Defending Against Flush+Reload Attack With DRAM Cache by Bypassing Shared SRAM Cache

Cache side-channel attack is one of the critical security threats to modern computing systems. As a representative cache side-channel attack, Flush+Reload attack allows an attacker to steal confidential information (e.g., private encryption key) by monitoring a victim's cache access patterns while generating the confidential values. Meanwhile, for providing high performance with memory-intensive applications that do not fit in the on-chip SRAM-based last-level cache (e.g., L3 cache), modern computing systems start to deploy DRAM cache between the SRAM-based last-level cache and the main memory DRAM, which can provide low latency and/or high bandwidth. However, in this work, we propose an approach that exploits the DRAM cache for security rather than performance, called ByCA. ByCA bypasses the L3 shared cache when accessing cache blocks suspected as target blocks of an attacker. Consequently, ByCA eliminates the timing difference when the attacker accesses the target cache blocks, nullifying the Flush+Reload attacks. To this end, ByCA keeps cache blocks suspected as target blocks of the attacker and stores their states (i.e., flushed by clflush or not) in the L4 DRAM cache even with clflush instruction; ByCA re-defines and re-implements clflush instruction not to flush cache blocks from the L4 DRAM cache while flushing the blocks from other level caches (i.e., L1, L2, and L3 caches). In addition, ByCA bypasses L3 cache when the attacker or the victim accesses the target blocks flushed by clflush, making the attacker always obtain the blocks from L4 DRAM cache regardless of the victim's access patterns. Consequently, ByCA eliminates the timing difference, thus the attacker cannot monitor the victim's cache access patterns. For L4 DRAM cache, we implement Alloy Cache design and use an unused bit in a tag entry for each block to store its state. ByCA only requires a single bit extension to cache blocks in L1 and L2 private caches, and a tag entry for each block in the L4 DRAM cache. Our experimental results show that ByCA completely eliminates the timing differences when the attacker reloads the target blocks. Furthermore, ByCA does not show the performance degradation for the victim while co-running with the attacker that flushes and reloads target blocks temporally and repetitively.1

Co-Adjusting Voltage/Frequency State and Interrupt Rate for Improving Energy-Efficiency of Latency-Critical Applications

As the power/energy consumption is one of the major contributors to the Total Cost of Ownership (TCO), improving power/energy efficiency is crucial for large-scale data centers where latency-critical applications are commonly accommodated while computing resources are usually under-utilized. For improving the power/energy efficiency of processors, most of the commercial processors support Dynamic Voltage and Frequency Scaling (DVFS) technology that enables to adjust Voltage and Frequency state (V/F state) of the processor dynamically. In particular, for the latency-critical applications, many prior studies propose power management policies using the DVFS for the latency-critical applications, which minimizes the performance degradation or satisfies the Service Level Objectives (SLOs) constraints. Meanwhile, although the interrupt rate also affects the response latency and energy efficiency of latency-critical applications considerably, those prior studies just introduce policies for V/F state adjustment while not considering the interrupt rate. Therefore, in this article, we investigate the impact of adjusting the interrupt rate on the tail response latency and energy consumption. Through our experimental results, we observe that adjusting interrupt rate along with V/F state management varies the performance and energy consumption considerably, and provides an opportunity to reduce energy further by showing latency overlap between different V/F states. Based on the observation, we show the quantitative potential in improving energy efficiency of co-adjusting V/F state and interrupt rate with a simple management policy, called Co-PI. Co-PI searches the most energy-efficient combination of the V/F state and interrupt rate from the latency and energy tables that we obtain through offline profiling, and reflect the combination to the core and NIC. Co-PI reduces energy consumption by 34.1% and 25.1% compared with performance and ondemand governors while showing the almost same tail response latency with the performance governor that operates cores at the highest V/F state statically. © 1991 BMJ Publishing Group. All rights reserved.1

Increasing trends in hospital care burden of atrial fibrillation in Korea, 2006 through 2015

ObjectiveTemporal changes in the healthcare burden of atrial fibrillation (AF) are less well known in rapidly ageing Asian countries. We examined trends in hospitalisations, costs, treatment patterns and outcomes related to AF in Korea.MethodsUsing the National Health Insurance Service (NHIS) database involving the entire adult Korean population (n=41 701 269 in 2015), we analysed a nationwide AF cohort representing 931 138 patients with AF. We studied all hospitalisations due to AF from 2006 to 2015.ResultsOverall, hospitalisations for AF increased by 420% from 767 to 3986 per 1 million Korean population from 2006 to 2015. Most admissions occurred in patients aged ≥70 years, and the most frequent coexisting conditions were hypertension, heart failure and chronic obstructive pulmonary disease. Hospitalisations mainly due to major bleeding and AF control increased, whereas hospitalisations mainly due to ischaemic stroke and myocardial infarction decreased. The total cost of care increased even after adjustment for inflation from €68.4 million in 2006 to €388.4 million in 2015, equivalent to 0.78% of the Korean NHIS total expenditure. Overall in-hospital mortality decreased from 7.5% in 2006 to 4.3% in 2015. The in-hospital mortality was highest in patients ≥80 years of age (7.7%) and in patients with chronic kidney disease (7.4%).ConclusionsAF hospitalisations have increased exponentially over the past 10 years in Korea, in association with an increase in comorbid chronic diseases. Mortality associated with AF hospitalisations decreased during the last decade, but hospitalisation costs have markedly increased.</jats:sec

Copper selenide film electrodes prepared by combined electrochemical/chemical bath depositions with high photo-electrochemical conversion efficiency and stability

Copper selenide (of the type Cu2-xSe) film electrodes, prepared by combined electrochemical (ECD) followed by chemical bath deposition (CBD), may yield high photo-electrochemical (PEC) conversion efficiency (~14.6%) with no further treatment. The new ECD/CBD-copper selenide film electrodes show enhanced PEC characteristics and exhibit high stability under PEC conditions, compared to the ECD or the CBD films deposited separately. The electrodes combine the advantages of both ECD-copper selenide electrodes (in terms of good adherence to FTO surface and high surface uniformity) and CBD-copper selenide electrodes (suitable film thickness). Effect of annealing temperature, on the ECD/CBD film electrode composition and efficiency, is discussed.The results of this work are partly based on K. Murtada M.Sc. Thesis, under direct supervision of H.S. Hilal. Other experimental measurements and calculations, including dark current experiments, film thickness measurement, electrical conductivity, SEM analysis, XRD &AFM analysis revisions were performed by A. Zyoud after the thesis completion. Additional film electrode stability experiments under PEC conditions, were also performed by A. Zyoud after the Thesis completion. SEM micrographs and EDX spectra were measured by T.W. Kim and H-J.C. at the KIER, Korea. The XRD patterns were measured by D-H. Park and H. Kwon at PUK. M.H.S. Helal and H. Bsharat contributed with literature search, discussions and modeling. M. Faroun measured AFM micrographs at Al-Quds University. H.S. Hilal acknowledges financial support from ANU, Islamic Development Bank, Al-Maqdisi Project and Union of Arab Universities. T.W. Kim and H-J. Choi acknowledge financial support from the framework of the Research and Development Program of the Korea Institute of Energy Research (B6-2523)

Effect of epicardial fat volume on outcomes after left atrial posterior wall isolation in addition to pulmonary vein isolation in patients with persistent atrial fibrillation

BackgroundGreater epicardial adipose tissue (EAT) is related to higher recurrences after atrial fibrillation catheter ablation (AFCA). We investigated the effects of posterior wall box isolation (POBI) in conjunction with circumferential pulmonary vein isolation (CPVI) on rhythm outcomes according to varying EAT volumes among patients with persistent atrial fibrillation (PeAF).Materials and methodsWe included 1,187 patients with PeAF undergoing a de novo AFCA including those receiving CPVI alone (n = 687) and those receiving additional POBI (n = 500). The rhythm outcomes at 2 years post-AFCA were compared in subgroups stratified by the EAT volume using propensity overlap weighting.ResultsA reduced EAT volume was linearly associated with more favorable rhythm outcomes for additional POBI than for CPVI alone (P for interaction = 0.002). Among the patients with smaller EAT volumes (≤116.23 mL, the median value, n = 594), additional POBI was associated with a reduced AF recurrence risk as compared to CPVI only [weighted HR (hazard ratio) 0.74, 95% CI (confidence interval) 0.56–0.99]. In contrast, among the remaining 593 patients with greater EAT volumes (&gt;116.23 mL), No difference was observed in the recurrence risk between the additional POBI and CPVI alone groups (weighted HR 1.13, 95% CI 0.84–1.52). Among 205 patients with repeat ablations, the POBI reconnection rate was more frequent in the large EAT group (77.4%) than in the small EAT group (56.7%, P = 0.034).ConclusionWhile PeAF patients with a smaller EAT volume averted AF recurrence by additional POBI after CPVI, no benefit of the POBI was observed in those with a greater EAT volume

Impact of frailty on early rhythm control outcomes in older adults with atrial fibrillation: A nationwide cohort study

PurposeRhythm-control therapy administered early following the initial diagnosis of atrial fibrillation (AF) has superior cardiovascular outcomes compared to rate-control therapy. Frailty is a key factor in identifying older patients’ potential for improvement after rhythm-control therapy. This study evaluated whether frailty affects the outcome of early rhythm-control therapy in older patients with AF.MethodsFrom the Korean National Health Insurance Service database (2005–2015), we collected 20,611 populations aged ≥65 years undergoing rhythm- or rate-control therapy initiated within 1 year of AF diagnosis. Participants were emulated by the EAST-AFNET4 trial, and stratified into non-frail, moderately frail, and highly frail groups based on the hospital frailty risk score (HFRS). A composite outcome of cardiovascular-related mortality, myocardial infarction, hospitalization for heart failure, and ischemic stroke was compared between rhythm- and rate-control.ResultsEarly rhythm-control strategy showed a 14% lower risk of the primary composite outcome in the non-frail group [weighted incidence 7.3 vs. 8.6 per 100 person-years; hazard ratio (HR) 0.86, 95% confidence interval (CI) 0.79–0.93, p &lt; 0.001] than rate-control strategy. A consistent trend toward a lower risk of early rhythm-control was observed in the moderately frail (HR 0.91, 95% CI 0.81–1.02, p = 0.09) and highly frail (HR 0.93, 95% CI 0.75–1.17, p = 0.55) groups.ConclusionAlthough the degree attenuated with increasing frailty, the superiority of cardiovascular outcomes of early rhythm-control in AF treatment was maintained without increased risk for safety outcomes. An individualized approach is required on the benefits of early rhythm-control therapy in older patients with AF, regardless of their frailty status

Optimizing the Design of a Vertical Ground Heat Exchanger: Measurement of the Thermal Properties of Bentonite-Based Grout and Numerical Analysis

We prepared bentonite-based grouts for use in the construction of vertical ground heat exchangers (GHEs) using various proportions of silica sand as an additive, and measured the thermal conductivity (TC) and specific heat capacity (SHC) of the grouts under saturated conditions. Furthermore, we performed numerical simulations using the measured thermal properties to investigate the effects of grout-SHCs, the length of the high-density polyethylene (HDPE) pipe, the velocity of the working fluid, and the operation time and off-time during intermittent operation on performance. Experimentally, the grout TCs and SHCs were in the ranges 0.728&ndash;1.127 W/(mK) and 2519&ndash;3743 J/(kgK), respectively. As the proportions of bentonite and silica sand increased, the TC rose and the SHC fell. Simulation showed that, during intermittent operation, not only a high grout TC but also a high SHC improved GHE performance. Also, during both continuous and intermittent operation, GHE performance improved as the working fluid velocity increased, and there was a critical working fluid velocity that greatly affected the performance of the vertical GHE, regardless of operation mode, high-density polyethylene (HDPE) pipe length, or grout thermal properties; this value was 0.3 m/s. Finally, during intermittent operation, depending on the operation time and off-time, critical periods were evident when the ground temperature had been almost completely restored and any beneficial effect of intermittent operation had almost disappeared