonstrate the privacy-preserving properties and efficiency of our proposed scheme.

Malware detection becomes mission critical as its threats spread from personal computers to industrial control systems. Modern malware generally equips with sophisticated anti-detection mechanisms such as code-morphism, which allows the malware to evolve into many variants and bypass traditional code feature based detection systems. In this paper, we propose to disassemble binary executables into opcodes sequences, and then convert the opcodes into images. By comparing the opcode images generated from binary targets with the opcode images generated from known malware sample codes, we can detect if the target binary executables contain variants of these known malwares. Theoretical analysis and real-life experiments results show that malware detection using visualized analysis is comparable in terms of accuracy, our approach can significantly improve 15\% of detection accuracy when the detection set contains a large quantity of binaries and the training set is small.

In the big data era, with the rapid development of location-based applications, GPS enabled devices and big data institutions, location correlation privacy raises more and more people's concern. Because adversaries may combine location correlations with their background knowledge to guess users' privacy, such correlation should be protected to preserve users' privacy. In order to deal with the location disclosure problem, location perturbation and generalization have been proposed. However, most proposed approaches depend on syntactic privacy models without rigorous privacy guarantee. Furthermore, many approaches only consider perturbing the locations of one user without considering multi-user location correlations, so these techniques cannot prevent various inference attacks well. Currently, differential privacy has been regarded as a standard for privacy protection, but there are new challenges for applying differential privacy in the location correlations protection. The privacy protection not only should meet the needs of users who request location-based services, but also should protect location correlation among multiple users. In this paper, we propose a systematic solution to protect location correlations privacy among multiple users with rigorous privacy guarantee. First of all, we propose a novel definition, private candidate sets which are obtained by hidden Markov models. Then, we quantify the location correlation between two users by using the similarity of hidden Markov models. Finally, we present a private trajectory releasing mechanism which can preserve the location correlations among users who move under hidden Markov models in a period of time. Experiments on real-world datasets also show that multi-user location correlation protection is efficient.

Recently, secure search over encrypted cloud data has become a hot research spot and challenging task. Some secure search schemes have been proposed to try to meet this challenge. In this paper, we propose a conjunctive multi-keyword secure search scheme for multiple data owners. To guarantee data security and system flexibility in the multiple data owners environment, we design an ingenious secure query scheme that allows each data owner to adopt randomly chosen temporary keys to build secure indexes for different data files. An authorized data user does not need to know these temporary keys of constructing indexes and can instead randomly choose another temporary query keys to encrypt query keywords while the cloud can correctly perform keywords matching over encrypted data files. Extensive experiments demonstrate the correctness and practicality of the proposed scheme.

Malware detection becomes mission critical as its threats spread from personal computers to industrial control systems. Modern malware generally equips with sophisticated anti-detection mechanisms such as code-morphism, which allows the malware to evolve into many variants and bypass traditional code feature based detection systems. In this paper, we propose to disassemble binary executables into opcodes sequences, and then convert the opcodes into images. By using convolutional neural network to compare the opcode images generated from binary targets with the opcode images generated from known malware sample codes, we can detect if the target binary executables is malicious. Theoretical analysis and real-life experiments results show that malware detection using visualized analysis is comparable in terms of accuracy, our approach can significantly improve 15% of detection accuracy when the detection set contains a large quantity of binaries and the training set is much smaller.

Software-Defined Networks (SDN) is a trend of research in networks. Rule placement, a common operation for network administrators, has become more complicated due to the capacity limitation of devices in which the large number of rules are deployed. Prior works on rule placement mostly consider the influence on rule placement incurred by the rules in a single device. However, the position relationships between neighbor devices have influences on rule placement. Our basic idea is to classify the position relationships into two categories: the serial relationship and the parallel relationship, and we present a novel strategy for rule placement based on the two different position relationships. There are two challenges of implementing our strategies: to check whether a rule is contained by a rule set or not and to check whether a rule can be merged by other rules or not.To overcome the challenges, we propose a novel data structure called OPTree to represent the rules, which is convenient to check whether a rule is covered by other rules. We design the insertion algorithm and search algorithm for OPTree. Extensive experiments show that our approach can effectively reduce the number of rules while ensuring placed rules work. On the other hand, the experimental results also demonstrate that it is necessary to consider the position relationships between neighbor devices when placing rules.