Lengths May Break Privacy – Or How to Check for Equivalences with Length

Security protocols have been successfully analyzed using symbolic models, where messages are represented by terms and protocols by processes. Privacy properties like anonymity or untraceability are typically expressed as equivalence between processes. While some decision procedures have been proposed for automatically deciding process equivalence, all existing approaches abstract away the information an attacker may get when observing the length of messages. In this paper, we study process equivalence with length tests. We first show that, in the static case, almost all existing decidability results (for static equivalence) can be extended to cope with length tests. In the active case, we prove decidability of trace equivalence with length tests, for a bounded number of sessions and for standard primitives. Our result relies on a previous decidability result from Cheval et al (without length tests). Our procedure has been implemented and we have discovered a new flaw against privacy in the biometric passport protocol

PELAKSANAAN KESELAMATAN DAN KESEHATAN KERJA DI BENGKEL TEKNIK MEKANIK OTOMOTIF SMK TAMANSISWA JETIS YOYAKARTA

Penelitian ini bertujuan untuk mengetahui pelaksanaan keselamatan dan kesehatan kerja (K3) yang dilihat dari perilaku praktik kerja, aspek perlengkapan keamanan pada manusia dan mesin, beberapa alat dan mesin yang rawan menyebabkan kecelakaan, serta upaya-upaya yang ditempuh berkaitan dengan keselamatan dan kesehatan kerja di bengkel praktik. Penelitian ini adalah penelitian deskriptif kualitatif. Penelitian berlangsung di bengkel Teknik Mekanik Otomotif SMK TAMANSISWA Yogyakarta. Data utama penelitian ini diperoleh dari praktikan, instruktur praktik, dan teknisi bengkel sebagai key informant, sedangkan data penunjang dikumpulkan dari berbagai dokumen yang ada di bengkel praktik. Data yang dikumpulkan melalui pengamatan, wawancara dan observasi. Data mentah yang diperoleh kemudian direduksi, dirangkum dan dikelompok-kelompokkan sesuai kategori yang ada yang akan memberikan gambaran terhadap hasil penelitian dalam bentuk narasi. Pemeriksaan keabsaan data dilakukan dengan memperpanjang waktu penelitian dan triangulasi. Hasil penelitian mengungkapkan bahwa: (1) pelaksanaan K3 di bengkel Teknik Mekanik Otomotif SMK TAMANSISWA Yogyakarta masih kurang. Hal ini terlihat dari beberapa perilaku praktikan yang membahayakan K3, diantaranya, praktikan tidak memakai alat pelindung diri dengan baik, beberapa sikap yang kurang baik yakni praktikan duduk di atas meja kerja bangku bahkan ada praktikan yang melihat rekannya sedang mengelas tidak menggunakan kaca mata las, praktikan menggunakan peralatan dan mesin tidak sesuai dengan fungsinya, praktikan menempatkan peralatan ataupun benda kerja tidak pada tempat yang semestinya; (2) keadaan alat pelindung diri belum memadai, dan beberapa perlengkapan jumlahnya perlu ditambah serta perlu penggantian beberapa perlengkapan yang sudah tidak layak digunakan. Peralatan tersebut misalkan, sarung tangan, apron dada, safety helmet, masker pelingdung hidung dan mulut, dan kaca mata bening; (3) beberapa mesin yang rawan menyebabkan kecelakaan, antara lain: mesin gerinda, mesin las, dan mesin bor. Untuk itu dalam penggunaan mesin-mesin tersebut perlu ditekankan lagi aspek keamanannya; (4) upaya yang dilakukan untuk pencegahan kecelakaan di bengkel dilakukan dengan berbagai kegiatan. Diantaranya: instruktur selalu memberi arahan tentang K3 sebelum praktik dimulai, dilakukan pengawasan saat praktik, pemasangan poster keselamatan kerja, dan melakukan maintenance mesin secara berkala

Provably correct Java implementations of Spi Calculus security protocols specifications

Spi Calculus is an untyped high level modeling language for security protocols, used for formal protocols specification and verification. In this paper, a type system for the Spi Calculus and a translation function are formally defined, in order to formalize the refinement of a Spi Calculus specification into a Java implementation. The Java implementation generated by the translation function uses a custom Java library. Formal conditions on such library are stated, so that, if the library implementation code satisfies such conditions, then the generated Java implementation correctly simulates the Spi Calculus specification. A verified implementation of part of the custom library is further presente

Comparing Profitability and Cash Flows of Agroforestry and Agriculture on Australian Farms

This paper is a summary of a project that compared the relative profitability of existing, emerging and prospective agroforestry systems with profitability of conventional agricultural land uses in the cropping zones of Western Australia and New South Wales. The project explored the economic boundary conditions under which several promising agroforestry systems may be viable in the lower rainfall zones. Partial budgeting and discounted cash flow techniques were used to conduct the comparative analysis of alternative land use scenarios. The profitability, cash flows and debt associated with each of the scenario are reported. The analysis underpinning this research provides estimates of the economic value of the temporal and spatial interaction effects of trees on agricultural crops and pastures.Farm Management,

An Alternative Origin for Hypervelocity Stars

Halo stars with unusually high radial velocity ("hypervelocity" stars, or HVS) are thought to be stars unbound to the Milky Way that originate from the gravitational interaction of stellar systems with the supermassive black hole at the Galactic center. We examine the latest HVS compilation and find peculiarities that are unexpected in this black hole-ejection scenario. For example, a large fraction of HVS cluster around the constellation of Leo and share a common travel time of $\sim 100$-200 Myr. Furthermore, their velocities are not really extreme if, as suggested by recent galaxy formation models, the Milky Way is embedded within a $2.5\times 10^{12} h^{-1} M_{\odot}$ dark halo with virial velocity of $\sim 220$ km/s. In this case, the escape velocity at $\sim 50$ kpc would be $\sim 600$ km/s and very few HVS would be truly unbound. We use numerical simulations to show that disrupting dwarf galaxies may contribute halo stars with velocities up to and sometimes exceeding the nominal escape speed of the system. These stars are arranged in a thinly-collimated outgoing ``tidal tail'' stripped from the dwarf during its latest pericentric passage. We speculate that some HVS may therefore be tidal debris from a dwarf recently disrupted near the center of the Galaxy. In this interpretation, the angular clustering of HVS results because from our perspective the tail is seen nearly ``end on'', whereas the common travel time simply reflects the fact that these stars were stripped simultaneously from the dwarf during a single pericentric passage. This proposal is eminently falsifiable, since it makes a number of predictions that are distinct from the black-hole ejection mechanism and that should be testable with improved HVS datasets.Comment: 4 pages, 4 figures. Replacement to match version accepted to ApJ

Hitting and returning into rare events for all alpha-mixing processes

We prove that for any $\alpha$-mixing stationnary process the hitting time of any $n$-string $A_n$ converges, when suitably normalized, to an exponential law. We identify the normalization constant $\lambda(A_n)$. A similar statement holds also for the return time. To establish this result we prove two other results of independent interest. First, we show a relation between the rescaled hitting time and the rescaled return time, generalizing a theorem by Haydn, Lacroix and Vaienti. Second, we show that for positive entropy systems, the probability of observing any $n$-string in $n$ consecutive observations, goes to zero as $n$ goes to infinity

Poisson approximation for search of rare words in DNA sequences

Using recent results on the occurrence times of a string of symbols in a stochastic process with mixing properties, we present a new method for the search of rare words in biological sequences generally modelled by a Markov chain. We obtain a bound on the error between the distribution of the number of occurrences of a word in a sequence (under a Markov model) and its Poisson approximation. A global bound is already given by a Chen-Stein method. Our approach, the psi-mixing method, gives local bounds. Since we only need the error in the tails of distribution, the global uniform bound of Chen-Stein is too large and it is a better way to consider local bounds. We search for two thresholds on the number of occurrences from which we can regard the studied word as an over-represented or an under-represented one. A biological role is suggested for these over- or under-represented words. Our method gives such thresholds for a panel of words much broader than the Chen-Stein method. Comparing the methods, we observe a better accuracy for the psi-mixing method for the bound of the tails of distribution. We also present the software PANOW (available at http://stat.genopole.cnrs.fr/software/panowdir/) dedicated to the computation of the error term and the thresholds for a studied word.Comment: 29 pages, 0 figure

Analisis Kestabilan dan Bifurkasi Solusi Sistem Autoparametrik dengan Osilator Tipe Rayleigh

Masalah resonansi autoparametrik pada sistem tereksitasi sendiri banyak terjadi pada struktur-struktur mekanika. Paper ini akan menganalisis model rekayasa dari struktur mekanika yang sesungguhnya. Sistem autoparametrik tipe Rayleigh dipelajari untuk melihat perilaku solusinya, kasus-kasus bifurkasi solusi yang mungkin