Research on performance enhancement for electromagnetic analysis and power analysis in cryptographic LSI

制度:新 ; 報告番号:甲3785号 ; 学位の種類:博士(工学) ; 授与年月日:2012/11/19 ; 早大学位記番号:新6161Waseda Universit

Understanding the spin-down rate changes of PSR B0919+06

We study the spin-down properties of PSR B0919+06 based on almost 30 years of radio observations. We confirm that the time derivative of the rotational frequency $\dot \nu$ is modulated quasi-periodically and show that it exhibits a repeating double-peaked structure throughout the entire observation span. We model the $\dot \nu$ variation of the pulsar assuming two spin-down rates with sudden switches between them in time. Our results show that the double-peak structure in $\dot \nu$ has a repetition time of about 630 days until MJD 52000 (April 2001) and 550 days since then. During this cycle, the pulsar spin varies from the lower spin-down rate to the upper spin-down rate twice with different amounts of time spent in each state, resulting in a further quasi-stable secondary modulation of the two-state switching. This particular spin-down state switching is broadly consistent with free precession of the pulsar, however, a strong evidence linked with this mechanism is not clearly established. We also confirm that the pulsar occasionally emits groups of pulses which appear early in pulse phase, so-called "flares", and these events significantly contribute to the pulse profile shape. We find the $\dot \nu$ modulation and the pulse shape variations are correlated throughout the observations. However, the flare-state is not entirely responsible for this correlation. In addition to the flare-state, we detect flare-like events from the pulsar in single pulse observations. During these events, the shift in pulse phase is small compared to that of the main flare-state and clearly visible only in single pulse observations.Comment: 10 pages, 12 Figures, Accepted by MNRAS on 10 October 201

The glitch-induced identity changes of PSR J1119-6127

We demonstrate that the high-magnetic field pulsar J1119-6127 exhibits three different types of behaviour in the radio band. Trailing the "normal" profile peak there is an "intermittent" peak and these components are flanked by two additional components showing very erratic "RRAT-like" emission. Both the intermittent and RRAT-like events are extremely rare and are preceded by a large amplitude glitch in the spin-down parameters. The post-glitch spin-down rate is smaller than the pre-glitch rate. This type of relaxation is very unusual for the pulsar population as a whole, but is observed in the glitch recovery of a RRAT. The abnormal emission behaviour in PSR J1119-6127 was observed up to three months after the epoch of the large glitch, suggestive of changes in the magnetospheric conditions during the fast part of the recovery process. We argue that both the anomalous recoveries and the emission changes could be related to reconfigurations of the magnetic field. Apart from the glitches, the spin-down of PSR J1119-6127 is relatively stable, allowing us to refine the measurement of the braking index (n=2.684\pm0.002) using more than 12 years of timing data. The properties of this pulsar are discussed in light of the growing evidence that RRATs do not form a distinct class of pulsar, but rather are a combination of different extreme emission types seen in other neutron stars. Different sub-classes of the RRATs can potentially be separated by calculating the lower limit on the modulation index of their emission. We speculate that if the abnormal behaviour in PSR J1119-6127 is indeed glitch induced then there might exist a population of neutron stars which only become visible in the radio band for a short duration in the immediate aftermath of glitch activity. These neutron stars will be visible in the radio band as sources that only emit some clustered pulses every so many years.Comment: 20 pages, 10 figures, Accepted for publication in MNRA

Resolving discrete pulsar spin-down states with current and future instrumentation

An understanding of pulsar timing noise offers the potential to improve the timing precision of a large number of pulsars as well as facilitating our understanding of pulsar magnetospheres. For some sources, timing noise is attributable to a pulsar switching between two different spin-down rates $(\dot{\nu})$. Such transitions may be common but difficult to resolve using current techniques. In this work, we use simulations of $\dot{\nu}$-variable pulsars to investigate the likelihood of resolving individual $\dot{\nu}$ transitions. We inject step-changes in the value of $\dot{\nu}$ with a wide range of amplitudes and switching timescales. We then attempt to redetect these transitions using standard pulsar timing techniques. The pulse arrival-time precision and the observing cadence are varied. Limits on $\dot{\nu}$ detectability based on the effects such transitions have on the timing residuals are derived. With the typical cadences and timing precision of current timing programs, we find we are insensitive to a large region of $\Delta \dot{\nu}$ parameter space which encompasses small, short timescale switches. We find, where the rotation and emission states are correlated, that using changes to the pulse shape to estimate $\dot{\nu}$ transition epochs, can improve detectability in certain scenarios. The effects of cadence on $\Delta \dot{\nu}$ detectability are discussed and we make comparisons with a known population of intermittent and mode-switching pulsars. We conclude that for short timescale, small switches, cadence should not be compromised when new generations of ultra-sensitive radio telescopes are online.Comment: 19 pages, 11 figure

What brakes the Crab pulsar?

Optical observations provide convincing evidence that the optical phase of the Crab pulsar follows the radio one closely. Since optical data do not depend on dispersion measure variations, they provide a robust and independent confirmation of the radio timing solution. The aim of this paper is to find a global mathematical description of Crab pulsar's phase as a function of time for the complete set of published Jodrell Bank radio ephemerides (JBE) in the period 1988-2014. We apply the mathematical techniques developed for analyzing optical observations to the analysis of JBE. We break the whole period into a series of episodes and express the phase of the pulsar in each episode as the sum of two analytical functions. The first function is the best-fitting local braking index law, and the second function represents small residuals from this law with an amplitude of only a few turns, which rapidly relaxes to the local braking index law. From our analysis, we demonstrate that the power law index undergoes "instantaneous" changes at the time of observed jumps in rotational frequency (glitches). We find that the phase evolution of the Crab pulsar is dominated by a series of constant braking law episodes, with the braking index changing abruptly after each episode in the range of values between 2.1 and 2.6. Deviations from such a regular phase description behave as oscillations triggered by glitches and amount to fewer than 40 turns during the above period, in which the pulsar has made more than 2.0e10 turns. Our analysis does not favor the explanation that glitches are connected to phenomena occurring in the interior of the pulsar. On the contrary, timing irregularities and changes in slow down rate seem to point to electromagnetic interaction of the pulsar with the surrounding environment.Comment: 11 pages, 8 figures, 3 tables; accepted for publication in Astronomy & Astrophysic

Power Side Channels in Security ICs: Hardware Countermeasures

Power side-channel attacks are a very effective cryptanalysis technique that can infer secret keys of security ICs by monitoring the power consumption. Since the emergence of practical attacks in the late 90s, they have been a major threat to many cryptographic-equipped devices including smart cards, encrypted FPGA designs, and mobile phones. Designers and manufacturers of cryptographic devices have in response developed various countermeasures for protection. Attacking methods have also evolved to counteract resistant implementations. This paper reviews foundational power analysis attack techniques and examines a variety of hardware design mitigations. The aim is to highlight exposed vulnerabilities in hardware-based countermeasures for future more secure implementations

Toward Reliable, Secure, and Energy-Efficient Multi-Core System Design

Computer hardware researchers have perennially focussed on improving the performance of computers while stipulating the energy consumption under a strict budget. While several innovations over the years have led to high performance and energy efficient computers, more challenges have also emerged as a fallout. For example, smaller transistor devices in modern multi-core systems are afflicted with several reliability and security concerns, which were inconceivable even a decade ago. Tackling these bottlenecks happens to negatively impact the power and performance of the computers. This dissertation explores novel techniques to gracefully solve some of the pressing challenges of the modern computer design. Specifically, the proposed techniques improve the reliability of on-chip communication fabric under a high power supply noise, increase the energy-efficiency of low-power graphics processing units, and demonstrate an unprecedented security loophole of the low-power computing paradigm through rigorous hardware-based experiments