No abstract

Cognitive control refers to the ability to produce flexible, goal-oriented behavior in the face of changing task demands and conflicting response tendencies. A classic cognitive control experiment is the Stroop-color naming task, which requires participants to name the color in which a word is written while inhibiting the tendency to read the word. By comparing stimuli with conflicting word-color associations to congruent ones, control processes over response tendencies can be isolated. We assessed the spatial specificity and temporal dynamics in the theta and gamma bands for regions engaged in detecting and resolving conflict in a cohort of 13 patients using a combination of high-resolution surface and depth recordings. We show that cognitive control manifests as a sustained increase in gamma band power, which correlates with response time. Conflict elicits a sustained gamma power increase but a transient theta power increase, specifically localized to the left cingulate sulcus and bilateral dorsolateral prefrontal cortex (DLPFC). Additionally, activity in DLPFC is affected by trial-by-trial modulation of cognitive control (the Gratton effect). Altogether, the sustained local neural activity in dorsolateral and medial regions is what determines the timing of the correct response.

Visual Abstract

Physical Unclonable Functions (PUF) are of increasing importance due to their many hardware security applications including chip fingerprinting, metering, authentication, anticounterfeiting, and supply-chain tracing, e.g., DARPA SHIELD. This paper presents BIST-PUF, the first built-in-self-test (BIST) methodology for online evaluation of weak and strong PUFs. BIST-PUF provides a paradigm shift in the evaluation of the unclonable circuit identifiers: unlike earlier known PUF evaluation suites that are software-based and offline, BIST-PUF enables onthe-fly assessment of the desired PUF properties all in hardware. More specifically, the BIST-PUF structure is designed to evaluate two main properties of PUFs, namely unpredictability and stability. These properties are important for ensuring robustness and security in face of operational, structural, and environmental fluctuations due to variations, aging or adversarial acts. For BIST-PUF unpredictability evaluation, we identify and adopt the tests of randomness that are amenable to hardware implementation. For stability assessment, the BIST-PUF suggests three distinct methods, namely, sensor-based, parametric interrogation, and multiple interrogations. Proof-of-concept implementation of the BIST-PUF in FPGA demonstrates its low overhead, effectiveness, and practicality.

In the recent years, new services and businesses leveraging location-based services (LBS) are rapidly emerging. On the other hand this has raised the incentive of users to cheat about their locations to the service providers for personal benefits. Context-based proofs-of-presence (PoPs) have been proposed as a means to enable verification of users' location claims. However, as we show in this paper, they are vulnerable to context guessing attacks. To make PoPs resilient to malicious provers we propose two complementary approaches for making context-based PoPs: one approach focuses on surprisal filtering based on estimating the entropy of particular PoPs in order to detect context measurements vulnerable to such attacks. The other approach is based on utilizing longitudinal observations of ambient modalities like noise level and ambient luminosity. It is capable of extracting more entropy from the context to construct PoPs that are hard to guess by an attacker even in situations in which other context sensor modalities fail to provide reliable PoPs.