LIPIcs

We revisit the problem of estimating entropy of discrete distributions from independent samples, studied recently by Acharya, Orlitsky, Suresh and Tyagi (SODA 2015), improving their upper and lower bounds on the necessary sample size n. For estimating Renyi entropy of order alpha, up to constant accuracy and error probability, we show the following * Upper bounds n = O(1) 2^{(1-1/alpha)H_alpha} for integer alpha>1, as the worst case over distributions with Renyi entropy equal to H_alpha. * Lower bounds n = Omega(1) K^{1-1/alpha} for any real alpha>1, with the constant being an inverse polynomial of the accuracy, as the worst case over all distributions on K elements. Our upper bounds essentially replace the alphabet size by a factor exponential in the entropy, which offers improvements especially in low or medium entropy regimes (interesting for example in anomaly detection). As for the lower bounds, our proof explicitly shows how the complexity depends on both alphabet and accuracy, partially solving the open problem posted in previous works. The argument for upper bounds derives a clean identity for the variance of falling-power sum of a multinomial distribution. Our approach for lower bounds utilizes convex optimization to find a distribution with possibly worse estimation performance, and may be of independent interest as a tool to work with Le Cam’s two point method

A Subgradient Algorithm For Computational Distances and Applications to Cryptography

The task of finding a constructive approximation in the computational distance, while simultaneously preserving additional constrains (referred to as simulators ), appears as the key difficulty in problems related to complexity theory, cryptography and combinatorics. In this paper we develop a general framework to \emph{efficiently} prove results of this sort, based on \emph{subgradient-based optimization applied to computational distances}. This approach is simpler and natural than KL-projections already studied in this context (for example the uniform min-max theorem from CRYPTO\u2713), while simultaneously may lead to quantitatively better results. Some applications of our algorithm include: \begin{itemize} \item Fixing an erroneous boosting proof for simulating auxiliary inputs from TCC\u2713 and much better bounds for the EUROCRYPT\u2709 leakage-resilient stream cipher \item Deriving the unified proof for Impagliazzo Hardcore Lemma, Dense Model Theorem, Weak Szemeredi Theorem (CCC\u2709) \item Showing that dense leakages can be efficiently simulated, with significantly improved bounds \end{itemize} Interestingly, our algorithm can take advantage of small-variance assumptions imposed on distinguishers, that have been studied recently in the context of key derivation

LIPIcs

De, Trevisan and Tulsiani [CRYPTO 2010] show that every distribution over n-bit strings which has constant statistical distance to uniform (e.g., the output of a pseudorandom generator mapping n-1 to n bit strings), can be distinguished from the uniform distribution with advantage epsilon by a circuit of size O( 2^n epsilon^2). We generalize this result, showing that a distribution which has less than k bits of min-entropy, can be distinguished from any distribution with k bits of delta-smooth min-entropy with advantage epsilon by a circuit of size O(2^k epsilon^2/delta^2). As a special case, this implies that any distribution with support at most 2^k (e.g., the output of a pseudoentropy generator mapping k to n bit strings) can be distinguished from any given distribution with min-entropy k+1 with advantage epsilon by a circuit of size O(2^k epsilon^2). Our result thus shows that pseudoentropy distributions face basically the same non-uniform attacks as pseudorandom distributions

Life Threatening Complication during Treatment of Erysipelas due to Undiagnosed Ischemia of the Calf

Erysipelas is a superficial skin infection due to streptococci strains, which usually responds well to conservative treatment. Coexisting undiagnosed ischemia of the extremity may lead to severe complications. 57-year-old man developed large, circumflex ulceration of his right calf within two weeks before the admission after three-month treatment of erysipelas. Computer angiography showed chronic occlusion of the superficial femoral artery and the above knee popliteal artery. Rapid debridement of the wound took control over the infection. Patient required complex vascular procedure which allowed to prepare the ulcer for meshed skin grafts. Patient was discharged home on 64th hospital day with completely healed ulcer

Rare sequelae of blunt chest trauma

Blunt chest trauma can lead to massive retrosternal haematoma due to injury to blood vessels. A 25-year-old male showed a plain chest x-ray two hours after he had experienced a blunt impact to his sternum. The result was normal. Twelve hours later a second x-ray revealed massive effusion in his right pleural cavity. Computed tomography showed large retrosternal haematoma, but all intrathoracic arteries seemed intact. Operation revealed an injury to the left internal mammary artery. All patients with blunt chest trauma should be diagnosed by means of computed tomography because of the possibility of delayed haematoma and difficulties in assessing the severity of the trauma.Tępy uraz klatki piersiowej może prowadzić do powstania dużego zamostkowego krwiaka z powodu uszkodzenia naczyń krwionośnych. Mężczyzna w wieku 25 lat doznał tępego urazu klatki piersiowej na skutek uderzenia w mostek. Dwie godziny później w szpitalnej izbie przyjęć wykonano u niego zdjęcie klatki piersiowej, na którym nie stwierdzono nieprawidłowości. Dwanaście godzin później z powodu narastającego bólu wykonano ponownie zdjęcie klatki piersiowej, w którym widoczna była duża ilość płynu w opłucnej prawej. W badaniu tomografii komputerowej odnotowano olbrzymi krwiak zamostkowy i krwiak opłucnej, a za pomocą angiotomografii wykluczono uraz dużych naczyń krwionośnych klatki piersiowej. W doraźnej operacji wykazano uraz lewej tętnicy piersiowej wewnętrznej, którą podwiązano. Przebieg pooperacyjny był prawidłowy. Wszystkich chorych po tępym urazie klatki piersiowej należy diagnozować, stosując tomografię komputerową, ponieważ istnieje możliwość powstania krwiaka śródpiersia z opóźnieniem, który jest niewidoczny w klasycznym zdjęciu

The Mother of All Leakages: How to Simulate Noisy Leakages via Bounded Leakage (Almost) for Free

We show that noisy leakage can be simulated in the information-theoretic setting using a single query of bounded leakage, up to a small statistical simulation error and a slight loss in the leakage parameter. The latter holds true in particular for one of the most used noisy-leakage models, where the noisiness is measured using the conditional average min-entropy (Naor and Segev, CRYPTO\u2709 and SICOMP\u2712). Our reductions between noisy and bounded leakage are achieved in two steps. First, we put forward a new leakage model (dubbed the dense leakage model) and prove that dense leakage can be simulated in the information-theoretic setting using a single query of bounded leakage, up to small statistical distance. Second, we show that the most common noisy-leakage models fall within the class of dense leakage, with good parameters. We also provide a complete picture of the relationships between different noisy-leakage models, and prove lower bounds showing that our reductions are nearly optimal. Our result finds applications to leakage-resilient cryptography, where we are often able to lift security in the presence of bounded leakage to security in the presence of noisy leakage, both in the information-theoretic and in the computational setting. Additionally, we show how to use lower bounds in communication complexity to prove that bounded-collusion protocols (Kumar, Meka, and Sahai, FOCS\u2719) for certain functions do not only require long transcripts, but also necessarily need to reveal enough information about the inputs

The consequences of covering the origin of the left subclavian artery by the coated part of the thoracic stent graft in patients with aneurysm or dissection of the descending aorta

Wstęp. Zastosowanie stentgraftów w leczeniu patologii aorty zstępującej jest metodą powszechnie uznaną. Implantacja stentgraftu, podczas której pokrywa się odejście lewej tętnicy podobojczykowej (LSA) może być przyczyną wystąpienia wielu powikłań, takich jak udar, niedokrwienie rdzenia kręgowego, niedokrwienie lewej kończyny górnej oraz struktur tylnego dołu czaszki. W poniższej pracy przedstawiono częstość występowania powikłań związanych z pokryciem LSA u 60 chorych, u których podczas implantacji stentgraftu do aorty piersiowej pokryto powlekaną częścią stentgraftu odejście lewej tętnicy podobojczykowej. Dodatkowo przedstawiono analizę związku pomiędzy częstością występowania powikłań a wiekiem chorych i typem patologii aorty zstępującej. Materiał i metody. Do badania zakwalifikowano 60 chorych, 12 kobiet i 48 mężczyzn, w wieku 23–83 lat. Średnia wieku wynosiła 56 lat. Spośród badanych 21 chorych operowano z powodu tętniaka prawdziwego, 9 z powodu tętniaka pourazowego, 22 z powodu rozwarstwienia aorty typu Stanford B i 8 z powodu rozwarstwienia typu Stanford A. Chorych oceniano pod kątem występowania udaru, niedokrwienia rdzenia kręgowego oraz objawów niedokrwienia struktur tylnego dołu czaszki oraz niedokrwienia lewej kończyny górnej. Częstość występujących objawów analizowano w podgrupach wyodrębnionych na podstawie patologii aorty będącej przyczyną operacji (tętniak prawdziwy, tętniak pourazowy, rozwarstwienie typu Stanford A i rozwarstwienie typu Stanford B) oraz w podgrupach wiekowych. Wyniki. Spośród 60 badanych chorych u żadnego pacjenta nie obserwowano niedokrwienia rdzenia. U 2 chorych (3,3%) odnotowano udar odwracalny (RIND) u 1 pacjenta (1,6%) — udar trwały. Objawy typowe dla zespołu podkradania, takie jak zawroty głowy, występowały u 10 (16,7%) chorych, zaburzenia równowagi u 2 (3,3%) chorych oraz osłabienie siły mięśniowej u 32 (53,2%) chorych, a gorsze ucieplenie dłoni u 26 (43,3%) chorych. W żadnym przypadku nie obserwowano bólu lewej kończyny górnej, ani spoczynkowego, ani wysiłkowego. Analiza statystyczna wykazała, iż nie istnieje związek pomiędzy wiekiem, ani typem patologii a częstością występowania powikłań. Wnioski. Pokrycie odejścia lewej tętnicy podobojczykowej jest procedurą bezpieczną. W większości przypadków chorzy nie wymagają operacji poprawiającej napływ do lewej tętnicy podobojczykowej. Acta Angiol 2011; 17, 4: 251–263Background. The usage of thoracic endografts in the treatment of thoracic aortic lesions is a universally recognized method. Intentional coverage of the left subclavian artery during deployment of the endograft could be associated with several complications such as stroke, spinal cord ischaemia, left arm ischaemia, and vertebrobasilar ischaemia. This study presents the incidence of complications associated with LSA coverage in 60 patients with LSA covered during placement of thoracic endograft. Additionally, the relationship between incidence of complications and factors such as age and type of pathology is analysed. Material and methods. Sixty patients were qualified to the study, 12 women and 48 men between the ages of 23 and 83 years. The mean age was 56 years. A total of 21 patients were operated on for true aneurysm, 9 for post-traumatic aneurysm, 22 for Stanford B dissection, and 8 for Stanford A dissection. Patients were assessed in terms of presence of stroke, spinal cord ischaemia as well as symptoms associated with left arm ischaemia and vertebrobasilar ischaemia. The incidence of present symptoms was analysed in separate subgroups based on the type of pathology of the aorta due to which patients were operated (true aneurysm, traumatic aneurysm, Stanford type A dissection, and Stanford type B dissection) and age subgroups. Results. In none of the 60 patients enrolled for the study spinal cord ischaemia was observed. Two cases (3.3%) of reversible stroke (RIND reversible ischaemic neurological deficit) and one case (1.6%) of stroke (complete ischaemic stroke CIS) were observed. Regarding symptoms typical for subclavian steal syndrome, dizziness occurred in 10 patients (16.7%), vertigo in 2 patients (3.3%), left arm weakness in 32 patients (53.2%), and coldness — in 26 patients (43.3%). Neither rest pain nor pain after exercise was observed in any case. Statistical analysis did not show any connection between the incidence of complications and age or type of pathology for which the patient had been operated. Conclusions. Planned coverage of the LSA is a safe procedure. In most of cases patients with covered LSA did not require any further reconstructions. Acta Angiol 2011; 17, 4: 251–26