Hang With Your Buddies to Resist Intersection Attacks

Some anonymity schemes might in principle protect users from pervasive network surveillance - but only if all messages are independent and unlinkable. Users in practice often need pseudonymity - sending messages intentionally linkable to each other but not to the sender - but pseudonymity in dynamic networks exposes users to intersection attacks. We present Buddies, the first systematic design for intersection attack resistance in practical anonymity systems. Buddies groups users dynamically into buddy sets, controlling message transmission to make buddies within a set behaviorally indistinguishable under traffic analysis. To manage the inevitable tradeoffs between anonymity guarantees and communication responsiveness, Buddies enables users to select independent attack mitigation policies for each pseudonym. Using trace-based simulations and a working prototype, we find that Buddies can guarantee non-trivial anonymity set sizes in realistic chat/microblogging scenarios, for both short-lived and long-lived pseudonyms.Comment: 15 pages, 8 figure

Two new instruments for analytical chemistry: A. Constant potential pulse polarography (CPPP) and differential CPPP (DCPPP) for determination of metals in the presence of oxygen in flowing systems; B. Versatile laser-based analytical instrument for detection of jet-cooled molecular species

Analytical chemistry as a field is composed largely of methods of measurement and analysis. The needs of analytical chemists have developed a complexity which must be matched by the capability of the techniques in use. This calls for the advent of new methods and techniques suitable for the problems at hand. Two new instruments are described in this work which are small steps in meeting some of the complex needs of analytical chemistry;The first instrument represents one of the older analytical methods, polarography, which has been in use in analytical chemistry for over 65 years. Polarography is a method which has seen a decline in use as more sensitive techniques are discovered, but which is still in wide use. The instrument described herein allows polarographic analysis of metals without removal of dissolved oxygen, previously a time-consuming necessity. Detection is accomplished by constant potential pulse polarography (CPPP). The instrument makes feasible detection in flowing samples by elimination of the required oxygen removal step. CPPP further offers a degree of freedom from interference due to reduction of hydrogen ion in acidic solution. The technique is shown to be sensitive, with a detection limit in the range of 10[superscript]-7 M for the metals studied. A differential method has also been developed, differential CPPP (DCPPP), which is shown to have increased selectivity over CPPP, offering resolution on the same scale as differential pulse polarography (DPP);The second instrument described represents one of the newer analytical techniques, supersonic jet spectroscopy. Analytical usage of this method has been only within the current decade, though recent development has been rapid, chiefly due to the immense selectivity resulting from the cooled analytes. The instrument designed for this work was intended to be versatile, allowing sample introduction by gas chromatography (GC) or by laser desorption (LD). Capabilities of the instrument are shown and a method for analysis is given. The detection limit for jet spectroscopy is hampered by the large dilution of sample which is necessary to accomplish the molecular cooling, but was found to be 9 ppm for aniline in Helium carrier gas under optimized expansion conditions for this instrument using multiphoton ionization (MPI)

Probing the chemistry of nickel/metal hydride battery cells using electrochemical impedance spectroscopy

Electrochemical Impedance Spectroscopy (EIS) is a valuable tool for investigating the chemical and physical processes occurring at electrode surfaces. It offers information about electron transfer at interfaces, kinetics of reactions, and diffusion characteristics of the bulk phase between the electrodes. For battery cells, this technique offers another advantage in that it can be done without taking the battery apart. This non-destructive analysis technique can thus be used to gain a better understanding of the processes occurring within a battery cell. This also raises the possibility of improvements in battery design and identification or prediction of battery characteristics useful in industry and aerospace applications. EIS as a technique is powerful and capable of yielding significant information about the cell, but it also requires that the many parameters under investigation can be resolved. This implies an understanding of the processes occurring in a battery cell. Many battery types were surveyed in this work, but the main emphasis was on nickel/metal hydride batteries

Development of a COTS-Based Computing Environment Blueprint Application at KSC

This paper describes a blueprint that can be used for developing a distributed computing environment (DCE) for NASA in general, and the Kennedy Space Center (KSC) in particular. A comprehensive, open, secure, integrated, and multi-vendor DCE such as OSF DCE has been suggested. Design issues, as well as recommendations for each component have been given. Where necessary, modifications were suggested to fit the needs of KSC. This was done in the areas of security and directory services. Readers requiring a more comprehensive coverage are encouraged to refer to the eight-chapter document prepared for this work

Keeping Authorities "Honest or Bust" with Decentralized Witness Cosigning

The secret keys of critical network authorities - such as time, name, certificate, and software update services - represent high-value targets for hackers, criminals, and spy agencies wishing to use these keys secretly to compromise other hosts. To protect authorities and their clients proactively from undetected exploits and misuse, we introduce CoSi, a scalable witness cosigning protocol ensuring that every authoritative statement is validated and publicly logged by a diverse group of witnesses before any client will accept it. A statement S collectively signed by W witnesses assures clients that S has been seen, and not immediately found erroneous, by those W observers. Even if S is compromised in a fashion not readily detectable by the witnesses, CoSi still guarantees S's exposure to public scrutiny, forcing secrecy-minded attackers to risk that the compromise will soon be detected by one of the W witnesses. Because clients can verify collective signatures efficiently without communication, CoSi protects clients' privacy, and offers the first transparency mechanism effective against persistent man-in-the-middle attackers who control a victim's Internet access, the authority's secret key, and several witnesses' secret keys. CoSi builds on existing cryptographic multisignature methods, scaling them to support thousands of witnesses via signature aggregation over efficient communication trees. A working prototype demonstrates CoSi in the context of timestamping and logging authorities, enabling groups of over 8,000 distributed witnesses to cosign authoritative statements in under two seconds.Comment: 20 pages, 7 figure

Exotic forms of matter created by interactions with free-electron lasers

In this thesis, we investigate the formation of atomic and molecular states with mul- tiple core electrons missing. These multiple-core-hole (MCH) states are of interest due to their sensitivity to their chemical environment. These MCH states are formed by successive single-photon ionisations of core electrons. This can be achieved by x-ray photons and a sufficiently large intensity such that the photo-ionisation rate competes with the Auger decay rate of core-hole states. To understand the pathways that lead to the formation of MCH states, we study the interaction of free-electron laser (FEL) pulses with atoms and molecules. These lasers are capable of producing short, high-intensity pulses with high photon en- ergy, which make them ideal for forming MCH states. In order to understand the interaction of an FEL with an atom or molecule, we model these interactions com- putationally. We construct rate equations and track how the population of an atom or molecule transitions between different states. These rate equations involve single- photon ionization processes and Auger transitions. To account for these processes, we compute photo-ionisation cross-sections and Auger decay rates. We develop a computational model that allows us to calculate the ion yields produced when an atom or molecule interacts with an FEL pulse. Further, by calcu- lating how the population transitions via different pathways of intermediate atomic and molecular states, we determine the proportion of the population which accesses MCH states. We also compute electron spectra, which provide measurable observ- ables indicating the formation of MCH states

Plan de comunicación externa para atraer talento millennial a la cadena Cineplanet en el contexto covid-19

En marzo del 2020, la Organización Mundial de la Salud (OMS) anunciaba al mundo que la nueva enfermedad por el coronavirus 2019 (COVID-19) pasaba a categorizarse como una pandemia. Desde ese momento, muchos países tomaron acciones inmediatas, entre ellos el Perú. Con el anuncio de la cuarentena llegó el cierre de escuelas, oficinas, supermercados, teatros, etc. La cadena de cines Cineplanet (Cineplex SA) fundada en 1999, fue una de las empresas más golpeadas desde el inicio de la pandemia. Con sus 39 complejos cerrados a nivel nacional, tuvo que iniciar trámites para dar suspensión perfecta a sus trabajadores. Acción que días más tarde terminó con cartas de despido desencadenando así una crisis de reputación. Este trabajo plantea un plan de comunicación externa para recuperar a sus talentos millennial que se decepcionaron de la empresa al percibir una falta de solidaridad cuando más lo necesitaban. Para lograrlo, se ha recurrido a la fuerte cultura organizacional que existía en la empresa y la marca empleadora. Demostrando que, para conseguir una buena comunicación externa, previamente se debe asegurar una correcta comunicación interna.In March 2020, the World Health Organization (WHO) announced to the world that the new coronavirus disease 2019 (COVID-19) was now being categorized as a pandemic. From that moment, many countries took immediate action, including Peru. With the announcement of the quarantine came the closure of schools, offices, supermarkets, theaters, etc. The chain of cinemas Cineplanet (Cineplex SA) founded in 1999, was one of the hardest hit companies since the start of the pandemic. With its 39 locations closed nationwide, it had to initiate procedures to give its workers a perfect suspension. Which after some days ended with dismissal letters, thus triggering a reputation crisis. This project proposes an external communication plan to recover their millennial talents who were disappointed in the company when they perceived a lack of solidarity when they needed it most. To achieve this, the strong organizational culture that exists in the company and the employer branding has been used. Demonstrating that, in order to achieve good external communication, correct internal communication must first be ensured

ColorFloat: Constant space token coloring

We present ColorFloat, a family of O(1) space complexity algorithms that solve the problem of attributing (coloring) fungible tokens to the entity that minted them (minter). Tagging fungible tokens with metadata is not a new problem and was first formalized in the Colored Coins protocol. In certain contexts, practical solutions to this challenge have been implemented and deployed such as NFT. We define the fungible token coloring problem, one specific aspect of the Colored Coins problem, to be the problem of retaining fungible characteristics of the underlying token while accurately tracking the attribution of fungible tokens to their respective minters. Fungible token coloring has a wide range of Web3 applications. One application which we highlight in this paper is the onchain yield-sharing collateral-based stablecoin

ColorTrace: Fungible token coloring and attribution

We formally define the fungible token coloring problem of attributing (coloring) fungible tokens to originating entities (minters), and present, to our knowledge, the first practical onchain algorithm to solve it. Tracking attribution of colored tokens losslessly using existing approaches such as the Colored Coins protocol is computationally intractable due to the per-wallet storage requirements growing in proportion to the number of minters. Our first contribution is an elegant solution to the single-chain token coloring problem, where colored tokens are atomically burned and minted to ensure each wallet only contains tokens of a single color. Our second contribution is an extension to this single-chain token coloring algorithm to allow safe and efficient crosschain token transfers. We present ColorTrace, an onchain algorithm to achieve globally consistent, economically feasible, fungible token coloring

Incremental Prognostic Value of Echocardiographic Strain and Its Association with Mortality in Cancer Patients

Background Left ventricular global longitudinal systolic strain (GLS) has been shown to be superior to ejection fraction in detecting subclinical dysfunction in patients with cancer and predicting mortality in patients with cardiovascular disease. Cancer-related fatigue is common in the later stages of neoplastic malignancies and may be indicative of nonovert heart failure. The aim of this study was to determine whether reduced strain by echocardiography was associated with all-cause mortality in a cancer cohort. Methods In this retrospective study, 120 patients with cancer undergoing or scheduled to undergo chemotherapy and with normal ejection fractions (>50%) underwent assessments of GLS. GLS was derived by averaging all speckle-tracking strain segments of the left ventricle. Results Over an average follow-up period of 21.6 ± 13.9 months, 57 of 120 patients died. Univariate predictors of all-cause mortality (P < .10) were Eastern Cooperative Oncology Group performance status, male sex, hematologic malignancy, β-blocker use, and GLS. Multivariate analysis of all significant univariate variables showed that Eastern Cooperative Oncology Group performance status (hazard ratio, 2.12; 95% confidence interval, 1.54–2.92; P < .001), male sex (hazard ratio, 1.93; 95% confidence interval, 1.14–3.27; P = .014), and GLS (hazard ratio, 0.89; 95% confidence interval, 0.81–0.97; P = .012) were significantly and independently associated with mortality. Stepwise analysis of the multivariate associations showed an increase in the global χ2 value after adding GLS (P = .011) to significant clinical variables. Conclusions Eastern Cooperative Oncology Group performance status, male sex, and GLS were significantly associated with all-cause mortality in patients with cancer with normal ejection fractions receiving chemotherapy. Adding GLS to significant clinical variables provided incremental prognostic information