Elliptic Curve Scalar Multiplication Combining Yao’s Algorithm and Double Bases

Abstract. In this paper we propose to take one step back in the use of double base number systems for elliptic curve point scalar multiplication. Using a mod-ified version of Yao’s algorithm, we go back from the popular double base chain representation to a more general double base system. Instead of representing an integer k as Pn i=1 2 bi3ti where (bi) and (ti) are two decreasing sequences, we only set a maximum value for both of them. Then, we analyze the efficiency of our new method using different bases and optimal parameters. In particular, we pro-pose for the first time a binary/Zeckendorf representation for integers, providing interesting results. Finally, we provide a comprehensive comparison to state-of-the-art methods, including a large variety of curve shapes and latest point addition formulae speed-ups

On the automatic construction of indistinguishable operations

An increasingly important design constraint for software running on ubiquitous computing devices is security, particularly against physical methods such as side-channel attack. One well studied methodology for defending against such attacks is the concept of indistinguishable functions which leak no information about program control flow since all execution paths are computationally identical. However, constructing such functions by hand becomes laborious and error prone as their complexity increases. We investigate techniques for automating this process and find that effective solutions can be constructed with only minor amounts of computational effort.Fundação para a Ciência e Tecnologia - SFRH/BPD/20528/2004

DNA Dosimetry Assessment for Sunscreen Genotoxic Photoprotection

Background: Due to the increase of solar ultraviolet radiation (UV) incidence over the last few decades, the use of sunscreen has been widely adopted for skin protection. However, considering the high efficiency of sunlight-induced DNA lesions, it is critical to improve upon the current approaches that are used to evaluate protection factors. An alternative approach to evaluate the photoprotection provided by sunscreens against daily UV radiation-induced DNA damage is provided by the systematic use of a DNA dosimeter. Methodology/Principal Findings: The Sun Protection Factor for DNA (DNA-SPF) is calculated by using specific DNA repair enzymes, and it is defined as the capacity for inhibiting the generation of cyclobutane pyrimidine dimers (CPD) and oxidised DNA bases compared with unprotected control samples. Five different commercial brands of sunscreen were initially evaluated, and further studies extended the analysis to include 17 other products representing various formulations and Sun Protection Factors (SPF). Overall, all of the commercial brands of SPF 30 sunscreens provided sufficient protection against simulated sunlight genotoxicity. In addition, this DNA biosensor was useful for rapidly screening the biological protection properties of the various sunscreen formulations. Conclusions/Significance: The application of the DNA dosimeter is demonstrated as an alternative, complementary, and reliable method for the quantification of sunscreen photoprotection at the level of DNA damage.Natura Inovacao e Tecnologia de Produtos LTDA (Sao Paulo, Brazil)Natura Inovacao e Tecnologia de Produtos LTDA (Sao Paulo, Brazil)FAPESP (Sao Paulo, Brazil)FAPESP (Sao Paulo, Brazil)CNPq (Brasilia, Brazil)CNPq (Brasilia, Brazil)Natura Inovacao e Tecnologia de Produtos LTDANatura Inovacao e Tecnologia de Produtos LTD

Effective-Range Expansion of the Neutron-Deuteron Scattering Studied by a Quark-Model Nonlocal Gaussian Potential

The S-wave effective range parameters of the neutron-deuteron (nd) scattering are derived in the Faddeev formalism, using a nonlocal Gaussian potential based on the quark-model baryon-baryon interaction fss2. The spin-doublet low-energy eigenphase shift is sufficiently attractive to reproduce predictions by the AV18 plus Urbana three-nucleon force, yielding the observed value of the doublet scattering length and the correct differential cross sections below the deuteron breakup threshold. This conclusion is consistent with the previous result for the triton binding energy, which is nearly reproduced by fss2 without reinforcing it with the three-nucleon force.Comment: 21 pages, 6 figures and 6 tables, submitted to Prog. Theor. Phy

Exposure to various ultraviolet radiations in human skin in situ: Biomarkers for oxidative stress

Following UV radiation, reactive oxygen species (ROS) are responsible for the generation of Comet assay (single-cell DNA gel electrophoresis) is widely used in photobiology and toxicology oxidative stress in human skin. ROS are considered to play an important role in developing to determine the degree of DNA damage induced by ultraviolet (UV) radiation or other agents. damage such as photoaging, immune suppression, cataract formation and carcinogenesis. The In principle, DNA fragments produced due to double-strand nicking by various mutagens or putative antioxidant defense system which protects human skin cells against developing such indirectly during DNA repair, are separated by electrophoresis from intact DNA. During singledamage consists of two different types of protective molecules (enzymatic and nonenzymatic cell electrophoresis the DNA fragments form a ''tail'' originating from cell nucleus, producing a pathways). In this manner, we investigated the behavior of two enzymatic radical scavengers, comet-like figure. Usually, the amount of DNA in the tail is measured by image analysis and superoxide dismutase (SOD) and heme oxygenase I (HO-1), in addition to heat shock protein 70 employed to quantify the degree of DNA damage. (Hsp 70) and ferritin following acute irradiation with UVA I, UVA I 1 II, and solar simulating We propose here an alternative method for DNA damage quantification that is based on measuring light. Analysis of the content of these biomarkers in human skin after acute irradiation was of DNA loss from the nucleus. The cells (HaCaT line or human peripheral lymphocytes) are performed by immunohistochemistry on biopsies from previously non-sun exposed sites of prepared and electrophoresed on microscope slides, as in the classic comet assay. DNA is stained individuals with skin type II-III. In general we have found that their induction or depletion seems with propidium iodie, and fluorescence is measured by laser scanning cytometry (LSC) directly to be dependent on cell type, wavelength specificity and UV dose. The distribution of the first on microscope slides. In control, untreated cells a normal DNA histogram with low CV (,5%) three of these proteins showed a uniform presence throughout the epidermis and ferritin was was obtained with easily discernible G0/G1, S, and G2/M subpopulations. After induction of restricted to the basal keratinocytes of each volunteer before irradiation although heterogeneity DNA damage by UVA radiation, a sub-G1 peak appeared on the DNA histogram. By re-scanning was marked. Following acute UVA I (340-400 nm) irradiation with a dose of 1 or 2 MED a and digital imaging of the cells in the sub-G1 fraction we confirmed that they represented nuclei considerable dose-dependent decrease in antibody staining intensity was seen for SOD, HO-1, containing damaged DNA (''comets''). The fluorescence integral of the cells in the sub-G1 fraction and Hsp 70 whereas ferritin was shown to increase or diffuse into supra-basal keratinocytes. The correlated inversely with the tail moment (a measure of DNA content in the tail). Thus, LSC is same responses concerning the content of SOD, Hsp 70 and ferritin occurred, but to a lesser a method for objective and fully automated DNA damage analysis. LSC enables precise extent, with UVA I 1 II and solar simulating radiation, whereas HO-1 was nearly unaffected by quantification of the degree of damage, the proportion of damaged cells and correlating the degree these two wavebands. It is obvious that the pro-antioxidant balance can be overwhelmed by acute of damage with the position in cell cycle. photo-oxidative stress and this is of importance to determine how these reactions can be avoided in order to provide protection against subsequent oxidative stress

Protection against pyrimidine dimers, p53, and 8-hydroxy-2'-deoxyguanosine expression in ultraviolet-irradiated human skin by sunscreens: difference between UVB + UVA and UVB alone sunscreens

As DNA damage induced by ultraviolet radiation plays an essential role in skin cancer induction, we pursued the measure of several DNA lesions induced by ultraviolet radiation in human skin for determining the efficacy of different topical photoprotectors. Non-exposed skin (buttocks from 20 individuals) was exposed to 10 doses of ultraviolet, which corresponded to three to four minimal erythema doses of solar-simulating radiation, and biopsies were taken at 24 h within the half and one minimal erythema dose sites and a nonirradiated, adjacent control area. We report that even suberythemal doses of ultraviolet radiation are capable of inducing substantial DNA damage, namely pyrimidine dimers, p53 induction, and the DNA base-modified product generated by oxidative stress, 8-hydroxy-2'-deoxyguanosine. All three lesions are induced in a dose-dependent manner. An additional eight individuals were treated with either ultraviolet B or ultraviolet B + ultraviolet A sunblock (sun protection factor 15) and exposed to 71/2 and 15 times the minimal erythema dose on each individual, with biopsies taken at 24 h post-ultraviolet. Pyrimidine dimer and p53 expression were rarely seen in nonirradiated skin but occasional staining was seen in all normal skin for 8-hydroxy-2'-deoxyguanosine. Applications of sunscreens to human skin before irradiation were shown to attenuate erythema but did not completely eliminate all three types of cellular damage when tested up to their sun protection factor 15. Furthermore, ultraviolet B + ultraviolet A sunscreens were less efficient than the ultraviolet B alone formulation for protection against all three lesions. These results suggest that DNA damage assessed in vivo by immunohistochemistry provides a very sensitive endpoint for determining the efficacy or photosensitivity of possible different protective measures in human skin

Use of sunscreens in families living in Switzerland.

BACKGROUND: The hazards due to sun exposure are well known. Many recent studies have emphasized the protection against the harmful effects of the sun by the use of sunscreens and, moreover, by staying in the shade and wearing long-sleeved shirts, hats and sunglasses. Switzerland has one of the highest rates of skin cancer induction in Europe and the incidence of melanoma in Switzerland is constantly increasing with an incidence of 10-12/100,000 inhabitants/year. Interestingly, some studies have evoked the possibility that sunscreen use can increase the risk of melanoma by increasing overall sun exposure. OBJECTIVE AND METHODS: In this context, the aim of our study was to estimate the amount of sun exposure of children, and their parents, living in Switzerland and to give a description of how they protect themselves against sun irradiation. Questionnaires were provided to pediatricians in every state (canton) in Switzerland and were given to families coming for consultation. RESULTS: A total of 328 forms including 1,285 individuals were returned from most of the cantons in Switzerland. The majority of the Swiss families had 2 children under 16 years of age with middle-aged parents (30-45 years) and a central European skin type (light skin of type II-III, brown or blue eyes, and brown to blond hair). An important sun exposure was noted even though the population seems to be conscious of the associated dangers. Sunscreens were the first-line defense against sun exposure with clothing and shielding oneself from the sun not being highly used. Moreover, sunscreens tended to be misused with most people applying them at the beach or swimming pool (instead of 15 min before exposure) and few applications throughout the day. CONCLUSIONS: Prevention should imperatively be emphasized for lower overall sun exposure as sunscreens are primarily used at the beach and not in routine daily exposure. In addition, it is agreed that prevention campaigns would be better directed towards children because up to 80% of detrimental sun exposure occurs during childhood