EHAP-ORAM: Efficient Hardware-Assisted Persistent ORAM System for Non-volatile Memory

Oblivious RAM (ORAM) protected access pattern is essential for secure NVM. In the ORAM system, data and PosMap metadata are maps in pairs to perform secure access. Therefore, we focus on the problem of crash consistency in the ORAM system. Unfortunately, using traditional software-based support for ORAM system crash consistency is not only expensive, it can also lead to information leaks. At present, there is no relevant research on the specific crash consistency mechanism supporting the ORAM system. To support crash consistency without damaging ORAM system security and compromising the performance, we propose EHAP-ORAM. Firstly, we analyze the access steps of basic ORAM to obtain the basic requirements to support the ORAM system crash consistency. Secondly, improve the ORAM controller. Thirdly, for the improved hardware system, we propose several persistence protocols supporting the ORAM system crash consistency. Finally, we compared our persistent ORAM with the system without crash consistency support, non-recursive and recursive EHAP-ORAM only incurs 3.36% and 3.65% performance overhead. The results show that EHAP-ORAM not only supports effective crash consistency with minimal performance and hardware overhead but also is friendly to NVM lifetime

Driving Consistency Errors Overestimate Crash Risk from Cellular Conversation in Two Case-Crossover Studies

The goal of this study is to help resolve the discrepancy in relative risk estimates between recent and early epidemiological studies of call-crash association. Recent epidemiological studies estimate a crash risk for cellular conversation near that of baseline driving – a relative risk of about one. In contrast, two early case-crossover studies estimated a relative crash risk of about four for cellular conversation while driving. One hypothesis to explain this fourfold discrepancy is that the early studies had less driving time in the control window on a day before the crash, than in the crash window just before the crash. This bias in driving exposure translated into relatively lower exposure to cellular conversation during control windows than during crash windows, thereby introducing an overestimate of the relative risk for cellular conversation while driving. To test this hypothesis, the present study developed a new driving consistency index (DCI), which measures the percentage overlap in driving times from one day to the next. The mean DCI for 240 vehicles in a Chicago GPS study with known driving times for two successive days was a surprisingly low 14.8%, substantially below the driving consistency estimates in the early case-crossover studies. After adjustment by the mean DCI, the relative risk estimates for cellular conversation while driving in the early case-crossover studies are about one, resolving the discrepancy with the more recent epidemiological studies