Large-scale Low Earth Orbit (LEO) constellations often experience high node failure rates caused by dynamic environmental factors (random failures), such as satellite maneuvers, or by cyber or physical attacks on critical nodes (targeted attacks), which pose unique challenges for routing optimization. Traditional algorithms such as Dijkstra suffer from limited parallel scalability on GPUs due to irregular neighbor distributions, while deep learning methods lack generalization ability. To address these challenges, we propose TRACE (Topology-aware Routing via Adjacent-Constraint Encoding), a graph-constrained Transformer architecture equipped with a cascaded multi-head attention decoder for distributed dynamic routing in LEO domains. To improve algorithm throughput and resilience against random failures and targeted attacks, we further design NFD (Navigator–Follower Distillation), a self-distillation framework which enables each agent to learn routing policies from Monte Carlo episodes. Furthermore, a hierarchical distributed routing architecture is developed to extend the proposed method to multi-domain scenarios. Simulation results demonstrate that TRACE with NFD achieves near-optimal routing accuracy with controllable inter-domain errors, while significantly improving throughput compared with mainstream routing algorithms.

To ensure the legitimacy of communicators while ad dressing the privacy concerns of vehicles in vehicular ad-hoc networks (VANETs), conditional privacy-preserving authentication (CPPA) schemes have been proposed. Given that existing schemes suffer from single point of failure due to centralized authorities, several distributed CPPA schemes have been proposed. However, these schemes all ignore the tight cementation between system secret keys and the authority, which could be a serious threat to system security, that the compromised authority may leak the system secret key. To address these issues, we propose a security enhanced decentralized conditional privacy-preserving authentication (DCPPA) scheme. DCPPA first introduces a decentralized system master key generation (DSMKG) mechanism without a centralized secret sharer, ensuring that the system secret key remains hidden from any single authority. Based on DSMKG, DCPPA then implements a lightweight verifiable pseudonym self-generation strategy without the system master secret key escrow problem, thus providing flexible pseudonym updating and reliable de-anonymization. Moreover, we implement DCPPA over a hyperelliptic curve cryptosystem (HECC) to balance the system performance. Considering the additional communication processes due to the decentralized feature, we introduce a symmetric balanced incomplete block design (SBIBD) to enhance the communication efficiency. We demonstrate the excellent security of DCPPA through an in-depth security analysis, while demonstrate that the overhead of DCPPA is at ms level through experiments.

With the advancement of smart terminals and communication technologies, the emergence of heterogeneous Service Subscribers (SSs) and diverse sensing demands has facilitated the development of multi-platform Mobile CrowdSensing (MCS) scenarios. However, unlike traditional single-platform scenarios, Mobile Users' (MUs) bidding privacy is hard to protect in multi platform MCS. Additionally, the privacy disclosure issue of SSs has not been well addressed. To tackle these issues, in this paper, we propose a bilateral, auction-based scheme to preserve bidding privacy in multi-platform MCS, thereby protecting the interests of both SSs and MUs. Specifically, since SSs and MUs strategically choose one another to maximize their utility, we construct the corresponding selection processes for both sides by taking advantage of auction pricing theory. We firstly design a user-oriented forward auction that integrates the 0-1 knapsack problem with the Paillier encryption algorithm to protect the bidding information of both SSs and MUs. Then, we employ the Chinese Remainder Theorem (CRT) to design a reverse auction that hides the bidding behaviors of MUs. Theoretical analysis demonstrates that our scheme can protect the bidding privacy of both parties while ensuring economic robustness. Extensive experiments on a real dataset demonstrate that, compared with existing works, our scheme enables both SSs and MUs to achieve satisfactory utility while maintaining low computational overhead.

The Internet of Vehicles (IoV) generates massive sensitive perception data, typically managed by manufacturer-specific domains. While encryption with domain-specific parameters protects confidentiality, many IoV applications require secure cross-domain data sharing to access complementary information, and expressive keyword search for efficient access. However, existing Attribute-Based Keyword Search (ABKS) schemes are designed for single-domain settings, and thus cannot address heterogeneous key management or provide traceability without a universally trusted authority. To address these issues, we propose TCroS, a traceable cross-domain data sharing scheme that generalizes CP-ABE via proxy re-encryption mechanism, enabling ciphertexts generated in one domain to be securely transformed for authorized requesters in another. To provide traceability, TCroS embeds requester identities into decryption keys using Boneh-Boyen signatures, allowing any party (rather than the universally trusted authority) to trace the source of a leaked key. We further extend TCroS to TCroSS, which incorporates privacy-preserving expressive keyword search supporting Boolean queries, thereby enabling efficient retrieval of authorized data while resisting keyword guessing attacks. Formal security analysis proves that our schemes achieve IND-SCPA and IND-SCKA security. Experimental results demonstrate their practicality, showing that cross-domain sharing can be realized with computation and storage overheads comparable to single-domain setting.

The combination of Deep Learning (DL) and Federated Learning (FL) makes it a popular paradigm to train powerful models securely on large-scale data in a distributed way. However, current solutions face challenges such as significant communication overheads for clients with limited resources, potential privacy risks arising from FL's distributed nature, and the inability to maintain model accuracy without loss under high compression ratios. To solve these issues, we propose a lightweight Communication-efficient and Privacy-preserving FL scheme CPFL by designing Cyclic Segmented Compressive Sensing (CSCS) and using efficient Symmetric Homomorphic Encryption (SHE), which greatly reduces the number of transmitted model weights without sacrificing model accuracy. Formal analysis shows the security of CPFL against known-plaintext attacks and ensures model convergence. Extensive experiments demonstrate that CPFL achieves remarkable model accuracy under more than 200× compression ratio, and even reduces the communication cost by 99.5% compared with previous solutions.

With the widespread use of encrypted spatial data, many range query schemes emerge to address potential security risks caused by access pattern leakage. However, most existing schemes rely on a dual-server model to hide access patterns and often involve complex spatial relation judgments during range comparisons, leading to low query efficiency. To address these issues, we propose a novel Fast and Access Hidden Range Query (FAHRQ) scheme. First, we introduce an efficient range membership verification technique based on Bloom filters and Lagrange interpolation function, combine homomorphic encryption to ensure the confidentiality of spatial data and the computational flexibility of related operations, and realize the access pattern hidden under single server. Then, we construct an index using R-tree and employ Bloom filters and prefix 0-1 encoding to accelerate the minimum bounding rectangle intersection judgment, enabling secure and efficient range queries over encrypted spatial data while maintaining retrieval accuracy. Finally, we give a formal security analysis to show that our scheme achieves access pattern hidden while protecting data security, and conduct extensive experiments to demonstrate that our scheme improves query efficiency by 5 – 7× compared to existing schemes.

Vehicular Ad Hoc Networks (VANETs) are the cornerstone of intelligent transportation systems and autonomous driving. Vehicle-to-road communication, as one of the core services, faces increasing risks of privacy breaches. Signcryption technology effectively ensures secure information transmission. However, existing signcryption schemes still have deficiencies in terms of transmission robustness and identity privacy protection. To solve these issues, this paper proposes a Robust Identity-based Signcryption scheme (RIBSC) for VANETs. In RIBSC, we first design an area session key distribution mechanism based on Chinese Residual Theorem (CRT), which can dynamically revoke the decryption ability of malicious Roadside Units (RSUs) in real time. Only RSUs approved by Trusted Detection Center (TDC) can obtain a valid session private key by conducting one modular operation. We then utilize the traceable pseudonym mechanism to protect the identity privacy of vehicles and RSUs, which can track their true identities when illegal activities occur. We finally provide a rigorous security proof under the random oracle model, and demonstrate the performance advantages of RIBSC through extensive experiments. More attractively, the session information is fixed at only 148 bytes, regardless of the number of RSUs.

With the widespread adoption of UAV technology, the physical attacks targeting UAVs have become increasingly diverse, garnering growing attention. Physical attacks pose significant threats to the security of critical hardware within UAV systems, potentially leading to severe consequences such as crashes or unauthorized hijacking. Therefore, conducting in-depth research into physical attack methods on UAV systems not only provides theoretical support and strategic guidance for designing defense measures but also facilitates the optimization and tool-based application of existing attack techniques, paving new pathways for the development of anti-UAV technologies. This review begins with a systematic decomposition and detailed introduction of UAV systems from the perspective of hardware functional structures. Subsequently, it delves into vulnerabilities of UAV systems when facing physical attacks and provides a comprehensive review of existing physical attack methods. Particular attention is given to evaluating the effectiveness, technical characteristics, strengths, and limitations of these methods. Additionally, the review explores emerging physical attack techniques and the potential security threats posed by hardware extensions of UAVs in novel application domains. Furthermore, this review proposes a quantitative risk assessment framework for UAV security, systematically evaluating various physical attack methods based on attack cost, effectiveness, and likelihood. Finally, the review discusses future research directions in the domain of physical attacks on UAV systems, emphasizing the need to enhance existing technologies to strengthen anti-UAV capabilities and highlighting the importance of developing comprehensive defense strategies against physical attacks.

Vertical federated learning (VFL) has been widely adopted in various domains for collaborative decision-making. However, recent studies have revealed critical privacy vulnerabilities in VFL, particularly label inference attacks, which significantly undermine label confidentiality and limit the applicability of VFL in privacy-sensitive scenarios. To mitigate such threats, several defense methods have been proposed by incorporating diverse privacy-preserving techniques. Nevertheless, existing defenses fail to effectively prevent the recently proposed model completion-based label inference attacks. To address this limitation, we propose a novel defense method, termed Label Compression-Based Defense (LCD), to defend against this class of attacks. The core idea of LCD is to train the VFL model using fake labels, thereby decoupling the ground-truth labels from the outputs of the malicious bottom model, which constitute the critical component exploited in the model completion-based attacks. Specifically, we introduce a multi-stage training strategy that decomposes the training process into different stages to deceive the malicious bottom model without affecting the original task. In addition, we design a deep feature-based label compression mechanism to generate fake labels for misleading the attacker. To further enhance the defense effectiveness, we propose an embedding compaction strategy based on center loss, which substantially increases the difficulty of label inference. Moreover, we theoretically prove the effectiveness of LCD from an information-theoretic perspective. Extensive experiments on both tabular and image datasets demonstrate that LCD can effectively defend against label inference attacks. The source code of LCD is publicly available at GitHub:https://github.com/YuanShunJie1/LCD.

Static analysis tools have evolved over time to assist in detecting bugs. However, the excessive false warnings can impede developers’ productivity and confidence in the tools. Previous research efforts have explored learning-based approaches to identify bug warnings. Nevertheless, their coarse granularity, focusing on either long-term warnings or function-level alerts, are insensitive to individual bugs. Also, they rely on manually crafted features or solely on source code semantics, which is inadequate for effective learning. In this paper, we propose DeepFWI, a learning-based approach that identifies bug-sensitive warnings at a fine-grained granularity. Specifically, we design a novel LSTM-based model that captures multi-modal semantics of source code and warnings from automated static analysis tools (ASATs) and highlights their correlations with cross-attention. To tackle the data scarcity of training and evaluation, we collected a large-scale dataset of 280,273 warnings. We conducted extensive experiments on the dataset to evaluate DeepFWI. The experimental results demonstrate the effectiveness of our approach, with an F1-score 67.06% for confirming true warnings in a finer-grained manner, significantly outperforming all baselines. Additionally, to validate the practicality of DeepFWI from the perspective of developers, we applied DeepFWI to four popular open-source projects. Our approach filtered out the vast majority of warnings, while still successfully surfacing 25 true bug-related warnings that were confirmed through manual analysis.

With the development of autonomous driving technology, Multi-Access Edge Computing (MEC) is an effective paradigm to support delay-sensitive applications in vehicular networks. However, achieving the real-time offloading strategy and resource allocation in MEC-empowered vehicular networks becomes a challenge. In this paper, we first formulate an offloading optimization problem to minimize system latency and energy consumption. To obtain the optimal policy in real time, the formulated problem is transformed into a Markov Decision Process (MDP) and then solved by the proposed Attention and Feature Fusion Deep Deterministic Policy Gradient (AFF-DDPG) algorithm, where a multi-head attention mechanism is combined with feature fusion to improve the accuracy of the decision. In addition, the exploration ability and learning efficiency of the AFF-DDPG algorithm are further enhanced by exploiting Ornstein-Uhlenbeck (OU) noise and the priority experience replay mechanism. The simulation results show that the proposed AFF-DDPG algorithm achieves a 9.44 % improvement over the DDPG algorithm.

Ensuring the security of data outsourced to cloud is a prerequisite for the application of Internet of Things (IoT) in actual production. Secure search based on homomorphic encryption can provide high security and require no expensive setup procedure, which can be applied to resource-limited devices in IoT. However, the existing schemes usually have poor search performance and do not consider multiowner setting. To solve these issues, we propose an efficient homomorphic encryption-based secure search scheme in multiowner setting. Specifically, we construct a secure search protocol based on multikey homomorphic encryption, which can be deployed in multiowner setting. Meanwhile, we improve the efficiency of our scheme by optimizing the search algorithm. Formal security analysis proves that our scheme is secure against chosen plaintext attack, and extensive experiments demonstrate that our scheme improves the search efficiency by$1000\times $when compared with state-of-the-art solutions.

Collaborative authentication, boasting-enhanced accuracy, robust resilience, and optimized efficiency, holds immense promise for autonomous aerial vehicle (AAV) networks. However, existing collaborative authentication methods overlook both the credibility evaluation and incentives of participating nodes, thereby compromising authentication accuracy and resulting in failures. Furthermore, reliance on trusted decision-fusion institution introduces vulnerabilities and single points of failure. To address these issues, we design a credibility-weighted soft authentication approach specifically for AAV networks, thereby enhancing accuracy by effectively integrating the trustworthiness of collaborating nodes. To further encourage active participation from nodes, we introduce an incentive-based reputation system. Finally, based on the above approaches, we propose a distributed authentication method by leveraging blockchain technology and optimization theory that not only emphasizes security but also optimizes resource selection in AAV networks. Theoretical analysis demonstrates our scheme’s distributed authentication with minimized resource consumption under specified security strength, mitigating single points of failure and fulfilling efficient mutual authentication requirements. Experimental results show a remarkable 78.45% increase in authentication accuracy and a 44.51% reduction in resource consumption compared to advanced solution.

With the popularity of social media, mobile devices and the Internet, a large amount of multimodal data (e.g, text, image, audio, video, etc.) is increasingly being outsourced to cloud to save local computing and storage costs. To search through encrypted multimodal data in the cloud, privacy-preserving cross-modal retrieval (PPCMR) techniques have attracted extensive attention. However, most of the existing PPCMR schemes lack the ability to resist quantum attacks and have low search efficiency on large-scale datasets. To solve above problems, we first propose a basic PPCMR scheme FECMR using the enhanced Single-key Function-hiding Inner Product Functional Encryption for Binary strings (SFB-IPFE) and cross-modal hashing technology, which achieves the measurement of similarity over encrypted multimodal data while resisting quantum attacks. Then, we design an efficient index KM-tree utilizing the K-modes clustering algorithm. On this basis, we propose an improved scheme FECMR+, which achieves sub-linear search complexity. Finally, formal security analysis proves that our schemes are secure against quantum attacks, and extensive experiments prove that our schemes are efficient and feasible for practical application.

Recruiting users in mobile crowdsensing (MCS) can make the platform obtain high-quality data to provide better services. Although the privacy leakage during the process of user recruitment has received a lot of research attention, none of the existing work considers the evaluation of the sensing quality of privacy-preserving data submitted by users, which makes the platform incapable of recruiting users suitably to obtain high-quality sensing data, thereby reducing the reliability of MCS services. To solve this problem, we first propose a sensing quality evaluation method based on the deviation and variance of sensing data. According to it, the platform can obtain the sensing quality of privacy-preserving data for each user during the recruitment. Then we model the user recruitment with a limited budget platform as aCombinatorial Multi-Armed Bandit (CMAB)game to determine the recruited users based on the sensing quality of data obtained by evaluation. Finally, we theoretically prove that our algorithm satisfies differential privacy and the upper bound on theregretof rewards is restricted. Experimental results show that our proposal is superior in various properties, and our method has a 73.67% advantage in accumulated sensing qualities compared with comparison schemes.

As a new distributed machine learning framework, vertical federated learning (VFL) has been widely applied in the industry. However, recent studies have demonstrated that VFL faces serious challenges from backdoor attacks, which significantly hinder its further development. Although a few studies have focused on defending against VFL backdoor attacks, these defenses either do not consider the latest attack methods or show limited effectiveness. Moreover, most existing backdoor defense efforts primarily focus on backdoor attacks in horizontal federated learning (HFL) and centralized learning. Due to the unique architecture of VFL models, these methods cannot be directly applied to backdoor defense in VFL. To mitigate the threat of backdoor attacks in VFL, we propose a general backdoor detection (GBD) scheme for backdoor defense, which detects backdoor samples by analyzing the correlation between backdoor samples and the target label, as well as by leveraging the response differences between clean and backdoor samples. Specifically, we propose two backdoor detection metrics: Class Activation Probability (CAP) and Class Activation Contribution (CAC), which are used to calculate the likelihood of a sample being a backdoor sample. We leverage these two metrics to identify backdoor samples during the inference stage. Evaluation results on both tabular and image datasets show that GBD can detect backdoor samples with high accuracy, demonstrating its effectiveness in backdoor defense. The source code of GBD is available at GitHub: https://github.com/YuanShunJie1/GBD.

To motivate data owners’ (DOs’) trading willingness, the existing incentive mechanisms allow DOs to independently disturb data following data consumer's (DC’s) availability requirement. However, they cannot motivate DOs’ honest disturbance, which is attributed to DOs’ independent disturbance without any supervision. Thus, we implement an incentive mechanism for privacy preserved data trading with verifiable data disturbance where an honest-but-curious disturbance generator (DG) is additionally introduced to supervise DOs’ local disturbance and assist disturbance verification between DOs and DC. Specifically, DG generates the disturbance strategies and secretly distributes to DOs following private information retrieval, guaranteeing DOs's local disturbance's privacy and verifiability with our proposed three-level verification algorithm. Subsequently, we model the trading as a game and disturbance verification results determine the compensation and punishment for trading bilateral utilities following Nash Equilibrium where DOs honestly disturb data. Theoretical analysis shows that DOs are motivated to honestly disturb data and their raw data privacy is preserved. Extensive experiments using the real-world dataset demonstrate that the deviating DOs in our scheme can be verified with a probability of more than 90% and the statistical result accuracy can be improved by more than 80% compared with the existing works.

Perturbation-based privacy-preserving truth discovery requires the Service Provider (SP) to calculate the truthful aggregation result from perturbed data of the Data Sources (DSs), which inevitably damages the aggregation accuracy due to perturbation noise added in the data. Thus, the existing works attempt to relieve the perturbation errors by reducing noise amounts or adjusting aggregation weights of DSs. However, the former sacrifices DSs' privacy preservation and the latter has the limited accuracy recovery performance. Aiming at it, we propose an accuracy-enabling differential privacy-preserving truth discovery consisting of an independence-guaranteed data perturbation module and a progressive-private noise elimination module. Specifically, in the first module, SP generates mass of noises following DS's desired perturbation parameters and DS privately obtains one of noise based on private information retrieval. Meanwhile, to realize the perturbation's traceability, SP preserves the ciphertext of DSs' acquired noises, assisting the following noise elimination. In the second module, SP first removes his preserved DS's encrypted noise from perturbed truth according to homomorphic encryption, and then requires DS to decrypt this cleaned truth. The above two processes are progressively and iteratively implemented until all DSs have been involved. Theoretical analysis shows that our scheme can protect DSs' raw data privacy in both truth discovery process and noise elimination process. Extensive experiments using the real-world dataset demonstrate that our scheme can effectively eliminate more than 90% of the perturbation noise effects on the truth discovery accuracy.

Federated learning (FL) is vulnerable to backdoor attacks due to its distributed nature. Existing unilateral defense mechanisms often fail against persistent attack strategies, primarily due to their limited perspectives. To address the challenge of model misclassification on the server side caused by overlooked model similarity drift, and gradient misjudgment on the client side caused by semantic learning imbalances across classes, this paper proposes a collaborative defense framework for federated learning, termed FL-CDF. FL-CDF establishes an end-to-end defense through a bidirectional client-server collaboration mechanism. Specifically: (1) On the client side, an adversarial perturbation-based malicious neuron detection module is introduced. This module measures neuron activation sensitivity by generating adversarial perturbations, and adaptively prunes backdoor neurons exhibiting high sensitivity. (2) On the server side, a multi-dimensional detection scheme is designed, which integrates neuron localization, adversarial sensitivity, and model parameters. By incorporating client-side feedback on malicious neurons, the server performs robust model aggregation. Theoretical analysis verifies the robustness of FL-CDF, and extensive experiments on public benchmarks demonstrate its effectiveness. In the best-case scenario, FL-CDF improves defense performance by 42.5% compared to current state-of-the-art (SOTA) defense.

Android system provides application developers with the ability to define custom permissions, which serve to regulate the sharing of resources and functionalities with other applications. However, developers' improper development practices can render the permission mechanism ineffective, facilitating easy exploitation by attackers. This paper presents a comprehensive examination of the problematic practices surrounding custom permissions employed by developers, referred to as Bad Practices of Custom Permissions (BPCP issues). To accomplish this, we conducted an empirical study and identified nine common BPCP issue patterns that can lead to various adverse consequences, such as installation failures, crashes, and even component hijacking. To automatically identify these patterns of bad practices, we devised PERMEAGRE, a static analysis tool. Employing PERMEAGRE, we performed a large-scale analysis of 83,085 applications obtained from seven major app markets, aiming to detect instances of BPCP issues. The results revealed that more than 26% of the analyzed apps contained at least one issue, and a significant number of apps had garnered millions of downloads. Our analysis delved into the underlying causes of these issues. Consequently, this analysis sheds light on the potential threat landscape associated with bad practices in custom permissions, emphasizing the urgent requirement for effective mitigation strategies.

In Unmanned Aerial Vehicle (UAV) networks, UAVs usually perform tasks in the form of groups. When tasks change, the Ground Control Station (GCS) will assign the complemental UAV to join the group for notification or reinforcement. Since UAVs communicate over open wireless channels, secure authentication is required for complemental UAV joining the group. However, one-by-one authentication between complemental UAV and the group members leads to high overhead and delays. At the same time, when the UAV group is far away from the coverage of the GCS, the GCS is unable to assist the authentication process in real-time. To solve the above problems, we propose a one-to-many UAV authentication scheme using Identity-Based Broadcast Encryption (IBBE) and batch authentication. This scheme does not require a trusted third party to be online in real time. We also design an algorithm based on reinforcement learning for identifying illegal requests during batch authentication, enhancing efficiency and ensuring successful authentication. Our scheme meets UAV networks’ security requirements, defending against various attacks. Experimental results show that it reduces computational overhead by 55.27% and communication overhead by 23.16% compared to similar schemes. Additionally, the illegal request identification algorithm reduces identification numbers by 15.44% to 25.72% and lowers latency by 14.64% to 25.12% compared to existing methods.

Allowing users to assure that their files are reliably stored into multiple replicas is critically important but challenging for secure cloud storage. Recently, Damgård et al. [1] designed the first publicly verifiable proof of replicated storage (abbreviated as PRI-POREP) in the private client setup without the fine-grained timing assumption. However, it relies on an “ideal” invertible random permutations (IRPs), whose construction with the structured domain/range remains open even in the random oracle model. Also, it is computationally inefficient in terms of both replicas generation and file update. To address challenges regarding both practicality and efficiency while guaranteeing the security of PRI-POREP, this paper aims at constructing a new proof of replicated storage scheme without timing assumption, named as μPRI-POREP. μPRI-POREP is secure against server-side deletion of replica blocks and it works efficiently, saving computation cost by orders of magnitude, compared to PRI-POREP. Moreover, we demonstrate that μPRI-POREP can also support efficient dynamic update and can be further applied to secure the RSA-Hourglass schemes. Finally, we evaluate μPRI-POREP with a prototype implementation and exhibit that it can achieve comparable performance compared to PRI-POREP and support efficient file update operation.

With the popularity of mobile devices, spatial-textual trajectory query has been deployed in applications such as trajectory-based navigation and travel route recommendation. Massive trajectory data have been outsourced to cloud servers for storage and sharing such as spatial keyword search. However, existing solutions only support similarity queries in the spatial dimension and still incur high storage and query costs, which cannot scale well in large-scale trajectory data scenarios. To solve the above issues, we first achieve an Efficient Range Query over Encrypted Trajectory Data (ERT) using Douglas-Peucker trajectory compression algorithm, random matrix multiplication, filtering-verification mechanism and polynomial fitting technology. Then, we further propose an enhanced Efficient Spatial Keyword Query over Encrypted Trajectory Data (ESKT) by constructing a unified spatial-textual index structure, which can find relevant trajectories that are within some arbitrary geometric range and contain all query keywords. Finally, we formally prove that our schemes are secure against chosen-plaintext-attack, and conduct extensive experiments to demonstrate that our schemes improve the query efficiency by almost 100× when compared with state-of-the-art solutions.

With the rapid expansion of data volumes in cloud computing, more data owners are opting to outsource their data to cloud service providers to reduce local storage and management costs. However, data outsourcing deprives data owners of direct physical control over their data, increasing the risk of unauthorized access and exposure of sensitive information. To mitigate these risks, various privacy-preserving keyword search schemes with access control have been developed, but many are vulnerable to leakage-abuse attacks due to the exposure of access, search or volume patterns, which can lead to privacy breaches in outsourced data and queries. To solve this problem, we propose an oblivious encrypted keyword search scheme with fine-grained access control, called OEKA. It enables efficient oblivious keyword search over encrypted multi-maps by using the adapted XOR filter and distributed point function, ensuring protection of access, search and volume patterns. Moreover, OEKA enforces role-based access control by using polynomial-based access strategy and keyword-based private information retrieval, allowing access policies of retrieved objects to be detecting without revealing the objects themselves. A formal security analysis verifies the scheme’s robustness, and experimental results demonstrate its practical efficiency.

Graph neural networks (GNNs) are extensively employed in location-related scenarios, relying on aggregation to gather features from neighboring nodes based on edge weights. Features are closely bound to nodes’ locations and edge weights mirror distance correlations. In this sense, certain privacy concerns exist while providing location-based services if there is insufficient privacy protection. To this end, we propose a privacy-preserving and distance-aware data aggregation framework (PEDA) for GNNs. Specifically, PEDA achieves location privacy by combining circular-based positional coding with inner product functional encryption. Because of the masks in the codes, the decryption returns masked distances, preventing distance leakage. Following this, in order to protect feature privacy, we employ secret sharing. To preserve the collection strategy’s privacy, we implement an oblivious transfer for collecting the shared features. Additionally, we securely generate the adjacency matrix and aggregate features based on multi-party computation. Thorough security analysis and comprehensive evaluation demonstrate the privacy, feasibility and practicality of our approach. When compared to related works, PEDA offers four types of privacy, maintains distance awareness and feature utility, and allows for oblivious data collecting with little computational cost sacrifice.

As a new paradigm of distributed learning, Federated Learning (FL) has been applied in industrial fields, such as intelligent retail, finance and autonomous driving. However, several schemes that aim to attack robust aggregation rules and reducing the model accuracy have been proposed recently. These schemes do not maintain the sign statistics of gradients unchanged during attacks. Therefore, the sign statistics-based scheme SignGuard can resist most existing attacks. To defeat SignGuard and most existing cosine or distance-based aggregation schemes, we propose an enhanced model poisoning attack, ScaleSign. Specifically, ScaleSign uses a scaling attack and a sign modification component to obtain malicious gradients with higher cosine similarity and modify the sign statistics of malicious gradients, respectively. In addition, these two components have the least impact on the magnitudes of gradients. Then, we propose MSGuard, a Multi-Strategy Byzantine-robust scheme based on cosine mechanisms, symbol statistics, and spectral methods. Formal analysis proves that malicious gradients generated by ScaleSign have a closer cosine similarity than honest gradients. Extensive experiments demonstrate that ScaleSign can attack most of the existing Byzantine-robust rules, especially achieving a success rate of up to 98.23% for attacks on SignGuard. MSGuard can defend against most existing attacks including ScaleSign. Specifically, in the face of ScaleSign attack, the accuracy of MSGuard improves by up to 41.78% compared to SignGuard.

The federated learning (FL) client selection scheme can effectively mitigate global model performance degradation caused by the random aggregation of clients with heterogeneous data. Simultaneously, research has exposed FL’s susceptibility to backdoor attacks. However herein lies the dilemma, traditional client selection methods and backdoor defenses stand at odds, so their integration is an elusive goal. To resolve this, we introduce Grace, a resilient client selection framework blending combinational class sampling with data augmentation. On the client side, Grace first proposes a local model purification method, fortifying the model’s defenses by bolstering its innate robustness. After, local class representations are extracted for server-side client selection. This approach not only shields benign models from backdoor tampering but also allows the server to glean insights into local class representations without infringing upon the client’s privacy. On the server side, Grace introduces a novel representation combination sampling method. Clients are selected based on the interplay of their class representations, a strategy that simultaneously weeds out malicious actors and draws in clients whose data holds unique value. Our extensive experiments highlight Grace’s capabilities. The results are compelling: Grace enhances defense performance by over 50% compared to state-of-the-art (SOTA) backdoor defenses, and, in the best case, improves accuracy by 3.19% compared to SOTA client selection schemes. Consequently, Grace achieves substantial advancements in both security and accuracy.

The prerequisite for implementing incentive mechanisms and reliable participant selection schemes in federated learning is to obtain the contribution of each participant. Available evaluation methods for participant contributions require the server to possess a test dataset, often impractical. Additionally, the excessively high complexity of these works is unacceptable when training complex models in large-scale federated learning system. To address these issues, we propose a lightweight contribution evaluation method for federated learning participants, named LCEFL, based on model projection theory, which does not require the server to provide a test dataset. In addition, a model compression method is designed to be used in LCEFL to reduce the computational complexity. Furthermore, a trusted aggregation method based on LCEFL is proposed, where the weight of each participant's local model is determined by its trust level, which can be calculated using its contribution evaluation result. Experimental results show that LCEFL can achieve nearly the same accuracy as schemes based on Shapley Value, while significantly reducing computational overhead by more than 50%. Compared to available aggregation methods, the proposed trusted aggregation scheme is able to accelerate the convergence speed of the global model and improve its accuracy by 2% to 45%.

With the rapid development of mobile computing and the popularity of mobile devices equipped with GPS technology, massive spatial data have become available. Enterprises upload encrypted spatial data to the mobile cloud to save local storage and computation costs. However, the existing secure Geometric Range Search (GRS) solutions are inefficient in terms of building, updating index structure and querying processes. Moreover, the index structures of existing GRS schemes based on Order Preserving Encryption (OPE) leak location order, which may lead to reconstruction attacks. To solve these issues, we first propose an efficient and secure GRS scheme using Radix-Tree, namely GRSRT-I. Specifically, we construct an index structure based on Radix-tree to achieve efficient search and update, then use homomorphic encryption NTRU to resist chosen-plaintext attack, finally design a dual-server architecture to alleviate the burdens on mobile users caused by multiple rounds of interactions. Furthermore, we propose an enhanced scheme, GRSRT-II, by combining Order-Revealing Encryption and OPE, which greatly improves the search efficiency while slightly reducing the security. We formally prove the security of our proposed schemes, and conduct extensive experiments to demonstrate that GRSRT-I can improve the query efficiency by up to at least 1.5 times when compared with previous solutions and GRSRT-II can achieve a higher level of search efficiency.

As a fundamental service in mobile cloud computing, range query has attracted extensive attention. But the existing secure range query schemes not only leak data privacy but also have low query efficiency. To address those issues, we first design a novel range-matched code to convert the range query into code set matching, which aims to hide the order relationship of outsourced data as well as the index of most significant different bit. Based on the designed range-matched code, we propose aPractical andLess LeakageRangeQuery scheme over encrypted mobile cloud data (PLRQ) by integrating XOR filter and multiset hash function. Security analysis shows that PLRQ achieves semantic security and avoids data privacy leakage. Extensive experiments using real datasets demonstrate that, compared with two state-of-the-art solutions-RngMatch and LSRQ, our proposed PLRQ improves the query efficiency both by 2 orders of magnitude, and reduces the storage cost on Cloud Service Provider by about 79.5% and 73.6% respectively.

Data is the essential fuel for deep neural networks (DNNs), and its quality affects the practical performance of DNNs. In real-world training scenarios, the successful generalization performance of DNNs is severely challenged by noisy samples with incorrect labels. To combat noisy samples in image classification, numerous methods based on sample selection and semi-supervised learning (SSL) have been developed, where sample selection is used to provide the supervision signal for SSL, achieving great success in resisting noisy samples. Due to the necessary warm-up training on noisy datasets and the basic sample selection mechanism, DNNs are still confronted with the challenge of memorizing noisy samples. However, existing methods do not address the memorization of noisy samples by DNNs explicitly, which hinders the generalization performance of DNNs. To alleviate this issue, we present a new approach to combat noisy samples. First, we propose a memorized noise detection method to detect noisy samples that DNNs have already memorized during the training process. Next, we design a noise-excluded sample selection method and a noise-alleviated MixMatch to alleviate the memorization of DNNs to noisy samples. Finally, we integrate our approach with the established method DivideMix, proposing Modified-DivideMix. The experimental results on CIFAR-10, CIFAR-100, and Clothing1M demonstrate the effectiveness of our approach.

Federated learning (FL) has become a popular mode of learning, allowing model training without the need to share data. Unfortunately, it remains vulnerable to privacy leakage and poisoning attacks, which compromise user data security and degrade model quality. Therefore, numerous privacy-preserving frameworks have been proposed, among which mask-based framework has certain advantages in terms of efficiency and functionality. However, it is more susceptible to poisoning attacks from malicious users, and current works lack practical means to detect such attacks within this framework. To overcome this challenge, we present DefendFL, an efficient, privacy-preserving, and poisoning-detectable mask-based FL scheme. We first leverage collinearity mask to protect users' gradient privacy. Then, cosine similarity is utilized to detect masked gradients to identify poisonous gradients. Meanwhile, a verification mechanism is designed to detect the mask, ensuring the mask's validity in aggregation and preventing poisoning attacks by intentionally changing the mask. Finally, we resist poisoning attacks by removing malicious gradients or lowering their weights in aggregation. Through security analysis and experimental evaluation, DefendFL can effectively detect and mitigate poisoning attacks while outperforming existing privacy-preserving detection works in efficiency.

With the popularity of blockchains, low transaction throughput has become a significant bottleneck in applications such as cryptocurrencies. Payment channel networks (PCNs) have received attention as a way to improve throughput. However, due to the difficulty of predicting future transactions for nodes, the transactions are prone to failure when the channel balances do not meet required conditions. It has been shown that increasing buffers (queues) in PCNs can increase the success rate of transactions and throughput. Nevertheless, there is no effective transaction scheduling strategy in buffers when transaction values are flexible and variable. To solve this problem, we first formulate the Scheduling Problem in PCNs (named PSP), and then prove it is NP-hard. We design a neural network solver based on the Sequence to Sequence (Seq2Seq) architecture and train the solver using the reinforcement learning method. With the solver, we first give two scheduling strategies to maximize transaction throughput, and then design a PCN simulator for performance evaluation. Extensive experiments are conducted to show the superiority and various performances of our proposal and illustrate that our proposal can get a significant advantage in terms of the transaction throughput compared to the existing works.

Unmanned Aerial Vehicle (UAV)-assisted IoT networks are receiving a lot of attention in academia and industry. For instance, a UAV can fly and hover over sensors, during which time the sensors simultaneously initiate batch access requests to the UAV. Typically, UAV employs batch authentication to efficiently handle these batch accesses. However, an attacker can initiate illegal requests, causing batch authentication to fail. There are various batch identification algorithms to find illegal requests, enabling legitimate sensors to establish service connections quickly. Existing work wants to choose a suitable one based on the specific attack scenario. However, existing work assumes that the percentage r% of illegal requests is known in advance, which is impractical in real-world scenarios. Besides, existing work only selects a suitable batch identification algorithm based on r%, limiting the performance of batch identification to the capabilities of the alternative algorithms. Drawing inspiration from the Kalman filter, we first propose an adaptive estimation algorithm for the number of illegal requests to address the above problems. Based on the estimated value e%, we design a combinatorial batch identification using reinforcement learning. This approach allows the combination of different algorithms to achieve superior performance. Extensive experiments demonstrate that, for the estimation algorithm, the relative error is less than 20% in 27 out of 40 experiments. Regarding the combinatorial algorithms, the delay can be reduced by approximately 7.15% to 30.86% compared to existing methods.

With the commercial launch of 5G technology, the development of the Internet of Things, and the proliferation of edge computing, wireless networks are having a profound impact on society. However, ensuring data security in the wireless network remains a challenging issue. The proposed cloud-network-end collaborative security architecture provides an effective approach to address this challenge. This paper presents a non-interactive key agreement and update scheme based on cloud-network-end architecture. Non-interactive secure association is achieved by using Chameleon Hash and Diffie-Hellman key exchange technology. Furthermore, a Key Derivation Function is introduced to implement a one-time padding update mechanism. Security analysis in Protocol Composition Logic shows that the proposed scheme satisfies authentication, key confidentiality and forward security for session keys. Finally, experiments confirm that our solution incurs minimal communication overhead on the user side and achieves efficient secure association and key update.

Web services have brought great convenience to our daily lives. Meanwhile, they are vulnerable to Denial-of-Service (DoS) attacks. DoS attacks launched via vulnerabilities in the services can cause great harm. The vulnerabilities in protocol implementations are especially important because they are the keystones of web services. One vulnerable protocol implementation can affect all the web services built on top of it. Compared to the vulnerabilities that cause the target service to crash, resource exhaustion vulnerabilities are equally if not more important. This is because such vulnerabilities can deplete the system resources, leading to the unavailability of not only the vulnerable service but also other services running on the same machine. Despite the significance of this type of vulnerability, there has been limited research in this area.

Searchable encryption (SE) can potentially be used to guarantee both data confidentiality and searchability over mobile cloud-assisted Internet of things. However, existing SE solutions mainly focus on user revocation rather than keyword revocation. The keyword revocation may be required in certain situations. For example, patients do not allow their doctors to access records on some diseases such as syphilis. Hence, we propose a basic Revocable Keyword Search (RKS) scheme over encrypted electronic medical records in the group setting, which supports keyword revocation (by using a revocation list) and authorized access permissions (via a group key exchange protocol). Then, we design an enhanced RKS (called RKS+) to significantly reduce the size of revoked keyword ciphertexts and the costs of token generation and ciphertext retrieval. Our schemes also support efficient user revocation by updating only one index component, and guarantee forward security. The formal security analysis proves that our schemes are secure against both chosen-keyword attacks and chosen-plaintext attacks, and findings from the empirical evaluations demonstrate that our schemes are efficient and practical.

Low Earth Orbit (LEO) mega-constellations enable the Internet of Things (IoT) industry to realize the vision of integrated space-air-ground-sea communication networks under B5G and 6G. However, due to the high complexity of O(|V|log|V|+|E|) of Dijkstra’s algorithm, existing LEO mega-constellations suffer from excessive routing reconvergence time under frequent topology changes caused by satellite-ground station link handovers and network failures. To this end, we propose MLDR, a Manhattan-like topology-and Low ISL Delay-based Routing scheme with an ultra-low routing complexity of O(|V|4) while maintaining near-optimal routing. Firstly, for any source satellite, MLDR divides the Manhattan-like topology of LEO mega-constellations into four non-interfering Minimum Hop (MH) areas. Secondly, MLDR concurrently and non-repeatedly computes MH paths for all destinations within each MH area and installs routing tables. Thirdly, MLDR incrementally computes and updates the MH paths by more optimal MH detour paths, which select other neighboring satellites as relaying nodes. Finally, by conducting extensive simulations on real-world LEO mega-constellations, our MLDR outperforms all state-of-the-art schemes by remarkably reducing reconvergence time and achieving the highest routing optimality.

Simulation is a vital method to test autonomous vehicle software. It provides a low cost and convenient virtual environment to verify the control program of autonomous vehicles. However, to deploy simulation, the vehicle software must either have built-in adaptability or undergo the source code level modification to adapt to simulators. Unfortunately, most autonomous vehicles on the market are not capable of adapting to simulators, and their source code is not available to the public. Therefore, we propose an innovative off-chip peripheral emulation-based methodology to assist drone software in adapting to simulators. The experiments demonstrate that our methodology can help simulate drones without modifying their software. This makes simulation more feasible for third-party analysts. Furthermore, we deployed a prototype called Dvatar and simulated a real-world drone using Dvatar for demonstration.

With the rapidly increasing number of bandwidth-intensive terminals capable of intelligent computing and communication, such as smart devices equipped with shallow neural network (NN) models, the complexity of multiple access (MA) for these intelligent terminals is increasing due to the dynamic network environment and ubiquitous connectivity in sixth-generation (6G) systems. Traditional MA design and optimization methods are gradually losing ground to artificial intelligence (AI) techniques that have proven their superiority in handling complexity. AI-empowered MA and its optimization strategies aimed at achieving high quality-of-service (QoS) are attracting more attention, especially in the area of latency-sensitive applications in 6G systems. In this work, we aim to: 1) present the development and comparative evaluation of AI-enabled MA; 2) provide a timely survey focusing on spectrum sensing, protocol design, and optimization for AI-empowered MA; and 3) explore the potential use cases of AI-empowered MA in the typical application scenarios within 6G systems. Specifically, we first present a unified framework of AI-empowered MA for 6G systems by incorporating various promising machine learning (ML) techniques in spectrum sensing, resource allocation, MA protocol design, and optimization. We then introduce AI-empowered MA spectrum sensing related to spectrum sharing and spectrum interference management. Next, we discuss the AI-empowered MA protocol designs and implementation methods by reviewing and comparing the state of the art and further explore the optimization algorithms related to dynamic resource management, parameter adjustment, and access scheme switching. Finally, we discuss the current challenges, point out open issues, and outline potential future research directions in this field.

Deep Convolution Neural Networks (CNNs) have become the cornerstone of image classification, but the emergence of adversarial image attacks brings serious security risks to CNN-based applications. As a local perturbation attack, the border attack can achieve high success rates by only modifying the pixels around the border of an image, which is a novel attack perspective. However, existing border attacks have shortcomings in stealthiness and are easily detected. In this article, we propose a novel stealthy border attack method based on deep feature alignment. Specifically, we propose a deep feature alignment algorithm based on style transfer to guarantee the stealthiness of adversarial borders. The algorithm takes the deep feature difference between the adversarial and the original borders as the stealthiness loss and thus ensures good stealthiness of the generated adversarial images. To ensure high attack success rates simultaneously, we apply cross entropy to design the targeted attack loss and use margin loss as well as Leaky ReLU to design the untargeted attack loss. Experiments show that the structural similarity between the generated adversarial images and the original images is 8.8% higher than the state-of-art border attack method, indicating that our proposed adversarial images have better stealthiness. At the same time, the success rate of our attack in the face of defense methods is much higher, which is about four times that of the state-of-art border attack under the adversarial training defense.

Federated Learning (FL) ensures collaborative learning among multiple clients while maintaining data locally. However, the traditional synchronous FL solutions have lower accuracy and require more communication time in scenarios where most devices drop out during learning. Therefore, we propose anAsynchronousFederatedLearning (AsyFL) scheme using time-weighted and stale model aggregation, which effectively solves the problem of poor model performance due to the heterogeneity of devices. Then, we integrate Symmetric Homomorphic Encryption (SHE) into AsyFL to proposeAsynchronousPrivacy-PreservingFederatedLearning (Asy-PPFL), which protects the privacy of clients and achieves lightweight computing. Privacy analysis shows that Asy-PPFL is indistinguishable under Known Plaintext Attack (KPA) and convergence analysis proves the effectiveness of our schemes. A large number of experiments show that AsyFL and Asy-PPFL can achieve the highest accuracy of 58.40% and 58.26% on Cifar-10 dataset when most clients (i.e., 80%) are offline or delayed, respectively.

The cloud-assisted mobile electronic health (e-health) system facilitates e-health data sharing between healthcare providers and patients, but also raises the security and privacy concerns of e-health data. Although Ciphertext-Policy Attribute-Based Encryption (CP-ABE) has been a promising technique to achieve fine-grained access control over encrypted e-health data, it still incurs high encryption and decryption burdens on mobile users such as smartphones and sensors. In addition, malicious cloud servers may conduct incorrect operations due to various interest incentives (e.g., leaking sensitive information to illegal users, saving computation and storage costs). To solve the above issues, in this paper we first propose an Outsourced CP-ABE (OABE) with verifiable encryption scheme by splitting secret keys corresponding to an attribute set and using the short signature, which not only reduces the encryption and decryption complexities of mobile users but also guarantees that cloud servers correctly perform encryption operations. Then, we extend OABE to construct outsourced CP-ABE with verifiable decryption (OABE+) by utilizing the verifiable tag mechanism, which guarantees that cloud servers correctly conduct the ciphertext transformation. Formal security analysis proves that our schemes are selectively secure against unauthorized accesses and malicious operations. Extensive experiments using various real-world datasets demonstrate that our schemes are efficient and feasible in real applications.

Due to the powerful representation ability and superior performance of Deep Neural Networks (DNN), Federated Learning (FL) based on DNN has attracted much attention from both academic and industrial fields. However, its transmitted plaintext data causes privacy disclosure. FL based on Local Differential Privacy (LDP) solutions can provide privacy protection to a certain extent, but these solutions still cannot achieve adaptive perturbation in DNN model. In addition, this kind of schemes cause high communication overheads due to the curse of dimensionality of DNN, and are naturally vulnerable to backdoor attacks due to the inherent distributed characteristic. To solve these issues, we propose anEfficient andSecureFederatedLearning scheme (ESFL) against backdoor attacks by using adaptive LDP and compressive sensing. Formal security analysis proves that ESFL satisfies$\epsilon$-LDP security. Extensive experiments using three datasets demonstrate that ESFL can solve the problems of traditional LDP-based FL schemes without a loss of model accuracy and efficiently resist the backdoor attacks.

To motivate data owner (DO) to trade data, the existing data trading allows DO to sell the disturbed data to the data consumer (DC), where the disturbance parameter and the data price are negotiated by them, and DO independently adds the disturbance noise to data (usually continuous type) following the negotiation result. However, DOs may violate the negotiated parameter and add more noise to data while obtaining the negotiated price, which damages DC's disturbed data availability. This deficiency is rooted in the absence of supervision and verifiability on DOs' independent disturbances. Aiming at the above problem, we devise a privacy-preserved data trading via verifiable data disturbance. Specifically, the honest-but-curious disturbance server (DS) is introduced to generate encrypted verifiable disturbance noises, and secretly distribute noises to DOs referring to the method of private information retrieval. Using homomorphic encryption, DOs finish data disturbance without knowing noises' specific sizes. Subsequently, DC selects DOs to verify with our proposed anti-forgery verification, where the anti-forgery on both disturbance noise and original data guarantees verification correctness. Theoretical analysis proves that DOs' original data is preserved in data trading. Extensive experiments using the real-world dataset demonstrate that our scheme can detect more than 80% of malicious DOs and decrease their utilities to punish malicious disturbance compared with existing works.

The increasing use of multi-biometric authentication has raised concerns about the security of biometric templates. Many template protection methods based on convolutional neural network have been presented, but most involve a trade-off between authentication accuracy and template security. In this paper, we present a cancelable multi-biometric template protection scheme that combines deep hashing with cancelable distance-preserving encryption (CDPE), which provides high template security without degrading the authentication performance. Specifically, a deep hashing based architecture that minimizes the quantization loss is designed to map face and iris traits to binary codes. Next, CDPE is proposed to generate a protected template given the face binary code and a user-specific key obtained from the iris binary code, which preserves the distance between original templates in the protected domain to ensure authentication performance equivalent to unprotected systems. Digital lockers instead of the key are stored to further enhance the security, which can be unlocked with genuine biometric traits to get the correct key during authentication. Theoretical and experimental results on real face and iris datasets show that our scheme can achieve equal error rate of 0.23% and genuine accept rate of 97.54%, while guaranteeing irreversibility, revocability and unlinkability of protected templates.

Federated Learning (FL) is an emerging distributed machine learning paradigm crucial for ensuring privacy-preserving learning. In FL, a fair incentive mechanism is indispensable for inspiring more clients to participate in FL training. Nevertheless, achieving a fair incentive mechanism in FL is an arduous endeavor, underscored by two significant challenges that persistently elude resolution within existing methodologies. Firstly, existing works overlook the issue of category distribution heterogeneity in contribution evaluation, leading to incomplete contribution evaluations. Secondly, the fact that malicious servers will dishonestly allocate rewards to save costs is not considered in existing work, which can be a barrier to client participation in FL. This paper introduces FDFL (Fair andDiscrepancy-aware incentive mechanism forFederatedLearning), a novel system addressing these concerns. FDFL encompasses two key elements: 1) Discrepancy-aware contribution evaluation approach; 2) Provable reward allocation approach. Extensive experiments on four model-dataset combinations demonstrate that, under the heterogeneous setting, our scheme improves accuracy by an average of 9.85% and 11.97% compared to FedAvg and FAIR, respectively.

Face and voice are two of the most popular traits used for authentication tasks in daily life, as they can be easily captured using low-cost visual and audio sensors on smartphones, laptops, tablets,etc. Many bimodal biometric authentication schemes based on these two traits have been presented to provide higher accuracy than unimodal systems. However, these schemes are inflexibility due to the requirement of submitting two traits simultaneously, and they lack template protection, which may lead to biometric data leakage. We present a cross-modal learning based bimodal biometric authentication scheme, which improves the flexibility of existing schemes while ensuring the biometric template security. We integrate cross-modal learning into the feature extraction to obtain a bimodal biometric shared representation given input face images and voice clips. In order to enhance biometric template security without sacrificing authentication accuracy, a residual network and polar codes based template protection method is proposed, which can eliminate the noise in shared representations due to intra-user variations and generate protected templates. We have evaluated the efficacy of the bimodal biometric scheme using a real video dataset containing face images and voice clips. Experimental results demonstrate that our scheme can achieve flexible authentication with high accuracy no matter the probe input is a face image, a voice clip or a combination of them. Furthermore, the security analysis demonstrates that our scheme provides irreversibility, unlinkability and revocability of protected templates.

To address the challenges posed by data silos and heterogeneity in distributed machine learning, privacy-preserving asynchronous Federated Learning (FL) has been extensively explored in academic and industrial fields. However, existing privacy-preserving asynchronous FL schemes still suffer from the problem of low model accuracy caused by inconsistency between delayed model updates and current model updates, and even cannot adapt well to Non-Independent and Identically Distributed (Non-IID) settings. To address these issues, we propose a Privacy-preserving Asynchronous Federated Learning based on the alternating direction multiplier method (PAFed), which is able to achieve high-accuracy models in Non-IID settings. Specifically, we utilize vector projection techniques to correct the inconsistency between delayed model updates and current model updates, thereby reducing the impact of delayed model updates on the aggregation of current model updates. Additionally, we employ an optimization method based on alternating direction multipliers to adapt the Non-IID settings to further enhance the global model accuracy. Finally, through extensive experiments, we demonstrate that our scheme improves the model accuracy by up to 12.53% when compared with current state-of-the-art solution FedADMM.

Federated learning not only realizes collaborative training of models, but also effectively maintains user privacy. However, with the widespread application of privacy-preserving federated learning, poisoning attacks threaten the model utility. Existing defense schemes suffer from a series of problems, including low accuracy, low robustness and reliance on strong assumptions, which limit the practicability of federated learning. To solve these problems, we propose a Robustness-enhanced privacy-preserving Federated learning with scaled dot-product attention (RFed) under dual-server model. Specifically, we design a highly robust defense mechanism that uses a dual-server model instead of traditional single-server model to significantly improve model accuracy and completely eliminate the reliance on strong assumptions. Formal security analysis proves that our scheme achieves convergence and provides privacy protection, and extensive experiments demonstrate that our scheme reduces high computational overhead while guaranteeing privacy preservation and model accuracy, and ensures that the failure rate of poisoning attacks is higher than 96%.

Boolean range query (BRQ) as a typical type of spatial keyword query that is widely used in geographic information systems, location-based services and other applications. It retrieves the objects inside the query range and containing all query keywords. Many privacy-preserving BRQ schemes have been proposed to support BRQ over encrypted data. However, most of them fail to achieve efficient retrieval and lightweight result verification while suppressing access and search pattern leakage. Thus, in this paper, we propose an efficient verifiable privacy-preserving Boolean range query with suppressed leakage. Firstly, we convert BRQ into multi-keyword query by using Gray code and Bloom filter. Then, we achieve efficient oblivious multi-keyword query by combining distributed point function and PRP-based Cuckoo hashing, which protects the access and search patterns. Moreover, we support lightweight and oblivious result verification based on oblivious query, aggregate MAC, keyed-hashing MAC and XOR-homomorphic pseudorandom function. It enables query users to verify the result integrity with a proof whose size is independent of the size of the outsourced dataset. Finally, formal security analysis and extensive experiments demonstrate that our proposed scheme is adaptively secure and efficient for practical applications, respectively.

The advanced data trading allows data generator’s (DG) disturbed data to be traded as both initial and reselling trading modes, which meets DG’s raw data privacy and data consumers’ (DCs) vast data requirement. However, the traded data truthfulness verifiability cannot be guaranteed in the privacy-preserved way. Firstly, due to DG’s independent and random disturbance, DC cannot verify whether the traded data is disturbed under his required disturbance parameter without carrying privacy leakage on DG. Secondly, because the reselling trading is allowed, DC can hardly verify the traded data’s origin truthfulness under the deceiving of data reseller (DR) while protecting his purchase privacy. Aiming at the above problems, we propose the privacy-preserved data disturbance and truthfulness verification for data trading. Specifically, an honest-but-curious trading server (TS) is introduced to assist our devised private-verifiable imprint-embedded disturbance method where imprint is blinding. Subsequently, TS implements the adaptive truthfulness verification by constructing imprint-embedded individual verification formula and requiring verified participants to decrypt the formula result. The verified participants cannot inform the blinding imprint value to forge the correct result, ensuring the accuracy of the devised verification method. Theoretical analysis proves that participants’ privacy is preserved and the traded data’s truthfulness can be guaranteed. Extensive experiments using the real-world dataset demonstrate that without any extra privacy cost, our scheme verifies 100% untruthful traded data compared with the existing solutions’ 50%.

To solve the data silos issue in distributed machine learning with privacy leakage, privacy-preserving federated learning (PPFL) has been extensively explored in both academic and industrial fields. However, the existing PPFL solutions still suffer from high computation and communication overheads, which result in excessive consumption of communication bandwidth and slow down the training process of FL. To address these issues, we propose a secure and communication-efficient FL scheme using improved compressed sensing and CKKS homomorphic encryption. Specifically, we implement a lossy compression of the model by using discrete cosine transform, then use CKKS homomorphic encryption to encrypt the data transmitted between clients and center server due to its high efficiency and support for batch encryption. Formal security analysis proves that our scheme is secure against indistinguishability under chosen plaintext attack and extensive experiments demonstrate that our scheme achieves a high accuracy at 0.05% compression rate.

When enjoying mobile crowdsensing (MCS), it is vital to evaluate the trustworthiness of mobile users (MUs) without disclosing their sensitive information. However, the existing schemes ignore this requirement in the multiple crowdsourcers (CSs) scenario. The lack of a credible sharing about MUs’ trustworthiness results in an inaccurate trust evaluation, disabling allocating tasks to reliable MUs. To address it, based on the analysis of the desired properties, we propose a scheme enablingdependabledata collection withmultiple crowdsourcerstrustsharing ($D^{2}MTS$). Specifically, we design the MU anonymous management. Two kinds of MU generated pseudonym systems without relationships are presented to mark each MU in trust evaluation and task execution, respectively. Through the devised pseudonym changes on these pseudonyms and the common token distribution algorithm,$D^{2}MTS$realizes privacy-preserving trust sharing. Moreover, to guarantee credible sharing, based on the hash chain,$D^{2}MTS$records MUs’ trustworthiness with the unforgeable signature on the blockchain established by multiple CSs which do not trust each other naturally. Extensive experiments show that compared with the other works,$D^{2}MTS$'s detection ratio of vicious MUs and the percentage of reliable MUs among the selected ones can increase by 208.61% and 28.27%. Both computational and communication delays are limited.

With the rapid development of geographic location technology and the explosive growth of data, a large amount of spatial data is outsourced to the cloud server for reducing the local high storage and computing burdens, but at the same time causes security issues. Thus, extensive privacy-preserving spatial data query schemes have been proposed. Most of the existing schemes use Asymmetric Scalar-Product-Preserving Encryption (ASPE) to encrypt data, but ASPE has proven to be insecure against known plaintext attack. And the existing schemes require users to provide more information about query range and thus generate a large amount of ciphertexts, which causes high storage and computational burdens. To solve these issues, based on enhanced ASPE designed in our conference version, we first propose a basic Privacy-preserving Spatial Data Query (PSDQ) scheme by using a new unified index structure, which only requires users to provide less information about query range. Then, we propose an enhanced PSDQ scheme (PSDQ$^+$) by using Geohash-based$R$-tree structure (called$GR$-tree) and efficient pruning strategy, which greatly reduces the query time. Formal security analysis proves that our schemes achieve Indistinguishability under Chosen Plaintext Attack (IND-CPA), and extensive experiments demonstrate that our schemes are efficient in practice.

To motivate users' assistance for protecting others' location privacy by distributedK-anonymity in Location-Based Service (LBS), many incentive mechanisms have been proposed, where users obtain monetary compensation for their assistance. However, most existing distributedK-anonymity incentive mechanisms rely on trusted third parties and ignore users' malicious strategies, which destroys LBS's distributed structure as well as leads to users' privacy leakage and incentive ineffectiveness. To solve the above problems, we propose aPrivacy-Enhanced incentive mechAnism for distributedK-anonymity (PEAK). With determining the monetary transaction relationship and location transmission between users, PEAK enables the anonymous cloaking region construction without the trusted server. Meanwhile, PEAK devises role identification mechanism and accountability mechanism to restrain and punish malicious users, which protects users' location privacy and implements effective motivation on users' assistance. Theoretical analysis based on the game theory shows that PEAK constrains users' malicious strategies while satisfying individual rationality, computational efficiency, and satisfaction ratio. Extensive experiments based on the real-world dataset demonstrate that PEAK improves security and feasibility, especially reaching the success rate of anonymous cloaking region construction to more than 90$\%$and decreasing the malicious users' utilities significantly.

There is substantial attention to federated learning with its ability to train a powerful global model collaboratively while protecting data privacy. Despite its many advantages, federated learning is vulnerable to backdoor attacks, where an adversary injects malicious weights into the global model, making the global model's targeted predictions incorrect. Existing defenses based on identifying and eliminating malicious weights ignore the similarity variation of the local weights during iterations in the malicious model detection and the presence of benign weights in the malicious model during the malicious local weight elimination, resulting in a poor defense and a degradation of global model accuracy. In this paper, we defend against backdoor attacks from the perspective of local models. First, a malicious model detection method based on interpretability techniques is proposed. The method appends a sampling check after clustering to identify malicious models accurately. We further design a malicious local weight elimination method based on local weight contributions. This method preserves the benign weights in the malicious model to maintain their contributions to the global model. Finally, we analyze the security of the proposed method in terms of model closeness and then verify the effectiveness of the proposed method through experiments. In comparison with existing defenses, the results show that BADFL improves the global model accuracy by 23.14% while reducing the attack success rate to 0.04% in the best case.

Electronic health (e-health) systems may outsource data such as patient e-health records to mobile cloud servers for efficiency gains (e.g., minimizing local storage and computation costs). However, such a move may result in privacy implications in the presence of semi-honest cloud servers. Searchable Encryption (SE) can potentially facilitate privacy-preserving searches based on keywords for encrypted data stored in the mobile cloud, but most existing SE solutions do not support temporal access control (i.e., a mechanism that grants access permissions to users for specified time ranges). Hence, in this paper we design a time-controllable keyword search scheme by using an attribute-based comparable access control. This allows users to match indexes encrypted at specified time intervals. Then, we improve the basic framework to support efficient user revocation using secret sharing. We then formally prove the security of our proposed frameworks against chosen-keyword attack and key collusion attack, as well as achieving keyword secrecy. We also evaluate the performance of our proposed approach using a real-world dataset to demonstrate their practical utility.

The mobile Internet of Vehicles (IoVs) has great potential for intelligent transportation, and creates spatial data query demands to realize the value of data. Outsourcing spatial data to a cloud server eliminates the need for local computation and storage, but it leads to data security and privacy threats caused by untrusted third-parties. Existing privacy-preserving spatial range query solutions based on Homomorphic Encryption (HE) have been developed to increase security. However, in the single server model, the private key is held by the query user, which incurs high computation and communication burdens on query users due to multiple rounds of interactions. Moreover, exposing data access patterns to semi-honest servers is highly vulnerable to frequency and statistical attacks. To solve these issues, in this paper we propose a secure spatial location query within arbitrary geometric range while protecting access pattern. Specifically, we apply Paillier algorithm and polynomial fitting technique to achieve secure arbitrary geometric range query, design secure and efficient search protocol to hide data access patterns and alleviate query users from high computation and communication burdens under dual-server model. Formal security analysis shows that our scheme is secure under semi-honest model, and extensive experiments demonstrate that our work can reduce users' communication costs by more than 90% compared to previous schemes under single server model, which is practice in real-world scenarios.

UAV-assisted mobile edge computing (UAV-MEC) has been proposed to offer computing resources for smart devices and user equipment. UAV cluster aided MEC rather than one UAV-aided MEC as edge pool is the newest edge computing architecture. Unfortunately, the data packet exchange during edge computing within the UAV cluster hasn't received enough attention. UAVs need to collaborate for the wide implementation of MEC, relying on the gossip-based broadcast protocol. However, gossip has the problem of long propagation delay, where the forwarding probability and neighbors are two factors that are difficult to balance. The existing works improve gossip from only one factor, which cannot select suitable forwarding probability and avoid redundant messages. Besides, these schemes do not consider the historical packet reception of new neighbors when UAVs fly around, which decreases forwarding efficiency. To solve these problems, we first propose a data structure called Bitgraph that can record the historical packet reception of UAVs. Then, we formulate gossip broadcasting as a partially observable Markov decision process. Based on Bitgraph, we design the reward function. Finally, we design a multi-agent reinforcement learning algorithm, Branching Deep Graph Network (BDGN), which simultaneously makes decisions on forwarding probability and neighbors. Extensive experiments illustrate that our proposal gets more than 29% advantage in terms of the propagation delay and 20% advantage in terms of the redundant messages compared to the existing works.

The adoption of SDN/NFV opens avenues for efficient network slicing deployment and cost control. However, the dynamic cost reduction brought by deployment location optimization is not suitable for all scenarios. To further reduce the cost, we recommend a sharing strategy in NFV. In this paper, we introduce a two-layer VNF multiplexing architecture, named PSMA, which guarantees both efficient VNF sharing operations and secure slicing during multiplexing. Leveraging the SDN/NFV features, the proposed scheme splits data processing and key management and establish secure connections using SDN’s programmable routing. The provided framework integrates comprehensive life-cycle management and key delivery mechanisms. The article substantiates its availability through extensive simulations of VNF reuse on a randomly generated network with Virtual Network Requests (VNR). The empirical results indicate a significant cost reduction of 5% to 10%, particularly pronounced in scenarios involving a substantial number of short-lived and transitional VNFs.

Mobile crowdsensing (MCS) has been applied in various fields to realize data sharing, where multiple platforms and multiple Mobile Users () have appeared recently. However, aiming at mutual selection, the existing works ignore making ’ utilities with the limited resources and platforms’ utilities while achieving the desired sensing data quality maximum as far as possible. Thus, they cannot motivate both and platforms to participate. To address this problem, standing on both sides of and platforms with conflicting interests, we propose a Progressive two-stage Auction-based Multi-platform Multi-user Mutual Selection scheme (). Specifically, in, we treat mutual selection as a two-stage auction and devise the auction models for and platform using forward and reverse auction ideas, presenting and maximizing the utilities from their respective perspectives. Then, based on the proposed progressive two-stage auction structure, we adopt 0-1 knapsack and Myerson’s price theory to construct the first stage -oriented auction and the second stage platform-oriented auction, achieving devised models. Theoretical analysis shows that is economically robust. Extensive experiments on the real dataset demonstrate that respectively promotes platforms’ and ’ utilities by 76.23% and 10.74 times, compared with the existing works.

The Proactive Recovery (PR) mechanism in Software-Defined Networking (SDN) provides good failure recovery resilience for the Beyond Fifth-Generation/Sixth-Generation (B5G/6G) delay-sensitive applications. However, PR’s fixed single backup path policy for any flow and fine-grained backup forwarding rule configuration poses severe challenges for post-recovery congestion management and limited Ternary Content Addressable Memory (TCAM) space in SDN switches. To this end, we propose K-backup, a load-and TCAM-aware multi-backup fast failure recovery scheme for SDNs. Firstly, K-backup formulates and solves the congestion-aware multi-backup path planning problem for various failure scenarios, exploiting the inherent load diversity of multi-backup paths to minimize the post-recovery maximum link utilization. Secondly, K-backup aggregates flows sharing the same backup-path-weight pair on a link into a cascading table of Fast-Failover and SELECT groups. Meanwhile, each outputted backup path is labeled, and a corresponding label-matching flow table is configured for each intermediate switch to aggregate all flows on that path. Thirdly, K-backup dynamically adjusts the backup path update period based on the network load stabilization to reduce unnecessary controller overhead. Compared with state-of-the-art, K-backup achieves the lowest controller overhead, the best load balancing performance, the near-fewest TCAM space usage, and the near-shortest recovery time.

The utilization of blockchain technology as a distributed information sharing system has gained widespread adoption across various domains. However, its application to Flying Ad-Hoc Network (FANET), characterized by severe packet loss, poses significant challenges. The high packet loss rates in FANETs can result in decreased consensus success rates and negatively impact information sharing consistency and efficiency. In this paper, we proposed RoUBC, a novel consensus scheme for Flying Ad-Hoc Networks (FANET), which is based on the Raft protocol and is designed to address the challenges posed by the severe packet loss network in FANET. The proposed scheme consists of two phases: leader election and block consensus. In the leader election phase, we integrate multi-criteria decision-making and link prediction algorithms to design an efficient stable-leader election method. In the block consensus phase, we propose a dynamic block verification algorithm based on historical verification information to achieve efficient block consensus. Our theoretical analysis demonstrates that the proposed consensus protocol is safe and live, effectively ensuring the consistency of message sharing in FANET. Experiment results show that our scheme outperforms traditional Raft schemes, with 35% increase in consensus success rate and 25% improvement in consensus efficiency.

With the accelerating adaption of Cloud and Edge computing, cloud-based networked deployment emerges to enable providers to deliver services in a cost-effective and elastic manner. However, security concern remains one of the major obstacles to its wider adaption. Trusted Execution Environment (TEE) has been advocated to protect cloud services in an isolated execution environment. In this paper, we present a new genre of side-channel attack called interface-based side-channel attack and demonstrate its effectiveness on the TEE-assisted networked service system. The root cause of this attack is the input-dependent interface invocation (e.g., interface information and invocation patterns) that can be observed by untrusted software to reveal the control flows inside the enclave. Our evaluation demonstrates that the attack can effectively re-identify encrypted web pages processed in the SGX enclave with an accuracy of 87.6% and a recall of 76.6%, and can reduce the search domain of the 1024 bits RSA private keys to$1.69 \times 10^{-6}$of the original search domain. As countermeasures, we propose, implement and evaluate a set of static analysis tools to mitigate the newly discovered threats. The key idea is to use inter-procedural dataflow analysis to identify potential leakage via the interface, and then mitigate them during compilation using techniques including branch obfuscation, loop obfuscation, and constant size wrapper.

With the rapid growth of data size, a large number of data providers outsource their private data to cloud servers to reduce the high storage and computation burdens, but it also leads to security issues such as privacy leakage. Therefore, many privacy-preserving range query schemes have been proposed. However, most of existing secure range query schemes suffer from low query efficiency and expensive computation and update overheads. To address these issues, we propose a novel Fast Range Query (FRQ) scheme for large-scale encrypted Key-Value (KV) data. First, we introduce REMIX, a space-efficient KV index data structure based on Log-Structured Merge-trees (LSM-trees), which maintains a global sorted view of KV pairs across multiple table files for efficient range queries. Besides, we exploit the write-efficiency compression strategy of LSM-trees to ensure efficient dynamic data updates. Finally, we use Czech Havas Majewski (CHM) to protect the index structure, which reduces the computation overhead and ensures the retrieval accuracy. Formal security analysis proves that our scheme can achieve an acceptable level of security. Extensive experiments demonstrate that our scheme improves the query efficiency by nearly$8\times$and update efficiency by$7\times$compared to state-of-the-art solutions over million-level datasets.

To motivate users to submit high quality data for mobile crowdsensing (MCS), some quality-aware incentive mechanisms have been proposed, which recruit and pay users strategically. However, in the existing mechanisms, the recruitment based only on tasks matching degree leads to the ineffective insistent data quality incentive. Meanwhile, the absence of the reasonable payment strategy cannot motivate users to submit high quality data in the current task. To address the above problems, we propose anOnlineall-phase quality-awareincentive mechanism (Oasis) to realize the quality incentive in both recruitment and payment phases. With the knapsack secretary, Oasis first devises a quality-aware pre-budgeting recruitment strategy, which decides whether the arriving user's long-term data quality and bid satisfy the recruited criterion. Then, in the payment phase, Oasis evaluates and updates the current and long-term data qualities of users. Based on the evaluation results, a two-level payment strategy is devised employing the Myerson theorem, where users submitting higher quality data can obtain more utilities under the budget constraint. Theoretical analysis proves that Oasis satisfies economic feasibility and constant competitiveness while achieving quality incentive in recruitment and payment phases. Extensive experiments using the real-world dataset demonstrate that the sensing result accuracy of Oasis increases 67% compared with the existing works.

Witnessing the blooming adoption of push notifications on mobile devices, this new message delivery paradigm has become pervasive in diverse applications. Accompanying with its broad adoption, the potential security risks and privacy exposure issues raise public concerns regarding its great social impacts. This paper conducts the first attempt to exploit the mobile notification ecosystem. By dissecting its structural elements and implementation process, a comprehensive vulnerability analysis is conducted towards the complete flow of mobile notification from platform enrollment to messaging. Meanwhile, for privacy exposure, we first examine the implementation of privacy policy compliance by proposing a three-level inspection approach to guide our analysis. Then, our top-down methods from documentation analysis, application network traffic study, to static analysis expose the illicit data collection behaviors in released applications. In addition, we uncover the potential privacy inference resulted from the notification monitoring. To support our analysis, we conduct empirical studies on 12 most popular notification platforms and perform static analysis over 30,000+ applications. We discover: 1) six platforms either provide ambiguous KEY naming rules or offer vulnerable messaging APIs; 2) privacy policy compliance implementations are either stagnated at the documentation stages (8 of 12 platforms) or never implemented in apps, resulting in billions of users suffering from privacy exposure; and 3) some apps can stealthily monitor notification messages delivering to other apps, potentially incurring user privacy inference risks. Our study raises the urgent demand for better regulations of mobile notification deployment.

Federated learning (FL) can push the limitation of "Data Island" while protecting data privacy has been a broad concern.However, the centralised FL is vulnerable to a single-point failure.While decentralised and tamper-proof blockchains can cope with the above issues, it is difficult to find a benign benchmark gradient and eliminate the poisoning attack in the later stage of global model aggregation.To address the above problems, we present a global to local based privacy-preserving federated consensus scheme against poisoning attacks (FedG2L).This scheme can effectively reduce the influence of poisoning attacks on model accuracy.In the global aggregation stage, a gradient-similarity-based secure consensus algorithm (SecPBFT) is designed to eliminate malicious gradients.During this procedure, the gradient of the data owner will not be leaked.Then, we propose an improved ACGAN algorithm to generate local data to further update the model without poisoning attacks.Finally, we theoretically prove the security and correctness of our scheme.Experimental results demonstrated that the model accuracy is improved by at least 55% than no defense scheme, and the attack success rate is reduced by more than 60%.

In unmanned aerial vehicle (UAV) performing tasks, the UAV often faces electricity shortages. The traditional scheme to charge a UAV needs to return to the ground. Using the charging UAV (CUAV) can avoid the waste of electricity caused by the return. However, the existing works only consider a fixed charging location for electricity replenishment. Moreover, fewer works focus on the matching relationship between multi-CUAV and multi-UAV. It is challenging to complete the expected charging work due to the mismatch between the electricity demand and supply. To address this problem, we propose a two-stage electricity scheduling scheme. Specifically, in the charging location selection stage, we solve the Nash equilibrium (NE) of flight consumption between CUAVs and UAVs through the exact potential game, thereby determining the accessible charging position. Then, in the electricity transaction stage, we adopt the Stackelberg game model to determine the Stackelberg equilibrium (SE) between the acceptance rate of CUAVs and the rejection rate of UAVs, ensuring that both CUAVs and UAVs are satisfied with the unit electricity prices and electricity demands. Based on the above two game stages, we propose a supply and demand scheduling (SDS) algorithm to achieve dynamic scheduling between CUAVs and UAVs. Theoretical analysis indicates the exits of NE and SE. Furthermore, the extensive experiments show that our scheme has significant advantages over the baselines in charging cost, charging price, and flight consumption.

To solve the data island issue in the distributed Internet of Things (IoT) without privacy leakage, privacy-preserving federated learning (PPFL) has been extensively explored in both academic and industrial fields. However, existing PPFL solutions still suffer from a single point of failure and incur untrusted aggregation results caused by a malicious central server, and even cause a loss of model accuracy in an asynchronous setting. To solve these issues, we propose a privacy-preserving asynchronous federated learning scheme by using blockchain. Specifically, we use blockchain to address single points of failure and untrustworthy aggregation results, implement reliable model aggregation utilizing a practical byzantine fault-tolerant protocol in an asynchronous setting, and leverage differential privacy to improve system robustness. Formal security analysis and convergence analysis demonstrate that the proposed scheme is secure and robust, and extensive experiments demonstrate that our scheme can effectively ensure the accuracy of the system when compared with state-of-the-art schemes.

Due to the distributed collaboration and privacy protection features, federated learning is a promising technology to perform the model training in virtual twins of Digital Twin for Mobile Networks (DTMN). In order to enhance the reliability of the model, it is always expected that the users involved in federated learning have trustworthy behaviors. Yet, available trust evaluation schemes for federated learning have the problems of considering simplex evaluation factor and using coarse-grained trust calculation method. In this paper, we propose a trust evaluation scheme for federated learning in DTMN, which takes direct trust evidence and recommended trust information into account. A user behavior model is designed based on multiple attributes to depict users’ behavior in a fine-grained manner. Furthermore, the trust calculation methods for local trust value and recommended trust value of a user are proposed using the data of user behavior model as trust evidence. Several experiments were conducted to verify the effectiveness of the proposed scheme. The results show that the proposed method is able to evaluate the trust levels of users with different behavior patterns accurately. Moreover, it performs better in resisting attacks from users that alternately execute good and bad behaviors compared with state-of-the-art scheme.

The traveling salesman problem (TSP) is one of the classic combinatorial optimization problems, which can be widely used in intelligent transportation and logistics field. Neural network has shown great potential in combinatorial optimization tasks. However, it faces privacy leakage when a TSP neural combinatorial optimization network and user's data are directly outsourced to a cloud platform to provide and request service. In order to address the issue, this article proposes a privacy-preserving service framework for a TSP-based neural combinatorial optimization network called PPSF. We first protect the service provider's model parameters and users’ data by different split methods in multiple cloud servers, providing a secure outsourced mode for the participators in the PPSF framework. Then, in the secure outsourced mode, a series of secure computation protocols are designed for the cloud servers to support performing the secure computing in each service task. Moreover, it can also protect the process that the cloud servers respond to users after data processing and achieve private service result recovery. Finally, we prove that the proposed framework can realize privacy protection for TSP-based combinatorial optimization service and verify its utility and efficiency by experiments.

With the rapid development of Location-Based Services (LBS), a large number of LBS providers outsource spatial data to cloud servers to reduce their high computational and storage burdens, but meanwhile incur some security issues such as location privacy leakage. Thus, extensive privacy-preserving LBS schemes have been proposed. However, the existing solutions using Bloom filter do not take into account the redundant bits that do not map information in Bloom filter, resulting in high computational overheads, and reveal the inclusion relationship in Bloom filter. To solve these issues, we propose an efficient Privacy-preserving Spatial Range Query (PSRQ) scheme by skillfully combining Geohash algorithm with Circular Shift and Coalesce Bloom Filter (CSC-BF) framework and Symmetric-key Hidden Vector Encryption (SHVE), which not only greatly reduces the computational cost of generating token but also speeds up the query efficiency on large-scale datasets. In addition, we design a Confused Bloom Filter (CBF) to confuse the inclusion relationship by confusing the values of 0 and 1 in the Bloom filter. Base on this, we further propose a more secure and practical enhanced scheme PSRQ+by using CBF and Geohash algorithm, which can support more query ranges and achieve adaptive security. Finally, formal security analysis proves that our schemes are secure against Indistinguishability under Chosen-Plaintext Attacks (IND-CPA) and PSRQ+achieves adaptive IND-CPA, and extensive experimental tests demonstrate that our schemes using million-level dataset improve the query efficiency by 100x compared with previous state-of-the-art solutions.

Federated Learning (FL) has been widely used in various fields such as financial risk control, e-government and smart healthcare. To protect data privacy, many privacy-preserving FL approaches have been designed and implemented in various scenarios. However, existing works incur high communication burdens on clients, and affect the training model accuracy due to non-Independently and Identically Distributed (non-IID) data samples separately owned by clients. To solve these issues, in this paper we propose a secure Model-Contrastive Federated Learning with improved Compressive Sensing (MCFL-CS) scheme, motivated by contrastive learning. We combine model-contrastive loss and cross-entropy loss to design the local network architecture of our scheme, which can alleviate the impact of data heterogeneity on model accuracy. Then we utilize improved compressive sensing and local differential privacy to reduce communication costs and prevent clients’ privacy leakage. The formal security analysis shows that our scheme satisfies (ε,δ)-differential privacy. And extensive experiments using five benchmark datasets demonstrate that our scheme improves the model accuracy by 3.45% on average of all datasets under the non-IID setting and reduces the communication costs by more than 95%, when compared with FedAvg.

As an important means of obtaining information of marine situation, the marine monitoring system relying on UAV has been paid more and more attention by all countries in the world, and the demand for tasks is growing continually. In UAV ad hoc networks, routing protocols with immutable routing policies that lack flexibility are generally incapable of maintaining effective performance due to the complicated and rapidly changing environmental situation and application requirements. In this paper, we propose an intelligent clustering routing approach (ICRA) for UANETs. The ICRA is composed of three components: the clustering module, the clustering strategy adjustment module and the routing module. In the clustering process, each node needs to calculate its utility. In order to maintain high topology stability and long network lifetime in different network states, the reinforcement learning based clustering strategy adjustment module needs continuous learning the benefits brought by adopting different strategies to calculate the nodes utility in a specific network state. With the learned knowledge, clustering strategy adjustment module could determine the optimal clustering strategy according to the current network state. In the routing phase, the proposed scheme can reduce the end-to-end delay and improve the packet delivery rate by introducing inter-cluster forwarding nodes to forward messages among different clusters. Extensive experiments have been conducted to verify ICRA’s robustness and superiority over existing schemes. The results demonstrate that ICRA could achieve better performance than its state-of-the-art counterparts with regard to the clustering efficiency, topology stability, energy efficiency and quality of service.

With the rapid development of Intelligent Transportation System (ITS), a large number of spatial data are generated in ITS. Although outsourcing spatial data to the cloud server can reduce the high local computation and storage overheads, it will also lead to security and privacy issues. Therefore, it is necessary to have a survey to specifically summarize these advanced privacy-preserving spatial data query schemes. However, the existing surveys considering both location information and keywords of spatial data only summarize the spatial keyword query scheme in plaintext environment, they do not consider the privacy of spatial data. Although there are some surveys on privacy-preserving spatial data query, they only focus on the location information of spatial data without considering descriptive keywords. Therefore, to understand the progress and research trends in the field, we give a comprehensive survey on secure spatial data query in ITS to summarize and analyze the most advanced solutions. Then, we make a comprehensive and detailed comparison of existing solutions in terms of query function, index structure, time complexity, security, etc. Finally, we show some open challenges and potential research directions for privacy-preserving spatial data query.

Federated learning is good for building better cooperative intelligent transportation system (C-ITS). Intellectual property protection in C-ITS brings many benefits to all vehicles. Although the protection of model intellectual property by watermark has received much research attention, the existing works only deploy watermark in centralized models. Due to the difference of watermark distribution among vehicles, the global model accuracy of watermark in federated learning is significantly reduced or the local watermark is invalid. To solve these problems, we propose a multi-party entangled watermark algorithm in federated learning. Specifically, in the local training, we propose a watermark enhancement algorithm, which solves the problem of local watermark failure. Then, in the global aggregation, we propose an entanglement aggregation algorithm, which solves the problem of a great loss of global model accuracy. We conduct extensive experiments on public datasets to show the superiority of our proposal. The results show that our scheme can obtain more than 16% and 31% advantages in model accuracy and watermark success rate, respectively, compared with existing watermark schemes in federated learning.

With increasingly popular GPS-equipped mobile devices (e.g., smartphones, tablets, laptops), massive spatio-textual data has been outsourced to cloud servers for storage and analysis such as spatial keyword search. However, existing privacy-preserving spatial keyword query schemes only support coarse-grained non-temporal access control in single-user sharing scenarios, which does not scale well in time-related scenes such as message valid period. To solve the above issues, we propose Privacy-preserving Boolean Range Query with Temporal access control in mobile computing (PBRQ-T). Specifically, we first achieve PBRQ with linear search complexity using the adapted Gray code, Bloom filter, and Katz-Sahai-Waters encryption. Then, we provide fine-grained and temporal access control in PBRQ based on the forward/backward derivation function and attribute-based encryption, where PBRQ is executed only when the spatio-textual data is accessible. Finally, an enhanced PBRQ-T (i.e., PBRQ-T+) with faster-than-linear search complexity is proposed by constructing a Quadtree index structure. Our formal security analysis shows that data privacy and index privacy can be guaranteed during the query process. Our extensive experiments using a real-world dataset demonstrate the efficiency and feasibility of our schemes.

Location-Based Services (LBSs) are one of the most frequently used mobile applications in the modern society. Geo-Indistinguishability (Geo-Ind) is a promising privacy protection model for LBSs since it can provide formal security guarantees for location privacy. However, Geo-Ind undermines the statistical location distribution of users on the LBS server because of perturbed locations, thereby disabling the server to provide distribution-based services (e.g., traffic congestion maps). To overcome this issue, we give a privacy definition, called DistPreserv, to enable the LBS server to acquire valid location distributions while providing users with strict location protection. Then we propose a privacy-preserving LBS scheme to benefit both users and the server, in which a location perturbation mechanism is designed to achieve the given definition under the guide of the incentive compatibility, and a retrieval area determination method is presented to ensure query accuracy of users by using the dynamic programming on the two-dimensional map plane. Finally, we theoretically prove that the designed mechanism can achieve the definition of DistPreserv and the property of incentive compatibility. Experimental explorations using a real-world dataset indicate that our proposal prominently improves the availability of users’ location distributions by over 90%, while providing high precision and recall of queries.

Symmetric Searchable Encryption (SSE), as an ideal primitive, can ensure data privacy while supporting retrieval over encrypted data. However, existing multi-user SSE schemes require the data owner to share the secret key with all query users or always be online to generate search tokens. While there are some solutions to this problem, they have at least one weakness, such as non-supporting conjunctive query, result decryption assistance of the data owner, and unauthorized access. To solve the above issues, we propose an O wner-free Di stributed S ymmetric searchable encryption supporting C onjunctive query (ODiSC). Specifically, we first evaluate the Learning-Parity-with-Noise weak Pseudorandom Function (LPN-wPRF) in dual-cloud architecture to generate search tokens with the data owner free from sharing key and being online. Then, we provide fine-grained conjunctive query in the distributed architecture using additive secret sharing and symmetric-key hidden vector encryption. Finally, formal security analysis and empirical performance evaluation demonstrate that ODiSC is adaptively simulation-secure and efficient.

With the popularity of location based services, spatial keyword query has become an important application. In order to save the storage and computational costs, most data owners will outsource the data to the cloud server, but this will lead to two problems, such as privacy leakage and heavy network bandwidth burden. To solve above problems, we propose a Privacy-preserving top-k Spatial Keyword queries based on Fog computing, namly PSKF. To further improve the search efficiency, we use the IR-tree to build the index and store it in the cloud server. Each fog server also saves a different subtree of the IR-tree, so that we can decide which fog server to participate in the query by pruning. Formal security analysis shows that our proposed PSKF achieves Indistinguishability under Known-Plaintext Attacks (IND-KPA), and extensive experiments demonstrate that our proposed scheme is efficient and feasible in practical applications.

Searchable encryption(SE) allows users to efficiently retrieve data over encrypted cloud data, but most existing SE schemes only support exact keyword search, resulting in false results due to minor typos or format inconsistencies of queried keywords. The fuzzy keyword search can avoid this limitation, but still incurs low search accuracy and efficiency. Besides, most of fuzzy keyword search schemes do not consider malicious cloud servers which may execute a fraction of search operations or forge some results due to various interest incentives such as saving computation or storage resources. To solve these problems, we propose an efficient and Verifiable Ranked Fuzzy Multi-keyword Search scheme, called VRFMS. VRFMS uses locality-sensitive hashing and bloom filter to implement fuzzy keyword search, and employs Term Frequency-Inverse Document Frequency(TF-IDF) to sort the relevant results. Aiming to further improve the search accuracy, we design an improved bi-gram keyword transformation method. Furthermore, the homomorphic MAC technique and a random challenge technique are utilized to verify the correctness and completeness of returned results, respectively. Formal security analysis and empirical experiments demonstrate that VRFMS is secure and efficient in practical applications, respectively.

In machine learning (ML), the massive data processing and dense computations based on matrices make outsourced inference computation a growing trend. The unreliability of cloud platforms makes privacy protection and inference correctness increasingly important in outsourced computations. Unfortunately, current works cannot provide an effective verification mechanism and privacy protection for outsourcing linear computing simultaneously. To address the issue, in the service architectures with malicious behaviors (such as curiosity, dishonesty, and collusion), we propose privacy-preserving and verifiable outsourcing inference computing (PPVLC) for the most fundamental linear computations in ML. PPVLC uses secret sharing and blinding techniques to protect privacy and achieve secure computation of matrix linear computation. Meanwhile, bilinear mapping based on matrix digest is utilized to verify computation correctness, ensuring the trustworthiness of the service. Security analysis and experiments demonstrate the reliability of our scheme and service efficiency.

Member Inference Attack (MIA) is a key measure for evaluating privacy leakage in Machine Learning (ML) models, aiming to distinguish private members from non-members by training the attack model. In addition to the traditional MIA, the recently proposed Generative Adversarial Network (GAN)-based MIA can help the adversary know the distribution of the victim's private dataset, thereby significantly improving attack accuracy. For traditional attacks and this new type of attack, previous defense schemes cannot handle the trade-off between privacy and utility well. To this end, we propose a defense solution using multi-model ensemble framework. Specifically, we train multiple submodels to hide membership signals and resist MIA, achieving reduced privacy leakage while guaranteeing the effectiveness of the target model. Our security analysis shows that our scheme can provide privacy protection while preserving model utility. Experimental results on widely used datasets show that our scheme can effectively resist MIAs with negligible utility loss.

Federated learning (FL) was once considered secure for keeping clients’ raw data locally without relaying on a central server. However, the transmitted model weights or gradients still reveal private information, which can be exploited to launch various inference attacks. Moreover, FL based on deep neural networks is prone to the curse of dimensionality. In this paper, we propose a compressed and privacy-preserving FL scheme in DNN architecture by using Compressive sensing and Adaptive local differential privacy (called as CAFL). Specifically, we first compress the local models by using Compressive Sensing (CS), then adaptively perturb the remaining weights according to their different centers of variation ranges in different layers and their own offsets from corresponding range centers by using Local Differential Privacy (LDP), finally reconstruct the global model almost perfectly by using the reconstruction algorithm of CS. Formal security analysis shows that our scheme achieves ϵ-LDP security and introduces zero bias to estimating average weights. Extensive experiments using MINIST and Fashion-MINIST datasets demonstrate that our scheme with minimum compression ratio 0.05 can reduce the number of parameters by 95%, and with a lower privacy budget ϵ = 1 can improve the accuracy by 80% on MINIST and 12.7% on Fashion-MINIST compared with state-of-the-art schemes.

Summary Most of the existing global positioning system (GPS) spoofing detection schemes are vulnerable to the generative GPS spoofing attack, or require additional auxiliary equipment and extensive signal processing capabilities, leading to defects such as low real‐time performance and large communication overhead which are not available for the unmanned aerial vehicle (UAV, also known as drone) system. Therefore, we propose a novel solution which employs information fusion based on the GPS receiver and inertial measurement unit. We use a real‐time model of tracking and calculating to derive the current position of the drones which are then contrasted with the position information received by the receiver to verify whether the presence or absence of spoofing attack. Subsequent experimental work shows that, the proposed method can accurately detect the spoof within 8 seconds, with a detection rate (DR) of 98.6%. Compared with the existing schemes, the performance of real‐time detecting is improved while the DR is ensured. Even in our worst‐case, we detect the spoof within 28 seconds after the UAV system starts its mission.

With the widespread development of intelligent systems, a considerable number of mobile devices are connected together, and continuously generate huge amounts of data. Although cloud storage provides perfect solution for effectively storing these massive data, how to ensure the integrity of the outsourced data becomes challenging. For this reason, the primitive of verifiable data streaming (VDS) protocol was introduced, and enables a data owner to continuously outsource streaming data to an untrusted cloud server, while capturing the integrity of the outsourced data. That is, when a data user retrieves some data item via its index from the server, he/she can publicly verify its integrity with the proof generated and returned by the server. Supporting data update is one of the major features of VDS, and allows the data owner to replace an old data item with a new one. Although many VDS protocols have been proposed to enhance the functionality and efficiency of the original VDS protocol, they all ignore the issue of preserving those updated data items. In fact, in various application scenarios of VDS, preserving and storing previously updated data items is actually necessary. For example, in the setting of DNA sequencing, there might be multiple versions of DNA fragments at the same location due to the genetic mutation. Obviously, for more precise treatment, all these DNA fragments need to be preserved. To this end, in this paper, we propose a VDS protocol that features of enabling the query of the update history of each data item. Specifically, we first put forward a new chameleon authentication tree with update history (UCAT), which consists of two CATs (the basic tree and the update history tree). In more detail, the basic tree is used to store the data item appended to the corresponding location for the first time, and the update history tree is utilized to preserve each updated version of the corresponding data item. Furthermore, based on UCAT, we propose a VDS protocol supporting update history queries, which allows a data user to retrieve any version of the data item. The theoretical analysis and performance evaluation indicate that our protocol outperforms previous ones in the field of functionality, and its computation/communication costs are acceptable. We also prove its security in the standard model.

Controller area network (CAN) bus anomaly detection on the Internet of Vehicles (IoV) is a topic of ongoing interest and increasing importance, particularly as IoV becomes commonplace. However, existing abnormal detection schemes are not ideal due to the lack of abnormal data in IoV and the difficulty of parsing the diverse message rules in existing vehicles. While single-classification of the support vector domain description (SVDD) algorithm can detect abnormalities only with normal message information, the approach has a high rate of false negatives when deployed directly in the in-vehicle network environment. In addition, the real-time data generation (e.g., IoV messages) compounds the challenge of designing effective detection approaches. Therefore, this article proposes a mechanism for car networking message classification for a broad range of data, and establishes a weak model for many simple redundant data in the vehicle Intranet. The detection can reduce the time and computation costs of detection while ensuring accuracy. Then, this article proposes two improved SVDD schemes: 1) M-SVDD scheme, which adds the Markov chain to detect time-related messages and 2) G-SVDD scheme, which maps the kernel function to the Gaussian kernel function to reduce the redundant area of the model and the false-negative rate. The experimental results show that our proposed schemes have higher accuracy, recall rate, and fewer computation overhead.

Distributed spatial cloaking (DSC) enables users to enjoy precise location-based service (LBS) with location privacy preserving. An incentive mechanism is necessary to encourage users to cooperate. However, due to the inappropriate design of incentive mechanisms, the existing works cause low user benefits and fail to encourage users, ruining the expected incentive effect. Moreover, introducing a third party to manage users’ information also causes the existing works to disclose users’ privacy and be unpractical. To address these issues, we propose a utility-aware incentive mechanism-based distributed spatial cloaking (RESAT). By the idea of utility theory and optimization theory, RESAT devises basic and extended incentive mechanisms. The two mechanisms for assuming that all users are honest and that malicious users provide unreasonable locations. RESAT proposes an incentive mechanism-based cloaking cooperation without a third party, incorporating the developed mechanisms based on the blind signature. Theoretical analysis indicates that RESAT achieves incentive compatibility and is secure. Extensive experiments on the real data set show that compared with the existing works, RESAT enables 1 time more users to cooperate at best while eliminating the malicious behaviors that provide unreasonable locations. The required DSC construction time delay is limited.

Acquiring the spatial distribution of users in mobile crowdsensing (MCS) brings many benefits to users (e.g.,avoiding crowded areas during the COVID-19 pandemic). Although the leakage of users’ location privacy has received a lot of research attention, existing works still ignore the rationality of users, resulting that users may not obtain satisfactory spatial distribution even if they provide true location information. To solve the problem, we employ game theory with incomplete information to model the interactions among users and seek an equilibrium state through learning approaches of the game. Specifically, we first model the service as a game in the satisfaction form and define the equilibrium for this service. Then, we design aLEFSalgorithm for the privacy strategy learning of users when their satisfaction expectations are fixed, and further designLSREthat allows users to have dynamic satisfaction expectations. We theoretically analyze the convergence conditions and characteristics of the proposed algorithms, along with the privacy protection level obtained by our solution. We conduct extensive experiments to show the superiority and various performances of our proposal, which illustrates that our proposal can get more than 85% advantage in terms of the sensing distribution availability compared to the traditional spatial cloaking based solutions.

Recently, federated learning has received widespread attention, which will promote the implementation of artificial intelligence technology in various fields. Privacy-preserving technologies are applied to users’ local models to protect users’ privacy. Such operations make the server not see the true model parameters of each user, which opens wider door for a malicious user to upload malicious parameters and make the training result converge to an ineffective model. To solve this problem, in this article, we propose a poisoning attack defense framework for horizontal federated learning systems called ADFL. Specifically, we design a proof generation method for users to generate proofs to verify whether it is malicious or not. An aggregation rule is also proposed to make sure the global model has a high accuracy. Several verification experiments were conducted and the results show that our method can detect malicious user effectively and ensure the global model has a high accuracy.

The development of Industrial Internet of Things (IIoT) provides massive abundant data resources for trading and mining. However, the existing data trading schemes achieve data usage control at the cost of high latency, thereby resulting in poor service quality as the values of IIoT data degrade over time. This article proposes a monitor-based usage control model to enforce data usage policies on the user side, which eliminates frequent interactions between owners and users. Based on that, a data trading scheme with efficient usage control for IIoT (called DTSI) is devised, which utilizes blockchain smart contract and software guard extensions (SGX) to enable owners to fully control users’ identities and operations at minimal overhead. Security analysis shows that DTSI effectively prevents data abuse and ensures the fair exchange of data. Meanwhile, extensive experiments are conducted on the DTSI prototype comparing with the state-of-the-art schemes with real-world IIoT datasets, which demonstrates the efficiency of DTSI.

Location-based routing is a widely adopted message transmission mechanism in Vehicular Ad Hoc Networks (VANETs). While the existing location-based routing schemes of VANETs ignore the location privacy protection of vehicles, leading that the drivers to be tracked, and further threaten the safety of their life and property. To address the above issue, we propose an All-Round and Highly Privacy-Preserving Location-Based Routing for VANETs (called ARPLR). Specifically, ARPLR first proposes a road side unit assisted location management with location privacy protection that prevents the destination vehicle’s location from being leaked by the arbitrary query. Then, a message routing based on location ciphertext with highly privacy protection is designed by order revealing encryption, in which a multi-hop routing between the source and destination vehicle is established only by comparing the encrypted locations between intermediate vehicles. Security analysis shows that, ARPLR can not only effectively provide location privacy protection for the intermediate and the destination vehicles in the whole routing process, but also ensure end-to-end secure communication between the source and destination vehicles. Extensive experiments based on real-road map indicate that, compared with two state-of-the-art solutions, the average transmission delay of ARPLR is respectively reduced by about 18% and 60%, meanwhile the average packet delivery rate also increases about 30% and 2%, respectively.

As a new computing paradigm, edge computing has appeared in the public field of vision recently. Owing to its advantages of low delay and fast response, edge computing has become an important assistant of cloud computing and has brought new opportunities for diverse smart applications like the smart grid, the smart home, and the smart transportation. However, the accompanying security issues, which have always been the focus of users' concern, still cannot be ignored. Therefore, we focus on the security issues in this overview. We first introduce some related definitions of edge computing and present the architecture for edge computing-based smart applications. After illustrating the smart applications, from the perspective of identity authentication and data security, we analyze the security protection requirements of these smart applications in the edge computing environment. Next, we review some state-of-the-art works on them. Furthermore, we present the extended discussions on the applicability of these current works in the edge computing environment. Finally, we briefly discuss the future work on authentication and data security of edge computing-based smart applications.

In a 5G network-sliced environment, mobility management introduces a new form of handover called inter-slice handover among network slices. Users can change their slices as their preferences or requirements vary over time. However, existing handover-authentication mechanisms cannot support inter-slice handover because of the fine-grained demand among network slice services, which could cause challenging issues, such as the compromise of service quality, anonymity, and universality. In this paper, we address these issues by introducing a fast and universal inter-slice (FUIS) handover authentication framework based on blockchain, chameleon hash, and ring signature. To address these issues, we introduce an anonymous service-oriented authentication protocol with a key agreement for inter-slice handover by constructing an anonymous ticket with the trapdoor collision property of chameleon hash functions. In order to reduce the computation overhead of the user side in the process of authentication, a privacy-preserving ticket validation with a ring signature is designed to finish in the consensus phase of the blockchain in advance. Thanks to the edge computing capabilities in 5G, distributed edge nodes help to store the anonymous ticket information, which guarantees that the legal users can finish authentication swiftly during handover. Our scheme's performance is evaluated through simulation experiments to testify the efficiency and feasibility in a 5G network-sliced environment. The results show that compared to other authentication schemes of the same type, the overall inter-slice handover delay has been reduced by 97.94%.

Nowadays, in machine learning based intrusion detection systems, ensemble learning is a commonly adopted method to improve the detection accuracy. Unfortunately, the existing works have not considered the accumulation and reuse of historical knowledge, as well as the sensitivity of the detection model to different types of attacks, which leads to a low detection accuracy. To address the issue, this article proposes a model based on sustainable ensemble learning. In the model training stage, by taking the individual classifiers probability output and classification confidence as the training data, we build multi-class regression models such that ensemble learning adapts to different attacks. Besides, in the updating stage, an iterative updating method is presented, where the parameters and decision results of the historical model are added to the training process of the new ensemble model to realize the incremental learning. Experiment results show that the proposed model significantly outperforms the existing solutions in terms of detection accuracy, false alarm, stability and robustness.

Authentication with unlinkability is one of the critical requirements for the security of VANETs. Unlinkability prevents attackers from linking multiple messages to infer vehicular privacy. Pseudonymous authentication schemes are widely adopted to achieve unlinkable authentication. However, they need multiple interactions with a trusted third-party to update pseudonym as well as the attached information. In order to address this issue and provide effective services in distributed systems, we propose a blockchain-based unlinkable authentication protocol called BUA, where Service Manager (SM) of each domain acts as the nodes of consortium blockchain to construct a distributed system. Each SM covers a certain logical area and maintains a sequence of consistent blocks, which hold vehicular registration data. Based on the system, vehicles use homomorphic encryption to self-generate any number of pseudonyms to achieve unlinkability. Pseudonymous validity and ownership can be verified locally by each SM. Performance evaluation results of the proposed scheme show that our protocol provides stronger security with less computation and communication overhead.

Vehicular networks have become a visible reality enabling information sharing between vehicles to enhance driving safety and provide value-added services to drivers and passengers. However, false information might be injected into the network because of defective sensors, malicious vehicles, and so on. Therefore, an efficient mechanism to guarantee the reliability of information used by vehicles is of great importance in vehicular networks. To solve this problem, this article proposes a context-awareness trust management model to evaluate the trustworthiness of messages received by vehicles to ensure bogus information will not influence the driving decision-making process. In the proposed scheme, the trust evaluation result of an evaluation request is determined by available related information and the evaluation strategy in the current situation, which is unaffected by the presence of conflicting evidence and the trust level of entities in the network. Moreover, we design a reinforcement learning model that allows vehicles to adjust the evaluation strategy so as to maintain an accurate evaluation result in different driving scenarios. Extensive experiments were conducted in different driving scenarios to verify the effectiveness of the proposed model. The results show that our model is adaptive to different driving scenarios with negligible time overhead, regardless of the proportion of malicious nodes in the network. Furthermore, compared with three types of state-of-the-art trust models in different scenarios, our scheme can achieve a higher evaluation precision rate with no more computational and communication overhead in nonrandom road conditions.

Nowadays, the pseudonym swap has become the mainstream technology for protecting vehicles' trajectory privacy in vehicle ad hoc networks. However, the existing pseudonym swap methods cannot strictly provide the unlinkability between the new pseudonym and old pseudonym of the vehicle due to the lack of theoretical privacy guarantee, resulting in severe leakages of vehicles' trajectory privacy. Our experiment also proves this point and we find that existing works may cause vehicle's pseudonyms to be linked with a probability higher than 60% because they always choose two vehicles with very different driving states (e.g., speeds, directions, and positions) to swap their pseudonyms. To solve this issue, we first give a formal privacy definition based on generalized differential privacy, called pseudonym indistinguishability, to provide a strict unlinkability for pseudonym swap. Then, we design an appropriate utility metric and a new pseudonym swap mechanism, which selects a pseudonym for a vehicle by adapting a differential privacy exponential mechanism to satisfy pseudonym indistinguishability. Abstracting from attackers' prior knowledge, we can strictly guarantee that if two vehicles have a high similarity of driving states, it is impossible for attackers to link the vehicles and their pseudonyms after the swap. Theoretical analyses prove that our mechanism satisfies the proposed privacy definition, thus ensuring the unlinkability between the new pseudonym and the old pseudonym. Extensive experiments on a real data set show that our work only requires about 50% of pseudonym quantities compared to other works and can make the vehicle successfully complete the swap process with a probability of more than 90%, which is higher than any of existing works.

Searchable encryption (SE) has been a promising technology which allows users to perform search queries over encrypted data. However, the most of existing SE schemes cannot deal with the shared records that have hierarchical structures. In this paper, we devise a basic cryptographic primitive called as attribute-based keyword search over hierarchical data (ABKS-HD) scheme by using the ciphertext-policy attribute-based encryption (CP-ABE) technique, but this basic scheme cannot satisfy all the desirable requirements of cloud systems. The facts that the single keyword search will yield many irrelevant search results and the revoked users can access the unauthorized data with the old or outdated secret keys make this basic scheme not scale well in practice. To this end, we also propose two improved schemes (ABKS-HD-I, ABKS-HD-II) for the sake of supporting multi-keyword search and user revocation, respectively. In contrast with the state-of-the-art attribute-based keyword search (ABKS) schemes, the computation overhead of our schemes almost linearly increases with the number of users' attributes rather than the number of attributes in systems. Formal security analysis proves that our schemes are secure against both chosen-plaintext attack (CPA) and chosen-keyword attack (CKA) in the random oracle model. Furthermore, empirical study using a real-world dataset shows that our schemes are feasible and efficient in practical applications.

Multi-stage attack is a new trend of cyber attack. It is difficult for existing schemes to identify multiple stages in an attack period and associate independent stages. To address these issues, we design a long and short-term memory network (LSTM) based on multi-feature layer. First, we introduce stage features layer, the historical data is stored and calculated to identify the different stages of variable durations in multi-stage attacks. Then, the time-series features layer is used to associate the independent attack stages to analyze whether the current data falls in an attack period. Extensive experiments indicate that our proposed scheme has a lower false positive rate than existing schemes by at least 65.83%, and the false negative rate is reduced by at least 65.26%.

Cloud-based mobile crowd-sourcing has been an attractive solution to provide data storage and share services for resource-limited mobile devices in a privacy-preserving manner, but how to enable mobile users to issue search queries and achieve fine-grained access control over ciphertexts simultaneously is still a big challenge for various circumstances. Although the ciphertext-policy attribute-based keyword search technology combining attribute-based encryption with searchable encryption has become a hot research topic, it just deals with equivalent attributes rather than more practical attribute comparisons, like “greater than” or “less than.” In this paper, we devise a practical cryptographic primitive called attribute-based multi-keyword search scheme to support comparable attributes through utilizing 0-encoding and 1-encoding. Formal security analysis proves that our scheme is selectively secure against chosen-keyword attack in generic bilinear group model and extensive experiments using real-world dataset demonstrate that our scheme can drastically decrease both computational and storage costs.

Since the dummy-based method can provide precise query results without any requirement for a third party or key sharing, it has been widely used to protect the user's location privacy in location-based services. However, the neighboring location sets submitted in consecutive requests always include a close spatiotemporal correlation, which enables the adversary to identify some dummies. Therefore, the existing dummy-based schemes cannot protect the user's location privacy completely. To solve this problem, based on the dummies generated by the existing schemes, this paper filters out the dummies that can be identified by taking into account of the spatiotemporal correlation from three aspects, namely time reachability, direction similarity and in-degree/out-degree. In this way, the rest dummies can satisfy the user's personalized privacy protection requirement. Security analysis shows that the proposed scheme successfully perturbs the spatiotemporal correlation between neighboring location sets, therefore, it is infeasible for the adversary to distinguish the user's real location from the dummies. Furthermore, extensive experiments indicate that the proposal is able to protect the user's location privacy effectively and efficiently.

As one of the most important techniques in IoT, NFC (Near Field Communication) is more interesting than ever. NFC is a short-range, high-frequency communication technology well suited for electronic tickets, micropayment, and access control function, which is widely used in the financial industry, traffic transport, road ban control, and other fields. However, NFC is becoming increasingly popular in the relevant field, but its secure problems, such as man-in-the-middle-attack and brute force attack, have hindered its further development. To address the security problems and specific application scenarios, we propose a NFC mobile electronic ticket secure payment and verification scheme in the paper. The proposed scheme uses a CS E-Ticket and offline session key generation and distribution technology to prevent major attacks and increase the security of NFC. As a result, the proposed scheme can not only be a good alternative to mobile e-ticket system but also be used in many NFC fields. Furthermore, compared with other existing schemes, the proposed scheme provides a higher security.

Summary Location‐based services (LBSs) via mobile handheld devices have been subject to major privacy concerns for users. Currently, most of the existing works concerning the continuous LBS queries mainly focus on users' privacy demands with little consideration of the service of quality (QoS). In this paper, we propose a demand‐aware location protection scheme for continuous LBS requests, allowing a user to customize not only location privacy but also QoS requirement, while this results that in considerably many queries points, the privacy and QoS requirement cannot be met together, and the location privacy protection cannot be provided for the continuous LBS queries. We point out that its underlying reason is that in few LBS query regions, the footprints are sparse or the privacy requirements are set unreasonably high. Therefore, a maximum demands‐aware query sequence algorithm is proposed in the scheme. Through identifying and restraining the queries in those regions, most of LBS queries are satisfied; thus, the longest LBS query sequence is obtained, which can satisfy a user's specific privacy and QoS requirements simultaneously. Furthermore, on the premise that the user's privacy requirement is met, in demand‐aware location protection scheme, we propose two algorithms to minimize the constructed cloaking regions, reducing the query latency and the server's workload and providing better QoS for users. Extensive simulations on a large dataset prove the effectiveness of our approach under various location privacy and QoS demands. Copyright © 2015 John Wiley & Sons, Ltd.

In recent years, since people pay more and more attention to the protection of their privacy, anonymous authentication in wireless networks has become a hot topic. Currently, most anonymous authentication schemes are based on the asymmetric keys whose tedious computation leads to serious resource consumption, therefore, they are unsuitable for mobile devices with limited capacity. To solve this problem, by introducing the k-pseudonym set we propose an anonymous authentication protocol based on a shared secret key. In the authentication process, the user sends the k- pseudonym set which includes his real identity and other k-1 pseudonyms. After the authentication server traversals the shared keys with each of the users in the set and verifies the authentication information, it can determine the real user and complete the authentication. In this methodology, the construction of the pseudonym set is a key issue, and we give two attack models and respectively present the construction methods of the k-pseudonym set under those two models. Compared with the existing schemes, our scheme outperforms them in the security and practicality. Especially, user untractability can be realized. A testbed is set up and extensive experiments are conducted, and the results show the authentication latency of our scheme is short and it changes a little with the increase of k.

Nowadays, with the rapid increase of WLAN-enabled mobile devices and the more widespread use of WLAN, it is increasingly important to have a more efficient initial link setup mechanism, and there is a demand for a faster access authentication method faster than the current IEEE 802.11i. In this paper, through experiments we observe that the authentication delay of 802.11i is intolerable under some scenarios, and we point that the main reason resulting in such inefficiency is due to its design from the framework perspective which introduces too many messages. To overcome this drawback, we propose an efficient initial access authentication protocol, FLAP, which realizes the authentications and key distribution through two roundtrip messages. We formally prove that our scheme is more secure than the four-way handshake protocol. Our practical measurement result indicates that FLAP can improve the efficiency of EAP-TLS by 94.7 percent. Extensive simulations are conducted in different scenarios, and the results demonstrate that when a WLAN gets crowded the advantage of FLAP becomes more salient. Furthermore, a simple and practical method is presented to make FLAP compatible with 802.11i.

Nowadays, with the rapid increase of WLAN-enabled mobile devices, new scenarios emerge which require a more efficient WLAN initial link setup mechanism, and an access authentication method faster than the current IEEE 802.11i is desired. Our analysis indicates that the essential reason resulting in the inefficiency of 802.11i is that it is designed from the framework perspective which introduces too many messages. To overcome the drawbacks, an efficient initial access authentication protocol is proposed which realizes the authentications and key distribution through 2 roundtrip messages between the mobile device and the networks. Analysis indicates that our proposal is of the same security as the 4-way handshake protocol. The experiment result shows that our scheme can improve the authentication delay of the EAP-TLS by 94.7%. Furthermore, a simple and practical method is presented to enable it to be compatible with 802.11i.