이동 통신 기술이 발달함에 따라 통신 기기간의 메시지 교환이 가능한 서비스가 생겨나고, 그 사용 횟수가 폭발적으로 늘고 있다. 기기간의 통신을 위해서는 통신 기기간의 서비스 구성원이라는 인증이 선행되어야 한다. 하지만, 기존 인증 기술은 Trusted party와 같은 제 삼자와의 통신이 수반되는데, 이로 인하여 대역폭이 낭비되거나, 기지국 범위 밖의 이동 통신 기기는 기기간 통신에 참여할 수 없다는 문제점이 발생할 수 있다.BR 본 논문에서는 제 삼자의 개입이 없는 새로운 이동 통신 기기간 인증 기법을 소개할 것이다. 제안된 기술에 대하여, 서비스의 가입 여부 및 서비스 가입 시간을 모두 검증해야 하므로, 이를 가능하게 하는 새로운 영지식 증명 기법을 개발하여 적용할 것이다. 또한, 이 영지식 증명 기법은 인증정보를 암호화된 그대로 검증하기 때문에 증명 하고자 하는 기기의 프라이버시가 보장이 되며, 질의-응답 방식을 사용하기 때문에 다른 기기의 인증 메시지를 재사용하는 공격으로부터 보호할 수 있다.
Jannik Dreier, Guillaume Dumas, Hugo Jonker, Pascal Lafourcade
An electronic auction protocol will only be used by those who trust that it operates correctly. Therefore, e-auction protocols must be verifiable: seller, buyer and losing bidders must all be able to determine that the result was correct. We pose that the importance of verifiability for e-auctions necessitates a formal analysis. Consequently, in the first part of the talk, we identify notions of verifiability for each stakeholder. We formalize these and then use the developed framework to study the verifiability of several examples. We provide an analysis of the protocol by Sako in the applied pi-calculus with help of ProVerif, finding it to be correct. Additionally we identify issues with the protocols due to Curtis et al. and Brandt. In the second part, we will analyze the protocol by Brandt in more detail. We show first that this protocol – when using malleable interactive zero-knowledge proofs – is vulnerable to attacks by dishonest bidders. Such bidders can manipulate the publicly available data in a way that allows the seller to deduce all participants’ bids. Additionally we discuss attacks on non-repudiation, fairness and the privacy of individual bidders exploiting authentication problems.
We're going to start by beating a retreat from QuantumLand, back onto the safe territory of computational complexity. In particular, we're going to see how, in the 1980s and 1990s, computational complexity theory reinvented the millennia-old concept of mathematical proof – making it probabilistic, interactive, and cryptographic. But then, having fashioned our new pruning-hooks (proving-hooks?), we're going to return to QuantumLand and reap the harvest. In particular, I’ll show you why, if you could see the entire trajectory of a hidden variable, then you could efficiently solve any problem that admits a “statistical zero-knowledge proof protocol,” including problems like Graph Isomorphism for which no efficient quantum algorithm is yet known. What is a proof? Historically, mathematicians have had two very different notions of “proof.” The first is that a proof is something that induces in the audience (or at least the prover!) an intuitive sense of certainty that the result is correct. In this view, a proof is an inner transformative experience – a way for your soul to make contact with the eternal verities of Platonic heaven.
Demonstrable data retention (DDR) is a technique which certain the integrity of data in storage outsourcing. In this paper we propose an efficient DDR protocol that prevent attacker in gaining information from multiple cloud storage node. Our technique is for distributed cloud storage and support the scalability of services and data migration. This technique Cooperative store and maintain the client’s data on multi cloud storage. To insure the security of our technique we use zero-knowledge proof system, which satisfies zero-knowledge properties, knowledge soundness and completeness. We present a Cooperative DDR (CDDR) protocol based on hash index hierarchy and homomorphic verification response. In order to optimize the performance of our technique we use a novel technique for selecting optimal parameter values to reduce the storage overhead and computation costs of client for service providers. Keyword: Demonstrable Data Retention, homomorphic, zero knowledge, storage outsourcing, multiple cloud, Cooperative, data Retention.
Henry‐York Steiner, Claire Halpin, Joseph M. Jez, John Kough · 8 authors
Plant breeding has a long history of developing varieties with desirable traits in response to the needs of both growers and consumers. Although the bases for most of these traits are not known genetically or biochemically, conventional breeding combines these multiple traits to create new hybrids and stable varieties that are safe and not generally subject to safety assessment. With the advent of genetic engineering, a tool for incorporating additional traits has become available to plant breeders. The safe application of genetic engineering to food and feed crops is widely acknowledged as a useful tool in addressing global agricultural challenges, including population growth and climate change. As used here, the term genetically engineered (GE) stack refers to a plant in which two or more transgenic events (i.e. single-locus insertions) that have been separately assessed for safety have been combined by conventional breeding (Table I). In recent years, increasing numbers of GE stacks have been planted, the first of which offered combinations of insect and herbicide tolerance genes to combat a wider range of pests and weeds than covered by the single events (Que et al., 2010; James, 2011). Two main questions arise when considering the food and feed safety of GE stacks: (1) does incorporation of more than one event increase genomic instability, and (2) can potential interactions between the products of the combined events impact safety? A related paper considered the stacking of events in light of the plasticity of plant genomes and concluded that enhanced genetic instability from a transgene or from common sequences in two or more transgenes is remote (Weber et al., 2012). This paper addresses the second question of potential interactions between events and their products combined in a stack, reviews the basic principles of plant breeding and its history of safe use, and extends these principles to the feed and food safety of events combined through the same processes used in conventional breeding of non-GE plants. Potential environmental impacts are outside the scope of food and feed safety. The new varieties developed through modern biotechnology are identified by a number of terms, including genetically modified (GM), GE, transgenic, biotech, recombinant, and plants with novel traits. The term GE is used here as defined by Weber et al. (2012). For these reasons, the term GE is preferred over the term GM. There are many methods encompassed by the general term conventional breeding, including wide crosses and selection, mutagenesis, and somaclonal variation. When the parental species are not closely related, the cross may be facilitated by embryo rescue, somatic hybridization, or x-ray-induced translocations. The term interaction, as used in this paper, refers to an effect, such as a new or modified metabolic activity, resulting from a combination of transgenes. An example of an interaction is protein-protein binding resulting in a novel effect only seen with a specific combination of proteins, for instance, protein cofactors or subunits for the same enzymatic complex or subcellular metabolic binding reaction. Examples can also include a direct metabolic interaction that would inhibit or activate components in a metabolic pathway shared by the proteins newly combined in the GE stack or components of independent metabolic pathways that indirectly interact by way of a common metabolite. Thus, interactions within GE stacks generally refer to the metabolic or physiochemical interplay between the products of transgenes or between the product of one transgene and the second gene, rather than between the two genes themselves. Conventional breeding has a long history of safe use despite the presence of antinutritional factors, toxins, and allergens in crops. There is no evidence that a random genomic change in a crop has resulted in a novel food or feed safety issue (Weber et al., 2012). Historically, humans have selected desirable traits that arise from the crop’s genomic plasticity and interactions between genes. As breeding became more advanced, new methods were applied to select and combine desired traits, which also modify the genome as a consequence. Plants produce a multitude of metabolites that provide various functions. These include signaling activities in response to environmental stress or attack from plant pathogens and pests. Some metabolites have beneficial effects, while others are toxic when fed at high levels to sensitive animal species (Ames et al., 1990). Although particular metabolites tend to be specific to some plant families, there are metabolites of concern in a number of common food and feed crops, including apple (Malus domestica), apricot (Prunus armeniaca), Brassica spp., celery (Apium graveolens), cucumber (Cucumis sativus), lima bean (Phaseolus lunatus), potato (Solanum tuberosum), cherry (Prunus avium or Prunus cerasus), and sorghum (Sorghum bicolor; Beier, 1990; D’Mello et al., 1991; Stewart, 2009). Examples of such metabolites include alkaloids, lectins, glucosinolates, furanocoumarins, cyanoglucosides, nicotines, and phytoestrogens. Some of these can impart bitter taste, and conventional breeding has repeatedly reduced their levels to acceptable concentrations (Drewnowski and Gomez-Carneros, 2000). There are few documented cases in which breeding led to an unacceptable level of a metabolite. Following reports of bitter taste, the potato var Lenape, which was developed from a cross of potato to a wild Solanum species, was found to contain doubled levels of glycoalkaloids (Anonymous, 1970). The only other documented incident of unacceptable metabolite levels associated with plant breeding is that of a disease-resistant celery containing elevated levels of furanocoumarins, which may have contributed to dermatitis among grocery store personnel (Berkley et al., 1986; Seligman et al., 1987). The environment can also play a role in impacting furanocoumarin levels; a later report of dermatitis among celery harvesters in southern Israel was attributed to delayed harvest, and hence more mature plants being handled, due to the Gulf War (Finkelstein et al., 1994). Similarly, reports of toxic squash (Rymal et al., 1984) and zucchini (Herrington, 1983) appear to have been limited to individual plants within otherwise widely grown varieties, suggesting the higher toxin levels were due to environmental conditions or mutations. Despite these few instances, these crops remain safe for food or feed use. Although breeders recombine tens of thousands of genes with virtually infinite potential interactions, to our knowledge, there has never been a report of a completely novel toxin or allergen appearing in a genus as a result of conventional breeding. The development of an interspecific somatic hybrid of potato (S. tuberosum and Solanum brevidens) containing demissidine (Laurila et al., 1996) has often been cited as proof that novel toxins can arise during breeding. In fact, Jadhav et al. (1981) documented the presence of demissidine in potato more than a decade before it was found in the hybrid. To guard against unexpected increases in levels of known toxins, breeders have instituted screens for these compounds in new varieties before they are released. Examples include cotton (Gossypium hirsutum), potato, lima bean, and canola (Brassica napus), because they contain known compounds that can impact food or feed safety. However, breeders cannot and do not screen for de novo compounds. Hundreds of thousands of varieties have been bred without the emergence of any novel allergens or toxins, indicating that the likelihood of such events is virtually zero (Stevens, 1974). Improved crop varieties produced by conventional breeding are the cornerstone of food production in the world today. Thus, the ways in which risks are managed during conventional breeding of non-GE crops, which includes testing for any known concerns, sets the framework for the food and feed safety assessment of GE stacks. As is the case for any other new variety or hybrid, GE stacks are only considered for market introduction if the combined traits have met the intended thresholds for efficacy and stability. Newly developed GE events undergo rigorous safety assessments by the developer and by regulatory agencies prior to their commercial release. These assessments evaluate the impact of both intended and potential unintended effects on food, feed, and other aspects of crop safety. Assessment criteria and objectives are based on national priorities and on international standards, such as those of the Joint Food Standards Program of the Food and Agriculture Organization of the United Nations and the World Health Organization (FAO/WHO, 1996, 2000), as well as Codex Alimentarius Commission recommendations for conducting food safety assessments of GE crops (Codex Alimentarius Commission, 2009). Codex principles and guidance are widely followed for single events. The key components of GE crop safety assessments include (1) descriptive information on the transgenes and inserted recombinant DNA; (2) detailed characterization of the DNA insert relative to the native genome, in planta concentration and stability of the products of the transgene(s), analysis of plant phenotype, and descriptive information such as efficacy, mechanism or mode of action of the new trait(s), and crop management considerations; (3) evaluation of the safety of the products of the transgene(s) in the context of common commercial crop practices and uses; and (4) comparative safety assessment for suitability as food and/or feed. Such analyses might include a determination of expression levels of known allergens and toxins, and overall composition, including nutrients, antinutrients, and selected metabolites for that crop (FAO/WHO, 1996, 2000; Cellini et al., 2004; Codex Alimentarius Commission, 2009; Thomas et al., 2009). Assessments of nutrient composition and agronomic characteristics, as well as an assessment of potential allergenicity and toxicity, are widely recognized as significant components of GE crop safety assessments (FAO/WHO, 1996, 2000; Metcalfe et al., 1996; Kuiper et al., 2001; Cellini et al., 2004; Delaney et al., 2008; Codex Alimentarius Commission, 2009; Thomas et al., 2009). Differences between the GE crop and appropriate comparators are evaluated in terms of biological relevance, magnitude of difference, exposure, and impact on food or feed safety to determine the need for further investigation. The comparators may include a closely related non-GE variety and other commercial GE and non-GE varieties. The International Life Sciences Institute’s Crop Composition Database (http://www.cropcomposition.org; International Life Sciences Institute, 2006) may also serve as a reference for comparison for some crops (Ridley et al., 2004). These holistic analyses also take into account interactions of the transgenes with endogenous genes and their products. Agriculturally important plants express approximately 25,000 to 50,000 genes at any given time. The safety assessment evaluates the GE crop phenotype, which includes interactions between the event and the host genome that may impact safety. Once the safety assessment is completed, conventional breeding is used to incorporate the event into different genetic backgrounds, without undergoing additional assessment. The developer of the resulting food and feed products is, however, responsible for the safety of those products and for meeting all relevant statutory and regulatory requirements, as is the case for all foods and feeds. Even within a single genus having species that differ in ploidy level, the number of genes within a plant can vary. For example, some 400 genes are not common in the historically important maize (Zea mays) inbreds B73 and Mo17; each of these genes is found in B73 but not in Mo17 or vice versa (Springer et al., 2009; Lai et al., 2010). Similarly, of the approximately 46,000 of genes in soybean (Glycine max), 856 genes were present in some but not all of the soybean genotypes tested (Lam et al., 2010). Of the two potato genotypes with sequenced genomes, 275 genes are found in only one or the other et al., 2011). Thus, different non-GE genotypes in novel combinations in novel interactions, but no safety have been this of novel interactions is to be by the stacking of transgenes. Despite the genetic in crop most regulatory agencies do not new non-GE varieties developed by conventional breeding there is a known safety concern or associated with the new variety of and Food and of the Food on Organization and Health Food This is based on the that conventional breeding is as As defined conventional breeding traits from genetic interactions of genes and their products are in breeding to produce new crop varieties. In plant breeders through crosses that combine different different et al., in some different genes et al., 2011). However, the are from and among have the that might be in et al., et al., et al., and et al., these that thousands of interactions are when genomes are combined by breeding. these interactions have led to which has been selected by plant breeders to desirable traits et al., 2010). these interactions of genes have a long history of food and feed the bases of these interactions are the information to a specific interactions between endogenous genes in conventional breeding do not to direct As information and methods to complex become it may be to such when GE events by breeding, it is to interactions between the events within the GE stack in a and can be developed for those specific with the historically used in conventional breeding to new traits into crop such as wide hybridization, genetic engineering a direct of a DNA that a specific into a the methods by which individual events are combined to produce a GE stack are to those used to combine multiple traits in new conventional crop varieties and two GE does not any in the genome is by two non-GE (Weber et al., the safety assessments for the individual events are to the GE The only safety question that the individual event assessments do not is that of interactions between the products of the combined transgenes. Two questions on the potential of interactions between the events in a particular GE (1) does a potential interaction between the products in each single event in the GE stack, and (2) would the potential interaction result in a food and feed safety In other are there of engineered and any interactions between these that might create A safety assessment of a crop produced by conventional breeding of parental into a GE stack can incorporate a that addresses interactions of the transgene products are and if they might food and feed safety. A for this is in which the overall development of a for potential interactions, with the and of the crop of the single and the prior food and feed safety assessments on the products. The question in the assessment is it or that the transgene expression products of the single events interact in the The only of interaction different in a GE stack from that seen in conventional breeding of non-GE plants is a metabolic or physiochemical interaction from the combination of the transgene products. other interactions are to those in bred non-GE plants. A for the safety assessment of a food and feed crop with a GE stack produced by conventional breeding of two or more events. if it is that novel interactions in the GE stack, can the interaction impact the safety of the GE This is a if there is no for a potential interaction, or if a potential interaction that does not the prior safety assessments on the individual events are for the GE a can be developed for an interaction that may food or feed further questions on the and of the A number of relevant be considered to a the presence and of interactions to a potential safety Although the of questions on the transgenes in the GE stack, these questions be to food and feed safety. Examples of questions that can be to a are in these questions on direct product interactions, expression and metabolic products of the transgenes. The same to genes expression of other such as transgenic and to the of endogenous genes. these of transgenes may expression of of other the and of by each transgene would be documented before each single event is used in be from the of the specific effects of each many products of conventional breeding of non-GE plants on known to have been from in or from et al., 2010). To the that conventional breeding has plants with associated with or in factors, there is no that metabolite have resulted in any novel to food or feed safety. In or there has not been the of novel toxins related to these metabolic of the specific of transgenes being assessment of the combined information from the single events can or a for The need for further safety assessment of the potential interaction is evaluated on a Examples of the can be used to at safety assessment are An interaction between the products of transgenes is not the single events combined in a GE stack proteins that are not known to interact or that on different metabolic pathways with no known or common metabolite between GE stacks that combine insect and herbicide tolerance are an In these crops, insect is by one or more genes toxin proteins from that are not native to but have a general history of safe use in the food as in conventional and and in GE crops. The proteins no known metabolic in plants and are in the or to tolerance is by a that an of a or that a that the of the herbicide For a herbicide tolerance stack, is there a that an interaction between these events The GE stack does not create a new The herbicide tolerance may or may not serve a metabolic in the and insect As herbicide tolerance may be engineered to be and in the or both and the protein herbicide tolerance be found in the same of the two transgenic traits the of interaction in the GE however, these proteins are not related, are not in the same metabolic and no common there is no biological pathway in which these products would or indirectly there is no or for the interaction of these proteins or their products in the GE stack that the need for a new safety evaluation The same to the stacking of transgenic with other transgenes in crops with events that have a safety assessment. the transgenes are not in the same or their products are not to the same there would be no new food or feed safety if the transgenic event the of endogenous there is no for a food or feed safety on an of the of some event combinations may have the potential to produce products that at For example, if individual events produce within metabolic pathways or produce that can for the same in a GE stack, a potential for interaction to the number of interactions, there are only a of direct interactions between metabolic and metabolic which are as through a a potential interaction does not that food or feed safety would be a of metabolites in plant pathways have been to have a role other than as in plant et al., 2000). An example a potential interaction within a pathway that does not impact food or feed safety can be found in the A in is the for and James, The product of the is used for Plant are of two subunits and two The two subunits are by different genes. In a GE stack, one event would an engineered of of higher levels of and the second event would an engineered of also of higher levels of In both single the level of is due to an level of from the would be in these traits to for an effect on In this example, the two genes would be for their direct genes expression and the proteins are in the same metabolic pathway and the same enzymatic interaction between the transgenes in these events is for the intended effect of further in a GE In this the GE stack does not a new pathway or metabolites only and effects are there is no potential impact on food or feed safety. is to a safety issue from a GE example which are produced plant metabolites in plant can be into and become toxic by by a and they in the plant response to from pests and pathogens et al., The is in the the is in the or In some the and its are in but to the of and no toxin is present in However, from insect and of enzymatic of the in the a toxic to the In this event the level of a particular that is present in the plant at resulting in a variety with to pests and Although event the level of this particular the is if found within the range of levels in this would no food or feed safety during the safety assessment of event which is also in a variety with a with enhanced that is to a The of this transgene into a host plant with levels of the particular of this no because the inserted the for toxin The safety assessment of each individual event would be to include an analysis of the safety of the event various environmental the of that enzymatic of the in the to produce a toxic would have been evaluated during the safety assessment of the individual events. However, for the of the combination of these two it is that this be more closely in the event than been with the individual events In such an additional assessment of the GE stack would be In over a of plant breeding, there are no known de novo effects from the breeding which has conventional plant breeding with a history of safety for food and feed. effects have have been can be between endogenous genes in a conventional breeding and transgenes by conventional breeding The between the endogenous genes combined conventional breeding and transgenes combined through conventional breeding is the of the transgenes and their products. This the development of food and feed safety. A safety assessment for a food or feed crop produced by conventional breeding of GE events first the likelihood of interactions if they do they might safety. the events are to no additional assessment be to a safety determination for the GE stack, because each individual event has independent safety When interactions are to the effects can be based on and safety assessment of the individual parental events. When there is a biological to an interaction, the of the interactions be evaluated to determine if there be an impact on food or feed safety. there is no impact of the interaction on food or feed no additional testing be to the GE if the identified interaction be to impact food or feed the GE stack would a food and feed on the specific interaction The need for such a further assessment and the used be on a on the specific interaction identified and into account the Codex Alimentarius principles for safety assessment (Codex Alimentarius Commission, 2009). International Life Sciences International Food and Plant and and and for and during the The also International Life Sciences and for their in this to also the of and in the of this The and would also to the for in the and for many and de de and of Standards Commission on of of of of Food and of and of of of Agriculture and and Plant Food and of and and genetically engineered genetically modified
Alcohol is the drug of choice among youth, with 12% of 8th-graders, 22% of 10th-graders, and 29% of 12th-graders reporting heavy episodic drinking. Although prevalence rates are at historic lows, alcohol use continues to be widespread among adolescents, and pediatricians must screen for underage and family alcohol use in health assessment visits.After completing this article, readers should be able to:National surveys make it clear that the use of alcohol among adolescents is both widespread and harmful. By the 12th grade, close to three-quarters of adolescents in high school report ever having an alcoholic drink, and more than one-quarter report having their first drink before age 13 years. Data from Monitoring the Future, an annual survey of youth in the United States, show that 71% of high school seniors reported some experience with alcohol in the past; 41% reported use in the last 30 days and, of great concern, 3% reported daily use. More than one-half (58%) of 10th-graders and more than one-third (36%) of 8th-graders report having consumed alcohol at some point in their lives, and more than one-third of 10th-graders (37%) and one of six 8th-graders (16%) report having been drunk in the past. (1) The good news is that the use of alcohol by teens, as well as the use of many of the illicit drugs, has declined over the past decade. The bad news is that, although these declines are encouraging, alcohol remains the drug of choice among youth.The pattern of alcohol use that is exhibited by many adolescents is one of drinking too much and at too early an age, thereby creating problems for themselves, for people around them, and for society as a whole. Underage drinking is a leading public health problem in this country. Underage drinkers consume, on average, four to five drinks per occasion approximately six times per month. By comparison, older adult drinkers, ages 26 and older, consume, on average, two to three drinks per occasion approximately nine times per month. A particularly worrisome trend is the high prevalence of heavy episodic or binge drinking in adolescents, which is defined often as five or more drinks in a row in a single episode. Monitoring the Future data show that 12% of 8th-graders, 22% of 10th-graders, and 29% of 12th-graders report engaging in heavy episodic drinking.Studies find that drinking alcohol often starts at very young ages. Moreover, studies indicate that the younger children and adolescents are when they begin to drink, the more likely they are to engage in behaviors that can harm themselves and others. Those who start to drink before age 13 years, for example, are nine times more likely to binge drink frequently as high school students than those who begin drinking later. Data from recent surveys show that approximately 10% of 9- to 10-year-olds have already started drinking; nearly one third of youth begin drinking before age 13, and more than one in four 14-year-olds report drinking within the past year. (2)(3)A number of studies show that the early onset of alcohol use, as well as the escalation of drinking in adolescence, are risk factors for the development of alcohol-related problems in adulthood. Initiating alcohol use earlier in adolescence or in childhood is a marker for later problems, including heavier use of alcohol and other drugs. Individuals who report initiation of alcohol use before age 15 years were four times more likely to meet criteria for alcohol dependence and two times more likely to meet criteria for alcohol abuse as those individuals who began drinking after age 21 years. (4)The consequences of underage drinking include a range of physical, academic, and social problems. Perhaps most frightening is the fact that alcohol is the leading contributor to morbidity and mortality in youth. Alcohol use is the leading contributor to death due to injuries, the primary cause of death in individuals younger than 21 years of age. Annually, 5,000 youth die of alcohol-related injuries that involve underage drinking. This includes injuries sustained in motor vehicle crashes (∼1,900), homicides (∼1,600), and suicides (∼300), as well as unintentional injuries not related to motor vehicle crashes. Among studies of adolescent trauma victims, alcohol is reported in 32% to 45% of hospital admissions. The association between alcohol use and violent behavior is well documented. Numerous studies of adolescents report that alcohol use is linked to both violent behavior and to violence-related injuries. (5)(6)Other harmful behaviors and negative consequences frequently related to excessive drinking among adolescents are high-risk sexual behaviors (unplanned and unprotected intercourse); sexual misconduct, including rape; and assaults. Having multiple sexual partners, failing to use condoms, and performing other high-risk sexual behaviors have been associated with alcohol use in adolescents. Furthermore, alcohol use by the offender, victim, or both has been linked to sexual assault, including date rape.As youth move from adolescence to young adulthood, they encounter dramatic physical, emotional, and lifestyle changes. Developmental transitions, such as puberty and increasing independence, have been associated with alcohol use. Because drinking is so widespread among adolescents, simply being an adolescent may be a key risk factor for initiation of alcohol use, as well as for drinking dangerously.Data from imaging studies show that the brain continues developing well into the twenties, during which time it continues to establish important communication connections and further refines its function. Many believe that this lengthy developmental period may help to explain some of the behaviors characteristic of adolescence, such as the propensity to seek out new and potentially dangerous situations. For some adolescents, thrill-seeking includes experimenting with alcohol use. Developmental changes also may offer a possible physiologic explanation for why teens act so impulsively, often not recognizing that their actions—such as drinking—have consequences.How adolescents view alcohol and its effects also influences their drinking behavior, including whether they begin to drink and how much. An adolescent who expects drinking to be a pleasurable experience is more likely to drink than one who does not. Beliefs about alcohol are established very early in life, even before entering elementary school. Before age 9 years, children generally view alcohol negatively and see drinking as bad and associated with adverse effects. By approximately age 13 years, however, their expectancies shift, becoming more positive. Accordingly, adolescents who drink the most also place the greatest emphasis on the positive and arousing effects of alcohol.Differences between the adult brain and the brain of the maturing adolescent may explain why many young drinkers are able to consume much larger amounts of alcohol than adults before experiencing the negative consequences of drinking, such as drowsiness, lack of coordination, and withdrawal or hangover effects. This unusual tolerance may help to explain the high rates of binge drinking among many adolescents and young adults. At the same time, adolescents appear to be particularly sensitive to the positive effects of drinking, such as feeling more at ease in social situations, and young people may drink more than adults because of these positive social experiences.Children who begin to drink at a very early age (before age 12 years) often share similar personality characteristics that may make them more likely to start drinking. Young people who are disruptive, hyperactive, and aggressive—often referred to as having conduct problems or being antisocial—as well as those who are depressed, withdrawn, or anxious, may be at greatest risk for alcohol problems. Other behavior problems associated with alcohol use include rebelliousness, difficulty avoiding harm or harmful situations, and a host of other traits seen in young people who act out without regard for rules or the feelings of others (ie, disinhibition).Some of the behavioral and physiologic factors that converge to increase or decrease a person’s risk for alcohol problems, including tolerance to alcohol’s effects, may be linked directly to genetic factors. For example, being a child of an alcoholic or having several alcoholic family members places a person at greater risk for alcohol problems. Children of alcoholics (COAs) are between 4 and 10 times more likely to become alcoholics themselves than are children who have no close relatives with alcoholism. (7) COAs also are more likely to begin drinking at a young age and to progress to drinking problems more quickly.Research shows that COAs may have subtle brain differences that could be markers for developing later alcohol problems. For example, by the use of newer brain-imaging techniques, scientists have found that COAs have a distinctive feature in one brainwave pattern (called a P300 response) that could be a marker for later alcoholism risk. (8) Some studies suggest that these brain differences may be particularly evident in people who also have certain behavioral traits, such as signs of conduct disorder, antisocial personality disorder, sensation-seeking, or poor impulse control. (9)Drinking and alcohol-related problem behavior reflect a complex interplay between inherited and social-environmental factors, the implications of which are only beginning to be explored in adolescents. And although even more is understood about the role and contribution of genetics, this knowledge still does not tell the entire story.Social and environmental factors, such as the influence of parents and peers, also play a role in alcohol use. For example, parents who drink more and who view drinking favorably may have children who drink more. Other influences, such as the impact of the media, have been examined and are felt to play an important role. Today, alcohol is widely available and aggressively promoted through television, radio, billboards, and the Internet.Although the severe health problems associated with harmful alcohol use are not as common in adolescents as they are in adults, studies show that adolescents who drink heavily may put themselves at risk for a range of health problems.Chronic heavy drinking during adolescence and into young adulthood appears to be associated with detrimental effects on brain development, brain functioning, and neuropsychological performance. Recent evidence suggests that heavy drinking during adolescence is associated with poorer neurocognitive functioning during the young adult years and is associated particularly with impairment of attention and visuospatial skills. (10)Brain imaging and studies of event-related potentials have demonstrated subtle but significant abnormalities in brain structure and function. In a recent study, researchers used magnetic resonance imaging to determine the effects of heavy drinking on the changing brain structure of teens and young adults with alcohol use disorders. Hippocampal volumes were smaller in youths with alcohol use disorders than in matched controls and correlated with the onset of alcohol use disorder and with the duration of alcohol use disorder. (11) The earlier an individual developed an alcohol use disorder and the longer the duration of the alcohol use disorder, the smaller was the volume of his or her hippocampus. (12) Other studies have looked at the effect of alcohol on the structure of white matter and have demonstrated that white matter integrity was reduced in the corpus callosum of youths with alcohol use disorders.Research studies indicate that a number of factors seem to influence how and to what extent alcohol affects the brain, including:Elevated liver enzymes, indicating some degree of liver damage, have been found in some adolescents who drink Young drinkers who are or liver enzymes, even with only of both and puberty is a period associated with including in the and in increase of other and factors, which are for alcohol during this period of and development (ie, before or during may the for development of and are the in the in of At the same time, they experience high rates of mortality and morbidity because of their behavior, including the use of many including adolescence is a time of risk and for many young people in some of that alcohol use. In adolescence is a period of increasing often For the social of adolescence may be by the risk for alcohol use. In this alcohol use has become with the developmental of The or problem use of alcohol affects development and is as well by developmental of problem drinking are of over drinking (ie, drinking more than or in and the of negative consequences from drinking the high-risk sexual problems, The development of is associated with heavy drinking over time, potentially as a to the pleasurable associated with drinking and heavy drinking also can to the development of physiologic by tolerance to alcohol and withdrawal between drinking is defined as the to drink greater amounts of alcohol to the same pleasurable effects that are when drinking Although frequently reported among adolescents than among adults, heavy drinking also can to alcohol withdrawal between drinking criteria for alcohol abuse and dependence are in the and of of the meet the of one of four abuse criteria must be meet a of three of dependence criteria must be In abuse is by a pattern of use by use consequences or use such use may be dependence is as a and disorder by of over use, and use as a Alcohol and and it the to and is At very high effect on is for its The of alcohol use can from a single The most common adverse effect is which is by and and may be by alcoholic is by the of and can in after only a drinks and, as the of alcohol so does the degree of of when consumed and on an can a or an of time for which the person key of or even entire alcohol is from the and and of alcohol is to and and the is in the and In the is able to about 30 or about one of consumed on an a of approximately in an adult of and in a of adult The of in is a of alcohol of is in of the of alcohol to the of is in of which in In the United States, one of A to of a of a of and a single of or amounts of of these is a drink, which of is important to be of the alcohol of a drink and consumed it is important to be of the alcohol of many and other Alcohol is often a of many and (ie, one a and a primary of alcohol and is The most important of of is to harm to the individual from severe and to the from with high alcohol is as as the and are with who have should be of is not This is particularly important because can with an risk for The risk of is more of a in younger children and particularly in those who are or a number of studies this in adolescents and adults have not found to be more common in with alcohol is however, to whether the who with alcohol has other in to because these may further the and the to The may some as of the is and In the in which is for in a most use of a and alcohol should be in who appears or Although the distinctive of alcohol may in by of is is a high between by and so that the may be used At greater than the adolescent is at risk of and greater than are associated with significant at or greater are associated with a the of appears excessive for the reported trauma or of other should be as possible of death from the alcohol is and must be the liver can amounts of alcohol from the In a who is not an in it to the of alcohol from to at a with the approximately per In may be when the is than but is because is and other drug use should be as a primary when or problems, as well as that be related to The and assessment of high-risk behaviors and risk factors are key in the early of alcohol-related problems. a of the adolescent should be an assessment of risk by risk factors and behaviors with youth and their risk and adolescence, and young adulthood is a health are of health for health and multiple for early and for adolescents by alcohol-related problems, including adolescents by as important role for their and and other early in to be that their and can influence and play a role in their it is important for the to the of the family alcohol use and to and early that are to the age and development of the adolescent and the family about alcohol and other drug use are into the family of a such may seem out of place to one with such to about that can in or can have an effect on the of may seem more and to to significant influence on adolescents and on the behaviors in which to of with alcohol or other problems is important to the of problem alcohol use among adolescents to include and family problem which often involve of and experiencing social and family as and also increase an risk of problem alcohol use. are particularly at risk parents are or or parents offer or seem of the conduct are an important likely to use alcohol or other are close to their and from their have who are of drug use, and are to with clear and conduct The parents of and feelings of and are sensitive to their for alcohol and other problems within must begin with a and about the and problems of and adolescents a from which the for can be of adolescent behavior problems, school family or changes in the are in by alcohol and other many family problems related to alcohol use are and them a and on the of a health problem or as a of problem in the may involve the adolescent directly that are and the of problem alcohol use in the can begin by a but important ever been about in family who is drinking alcohol or other This the for possible later also the adolescent and family that believe problem alcohol or other drug use is a health concern, and that are and able to The an of and on the of the high prevalence of alcohol use, many that adults be with a survey such as the or the Alcohol The is but was to alcohol The is longer but a of drinking. is a alcohol with demonstrated for primary in and The whether the has ever to on drinking; felt by about drinking; felt about drinking; an or a drink in the to the of to these is to them to members of the The is a of the used that simply the to include in can use the to a report such as a or an older example, the is a who is not alcohol or other but is about a use of the could screen for about the alcohol use by the to the child in the to on her alcohol at about her ever act about her drinking or that was ever have a drink early in the as an or more positive to the can be a positive which the for is to screen for alcohol problems in not to family alcoholism. A positive on the a greater risk for alcoholism in the family and should be by a more In a recent study, one positive on the was more sensitive than about family alcohol problems. The of the for family alcohol problems was the positive the and the negative The also with family family communication problems, and use of other than to use the in this the for greater for the adolescent encounter and for a of about or from and By the drug use for drinking, the also can be used to screen for use of other than signs and of alcohol use disorders in adolescents often are More than signs may be the of A in school or in other may become more as alcohol or other drug use with or the often become more evident as use such as in and or and or may be of problem alcohol assessment of an functioning is the most important of a for alcohol or may be to begin with a of including and family school and and and and The can to a of whether alcohol or other drug use is a cause of behavioral and to the degree of is no single screen that has been for adolescents, the which has been in adolescents, is a that has been used by many and is to use. find such as the to be because it about drinking and binge behavior, with about the consequences of drinking. A recent developed by the on Alcohol and a more and suggests that a of two one about drinking and one about the drinking The on to on positive and negative and for and help to those individuals most likely to have a problem related to alcohol or other drug use. should help to whether is a for assessment by the primary or a is to in that is an important and first to the of a but that from assessment and a is a more and lengthy to determine the extent of the and in Although the to an assessment and make an may be the time and of many primary are for and or Moreover, adolescent and other primary health can play an important role in adolescents for behavior in an to the adverse health associated with adolescent alcohol of how problem alcohol use to developmental transitions, including how individual characteristics and to these an important for and in adolescents. the past in this related to adolescents out that the many that during adolescence of for to the many of behavior of adolescents that are already The suggests that by potentially developmental can not only in of but also can the for health and adolescence and young and have five that can be used to and family members in and with to The and for begin with the that the and for within the or family the is to a of that the or the family for and to The health is to the of those individuals as well as those positive in their The this role is to great for the adolescent and or should be a of person and for the of the The and family of and for are is important to to the adolescent that person’s drinking or drug use is not their and that they be for changing they are for and can their drinking is and on the that is to the adolescent or family The role of the is than The of such is widely in is a key to an of also them in the of for when people a between they are and they to The to and attention on such with regard to the drinking In certain it may be first to the of the by the of the consequences related to alcohol which to should be to have the or a The does not seek to or by or the the adolescent and family in the of the drinking used the adolescent or family and not the the for not meet but the with a of adolescent and family in the is as not and is explored are from the adolescent or family than by the who are that they have a problem still not move is for is a of behavior in the that one can a behavior or a (ie, to a In this of be or The can be a and play an important role by the and family with and The is to the about in in a of and is the of this article, it is to in these when having a with or to adolescents and family This often adolescents and family members with on health and associated the adolescent or family for and the impact of failing to clear or the for in a and than a of for as a for to the on and and and that the adolescent or family can important of to behavior changes in adolescents and use of the of is to the of the entire in clear and and to the use of and when not the influence of and family members and the role that they play in the of
Bid validity proof and verification is an efficiency bottleneck and privacy drawback in homomorphic e‐auction. The existing bid validity proof technique is inefficient and only achieves honest‐verifier zero knowledge (ZK). In this study, an efficient proof and verification technique is proposed to guarantee bid validity in homomorphic e‐auction. The new proof technique is mainly based on hash function operations and only needs a very small number of costly public key cryptographic operations. Moreover, it can handle untrusted verifiers and achieve perfect ZK. As a result, efficiency and privacy of homomorphic e‐auction applications are significantly improved. To the best of authors’ knowledge, it proof technique is the first to handle untrusted verifiers in e‐auction applications.
In this decade, establishing structure-function relationships in human brain has become one of the most influential concepts in modern cognitive neuroscience since interactions among cerebral components are fundamental to explain cortical activities ([1]; [2]; [3]). \nIn literature such relationships have been defined in terms of structural, functional and effective connectivity. This distinction, mainly focused on the theoretic concept, is also related to the different measurement instruments and analytical tools used for acquiring and processing the data. The structural connectivity refers to a pattern of anatomical links among brain regions. Its analysis aims to characterize the architecture of complex networks underlying the cerebral functional organization. Magnetic Resonance Imaging and especially Diffusion Tensor Imaging can be used to convey information concerning the physical connection between neuronal populations. Functional/effective connectivity aims at identifying the presence and the strength of connections in terms of statistically significant dependency. The former is defined as the temporal correlation between neurophysiological events occurring in distributed neuronal groups and areas. The latter describes the causal influence that one neural system exerts over another either directly or indirectly in terms of temporal precedence and physical control ([4];[5]). Functional and effective connectivity can be estimated exploiting both Functional Magnetic Resonance Imaging (fMRI) and electrophysiological signals, such as Electroencephalography (EEG) and Magnetoencephalography (MEG), with different advantages and drawbacks, respectively. fMRI provides high spatial resolution (mm) but poor temporal precision (s) while EEG/MEG has more limited spatial resolution (cm) and higher temporal precision (ms). Because functional and effective connectivity are largely estimated over time, EEG and MEG are more suitable for calculating such connectivity. In literature several methods have been developed to characterize brain connectivity in terms of network topology, connections strength and causality, following two main approaches: the data-driven, where topology, causality and strength are all inferred from data, and the neural model-based, where the model topology is postulated from a priori knowledge and only the connections strength is estimated from the data. \n-\tData driven approach. The data driven approach includes linear, non-linear and information-based techniques. The linear ones provide a battery of indices derived by multivariate autoregressive models (MVAR) based on Granger causality principles ([6]) or MVAR frequency response ([7]). Such are Ordinary Coherence, Partial Coherence, Directed Transfer Function (DTF) and Partial Directed Coherence (PDC). These indexes measure the strength of the linear coupling between two signals; in addition DTF and PDC provide information about causal influence ([8]). \no\tAmong the non-linear techniques, phase synchronization has been shown to be very effcient in detecting interactions between oscillators. The phase locking values approach assumes that two dynamic systems may have their phases synchronized even if their amplitude are zero correlates ([9]). \no\tThe most representative information-based technique is the cross mutual information that measures the mutual dependence between two signals by quantifying the amount of information gained about one signal from measuring the other, as a function of delay between these two signals ([10]). \n-\tNeural model based approach. Representative methods are the Structural Equations Modelling (SEM) and the Dynamic Causal Modelling (DCM) ([11]; [12]). They are multivariate technique used to test hypothesis regarding the influences among interacting variables, but different concepts underlies these two methods. SEM approach assumes that neuronal dynamics are very fast in relation to signals uctuations and, hence, is based on a static neuronal model. This case, the neuronal activity has reached steady-state and changes in connectivity are led directly by changes in the covariance structure of the observed time series ([13]). On the other hand, in DCM the observed time series are modelled as a deterministic dynamical system in which external inputs causes changes in neural activity and therefore in connectivity values ([14]). \nMost approaches, like those based on Granger causality principles, have been examined in literature to quantify their ability in revealing cerebral connections ([15];[16]; [11]) but their simulation studies do not provide a comprehensive analysis because they use in silico data generated by self-referential linear methods which do not reproduce the complexity of brain. To overcome this issue, an innovative simulation approach has been developed in this work, based on a nonlinear neural mass model ([17]) totally independent of SEM and MVAR linear equation and able to address the complexity of neural networks. This no-self referential approach was exploited to generate in silico network data to be used as a benchmark, to quantitatively compare obtained results with true connections. The main objective of this work was to understand limits and advantages of MVAR indexes and SEM by exploiting the simulation study. Thus, it mainly serves as a proof-of-concept for connectivity measures under ideal conditions. Our purpose was to derive from simulation results some practical procedures in order to classify different brain states to support both cognitive research and clinical activity. First, research activity was focused to address connectivity on simulated data obtained on three regions networks characterized by different strength connections and based on different levels of non linearity. Second, a dataset, made available by Department of Medicine, University of Padova was used to explore application of these methods to real data by applying the simulation study suggestions. \nThis thesis consists of three main section. \nThe ffrst one includes Chapter 1-2-3 describing in detailed the considered connectivity measures, such are those based on Multivariate Autoregressive models and the Structural Equation Modelling, and the simulation study. The second part depicts in silico results and the application to EEG data. Finally, comments are reported in Discussion and Conclusions. \nChapter 1 explains how the connecting parameters of MVAR and SEM models are identified on EEG data and describes procedures commonly exploited to analyse connectivity. Chapter 2 reports an overview about the principal models used to generate in silico data, namely the neural mass models, and described the neural mass model exploited in this work. Finally, it characterizes network models adopted to simulate data and lists the procedure followed to generate in silico datasets. Chapter 3 summarizes the computations implemented to have more insights on our data by analysing the output of each methods. It describes the procedure used to evaluate the statistical signiffcance of each index results, such are the F-test for Granger causality index and the null distribution threshold using surrogate data for MVAR frequency indexes. Chapter 4 illustrates the results obtained with the simulation study. First, we reported the complete analysis for a representative subset of experiments, then for all datasets we showed topology and strength estimates. Chapter 6 delineates the procedure followed to study the connectivity in case of hepatic encephalopathy. Chapter 7 covers the Discussion and Conclusions. The Appendix is a parallel work aimed to understand the meaning of connectivity indexes computed via Structural Equation Modelling. By exploiting the neural mass model used to simulate cortical data, the objective is to quantify which measure its estimates represent. We demonstrated that Granger causality is a good estimator with high values both of sensitivity and specificity, while frequency indexes, DTF and PDC, are too much affected by the threshold choice and their interpretation in terms of absolute strength connection is not clear. As regard SEM, we proved the difficulty of its approach to describe just simple situations. Even if SEM is based on linear regression as well as MVAR models, it differently assumes there is no connection with past information, as if brain connectivity could describe time series relationships by the instant we observe it. Hence, it is not sufficiently robust to characterize neuronal dynamic activity. \n
Maryam Rajabzadeh Asaar, Ali Vardasbi, Mahmoud Salmasizadeh
Strong designated verifier signature (SDVS) is characterized by two properties; namely the non-transferability and the privacy of the signer's identity (PSI). Non-transferability prevents anyone else other than the designated verifier to verify the signature, while PSI prevents a third party to distinguish between two different signers. In this paper, we propose a non-delegatable SDVS which uses a trusted third party for the key generation. Our signature scheme does not use bilinear pairings which makes it suitable for the resource constraint applications. Using one-way homomorphic functions, our scheme is presented at an abstract level, the unification of which was noticed by Maurer in the context of zero knowledge proofs of knowledge in Africacrypt 2009. The security of the proposed scheme is proved in the random oracle model, provided that the homomorphism one-wayness and the gap Diffie-Hellman assumptions hold. When a Schnorr-like homomorphism is used to construct our scheme, six exponentiations are needed in the signing step and seven for the verification step. This means a meaningful gap between the performance of our scheme and that of its predecessors which use pairings in their signing and/or verification steps.
An existence theorem for a bias of the mean in the presence of data dispersion is proved. The aims are to use this theorem in experiments interpretation, probability theory, statistics, economics and management. The ultimate aims are to explain the well-known problems of utility and decision theories, such as risk aversion, the underweighting of high and the overweighting of low probabilities, the Allais paradox, etc. The results may be used to estimate preferences, choices, decisions, (ir)rational behavior at data uncertainty, noises, experimental errors in management, investment, insurance, etc.
El termino privacidad engloba un amplio campo de investigacion compuesto por diferentes areas. Esta tesis doctoral se centra en dos de ellas. La primera son las comunicaciones privadas en grupos restringidos, o secure multicast. Un grupo de participantes desea mantener comunicaciones de forma que ningun oyente externo al grupo sea capaz de interpretar la informacion transmitida. Este problema tiene diferentes aplicaciones como servicios pay-per-view en plataformas de streaming multimedia o multiconferencias privadas en el ambito empresarial e incluso militar.
La solucion estandar al problema consiste en establecer una clave de cifrado simetrico comun al grupo, llamada session key o clave de sesion, con la cual todos los participantes cifran o descifran la informacion transmitida. Sin embargo, las implicaciones practicas de esta solucion no son triviales por dos motivos: el uso de una misma clave de cifrado durante largo tiempo la hace vulnerable a ataques, y los cambios en la composicion del grupo (un fenomeno conocido como churn), de ocurrir, fuerzan a cambiar la clave despues de cada entrada o salida de participantes. Por ello es necesario refrescar la clave de sesion periodicamente, y en especial despues de cada cambio en la composicion del grupo. El capitulo 1 introduce mas formalmente estos conceptos y da al lector una vision mas amplia del problema.
Las propuestas de secure multicast existentes pueden clasificarse en tres categorias dependiendo de como realicen la renovacion de la clave de sesion: centralizadas, descentralizadas y distribuidas. En las primeras, una entidad central, el Key Server o Servidor de Claves, esta a cargo del establecimiento de nuevas claves de sesion y la distribucion a toda la red. Esta es la forma mas sencilla y popular de resolver el problema a cambio de soportar tamanos de grupo limitados. La segunda categoria, las propuestas descentralizadas, es una extension natural de la primera: para conseguir mayores tamanos de grupo los participantes se distribuyen en subgrupos disjuntos, cada uno gestionado por un Servidor de Claves secundario mediante secure multicast centralizado. Finalmente, en las propuestas distribuidas no existe una unica entidad a cargo del proceso de renovacion de claves. En su lugar, todos los participantes colaboran en la generacion del material criptografico cada vez que sea necesario. Los esquemas distribuidos ofrecen por tanto mas fiabilidad al evitar un unico punto de fallo a cambio de una escalabilidad muy limitada.
Esta tesis se enfoca hacia la categoria centralizada debido a su importancia como solucion en si misma y como pilar de construcciones descentralizadas. El capitulo 2 realiza una amplia revision del estado del arte, y el capitulo 3 presenta (i) un nuevo esquema centralizado, discute sus propiedades y pone a prueba su rendimiento. Los fundamentos matematicos del esquema se basan principalmente en el Algoritmo Extendido de Euclides, gracias al cual tambien hemos desarrollado (ii) una solucion de autenticacion para los mensajes de renovacion provenientes del Servidor de Claves, y (iii) una prueba de conocimiento cero (zero-knowledge proof) que permite a miembros legales del grupo verificar la legalidad de otros.
Los tres esquemas han sido ya objeto de criptoanalisis por parte de otros investigadores, los cuales han hallado algunas vulnerabilidades en el segundo y tercero (autenticacion de mensajes y prueba de conocimiento cero). Sin embargo, el esquema principal de secure multicast sigue siendo seguro a dia de hoy. Mencionaremos las vulnerabilidades encontradas por el criptoanalisis, asi como soluciones propuestas por otro conjunto de investigadores. Dichas soluciones no son merito del autor de esta tesis y se muestran aqui con el unico proposito de dar al lector una perspectiva completa.
La segunda parte de esta tesis se centra en computaciones distribuidas con preservacion de privacidad. En este caso, los nodos que conforman una red desean seguir la evolucion de una variable global a la que todo el mundo contribuye. Sin embargo, las contribuciones individuales hechas por cada nodo no deberian ser conocidas por los demas. Un ejemplo tipico, muy ilustrativo, es el Problema de los millonarios: dos millonarios quieren saber quien es mas rico sin revelar la cuantia de sus fortunas. Situaciones similares, especialmente aquellas que involucran un numero indeterminado de participantes y el computo de otras funciones, son utiles a la hora realizar agregacion de datos, calculo de confianza y mineria de datos, operaciones todas de creciente interes.
El problema de la preservacion de privacidad en computacion distribuida no es nuevo: existen ya un amplio numero de soluciones. Sin embargo, la mayoria de ellas es aplicable solo a un grupo reducido de participantes y no suelen ser tolerantes a fallos. El autor de esta tesis cree que esas dos caracteristicas van a cobrar mucha importancia con el tiempo debido a la popularizacion de diferentes tipos de redes. Por ejemplo, en redes peer-to-peer los nodos pueden entrar y salir de la red de forma inesperada (tal y como hemos comentado previamente para los escenarios de secure multicast), y los calculos no deberian detenerse o reiniciarse por ello. En redes de sensores (wireless sensor networks) el medio de transmision es propenso a fallos, y tambien los participantes pueden aparecer y desaparecer sin previo aviso. El capitulo 4 repasa de la literatura disponible en este campo.
En vista de la importancia de la tolerancia a fallos y al dinamismo de las redes, en el capitulo 5 hemos desarrollado un algoritmo de computo distribuido iterativo con preservacion de privacidad enfocado a redes peer-to-peer que se adapta a ese tipo de situaciones practicas. Nuestro algoritmo sigue un modelo de paso de mensajes asincrono que tolera churn y perdida o retraso de mensajes de forma natural, en oposicion a los algoritmos sincronos. Para demostrarlo, lo comparamos con una propuesta sincrona parecida tomada de la literatura. Creemos que nuestro algoritmo es el primero de este tipo.
La literatura en este campo considera dos modelos de adversario a tener en cuenta: semi-honestos y maliciosos. Los primeros analizan cualquier dato a su disposicion para obtener informacion privada de otros participantes, pero se asume que ejecutan el protocolo de forma correcta. De los segundos se espera que lleven a cabo acciones arbitrarias para obtener la informacion privada deseada, tales como enviar mensajes falsos. Nuestro algoritmo tolera adversarios semi-honestos.
A modo de resumen de lo anterior, la presente tesis (i) analiza el estado del arte en algoritmos de secure multicast centralizado, (ii) presenta una solucion de secure multicast centralizada con bajos requerimientos computacionales asi como algoritmos complementarios para la autenticacion de los mensajes de refresco y los miembros, (iii) repasa el estado del arte en computacion distribuida con preservacion de privacidad y (iv) presenta un algoritmo iterativo asincrono para computacion distribuida con preservacion de privacidad que tolera churn y fallos en el envio de mensajes.
High throughput DNA sequencing technologies have revolutionized the field of genomics.It is now possible to generate huge amounts of sequencing data at significantly lower costs and greater speed.In this study, we have utilized Illumina deep sequencing to analyze the fitness landscape of the four-helix bundle protein ROP.All possible single point mutants of the 63 amino acid protein ROP were constructed.From the library of single point mutants of ROP, variants were enriched 1,000 fold for activity by a growth selection for six rounds, which works based on ROP's role in plasmid copy number regulation.The enrichment was monitored by a cell-based screen using a GFP reporter.As a proof of principle experiment, point mutant libraries at positions 14, 30 and 43 were individually subjected to growth selection, and colony sequencing of random variants from sixth round were mostly actives as expected based on prior knowledge of these positions.Colony sequencing of rounds zero (naives) and six from the actual library enrichment yielded promising results.Illumina deep sequencing was performed on rounds zero, three, six and eight.Paired-end reads were generated with each sequence containing short barcodes at each end to reveal the round and orientation.From the data analysis, relative enrichment for variants from different rounds lets us delve into the fitness landscape of ROP.iii Dedication To my mom, dad and family
Cloud computing is one of the fastest growing segments of IT industry since the users commitments for investment and costs are in relation to usage.The goal of cloud computing is to apply traditional supercomputing or high performance computing power, normally used by military and research facilities to perform tens of trillions of computations per second, in consumer oriented applications such as social networks, financial portfolios, to deliver personalized information, to provide data storage or to power large immersive computer games. Social networks in cloud are used to reflect real world relationships that allow users to share information and form connections between one another, essentially creating dynamic Virtual Organizations. It can be used to share/store data and information within a community ranging from low level computation or storage through high level mash-ups such as photo storage. Anonymous authentication is a technique enabling users to prove the privilege without disclosing real identities. Many existing anonymous authentication protocols assume absolute trust to the cloud provider where all private keys are stored. This trust result in serious security and privacy issues in cloud provider. In the proposed work secure and efficient anonymous mutual authentication protocol using Radio Frequency Identification (RFID) technology for cloud services are implemented based on zkp technique. Zero Knowledge Proof (ZKP) is an interactive system where one party wants to prove its identity to a second party using a password but does not want the second party to learn anything about the password. A mandatory access control (MAC) mechanism is to enforce confidentiality and integrity between a large numbers of users by providing a set of standard questions within a group. Finally present experimental results and validate the acceptable performance impact of our deployment on a modern social network.
The main aim of cryptography is to provide the frameworks and solutions for information security. The fundamental weapons to protect information are interactions and private randomness. Since the breakthrough result, zero-knowledge proof system, by Goldwasser, Micali, and Rackoff in mid 80s, the cryptography community has endeavored to propose the new notions of information security and the relative solutions which more closely reflect the modern computing environment. Concurrent security first introduced by Dwork, Naor, and Sahai was suggested to capture the information security in the modern internet environment. That is, the adversary may interact with a honest parties in many concurrent executions of a protocol where the messages are scheduled in any adversarial way.Resettable security was first introduced by Canetti, Goldreich, Goldwasser, and Micali, which models the security issues in which parties have a limited source of private randomness. In other words, an adversary might interact with honest parties in many executions of a protocol while the honest parties are only allowed to use the polynomially bounded number of (hard-wired) randomness.An important question is: "How much efficient protocol can we construct to achieve the above security in terms of round complexity?" Unfortunately, it has been showed that the best possible round complexity for such protocols is poly-logarithmic in the security parameter based on black-box simulation without help of external set-up assumptions. Thus, the question is now to minimize the round complexity of protocols with a minimal set-up assumption.In this thesis, we positively answer the above question with help of set-up assumptions. Specifically, we consider two set-up assumptions, the Bare Public Key (BPK) model and the Cross-Domain (CD) model. The BPK model was first introduced by Canetti, Goldreich, Goldwasser, and Micali. In the BPK model, each party is required to register their public keys before the start of interacting with each other. The CD model is a newly proposed model in this work. In the CD model, we have domains which models key certification authorities in the real world and each party belongs to one of the domains.In the BPK model, we show a constructions of constant-round simultaneously resettable zero-knowledge argument of knowledge with a standard cryptographic assumptions. As a main building block for this result, we show a construction of constant-round simultaneously resettable witness-indistinguishable argument of knowledge.In the CD model, we show a construction of constant-round concurrently secure multi-party computation protocol with the fixed number of domains. On the other hand, we prove that if the number of domains is not fixed, such a constant-round protocol does not exist.
There is a great demand for publicly verifiable encryption in key escrow,optimistic fair exchange,publicly verifiable secret sharing and secure multiparty computation,but the current schemes are either chosen plaintext secure or chosen ciphertext secure in the random oracle model,which obviously are not secure enough to be applied in the complicated circumstances.Based on the analysis of the current schemes and application of the reality,this paper proposed a new publicly verifiable encryption scheme by combining the CS encryption scheme with the non-interactive zero knowledge proof protocol.The new scheme enabled any third party other than the sender and receiver to verify the validity of the ciphertext,but leaked no information about the message.Finally,without using the random oracle,the adaptively chosen ciphertext security of the scheme is proved in the standard model.
As a tool for cross-disciplinary collaboration, energy and emissions calculations were central as common reference point throughout the whole process studied here. Considering only the design phase, it is clear that particularly the energy account was useful in defining both the necessary amount of work and the methods of the collaborative work. One of the merits was its ability to force each participant onto neutral ground based on shared information and work requirements. The energy account served as a boundary object (Star 2010) in this way as it provided “something” around which to collaborate across disciplinary boundaries and something that could translate different disciplinary specialities into a mutually comparable success criterion: the primary energy factor. The primary energy factor was both the what and the why of this collaboration, simultaneously a process of creation and a guiding force. The effort that went into creating the energy account and collaboration in workshops, which were employed as a sort of management tool, were argued by some informants to have made the process ‘heavy on the nose’. This was largely due to design aspects and the signal effect, which was important for PH Kjørbo as a pilot project. As this was a pilot project, it has received a certain degree of special attention from all involved institutions. The participants describe the special requirements connected to this building as \n• trust in the concept,\n• broad participation in the project’s definition process,\n• trust between partners, and\n• high level decision making at the different partners’ companies to cater to an acceptable risk allocation for all parts.\nAccording to the respondents, the design process benefited much from the oversight of a dedicated process manager, a role that was served by one of the project’s senior architects. In fact, many respondents noted the exact point in time when the process manager exited the project was also the point when the project encountered problems. \nThe participants agree that “closeness” (in terms of frequent communication both face-to-face and by other means) between the central and defining actors in the project team was a key to success. Failures accrued once the distance between actors increased due to their involvement in other projects. According to respondents, one important role for a process manager in the later stages could have been as a liaison between project management levels (contractor) and subcontractors. Some problems that appeared in this phase involved the sheer disbelief shared by the subcontractors when they first became acquainted with the calculations, the functional demands, and the specifications that had resulted from the design process - a process they knew little about. This constituted a failure on behalf of the PH collaboration to translate the concept to the hired hands, which complicated the execution phase. \nContract frameworks were also mentioned as a contributing source of errors as turnkey contract frameworks dis-incentivised subcontractors from making order changes also after they were clearly deemed necessary by consulting engineers. This is not an unusual mode of contracting in the construction business from a traditional viewpoint and could perhaps prove to work better in the future as the concept matures along with the market. A greater level of detailing in the design phase is one way to address this. However, in light of the experiences gathered at PH Kjørbo, the question is whether a more collaborative framework could have been applied to allow subcontractors to identify and share in ZEB Project report 25-2015 Page 6 of 32 the risk taking with the main contractors and/or project owner - or, in fact, to take part in the social learning that occurs as actors make the project ‘their own’. One way to incentivise junior contractors to join in more time-consuming, perhaps less profitable, contract arrangements could be to highlight the skill and knowledge development benefits available for participants in such projects. This would, however, require some proof of concept to be sufficiently translated into a clear added value for\nsuppliers. At this juncture, the newly constructed Powerhouse is one such proof. In replicating elements of the Kjørbo project, it is likely that resources can be saved on design and parts of the pre-project phase. However, to avoid the amount of order changes seen in the execution of PH Kjørbo (especially for different projects), more resources must be spent on learning for junior contractors. \nFinally, the symbolic value that was characteristic of Powerhouse Kjørbo contributed to both its ability to be realised and concrete benefits for actors involved in the time after completion. Many have drawn parallels between PH Kjørbo and Tesla, implying that PH Kjørbo is for the building industry what that electric car is for the automotive industry. As many of the respondents emphasised, the building is a statement that says “it’s possible.” The goal had never been accomplished, let alone attempted, before, and success hinged on the project participants’ belief in that final statement. A radically different approach combined with an ambitious goal made that belief possible, and it was reinforced by the interdisciplinary work that was the basis of the project. This extra effort was a necessity in this project, but it might not be in the next. Some of it can most likely be implemented in other projects. However, as this report also demonstrates, picking pieces out of the success story PH Kjørbo may not yield equally impressive results because there is a connection between the pieces that is important for the whole building to succeed.\n1.2 Summary of part 2: Taking a zero emission office building in use\nThe second part of this report examined the early use phase of PH Kjørbo, which was undertaken by local actors with the tenant as well as the project team. Although it is clear that the planning and design phase and the technological solutions played important roles in the success of PH Kjørbo, the way in which the running-in period was handled contributed some crucial finishing touches to the users’ overall very positive experience with PH Kjørbo. Notwithstanding the technical calibrations themselves (which are outside the purview of this inquiry), the way user expectations were met by specific consideration of practical and cognitive aspects of the use of the building created a good use experience and not just an energy-saving machine. Great care was taken to prevent technical shortcomings from interfering with work and causing frustrations, even when it has compromised energy targets temporarily. A positive use experience was considered “elementary”, an attitude that, at least in theory, denied allowing money to become an issue in this pulling contest between energy efficiency and user experience. Challenges experienced in the running-in period overall were experienced by the tenant as lower or not above what was considered normal based on experience with previous moving processes. In PH Kjørbo the ventilation system was allowed to let temperatures drift more than in a normal building.\nHowever, this system also proved that indoor temperatures experienced as normal do not necessarily require them to stay consistently at “22.2 degrees” - in fact, a drift in temperature between 20-25 degrees was found to be perfectly acceptable by the occupants. Temperatures in the lower end of this range were considered cold by some but were manageable by providing information and handling practical and cognitive expectations - or, simply speaking, a sweater kept handy. Indoor temperatures in the top range or above, should they occur at all in the Nordic climate, are equally badly handled in most Norwegian buildings, according to the informants. Again, handling users’ expectations with care in this phase proved helpful in improving user acceptance. This same characteristic of the running-in period at PH Kjørbo was found when examining the acoustic issues posed by the extensive use of exposed concrete. Negative experiences were reported largely by ZEB Project report 25-2015 Page 7 of 32 users who were used to extremely silent conditions. Addressing the reasons for the design choices openly (thermal mass) allowed users to settle into their new surroundings. As one of the respondents noted, when viewing the experience of this particular building as a whole, the somewhat increased noise levels caused by scarce sound roofing due to a minimal ventilation system meant that the ventilation noise normally endured in other buildings was totally eliminated, but the indoor climate was still described as extremely good. The result was a sum of experiences that evidently surpassed any conventional building.\nPH Kjørbo shows that treating the user as a form of “sensor” and devoting resources to the “processing” of information from such “sensors” in the running-in period provides substantial insight into the user experience that is crucial for improving the use experience. At Kjørbo, user experiences were collected through the office link system by the office manager, who then bore witness for the users in the user forums that guided the work of the running-in team. This provided a unique data source for detecting the comfort threshold. When complaints started to come in, they could be addressed quickly - either through informing about the reasons or through actual technical fixes. According to our informants, at the time of the interviews, as issues were picked up, negotiated and solved, complaints began to disappear.
Lately,Canard et al.(CANARD S,JAMBERT A.Untraceability and profiling are not mutually exclusive [C]// TrustBus 2010:Proceedings of the 7th International Conference on Trust,Privacy and Security in Digital Business,LNCS 6264.Berlin:Springer-Verlag,2010:117-128) introduced the notion of multi-service subscription and proposed several instantiations.Unfortunately,their systems only satisfied a weaker variant of anonymity called revocable-anonymity and they were not fit for services.To this end,a revised multi-service subscription system was put forward to extending Canard et al's system.The new system achieved pay-per-use subscriptions by incorporating the anonymous payment system raised by Liu et al.(LIU J K,AU M H,SUSILO W,et al.Enhancing location privacy for electric vehicles(at the right time).[2012-08-01].http://eprint.iacr.org/2012/342).To allow users to prove in zero-knowledge that their account balance is enough for making a payment for the required access,it also utilized the Peng-Bao range proof for small ranges.Furthermore,it was constructed on several 4-round perfect zero-knowledge proofs of knowledge,which were obtained by applying a technique by Cramer et al.to the underlying Sigma-protocols.Compared with typical systems in the literature,the new solution gains advantages in terms of security.Concretely,it can be proved secure in the standard model.Moreover,it matches the strongest level of three crucial security notions,such as inseparability for spendable tokens,anonymity for users,and zero-knowledge for underlying proof systems.
One of the most fundamental goals in cryptography is to design protocols that remain secure when adversarial participants can engage in arbitrary malicious behavior. In 1986, Goldreich, Micali, and Wigderson presented a powerful paradigm for designing such protocols: their approach reduced the task of designing secure protocols to designing protocols that only guarantee security against “honest-but-curious” participants. By making use of zero-knowledge proofs, the GMW paradigm enforces honest behavior without compromising secrecy. Over the past two decades, this approach has been the dominant paradigm for cryptographic protocol design.