Convolution-based unlearnable examples (UEs) employ class-wise multiplicative convolutional noise to training samples, severely compromising model performance. This fire-new type of UEs have successfully countered all defense mechanisms against UEs. The failure of such defenses can be attributed to the absence of norm constraints on convolutional noise, leading to severe blurring of image features. To address this, we first design an Edge Pixel-based Detector (EPD) to identify convolution-based UEs. Upon detection of them, we propose the first defense scheme against convolution-based UEs, COrrupting these samples via random matrix multiplication by employing bilinear INterpolation (COIN) such that disrupting the distribution of class-wise multiplicative noise. To evaluate the generalization of our proposed COIN, we newly design two convolution-based UEs called VUDA and HUDA to expand the scope of convolution-based UEs. Extensive experiments demonstrate the effectiveness of detection scheme EPD and that our defense COIN outperforms 11 state-of-the-art (SOTA) defenses, achieving a significant improvement on the CIFAR and ImageNet datasets.

Positron emission tomography (PET) is a nuclear medical imaging technique where image quality depends on the dose of radionuclides administered to the patient. While standard-dose PET (SPET) offers high-quality imaging, it also poses radiation risks. If reconstructing low-dose PET (LPET) images can guarantee the same level of imaging quality, LPET could serve as a safer alternative by reducing patient radiation exposure. Recent approaches using convolutional neural networks (CNNs) struggle to capture complex features of LPET images due to the fixed convolutional kernels and local receptive fields. Generative adversarial network (GAN)-based methods may suffer from mode collapse and unstable training. Diffusion model-based works can ensure stability and high-quality sample generation but come with high computational costs. Furthermore, all these methods focus solely on spatial domain information, neglecting crucial frequency domain information.To address these issues, we propose an efficient residual-based LPET reconstruction framework combining CNN and diffusion model. Our framework includes a multi-scale dynamic convolution network with a wavelet reconstruction module (MN-WR) to leverage multi-scale spatial and frequency domain information. We also introduce a residual-based diffusion model (ReD) to enhance local detail reconstruction while reducing computational costs. Finally, we design a wavelet-based frequency domain fusion (WFF) module to combine low-frequency edge information from MN-WR with high-frequency details from ReD. Experimental results on public LPET datasets show that our method outperforms state-of-the-art techniques and significantly reduces computational costs. Code is available at https://github.com/TAI-Medical-Lab/LPET-Reconstruction.

Automatic speech verification (ASV) authenticates individuals based on distinct vocal patterns, playing a pivotal role in many applications such as voice-based unlocking systems for devices. The ASV system comprises three stages: training, registration, and validation. The model refines using voice data in training, extracts vocal features in registration, and contrasts these with speech patterns in validation. Modern ASV models, primarily grounded in DNN architectures, require extensive data for training. Federated learning (FL) fosters model-sharing across multiple clients while ensuring data privacy. Due to its open architecture, FL is vulnerable to backdoor attacks. However, training a stealthy backdoor attack in FL presents challenges, including diminished attack generalization owing to data heterogeneity, and conspicuous triggers that render them easily detectable. In this paper, we propose a Federated Stealthy Backdoor Attack method ($FedSBA$). FedSBA aims to improve the attack model’s generalization, enhance its persistence, and elude anomaly detection under the heterogeneous data distribution. FedSBA constructs an attack model based on a personalized transformer and encompasses a stealthy trigger. Moreover, we also propose a defensive strategy that utilizes an adaptive weight aggregation scheme. The stealthiness and effectiveness of FedSBA are demonstrated by exhibiting superior performance in comparison to previous works.

Federated learning (FL) is a nascent distributed learning paradigm to train a shared global model without violating users' privacy. FL has been shown to be vulnerable to various Byzantine attacks, where malicious participants could independently or collusively upload well-crafted updates to deteriorate the performance of the global model. However, existing defenses could only mitigate part of Byzantine attacks, without providing an all-sided shield for FL. It is difficult to simply combine them as they rely on totally contradictory assumptions.