547 research outputs found

    A novel approach to security enhancement of chaotic DSSS systems

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    In this paper, we propose a novel approach to the enhancement of physical layer security for chaotic direct-sequence spread-spectrum (DSSS) communication systems. The main idea behind our proposal is to vary the symbol period according to the behavior of the chaotic spreading sequence. As a result, the symbol period and the spreading sequence vary chaotically at the same time. This simultaneous variation aims at protecting DSSS-based communication systems from the blind estimation attacks in the detection of the symbol period. Discrete-time models for spreading and despreading schemes are presented and analyzed. Multiple access performance of the proposed technique in the presence of additional white Gaussian noise (AWGN) is determined by computer simulations. The increase in security at the physical layer is also evaluated by numerical results. Obtained results show that our proposed technique can protect the system against attacks based on the detection of the symbol period, even if the intruder has full information on the used chaotic sequence.Peer ReviewedPostprint (author's final draft

    Practical use of reactor anti-neutrinos for nuclear safeguard in Vietnam

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    One of the most abundant man-made sources of low energy (few~MeVs) neutrinos, reactor neutrino, is not only useful for studying neutrino properties, but it is also used in practical applications. In this study, we investigate the practical use of reactor neutrino detectors for nuclear safeguard in Vietnam, specifically at the Dalat Nuclear Reactor, a future research facility, and presumably commercial reactors with 500~kW, 10~MW, and 1000~MW thermal powers, respectively. We compute the rate of observed inverted beta decay events, as well as the statistical significance of extracting isotope composition under the practical assumptions of detector mass, detection efficiency, and background level. We find that a 1-ton detector mass can allow us to detect the reactor's on-off transition state from a few hours to a few days, depending on the standoff distance and reactor thermal power. We investigate how background and energy resolution affect the precision of the extracted weapon-usable 239Pu{}^{239}\text{Pu} isotope. We conclude that in order to distinguish the 10\% variation of the 239Pu{}^{239}\text{Pu} in the 10~MW thermal power reactor, a 1-ton detector placed 50~m away must achieve 1\% background level. Increasing the statistics by using a 10x larger detector or placing it 10\sqrt{10} times closer to the reactor alleviates the requirement of the background level to 10\%

    Stringent constraint on CPT violation with the synergy of T2K-II, NOν\nuA extension, and JUNO

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    Neutrino oscillation experiments have measured precisely the mass-squared differences of three neutrino mass eigenstates, and three leptonic mixing angles by utilizing both neutrino and anti-neutrino oscillations. The possible CPT violation may manifest itself in the difference of neutrino and anti-neutrino oscillation parameters, making these experiments promising tools for testing CPT invariance. We investigate empirically the sensitivity of the CPT test via the difference in mass-squared splittings (Δm312−Δm‾312\Delta m^2_{31} - \Delta \overline{m}^2_{31}) and in leptonic mixing angles (sin⁡2θ23−sin⁡2θ‾23\sin^2\theta_{23} - \sin^2\overline{\theta}_{23}) with the synergy of T2K-II, NOν\nuA extension, and JUNO experiments. If the CPT symmetry is found to be conserved, the joint analysis of the three experiments will be able to establish limits of ∣Δm312−Δm‾312∣|\Delta m^2_{31} - \Delta \overline{m}^2_{31}| < 5.3×10−3eV25.3\times 10^{-3} \text{eV}^2 and ∣sin⁡2θ23−sin⁡2θ‾23∣|\sin^2\theta_{23} - \sin^2\overline{\theta}_{23}| < 0.100.10 at 3σ\sigma C. L. on the possible CPT violation. We find that with (Δm312−Δm‾312\Delta m^2_{31} - \Delta \overline{m}^2_{31}), the dependence of the statistical significance on the relevant parameters to exclude the CPT conservation is marginal, and that, if the difference in the best-fit values of Δm312\Delta m^2_{31} and Δm‾312\Delta \overline{m}^2_{31} measured by MINOS(+) and NOν\nuA persists as the true, the combined analysis will rule out the CPT conservation at 4σ\sigma C. L.. With the (sin⁡2θ23−sin⁡2θ‾23\sin^2\theta_{23} - \sin^2\overline{\theta}_{23}), the statistical significance to exclude CPT invariance depends strongly on the true value of θ23(θ‾23)\theta_{23}(\overline{\theta}_{23}). In case of maximal mixing of θ23\theta_{23}, the CPT conservation will be excluded at 3σ\sigma C. L. or more if the difference in the best-fit values of θ23\theta_{23} and θ‾23\overline{\theta}_{23} remains as the true.Comment: 10 pages, 10 figure
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