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Physical unclonable function (PUF) leverages the immensely complex and irreproducible nature of physical structures to achieve device authentication and secret information storage. To enhance the security and robustness of conventional PUFs, reconfigurable physical unclonable functions (RPUFs) with dynamically refreshable challenge-response pairs (CRPs) have emerged recently. In this paper, we propose two novel physically reconfigurable PUF (P-RPUF) schemes that exploit the process parameter variability and programming sensitivity of phase change memory (PCM) for CRP reconfiguration and evaluation. The first proposed PCM-based P-RPUF scheme extracts its CRPs from the measurable differences of the PCM cell resistances programmed by randomly varying pulses. An imprecisely controlled regulator is used to protect the privacy of the CRP in case the configuration state of the RPUF is divulged. The second proposed PCM-based RPUF scheme produces the random response by counting the number of programming pulses required to make the cell resistance converge to a predetermined target value. The merging of CRP reconfiguration and evaluation overcomes the inherent vulnerability of P-RPUF devices to malicious prediction attacks by limiting the number of accessible CRPs between two consecutive reconfigurations to only one. Both schemes were experimentally evaluated on 180-nm PCM chips. The obtained results demonstrated their quality for refreshable key generation when appropriate fuzzy extractor algorithms are incorporated.Index Terms-Reconfigurable physical unclonable function, phase change memory, physical unclonable function, hardware security.

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In this paper, we investigate the impact of Ge-enrichment coupled to N-or C-doping in Ge 2 Sb 2 Te 5 based materials on low-resistance state (LRS or SET) performance combined with high-resistance state (HRS or RESET) high-temperature data retention (HTDR) in Phase-Change Memories (PCM). These innovative materials have been integrated in state-of-the-art memory cell prototypes. For the first time, a focus on the trade-off between SET stability (which is affected by resistance drift) and RESET HTDR is proposed. This aspect has been extensively characterized. Through physico-chemical analysis and electrical characterization we demonstrate the need for a specific "programming-current-vs-time-profile" to finally achieve an LRS stable at high-working temperature with programming times compatible with industrial applications. Finally, the reliability of the HRS and the LRS obtained with our optimized programming procedure has been demonstrated through Reflow Soldering Temperature Profile (RSTP) tests. The last result fully enables PCM for embedded applications, in which data integrity after the peak temperature of reflow soldering must be ensured.

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How language is encoded by neural activity in the higher-level language areas of humans is still largely unknown. We investigated whether the electrophysiological activity of Broca's area correlates with the sound of the utterances produced. During speech perception, the electric cortical activity of the auditory areas correlates with the sound envelope of the utterances. In our experiment, we compared the electrocorticogram recorded during awake neurosurgical operations in Broca's area and in the dominant temporal lobe with the sound envelope of single words versus sentences read aloud or mentally by the patients. Our results indicate that the electrocorticogram correlates with the sound envelope of the utterances, starting before any sound is produced and even in the absence of speech, when the patient is reading mentally. No correlations were found when the electrocorticogram was recorded in the superior parietal gyrus, an area not directly involved in language generation, or in Broca's area when the participants were executing a repetitive motor task, which did not include any linguistic content, with their dominant hand. The distribution of suprathreshold correlations across frequencies of cortical activities varied whether the sound envelope derived from words or sentences. Our results suggest the activity of language areas is organized by sound when language is generated before any utterance is produced or heard.A n important aspect of human language is speech production, although language may be generated independently from sound, as when one writes or thinks. However, introspection seems to suggest that our thoughts resound in our brain, much as if we were listening to an internal speech, yielding the impression/illusion that sound is inseparable from language.When human subjects listen to utterances, the neural activity in the superior temporal gyrus is modulated to track the envelope of the acoustic stimulus. The correlation between the power envelope of the speech and the neural activity is maximal at low frequencies (2-7 Hz, theta range) corresponding to syllable rates, and becomes less precise at higher frequencies (15-150 Hz, gamma range) corresponding to phoneme rates (1). Entrainment of neural activity to the speech envelope in auditory regions has allowed recognition of the phonetic features heard during speech perception (2-5), and even the reconstruction of simple words (6). This evidence indicates that during listening, speech representation in the auditory cortex and adjacent areas of the superior temporal lobe reflects acoustic features directly related to linguistically defined phonological entities such as phonemes and syllables. The relationship of specific patterns of sound amplitude and frequency to all similar patterns experienced over phylogeny and individual ontogeny is then responsible for sound perceptions (7). Moreover, as for subjects listening to natural speech, spatiotemporal features of the acoustic trace representative of the sound of the listened words have also been detec...

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