Explainable Adversarial Learning Framework on Physical Layer Secret Keys Combating Malicious Reconfigurable Intelligent Surface

The development of reconfigurable intelligent surfaces (RIS) is a double-edged sword to physical layer security (PLS). Whilst a legitimate RIS can yield beneficial impacts including increased channel randomness to enhance physical layer secret key generation (PL-SKG), malicious RIS can poison legitimate channels and crack most of existing PL-SKGs. In this work, we propose an adversarial learning framework between legitimate parties (namely Alice and Bob) to address this Man-in-the-middle malicious RIS (MITM-RIS) eavesdropping. First, the theoretical mutual information gap between legitimate pairs and MITM-RIS is deduced. Then, Alice and Bob leverage generative adversarial networks (GANs) to learn to achieve a common feature surface that does not have mutual information overlap with MITM-RIS. Next, we aid signal processing interpretation of black-box neural networks by using a symbolic explainable AI (xAI) representation. These symbolic terms of dominant neurons aid feature engineering-based validation and future design of PLS common feature space. Simulation results show that our proposed GAN-based and symbolic-based PL-SKGs can achieve high key agreement rates between legitimate users, and is even resistant to MITM-RIS Eve with the knowledge of legitimate feature generation (NNs or formulas). This therefore paves the way to secure wireless communications with untrusted reflective devices in future 6G.

Sequential Bayesian Detection of Spike Activities from Fluorescence Observations

Extracting and detecting spike activities from the fluorescence observations is an important step in understanding how neuron systems work. The main challenge lies in that the combination of the ambient noise with dynamic baseline fluctuation, often contaminates the observations, thereby deteriorating the reliability of spike detection. This may be even worse in the face of the nonlinear biological process, the coupling interactions between spikes and baseline, and the unknown critical parameters of an underlying physiological model, in which erroneous estimations of parameters will affect the detection of spikes causing further error propagation. In this paper, we propose a random finite set (RFS) based Bayesian approach. The dynamic behaviors of spike sequence, fluctuated baseline and unknown parameters are formulated as one RFS. This RFS state is capable of distinguishing the hidden active/silent states induced by spike and non-spike activities respectively, thereby \emph{negating the interaction role} played by spikes and other factors. Then, premised on the RFS states, a Bayesian inference scheme is designed to simultaneously estimate the model parameters, baseline, and crucial spike activities. Our results demonstrate that the proposed scheme can gain an extra $12\%$ detection accuracy in comparison with the state-of-the-art MLSpike method.