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  1. Ensuring the integrity of embedded programmable logic controllers (PLCs) is critical for safe operation of industrial control systems. In particular, a cyber-attack could manipulate control logic running on the PLCs to bring the process of safety-critical application into unsafe states. Unfortunately, PLCs are typically not equipped with hardware support that allows the use of techniques such as remote attestation to verify the integrity of the logic code. In addition, so far remote attestation is not able to verify the integrity of the physical process controlled by the PLC. In this work, we present PAtt, a system that combines remote softwaremore »attestation with control process validation. PAtt leverages operation permutations—subtle changes in the operation sequences based on integrity measurements—which do not affect the physical process but yield unique traces of sensor readings during execution. By encoding integrity measurements of the PLC’s memory state (software and data) into its control operation, our system allows to remotely verify the integrity of the control logic based on the resulting sensor traces. We implement the proposed system on a real PLC controlling a robot arm, and demonstrate its feasibility. Our implementation enables the detection of attackers that manipulate the PLC logic to change process state and/or report spoofed sensor readings (with an accuracy of 97% against tested attacks).« less
  2. An understanding of the normal state in the high-temperature superconducting cuprates is crucial to the ultimate understanding of the long-standing problem of the origin of the superconductivity itself. This so-called “strange metal” state is thought to be associated with a quantum critical point (QCP) hidden beneath the superconductivity. In electron-doped cuprates—in contrast to hole-doped cuprates—it is possible to access the normal state at very low temperatures and low magnetic fields to study this putative QCP and to probe the T ➔ 0 K state of these materials. We report measurements of the low-temperature normal-state magnetoresistance (MR) of the n-type cupratemore »system La 2− x Ce x CuO 4 and find that it is characterized by a linear-in-field behavior, which follows a scaling relation with applied field and temperature, for doping ( x ) above the putative QCP ( x = 0.14). The magnitude of the unconventional linear MR decreases as T c decreases and goes to zero at the end of the superconducting dome ( x ~ 0.175) above which a conventional quadratic MR is found. These results show that there is a strong correlation between the quantum critical excitations of the strange metal state and the high- T c superconductivity.« less
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