Deep neural networks (DNNs) have enabled success in learning tasks such as image classification, semantic image segmentation and steering angle prediction which can be key components of the computer vision pipeline of safety-critical systems such as autonomous vehicles. However, previous work has demonstrated the feasibility of using physical adversarial examples to attack image classification systems. \par In this work, we argue that the success of realistic adversarial examples is highly dependent on both the structure of the training data and the learning objective. In particular, realistic, physical-world attacks on semantic segmentation and steering angle prediction constrain the adversary to add localized perturbations, since it is very difficult to add perturbations in the entire field of view of input sensors such as cameras for applications like autonomous vehicles. We empirically study the effectiveness of adversarial examples generated under strict locality constraints imposed by the aforementioned applications. Even with image classification, we observe that the success of the adversary under locality constraints depends on the training dataset. With steering angle prediction, we observe that adversarial perturbations localized to an off-road patch are significantly less successful compared to those on-road. For semantic segmentation, we observe that perturbations localized to small patches are only effective at changing the label in and around those patches, making non-local attacks difficult for an adversary. We further provide a comparative evaluation of these localized attacks over various datasets and deep learning models for each task.

Most computer systems authenticate users only once at the time of initial login, which can lead to security concerns. Continuous authentication has been explored as an approach for alleviating such concerns. Previous methods for continuous authentication primarily use biometrics, e.g., fingerprint and face recognition, or behaviometrics, e.g., key stroke patterns. We describe CABA, a novel continuous authentication system that is inspired by and leverages the emergence of sensors for pervasive and continuous health monitoring. CABA authenticates users based on their BioAura, an ensemble of biomedical signal streams that can be collected continuously and non-invasively using wearable medical devices. While each such signal may not be highly discriminative by itself, we demonstrate that a collection of such signals, along with robust machine learning, can provide high accuracy levels. We demonstrate the feasibility of CABA through analysis of traces from the MIMIC-II dataset. We propose various applications of CABA, and describe how it can be extended to user identification and adaptive access control authorization. Finally, we discuss possible attacks on the proposed scheme and suggest corresponding countermeasures.