Deep learning-based synthetic aperture radar (SAR) automatic target recognition (ATR) algorithms have achieved outstanding performance under the condition of hundreds or thousands of training samples in recent years. Nevertheless, it is often rare to acquire great quantities of target samples in real SAR application scenarios. This article proposes a novel ATR method called transductive prototypical attention reasoning network (TPARN) to solve the problem of SAR target recognition with only a few training samples. To be specific, a region awareness-based feature extraction model is first developed, which can effectively focus on the target region of interest and suppress the background clutter by embedding direction-aware and position-sensitive information to extract more transferable knowledge. To heighten the discrimination of the sample features, a cross-feature spatial attention module is then proposed following the feature embedding model. Finally, a transductive prototype reasoning method is presented to realize the identity reasoning of the target, which can continuously update each class prototype with training samples and test samples together, thereby improving the classification accuracy. In addition, a marginal adaptive hybrid loss is proposed to obtain a discriminative feature embedding space with intra-class compactness and inter-class divergence, aiming to facilitate subsequent target identity reasoning. Extensive experiments on the moving and stationary target acquisition and recognition (MSTAR) benchmark dataset reveal that the proposed method outperforms some state-of-the-arts under different few-shot SAR ATR tasks.

Data-driven automatic target recognition (ATR) methods have become the mainstream in the synthetic aperture radar (SAR) community at this stage. However, in real SAR application scenarios, the scarcity of training samples is a common problem. Especially in military application scenarios, only a small number of samples of each type of target are usually available. In the case of limited available samples, it is bound to bring challenges to the feature extraction model and classifier inference learning. In this paper, we propose a novel method called adaptive convolutional subspace reasoning network (ACSRNet) to address few-shot SAR target recognition tasks. To be specific, we first present a dynamic-aware convolutional feature embedding network based on the siamese architecture, which can not only learn more transferable knowledge for the few-shot tasks, but also dynamically adjust the convolution kernel according to the input data to extract more discriminative features. To effectively achieve target identity reasoning, we then resort to high-order information of samples, i.e., the idea of adaptive subspace learning, to develop a few-shot subspace classification module, which can online reason the identity of the unknown target through the spanning subspace of training samples. Meanwhile, a dual-loss is designed to train a feature embedding space with intra-class compactness and inter-class divergence, aiming to facilitate subsequent classification. Meta-learning integrating random sampling episode way is introduced into the process of model training to realize few-shot SAR ATR tasks by emulating the human cognitive process. Experimental results on the moving and stationary target acquisition recognition (MSTAR) dataset demonstrate that the proposed method is competitive with some state-of-the-arts for few-shot SAR ATR tasks.

This paper proposes a Bi -similarity prototypical network with capsule-based embedding to solve the problem of few-shot SAR target recognition. The proposed method comprises two procedures, i.e., feature embedding module and Bi-similarity reasoning module. Specifically, we build a feature embed-ding network with capsule operation, which can enable a feature embedding network to extract more informative features by effectively encoding relative spatial relationships between features. To reason the identity of target robustly, we develop a reasoning module based on Bi-similarity metric. Moreover, a mixed loss is proposed to train a discriminative representation space with both intra-class aggregation and inter-class separation. Experimental results on moving and stationary target acquisition and recognition (MSTAR) dataset show that the proposed method is effective and superior to some state-of-art methods in few-shot SAR target recognition tasks.

Sufficient training samples are prerequisite for most existing automatic target recognition (ATR) algorithms to obtain satisfactory recognition performance. Nevertheless, sometimes only a few samples are available in real synthetic aperture radar (SAR) application scenarios. Therefore, this paper proposes a Siamese subspace classification network to address the problem of SAR ATR with insufficient training samples. To be specific, the proposed method first establishes a feature embedding network based on Siamese structure, and leverages contrastive learning to train a low-dimensional representation space with both intra-class compactness and inter-class divergence. A subspace learning-based classifier is then designed to reason the identity of the target. Experimental results on moving and stationary target acquisition and recognition (MSTAR) benchmark data set demonstrate the effectiveness and superiority of the proposed method.

As a promising data-driven technology, deep learning has been widely employed in a variety of Internet-of-Things (IoT) applications. Examples include automated navigation, telemedicine, and smart home. To protect the data privacy of deep-learning-based IoT applications, a few privacy-preserving approaches have also been exploited, designed, and implemented in various scenarios. However, state-of-the-art works are still defective in accuracy, efficiency, and functionality. In this article, we propose the privacy-aware and asynchronous deep-learning-assisted IoT applications (PADL), a privacy-aware and asynchronous deep learning framework that enables multiple data collecting sites to collaboratively train deep neural networks (DNNs), while keeping the confidentiality of private data to each other. Specifically, we first design a layerwise importance propagation (LIP) algorithm to quantify the importance of the model's weights held by each site. Then, we present the customized perturbation mechanism, a precise combination of the LIP algorithm and differential privacy mechanism, which helps to make optimal tradeoffs between the availability and privacy of local models. Furthermore, to fully use the computing resources of all sites, for the first time, we propose an advanced asynchronous optimization (AAO) protocol to perform global updates without waiting. Theoretical analysis shows that the PADL is robust to extreme collusion even with only one reliable site while supporting lock-free optimization. Finally, extensive experiments conducted on real-world data sets using TensorFlow library show that the PADL outperforms the existing systems in terms of efficiency and prediction accuracy.

As an emerging training model with neural networks, federated learning has received widespread attention due to its ability to update parameters without collecting users' raw data. However, since adversaries can track and derive participants' privacy from the shared gradients, federated learning is still exposed to various security and privacy threats. In this paper, we consider two major issues in the training process over deep neural networks (DNNs): 1) how to protect user's privacy (i.e., local gradients) in the training process and 2) how to verify the integrity (or correctness) of the aggregated results returned from the server. To solve the above problems, several approaches focusing on secure or privacy-preserving federated learning have been proposed and applied in diverse scenarios. However, it is still an open problem enabling clients to verify whether the cloud server is operating correctly, while guaranteeing user's privacy in the training process. In this paper, we propose VerifyNet, the first privacy-preserving and verifiable federated learning framework. In specific, we first propose a double-masking protocol to guarantee the confidentiality of users' local gradients during the federated learning. Then, the cloud server is required to provide the Proof about the correctness of its aggregated results to each user. We claim that it is impossible that an adversary can deceive users by forging Proof, unless it can solve the NP-hard problem adopted in our model. In addition, VerifyNet is also supportive of users dropping out during the training process. The extensive experiments conducted on real-world data also demonstrate the practical performance of our proposed scheme.

By leveraging deep learning-based technologies, industrial artificial intelligence (IAI) has been applied to solve various industrial challenging problems in Industry 4.0. However, for privacy reasons, traditional centralized training may be unsuitable for sensitive data-driven industrial scenarios, such as healthcare and autopilot. Recently, federated learning has received widespread attention, since it enables participants to collaboratively learn a shared model without revealing their local data. However, studies have shown that, by exploiting the shared parameters adversaries can still compromise industrial applications such as auto-driving navigation systems, medical data in wearable devices, and industrial robots' decision making. In this article, to solve this problem, we propose an efficient and privacy-enhanced federated learning (PEFL) scheme for IAI. Compared with existing solutions, PEFL is noninteractive, and can prevent private data from being leaked even if multiple entities collude with each other. Moreover, extensive experiments with real-world data demonstrate the superiority of PEFL in terms of accuracy and efficiency.

As a promising training model with Neural Network, distributed deep learning has been widely applied in various scenarios, where clients and the cloud server work together only by sharing local gradients and global parameters. However, research has shown that the adversary can still reconstruct the users' private information even if little information is leaked. To address this problem, several approaches of privacy-preserving distributed training have been exploited with existing mature technologies, such as Differential Privacy, Secure Multi-party Computation and Homomorphic Encryption. However, state of-the-art results are still defective in security, functionality and efficiency. In this paper, we propose an Efficient Privacy Preserving Scheme (EPPS) for distributed deep learning. We claim that our solution achieves the best performance tradeoff between security, efficiency and functionality. Specifically, we adopt the threshold Paillier encryption as the underlying structure to construct our secure training model. Hence, the confidentiality of honest users' of local gradients can be guaranteed, even the cloud server colluding with multiple users. In addition, since users are often accidentally offline due to either network environment or equipment damage, our EPPS can also support users exiting at any phases of the entire work process. Further more, we conducted extensive experiments on real-world data to demonstrate the preferable performance of our proposed scheme.

Deep learning has been applied in many areas, such as computer vision, natural language processing and emotion analysis. Differing from the traditional deep learning that collects users' data centrally, federated deep learning requires participants to train the networks on private datasets and share the training results, and hence has more gratifying efficiency and stronger security. However, it still presents some privacy issues since adversaries can deduce users' privacy from local outputs, such as gradients. While the problem of private federated deep learning has been an active research issue, the latest research findings are still inadequate in terms of security, accuracy and efficiency. In this paper, we propose an efficient and privacy-preserving federated deep learning protocol based on stochastic gradient descent method by integrating the additively homomorphic encryption with differential privacy. Specifically, users add noises to each local gradients before encrypting them to obtain the optical performance and security. Moreover, our scheme is secure to honest-but-curious server setting even if the cloud server colludes with multiple users. Besides, our scheme supports federated learning for large-scale users scenarios and extensive experiments demonstrate our scheme has high efficiency and high accuracy compared with non-private model.

Recent years have witnessed tremendous academic efforts and industry growth in machine learning. The security of machine learning has become increasingly prominent. Poisoning attack is one of the most relevant security threats to machine learning which focuses on polluting the training data that machine learning needs during the training process. Specifically, the attacker blends crafted poisoning samples into training data in order to make the learned model beneficial to him. To the best of our knowledge, existing researches about poisoning attack focused on either integrity attack or availability attack, which did not unify these two attacks together. Aside from that, from the attacker's perspective, attacker's strategy is not flexible enough. Finally, existing proposals only concentrated on increasing the test error of the learned model but ignored the importance of the concealment of attack. To overcome these issues, we firstly present a thorough adversarial model for poisoning attack in which attacker's strategy is defined from two aspects, i.e., the effect of attack and the concealment of attack. Then we unify integrity attack and availability attack together in similar formulations. Furthermore, in order to enhance flexibility, a tradeoff parameter is inserted into attacker's objective function which means the attacker can balance the attraction of effect against the requirement of concealment. Finally, as examples, extensive experiments are conducted on linear regression and logistic regression to demonstrate the effectiveness of attack.