We present a new type system for verifying the security of reference implementations of cryptographic protocols written in a core functional programming language. The type system combines prior work on refinement types, with union, intersection, and polymorphic types, and with the novel ability to reason statically about the disjointness of types. The increased expressivity enables the analysis of important protocol classes that were previously out of scope for the type-based analyses of reference protocol implementations. In particular, our types can statically characterize: (i) more usages of asymmetric cryptography, such as signatures of private data and encryptions of authenticated data; (ii) authenticity and integrity properties achieved by showing knowledge of secret data; (iii) applications based on zero-knowledge proofs. The type system comes with a mechanized proof of correctness and an efficient type-checker.
The cloud storage offers users with infrastructure flexibility, faster deployment of applications and data, cost control, adaptation of cloud resources to real needs, improved productivity, etc. Inspite of these advantageous factors, there are several deterrents to the widespread adoption of cloud computing remain. Among them, security towards the correctness of the outsourced data and issues of privacy lead a major role. In order to avoid security risk for the outsourced data, we propose the dynamic audit services that enables integrity verification of untrusted and outsourced storages. An interactive proof system (IPS) with the zero knowledge property is introduced to provide public auditability without downloading raw data and protect privacy of the data. In the proposed system data owner stores the large number of data in cloud after e encrypting the data with private key and also send public key to third party auditor (TPA) for auditing purpose. TPA in clouds and it's maintained by CSP. An Authorized Application (AA), which holds a data owners secret key (sk) and manipulate the outsourced data and update the associated IHT stored in TPA. Finally Cloud users access the services through the AA. Our system also provides secure auditing while the data owner outsourcing the data in the cloud. And after performing auditing operations, security solutions are enhanced for the purpose of detecting malicious users with the help of Certificate Authority.
The main goal of this work is the design and analysis of passive components employing metamaterial structures and in particular the wire medium metamaterial. Although there has been a lot of research interest in the physics of such metamaterial structures, there are not many resources available describing the behaviour of classical components, such as waveguides and cavity resonators, that are formed by metamaterials. Therefore, the aforementioned widely used devices, are realized with the deployment of the "Fakirs bed of nails" and their performance is analyzed. Our motivation is to expand existing analytical models and their applications to commonly used passive electromagnetic components, with a view to explore potentially new applications. As a means of study analytical techniques together with numerical simulations and measurements were used. This thesis is structured in the following chapters. The first chapter is an introduction to the basic principles of electromagnetics and their use on the framework of metamaterials; as illustrations some state of the art applications are presented. The next chapter is a literature review covering the work that has been done in the area of our main research interest (i.e., the Fakir's bed of nails as a metamaterial). An overview of the mathematics describing its behaviour is given as well as applications of the proposed structure. Attention has been paid on the latest studies because they provide complete physical insight. Some results from this chapter are used later as background knowledge for the analysis of passive components. This chapter is intended to lay the foundations for the reader to continue reading the rest of this work without the need to look in the literature. Chapter three investigates the dispersion effects in parallel-plate waveguides with both plates being realized by the Fakir's bed of nails. This chapter serves as an example as to how the Fakir's bed of nails can be used to form components. An analytical solution describing the behaviour of the waveguide is presented and compared against full wave numerical simulations. Chapter four presents a theoretical study of the resonant behaviour of metallic nanorods. A clear analogy between the coupled rods and the split rings/split squares is shown. The decline in the resonant frequency as the gap decreases, previously described in terms of self-capacitance, is interpreted by surface plasmons coupled across the gap. Chapter five presents a new enabling technology for implementing tunable rectangular waveguide components and circuits with the use of 2D and 3D metamaterials; a holey metal surface and wire media, respectively. As proof of concepts, results for tunable rectangular waveguide filters are presented with the use of pin block inductive irises and capacitive posts. Furthermore, by adapting the traditional metal-pipe rectangular waveguide for tunability, regions of the solid metal walls are replaced by holey metasurfaces. Prototype tunable structures were measured for verification and good agreement is achieved between full-wave numerical simulations and measurements. Chapter six analyzes a radically new design of waveguide verification device, suitable for measuring instruments such as Vector Network Analyzers. The device is designed to enable its roperties to be changed, by known amounts, after the device has been connected to the system that requires verification. The performance of the device is based on introducing relative changes in the transmitted and reflected signals and so is insensitive to errors introduced by waveguide flange imperfections. This makes the technique, in principle, ideally suited for waveguide VNAs operating at millimeter- and submillimeter-wave frequencies where these flange errors can dominate the measurements. A verification device is designed, simulated and tested in WR-15 waveguide (50-75 GHz). The last part of this thesis presents a rigorous analysis of lossy spherical cavity resonators starting from first principles. The electromagnetic field inside the spherical cavity is expanded in normal waveguide modes and the eigenfrequencies of the cavity resonator are obtained analytically by enforcing the appropriate boundary conditions at the cavity wall. Unlike perturbation techniques, used when low losses are present, there are no inherent limitations in the presented analysis and, therefore, its applicability range is much broader. Exact analytical results, acting as a benchmark reference standard, are compared to those generated independently by two commercial full-wave simulation software packages (HFSS and COMSOL). When the wall transforms from being a perfect electrical conductor to free space, as its intrinsic conductivity decreases from infinity to zero, it is found that the eigenmode solvers with both software packages increasingly fail. With both software packages, all possible modeling strategies have been investigated and their associated limitations identified. Moreover, a plane-wave approximation model is proposed that accurately predicts the numerical simulation results.
The following reminiscence by Cedric Raine is the 10th autobiography in a series published in the Journal of Neuropathology and Experimental Neurology. These have been solicited from senior members of the neuropathology community who have been noted leaders and contributors to neuroscience and to the American Association of Neuropathologists (AANP) and have a historical perspective of the importance of neuropathology in diagnosis, education, and research. His is the first autobiography by a distinguished PhD member (as well as former president) of the AANP, highlighting the contributions and integral roles of basic neuroscientists in our Association. It is hoped that this series will entertain, enlighten, and present members of the AANP with a better sense of the legacy that we have inherited, as well as reintroduce our respected members as humans having interesting lives filled with adventures, joys, and sorrows, and allow them to present their lives in their own words. MNH, RAS “A man is the product of his thoughts. What he thinks he becomes.” Mahatma Gandhi Lacking a more original arresting opening, let me begin by saying that to be invited to join the list of esteemed neuropathologists featured in the Journal's Autobiography Series, following icons like Asao Hirano, Robert Terry, and Nicholas Gonatas, is both a privilege and a challenge. Never known for being conventional and sporting a background completely at odds with the standard training of most members of the American Association of Neuropathologists (AANP), I would like to take off on a different foot by thanking my colleagues in the Association for welcoming and accepting me, among the first PhDs, into the fold as an Active Member. When Mike Hart rang me a few months ago asking me to prepare a piece for the Series, my knee-jerk reaction was to decline on the grounds of juvenility and inappropriateness. Recognizing that autobiographies usually represent one's own self-chosen, self- redacted reminiscences, I was in no hurry to wax solipsistic to the readership and my colleagues. As we spoke, however, I rationalized the issue by recalling how many years had flown by since I became involved with the AANP (actually, 44) and how my own development as an investigator had paralleled and benefited from my affiliation with the Association and its mouthpiece, the Journal of Neuropathology and Experimental Neurology (JNEN). Setting feelings of uncertainty aside and with Mike still on the line, I thought, “this is the academic body that gave me the legs to stand on in neuropathology; of course, I'm qualified; I'll do it.” So, for an autobiography garnished more with anecdotes than achievements, read on. I was born in May 1940 in Eastbourne, England, to a single mother; the vivid description of WWII events from her provided me with images difficult to distinguish from actual memories. She used to talk about the Dunkirk evacuation and the dogfights overhead between Spitfires, Hurricanes, and ME 109s, with their contrails slicing the summer sky, all occurring while I was in my push-chair. Moreover, this coastline was also the planned landing site for the German invasion barges waiting to depart Belgium, but thanks to the Royal Air Force and the Valiant Few, it never came to pass. Not surprisingly, Eastbourne residents were advised to evacuate to safer havens, particularly as German bombers driven from the London Blitz fled our airspace and jettisoned unspent bombs along the coast. My mother decided to return to her parents' home in Carlisle, Cumberland, 400 miles north, 8 miles south of the Scottish border. We arrived in Carlisle in 1942, unannounced and definitely not welcome. Apparently, she had left Carlisle about 10 years earlier under a cloud and had not been heard of since. However, her odyssey had ended; her funds had run dry and she had come home. Aunt Maureen, who is 7 years older than me, answered the doorbell and found her sister who she had never seen, standing on the doorstep with “a beautiful little boy in a green woolen suit with small pink flowers across the front.” We were admitted into the house by my grandmother; my grandfather was summoned from his victory garden and there followed an unpleasant confrontation ending with my grandmother (my life's best friend and savior), taking me by the hand out of the fray saying “T am going to put this young man through university, “ and she did. Shortly thereafter, real memories began to form. There were 4 sisters in the house; 3 of them rather like the ugly sisters of Cinderella constantly battled with my mother and abused me at their convenience. I was terrified; I used to hide a lot and developed a bad stutter, which stayed with me until I came to the States in the late 1960s. My mother kept my hair long and in a pageboy style (remember Cedric of “Little Lord Fauntleroy?) and had me attend dancing classes at the age of 3 (Fig. 1). About 12 months later, the hair came off, my mother took a war-related job, and I was released to the Carlisle streets to become a grubby member of the populace. The dance class of Florence Wilkinson (rear center), Carlisle, 1943. That's me, fifth from left, front row, hands on knees. Note pageboy hairstyle. My aunt Maureen (extreme right, in front of man) delivered me to the class. It was wartime and, like many cities in the United Kingdom, Carlisle was in the thick of it. The United States had by now entered the war (thank heavens!), and being a center for about 6 railroad companies and situated on the only road south from Glasgow (the main port for traffic from North America), everything had to come through Carlisle, much to the delight of the local kids. The roadside and railway embankments became our playgrounds as convoys and trains of US and Canadian troops, lines of gray-painted trucks with long trailers carrying airplanes with folded wings, and tanks (oh, the tanks!) trundled through the cobbled streets of Carlisle. Near our street was a long lay-by where tanks would stop as crews took a break. I can still smell the hot oily fumes. We would race like mad to them and climb aboard shouting, “Any gum, chum?” Our reward was usually sticks of Wrigley's gum and/or a Hershey bar—what a delight to kids from families on severe rationing! On 1 occasion, an American soldier, noticing my dirty face, gave me a bar of perfumed soap with which I ran home to give my mother who had not seen its like for some years. The war had a toughening effect on kids: fathers were not around, we lived in a matriarchal society, and we grew up fast. My grandmother, anxious to get me out of the house, walked me down to Brook Street School just after I turned 4 and enrolled me as a 5-year-old in the infants' class. That worked fine until I was to take the 11-plus examination, a to the at the age of and the to a education, at which were My age was and I was to to take the the following I the 11-plus some and a and a on the I and began by saying that I had to the to a a I thought, but was by a about in I still from I of from Brook Street the to 8 but years at Carlisle an in the It was of a at the were and (Fig. the age of well on the of and to to become an My mother no worked and I was by my age from the My grandmother put her foot down and to her she going to I to the following to join the to be for the which I me a to I was by a in by local who I had while (as I summer from the age of to a while to a few taking off for the of the I that I had been by of to become the of What a I thought, as I my for the long home. The following I at to for a my Carlisle School was I mad for about years (Fig. but to down in my to on the which I with a my at I had a with a Maureen (my who I had in in the of where I many at the home of an aunt and with Maureen was after she left and I entered the but after I entered my her and, a gave her my much of my at I had my Maureen to me on the as I and she through to become a at in in were and with a in and a to the and in the United Kingdom, I entered the I the and of on my to be for as a out to with no but 3 I gave up and took a as a in the a house in a of Carlisle. well for me until the I and the local a man who had the many of he would be the to get as and I was with I was in the of a of with a by a he at me the I released the it and the under the On on the he and to climb His hands and he more his on the more he it but I to the is I the Carlisle arrived and took his a had been for earlier the he had the down the road from the many thereafter, would come into the asking to who up and I would them the that it. was to months in and I gave up my as a About a after I left I a who me of a for an at the in The was to and its was I had read of American that featured and on by and in the of and I was with through an who was a of the I to and an was I arrived at the and was up to the of a house, through which where I was to my (Fig. The was to with me about my and my where I had about and I with I the and was a As I left his me to my of some with at a in long after I left the I turned a into a My and training me in I was to the and of the from in and in and became in and The was for basic and was by which many members to and were his His was on and on were and members were to like in their and would stop at to his on my a to the of a of from the community to a by that a he had had for The in the of a for a while he up a series of a of of and from and was to be by my and the left for the to return the following to the the entered my the some of the and the to The the were the was and thereafter, being with the left the by to the were and the became members became of had not of a who would have the was home to a of and among was and only the for to were the I 6 years in the I grew to my on and, I a PhD to he me the to a not to a of to a of and with many my own was not and many young as a of and bad like and we the to the to be the on. it would be to most of the was a and that his was the in the the however, he a he would a for my and me the me to the and and prepare the for When began to and was I was from he be However, as I became more in and and more his me as his unpleasant its ugly he who I to and with me that I would this for my it I never his to get me but it put a on many a after 4 years of Maureen 1 that she had a as a for me to get down to my PhD It worked and I the in 3 but its was a that it be of and that I was not to from the As would have decided to take a to from in and I took the as the to the for my with my own after he I the product to the and for to a as my that I had my and the as a When entered the I to the for me to the to the for at the to and walked became a an with out the I would home and Maureen, no On the 10th I and I of his His he his and later, the was with the the that the for PhD in the United a that the me, and an my to 3 the decided for no to from my much and around, I to the of to into the more but it The the as I was the came in and me with a that I was as of that I my was a and home. Not I came in and was about to attend the a in with its and The and I was a PhD in there was more to had me on a my would to about a in On of the the after my he out different from were and at the of a I to the and was a of was on the that 1 would the of the following The effect was that my PhD me to and a few later, he my a friend with a PhD in at a of and I was to in I decided to there was a of for in the United Kingdom, which was in the of a to the and the United I at 1 to on of the of my but the academic in the and were Maureen and I decided to the United and, I an of a with Robert Terry, an known at the of in the I it. had also heard about me from my friend a who had left for 1 in my as a in the had become a of and had about the to his he was advised to Maureen and I to come to the United I for the of with for the and took them to for in the with a my with and to the for and to to We had no but to put our house on the of it for the small from the going and funds in and for our in England, we in with miles later, in after I the for at the AANP in the to It was a from who had been about to to take up a in became of Neurology at the of me, the in the and me he would take in the of the to he the following to the United Our in were particularly I was from training my and the me advised me not to up and to that was to while on the with the down to and the as I the he entered the I was and that I stop and the to I to until I was began to I to and to with and I and, from that was an of and that a of it was on the I into had the with his the of the and I have vivid memories of I took the and some of the at his much and into the and more was and began for I kept and and he kept and I and to me to I was me and out as he the get for I heard more about this but he never me years later, I this to an of young as of a talk a were I a better than for the On my in the I delivered the to for and would the at the up and into to for our to the to the and to As I left the with my I to he to the of the which he me my training in in the United was of his as of the by an on from and with members and never a in On a arrived at with a Maureen and a to in research. My in was I only We were by who delivered to his in where we his and their 3 and where we stayed for while I in at and Maureen the to an The me into to who was in to took me to the of the I have little more than with into small at I still it how much neuropathology had from that small (the foot in product have been waiting for me, was the (Fig. with in at an in Our was no more than off to attend to while his for I would run the until a the was in I would to a I would my on and would a between the and that of a on of a on which I had also worked and published in been my he left, gave me a of where I the and friend and and a who would become my for in the My first was an to out for there was an of in and out of that small Mike and of them were about to and were to their on These were for the most in the with a of to and were well and with the best the was this from Carlisle in a still the with a an and little from to get a foot on the and not to I the found an a some on and after a little more than 1 at and much the left had a for and, my first I with and of of which would The with and, my I would the just to read and more and more and many for What a from and the into my just as and I (Fig. were a series of on and the AANP in walked into the and me an for an from the of me to prepare the and Experimental and he would the a and the to that The was and 3 (my own an and to the in our the was and and, the to me to at the me up to with a in of a senior to an to a young was my as an investigator at The in thanks to and my colleagues at my was and after into the I was to and an training for and funds for 3 a and and a My was to a home with and that would be to and who would be to on their rather than and of more than years in my was that my from and I was at the on the (Fig. and background with my of with I an for a training and a to which my of will the with and of my in the Raine Note the I was most to a with and that in on and left the 3 of much to our own his of he was there was and we never I also an with and our many contributions to the of the of on as became more this would into the of the and the of in a PhD was for into my at a as were in My into was more by my up with and our on in the much a and of the and most I have known in (Fig. late the the of also in my of which was with of my of the at from its in until his in (Fig. was a and and an the of and our we a of for the first of in the and the of from Moreover, we worked and many of in the and as began to take center I up with and members of his at my own and to and into and our into the of with and was with and which in the first of to in in and the of a of to to and in As we entered the the began to for neuropathology in as of the and as and as began to and as became and more as for our and the at AANP Neuropathology at was also about to a with to in a by the of the decided to but only would with both left, a was was no our was and members became and began to to our Neuropathology became a of a the for a while but and to join the in left for and the was to who the for a few but of the and the he to in the and to run a a of its former (Fig. my own on had been to the it me to my colleagues on. I to (Fig. I a with the of and had the of a who me my from the of the to in in I was to the of with a of from for and and a of by the of we entered the with a of which to Neuropathology and and The were also in my and were in and at of the best I with in the my and with and the of to a of and the most of my years at came through my to and an of and into the of by a and with and were to between to of became a of my the the of an of through my 1 present them in list will me for the German (the 4 with (the 4 with and in a with the following also training with Mike and all the I my thanks for the and into my I their was and I from them at As for some of my I he with from his to his and in (Fig. As for Terry, in 3 of and to to up with a with some by (Fig. was in fine and I was to his the many the at were as as in on a from The of Terry, and we have my and I am left with my to my who my my and my and for years. was my first and as I a for from through the a was with me from the late until ran the of the Journal of which I in from to and it and my (Fig. to I be my and in from to the present My would I be my training a of and the standard for me were to have in About 12 months into my at and I our first on the of in to and I was it was On the I the of was a for a to which I was I and with and I at the I my to the up front and my me into an a in a I with the much to their was I with and my first in The AANP been the for my academic and (Fig. and its was usually the of my of the at I was into from the at a were for Active The was into the most being the the Association to and by I was to the for the and after about 3 years of and we in the AANP that be admitted as Active many years thereafter, was and the basic by who would have on the of I a AANP and on and/or delivered and for 1 was to be being the of and the and the for to Neuropathology I on the of from to academic I have I more to the AANP than to the of a few lines on Maureen and I were never with of our but in while as a in a for Maureen was to a young boy with who had been abused and by his She became of and, he was for she decided we a home. So, in at the age of he entered our lives our and, a of we entered to read and had and a a home and developed a beautiful he worked as an in a a at which he that for began he Maureen, and he never let his get in the of his was with for 12 years and became a and member of our however, the on in his years and his many years on up with and he in thereafter, in Maureen was as having and, as a my at became I began to my to and in until Maureen her like a but after a she in 7 months we had from to Maureen to as a grandmother in the young of and having to in a and her an Maureen lived long to but was never well to from the would have I Maureen much in to the years we were it was of her that I was to it along the road to Neuropathology (Fig. I have just the first is in the center with Mike Hart Maureen, my and Maureen in as a me to my which I and a with I am in There on my for colleagues me and images for of still and I am more to attend So, me on the do and
Zero-knowledge proofs were introduced by Goldwasser, Micali, and Rackoff. A zero-knowledge proof allows a prover to demonstrate knowledge of some information, for example that they know an element which is a member of a list or which is not a member of a list, without disclosing any further information about that element. Existing constructions of zero-knowledge proofs which can be applied to all languages in NP are impractical due to their communication and computational complexity. However, it has been known since Guillou and Quisquater's identification protocol from 1988 and Schnorr's identification protocol from 1991 that practical zero-knowledge protocols for specific problems exist. Because of this, a lot of work was undertaken over the recent decades to find practical zero-knowledge proofs for various other specific problems, and in recent years many protocols were published which have improved communication and computational complexity. Nevertheless, to find more problems which have an efficient and practical zero-knowledge proof system and which can be used as building blocks for other protocols is an ongoing challenge of modern cryptography. This work addresses the challenge, and constructs zero-knowledge arguments with sublinear communication complexity, and achievable computational demands. The security of our protocols is only based on the discrete logarithm assumption. Polynomial evaluation arguments are proposed for univariate polynomials, for multivariate polynomials, and for a batch of univariate polynomials. Furthermore, the polynomial evaluation argument is applied to construct practical membership and non-membership arguments. Finally, an efficient method for proving the correctness of a shuffle is proposed. The proposed protocols have been tested against current state of the art versions in order to verify their practicality in terms of run-time and communication cost. We observe that the performance of our protocols is fast enough to be practical for medium range parameters. Furthermore, all our verifiers have a better asymptotic behavior than earlier verifiers independent of the parameter range, and in real life settings our provers perform better than provers of existing protocols. The analysis of the results shows that the communication cost of our protocols is very small; therefore, our new protocols compare very favorably to the current state of the art.
The minmax regret problem for combinatorial optimization under uncertainty\ncan be viewed as a zero-sum game played between an optimizing player and an\nadversary, where the optimizing player selects a solution and the adversary\nselects costs with the intention of maximizing the regret of the player. The\nexisting minmax regret model considers only deterministic solutions/strategies,\nand minmax regret versions of most polynomial solvable problems are NP-hard. In\nthis paper, we consider a randomized model where the optimizing player selects\na probability distribution (corresponding to a mixed strategy) over solutions\nand the adversary selects costs with knowledge of the player's distribution,\nbut not its realization. We show that under this randomized model, the minmax\nregret version of any polynomial solvable combinatorial problem becomes\npolynomial solvable. This holds true for both the interval and discrete\nscenario representations of uncertainty. Using the randomized model, we show\nnew proofs of existing approximation algorithms for the deterministic model\nbased on primal-dual approaches. Finally, we prove that minmax regret problems\nare NP-hard under general convex uncertainty.\n
All is not well for nursing in the new world. The use of social media to share research, access information and build professional networks – although gaining in popularity – has been met mostly with a slow response from those in nursing and its research (Ferguson 2013). Twitter is used by over 550 million people, with 135,000 new users every day (Statistics Brain 2012). Approximately 11% of nurses use Twitter compared with 20% of adults – which places nurses a year behind the general population's usage (Robinson 2013). This inertia is curious, given that reputable health organizations, such as the World Health Organization, now use Twitter (Redfern 2013). Do nurses understand the potential benefits of Twitter? With mainstream popularity and increasing reliance in daily social life, Twitter can allow nurse researchers to connect directly, rapidly and cheaply with communities, disseminate information, and promote translation of research into practice and policy. It has also been found to be effective in engaging with and recruiting potentially hard-to-reach populations (O'Connor et al. 2014). This provides huge potential for methods and dissemination and broadens our understanding of change. Academic institutions now have to consider the merits of ‘virtual impact’ alongside traditional metrics of evaluation, such as publications. As Ferguson lamented in JAN: ‘it is time for the nursing profession to leverage social media’ (2013, p. 745). However, identifying this need does nothing to address how nurses can use Twitter better. Diffusion of Innovations Theory can help. Proposed by sociologist Everett Rogers in 1962, Diffusion of Innovations Theory has become a commonly applied theory for understanding how and at what rate innovations are adopted in different settings. Five characteristics of innovations influence this rate (Rogers 1962/2003): • Relative advantage: ‘…the degree to which an innovation is perceived as being better than the idea it supersedes’. (Rogers 1962/2003, p.229) The purpose of Twitter may not be apparent to nurse researchers. Is Twitter a social networking site; a venue to confer and communicate celebrity status; a networking platform; a venue to disseminate research findings; a site for recruiting participants; or all of the above? This versatility of Twitter actually reduces its perceived relative advantage because it is unclear what Twitter can and should be compared to. Most of these appraisals of Twitter occur in an evidence vacuum. While other widely used forms of media – such as textbooks, television and the internet – are not subject to a similar burden of proof, academics focused on evidence and value may well bemoan the lack of evaluation measures available for Twitter. Given the lack of previous comparable social media platforms, the added value of Twitter to busy professional lives may be unclear. Twitter can create a new world that is highly responsive to each member's needs and interests. Because only tweets (messages of 140 characters or fewer) from followers are viewed, twitter ‘feeds’ tend to reflect common themes. Hashtags can be used to categorize tweets and organize twitter feeds. Based on these tailored preferences, papers, blogs and news stories come to one's attention that would not otherwise have done so. This ability to both benefit from and contribute to tailored twitter feeds is a reciprocal advantage that is very useful. The relative advantage of innovations such as Twitter can be expressed through economic gains and social visibility. Academics can ‘tweet’ at zero cost. Other cost investments such as buying open access for publications can be leveraged through Twitter by tweeting links to online papers and web profiles. Academics may conflate social visibility with social prestige – reflecting a lingering perception of Twitter as a celebrity-oriented/pop culture social platform. However, as high-profile organizations such as the Canadian Nurses Association and leading journal editors in nursing harness Twitter, the social status draw of Twitter may gain appeal for nursing academics. Using Twitter may come to symbolize contemporary thinking and innovation. • Compatibility: ‘The degree to which an innovation is perceived as consistent with existing values, past experiences and needs of potential adopters’. (Rogers 1962/2003, p. 229). (Rogers 1962/2003, p. 240) Twitter's predecessors, particularly Facebook, also influence perceptions of Twitter. Largely a social platform, Facebook's infamous ‘status updates’ contributed to perceptions of Twitter as a social site for quick quips and celebrity updates. Although researchers may not distinguish between such forms of social media, in reality, different platforms can serve distinct purposes (Ferguson 2013). This perception of Twitter as another social media site means that it has come to be seen as being part of a ‘technology cluster’ – a ‘set of distinguishable elements of technology that are perceived by individuals as being interrelated’ (Rogers 1962/2003, p. 249). The implication of the technology cluster is the tendency for users to group otherwise distinguishable technological innovations together (e.g. Twitter, Facebook, LinkedIn) without recognizing their distinctive nature and merits. When the blurring of boundaries occurs for adopters, the potential benefits of specific platforms may not be recognized. That said, introducing innovations as part of a technology cluster may increase uptake and harness synergies between innovations. Twitter can be used with LinkedIn (a professional networking profile site) through which strategic use of a tweet can refer followers to a full professional profile. As the introduction of technologies has been sequential, beginning with email, faculty websites, LinkedIn, Facebook and many more that have preceded Twitter, the ‘added benefit’ of new social media innovations may not be recognized. It is natural to contrast the anticipated processes of Twitter to how academic dissemination has previously occurred – through longer formal academic journal articles that are read mostly by other academics. Twitter has been proposed as an alternative means to disseminate academic research; however, assuming that Twitter would be accepted readily as a supplementary form of dissemination risks committing the ‘empty vessels fallacy’ (Rogers 1962/2003, p. 256) wherein the previous knowledge and experiences of potential adopters are neglected. Compatibility with existing experiences is important and necessary for Twitter to ‘fit’ with nurse's existing knowledge related to academic dissemination. Developing links between Twitter and traditional avenues of dissemination can increase compatibility. For instance, integrating Twitter into conference activities by use of a conference hashtag, for example, may help. Indeed, Twitter's name alone could challenge many academics' values. Twitter is synonymous with chatter – the antithesis of academic discourse. Views of Twitter as a time-consuming platform not meritorious for academic career progression and promotion can further reduce its compatibility with extant values. As such, how Twitter is positioned within the nursing community, how it is incentivized as a knowledge translation tool and which of its benefits are emphasized influence its adoption. • Complexity: ‘The degree to which an innovation is perceived as relatively difficult to understand and use’ (Rogers 1962/2003, p. 257) As with any innovation, Twitter has a learning curve. New terminology (e.g. Tweet, Twittersphere, twitterites) and ostensibly mysterious abbreviations (e.g. RT, FFF, BFN, T/J etc.) abound and necessitate a ‘Twittonary (n.d)’ of key definitions (see http://twittonary.com/ for an example). This learning is complex, especially for people less familiar with technology. Generally, different generations define and use social media in different ways (Cain et al. 2010, Taylor et al. 2010, Jones & Hayter 2013). Generational divides in the use of Twitter persist, but may diminish as technological literacy increases (Cresci et al. 2010). As such, the demographic characteristics and background of researchers in nursing also influence perceptions of complexity and use. • Trialability: ‘degree to which an innovation may be experimented with on a limited basis’ (Rogers 1962/2003, p. 258) Trialability is a mixed bag for Twitter. Twitter can be experimented with easily through establishing, trying and deleting a user account. However, it takes time and effort to establish followers, identify other users to follow and both read and produce tweets regularly. Time and efforts are needed to understand the potential benefits of Twitter, but these also reduce its perceived trialability. This trialability is also constrained by preconceptions. For many academics, tweeting is a formative risk – tweets can potentially be read by many people, cannot be retracted and have been subject to high-profile legal debate and litigation in some countries. For those who have experimented with or regularly use Twitter, perceptions of such risk are diminished as tweets are only shared with and read by one's followers. Trialability is greatly enhanced by personal trials – suggesting a potential avenue for institutions looking to facilitate the uptake of Twitter by academic staff – via peer presentations on social media or hands-on ‘Twitter-sessions’ similar to library database search sessions. • Observability: ‘The degree to which the results of an innovation are visible to others’ (Rogers 1962/2003, p. 258) Twitter is a virtual innovation that requires no new hardware and an internet connection. The platform itself is less observable. Aside from the occasional tweet showcased in print, radio or television, tweets are not visible to those not on Twitter. Promoting Twitter through educational sessions and generating awareness of communities of scholars who have adopted the innovation may enhance Twitter's observability. Finally, as researchers and academic institutions alike can be outcomes-driven, finding ways to qualify the impact and effectiveness of Twitter, and to communicate and value these measures within academic research communities are important. Diffusion of Innovations Theory promotes understanding of how academics use Twitter and offers some direction for developing strategies to increase its use in academic settings. Twitter's popularity is increasing and may soon reach a critical mass, tipping the balance in favour of further adoption (Toole et al. 2012). As the time for early adoption of Twitter has passed, waiting for this critical mass is not enough. Institutions can help by emphasizing the relative advantages of Twitter, such as its low cost, possible reach and high impact potentials. Highlighting parallels between Twitter and other dissemination strategies can promote compatibility with values and experiences. To minimize complexities, promote trialability and increase observability guidelines on Twitter, researchers should benefit from guidelines (e.g. Mollett et al. 2011), Twitter training opportunities and better integration of Twitter into professional conferences and meetings. M.A. acknowledges the Canadian Child Health Clinician Scientist Program and the Women and Children's Health Research Institute.
A scheme for anonymous tag based anonymous credentials is enhanced. Different from existing zero knowledge proof based anonymous credential schemes that require numbers of challenges and responses between verifiers and credential holders, the anonymous tag based scheme requires only small number of challenges and responses between verifiers and credential holders. This is because the scheme in this paper can be easily made sound even in environments where verifiers also may behave dishonestly. However, the original scheme has probabilistic features, i.e. verifiers must generate dummy fake challenges; therefore overheads for managing anonymous systems cannot be reduced to the minimum. The enhanced anonymous tag based scheme excludes these probabilistic features from interactions between verifiers and credential holders. The scheme also corrects several design errors included in the original scheme.
The practical deployment of vehicular networks is still a pending issue. In this paper we describe a new self-organized method of authentication for VANETs, which allows their widespread, fast and secure implementation. Our proposal does not involve any central certification authority because the nodes themselves certify the validity of public keys of the other nodes. On the one hand we propose an algorithm that each node must use to choose the public key certificates for its local store. On the other hand, we also describe a new node authentication method based on a cryptographic protocol including a zero-knowledge proof that each node must use to convince another node on the possession of certain secret without revealing anything about it, which allows non-encrypted communication during authentication. Thanks to the combination of the aforementioned tools, the cooperation among vehicles can be used for developing several practical applications of VANETs, such as detection and warning about abnormal traffic conditions. One of the most interesting aspects of our proposal is that it only requires existing devices such as smartphones, because the designed schemes are fully distributed and self-organized. In this work we include an analysis of both an NS-2 simulation and a real device implementation of the proposed algorithms, which enables us to extract promising conclusions and several possible improvements and open questions for further research.
We examine the strategy-proof allocation of multiple divisible and indivisible resources; an application is the assignment of packages of tasks, workloads, and compensations among the members of an organization. We find that any allocation mechanism obtained by maximizing a separably concave function over a polyhedral extension of the set of Pareto-efficient allocations is strategy-proof. Moreover, these are the only strategy-proof and unanimous mechanisms satisfying a coherence property and responding well to changes in the availability of resources. These mechanisms generalize the parametric rationing mechanisms (Young, 1987), some of which date back to the Babylonian Talmud.
Consider a market for a resource under disequilibrium prices where suppliers and demanders are privately informed about their optimal supply and consumption levels. Strategy-proof market clearing mechanisms give suppliers and demanders dominant strategy incentives to truthfully reveal this information. We describe the class of strategy-proof and efficient mechanisms responding well to changes in supplies and demands, as formalized by the “replacement principle" (Thomson, 2007). Since no symmetry or anonymity conditions are imposed, these mechanisms can implement a wide array of distributional objectives in both indivisible and divisible resource allocation situations. These mechanisms apply to allocation problems involving network constraints modeling necessary conditions for a transfer of the resource from a supplier to a demander.
Cloud computing is the vast computing utility, where users can remotely store their data into the cloud so to have the benefit of the on-demand availability of huge and different applications and services from a shared pool of configurable computing resources.Cloud-based outsourced storage space reduces the patron load of storage management. It also reduces the maintenance load of customer by providing a comparably low-cost, scalable, locationindependent platform.This new model of data hosting service commence a new security challenges, which requires an independent auditing service which audit the data integrity of cloud. There are different existing auditing services available in cloud which audit data integrity remotely in static motion but these are not applicable whenever data is dynamically updated in cloud. Since it require efficient and secure dynamic auditing method for data owner. However in cloud, the clients no have direct physical possession of data. It shows client faces different formidable risk like missing or corruption of data. To keep away from the security and integrity risk of data, audit services are essential to ensure the integrity and availability of outsourced data and to achieve digital forensics and credibility on cloud computing.Provable data possession (PDP), which is a cryptographic technique for verifying the integrity of data without retrieving it at an untrusted server, can be used to realize audit services. In this paper, profiting from the interactive proof system, we address the construction of an interactive PDP protocol to prevent the fraudulence of prove (soundness property) and the leakage of verified data (zero-knowledge property).
This paper introduce a dynamic audit service for integrity verification of untrusted and outsourced storages. Our audit service is constructed based on the techniques, fragment structure, random sampling, and index-hash table, supporting provable updates to outsourced data and timely anomaly detection. Constructed on interactive proof system (IPS) with the zero knowledge property, our audit service can provide public auditability without downloading raw data and protect privacy of the data. Also, our audit system can support dynamic data operations and timely anomaly detection with the help of several effective techniques, such as fragment structure, random sampling, and index-hash table (IHT). We also propose an efficient approach based on probabilistic query and periodic verification for improving the performance of audit services. A proof-ofconcept prototype is also implemented to evaluate the feasibility and viability of our proposed approaches. Our experimental results not only validate the effectiveness of our approaches, but also show that our system does not create any significant computation cost and require less extra storage for integrity verification.
This thesis discusses symmetric random walk, its definition and basic properties. The outset is focused on the probabilistic model and subsequently on basic properties, such as the final position at time n, its mean value and variance. Furthermore, we will see what the scaling must be for the walk to converge to zero, precisely what is the consequence of the strong law of large numbers. In the second chapter we will examine the distribution of the maximum of the symmetric random walk. In chapter 3 we will define stopping time and Markov property of random walks. Then we proof many auxiliary lemmas using basic knowledge of combinatorics. The final part is devoted to the proof of the arcsine distribution, which shows great persistence of the symmetric random walk. Powered by TCPDF (www.tcpdf.org)
Risk and reliability analysis is presently being performed in almost all fields of engineering depending upon the specific field and its particular area. Probabilistic risk analysis (PRA), also called quantitative risk analysis (QRA) is a central feature of hydraulic engineering structural design. Actually, probabilistic methods, which consider resistance and load parameters as random variables, are more suitable than conventional deterministic methods to determine the safety level of a hydraulic structure. In fact, hydraulic variables involved in hydraulic structures, such as discharge, flow depth and velocity, are stochastic in nature, which maybe represented by relevant probability distributions. Therefore, the optimal design of hydraulic structures needs to be modelled by probabilistic methods. Reliability analysis methods are being adopted for use to develop risk management programs. Implementing the programs will ensure that safety is maintained to a robust and acceptable level. Any simple reliability analysis should include the following steps: The main work carried out relates to three different subjects in the general area of dam structures failure. These included the probabilistic methods work on: o Geometry of plunge pool downstream of flip bucket spillway o Evaluation of superelevation in open channel bends o Hydrodynamic loading on buildings by floods 1. Geometry of plunge pool downstream of flip bucket spillway Extreme scouring can gradually undermine the foundations of structures such as spillway and body dams and the areas downstream of dams. Extensive plunge pools downstream of flip bucket spillway structures, which are caused by jets of different configurations, form an important field of research. The plunge pool mechanism is more complex because of difficulties arising from the modelling of bed rock and sediment load flow in and around the scour hole caused by the jet effect of the flow downstream of flip bucket spillway. The experimental study of plunge pool has been limited to the consideration of variables involved in the plunge pool geometry. The reliability-based assessment of the geometry of the plunge pool downstream of a flip bucket spillway. Experimental data obtained from a model of a flip bucket spillway has been used to develop a number of equations for the prediction of scour geometry downstream from a flip bucket spillway of a large dam structure. The accuracy of the developed equations was examined both through statistical and experimental procedures with satisfactory results. 2. Evaluation of superelevation in open channel bends The so-called centrifugal force caused by flow around a curve results in a rise in the water surface at the outside wall and a depression of the surface along the inside wall. This phenomenon is called superelevation. The problems associated with flow through open channel bends deserve special attention in hydraulic engineering. Water surface slopes have been frequently reported to be a function of the curvature. But due to the difficulties in operation, the theoretical basis of superelevation has been discussed in depth in the literature. Furthermore, experience indicates that existing theory does not lead to good results at the present status. Superelevation in the Ziaran Flume (Iran) has led to severe erosion of the bank and has undermined the structure. Therefore, this study aims to cast light on the cause of overtopping by superelevation. By means of direct observation on the flume’s hydraulic performance, during full discharge, and from generalization of the field data, a more reliable prediction method of the magnitude of superelevation has become possible. The probabilistic analysis is shown to have several advantages in comparison with deterministic analysis methods. 3. Hydrodynamic loadings on buildings by floods Assessing the vulnerability of buildings in flood-prone areas is a key issue when evaluating the risk induced by flood events, particularly because of its proved direct influence on the loss of life during catastrophes. Hydrodynamic loads are caused by water flowing along, against and around a structural element or system. Hydrodynamic loads are basically of the lateral type and are related to direct impulsive loads by the moving mass of water, and to drag forces as the water flows around the obstruction. Where application of hydrodynamic loads is required, the loads shall be calculated or estimated by recognized engineering and reliable methods. A comprehensive methodology for risk assessment of buildings subjected to flooding is nevertheless still missing. A new set of experiments has been performed in this thesis with the aim of shedding more light on dynamics of flood induced loads and their effects on buildings with state of the art benchmarks. In this research, an overview is given of flood induced load on buildings, the new experimental work is then presented, together with results from preliminary analysis. Initial results suggest that use of existing prediction methods might be unsafe and that impulsive loading might be critical for both the assessment of the vulnerability of existing structures and the design of new flood-proof buildings. The research presented in this thesis is focused on developing and applying probabilistic design, safety, system reliability and risk based design in the field of hydraulic structures design in the open channel bends, plunge pool downstream of flip bucket spillway and dam break analysis. Probabilistic design approach is a powerful tool in reliability assessment of civil hydraulic engineering. Uncertainty and risk are central features of hydraulic engineering. Hydraulic design is subject to uncertainties due to the randomness of natural phenomena, data sample limitations and errors, modelling reliability and operational variability. Uncertainties can be measured in terms of the probability density function, confidence interval, or statistical moment such as standard deviation or coefficient of variation of the stochastic parameters. Outcomes from this thesis are beneficial to the design of hydraulic structures in many ways; not only minimizing cost, but also educating and providing valuable knowledge for structural operators. Probabilistic methods and reliability analysis can increase the quality and value of the achievements compared to traditional dam engineering approaches. Since the goal is to avoid the dam failures by reducing risk to almost zero with optimum cost, dam safety risk analysis has a key role in modern dam safety programs. It is hoped that illustrations provided in this thesis are applicable to other civil engineering structures of similar concerns.
Sebastian Faust, Pratyay Mukherjee, Jesper Buus Nielsen, Daniele Venturi
Non-malleable codes are a natural relaxation of error correcting/detecting codes that have useful applications in the context of tamper resilient cryptography. Informally, a code is non-malleable if an adversary trying to tamper with an encoding of a given message can only leave it unchanged or modify it to the encoding of a completely unrelated value. This paper introduces an extension of the standard non-malleability security notion ‐ so-called continuous non-malleability ‐ where we allow the adversary to tamper continuously with an encoding. This is in contrast to the standard notion of non-malleable codes where the adversary only is allowed to tamper a single time with an encoding. We show how to construct continuous non-malleable codes in the common split-state model where an encoding consist of two parts and the tampering can be arbitrary but has to be independent with both parts. Our main contributions are outlined below: 1. We propose a new uniqueness requirement of split-state codes which states that it is computationally hard to find two codewords C = (X0;X1) and C 0 = (X0;X 0 1 ) such that both codwords are valid, butX0 is the same in bothC andC 0 . A simple attack shows that uniqueness is necessary to achieve continuous non-malleability in the split-state model. Moreover, we illustrate that non of the existing constructions satisfies our uniqueness property and hence is not secure in the continuous setting. 2. We construct a split-state code satisfying continuous non-malleability. Our scheme is based on the inner product function, collision-resistant hashing and non-interactive zero-knowledge proofs of knowledge and requires an untamperable common reference string. 3. We apply continuous non-malleable codes to protect arbitrary cryptographic primitives against tampering attacks. Previous applications of non-malleable codes in this setting required to perfectly erase the entire memory after each execution and and required the adversary to be restricted in memory. We show that continuous non-malleable codes avoid these restrictions.
Technology is linking the slightest of our actions to the virtual world. In such connected environments, cryptography aims at building schemes with provable security in order to mathematically protect the users' security in electronic exchanges. Relying on the existence of pairings in bilinear groups wherein the discrete logarithm problem is hard, this thesis puts forth mechanisms to efficiently enhance the privacy in three of the most fundamental cryptographic primitives, namely, digital signatures, encryption schemes and zero-knowledge proofs. Furthermore, these mechanisms support public verifiability so as to force the honesty of all participants in the standard model. We first focus on group signatures, a primitive proposed some 20 years ago, for which we propose the first efficient revocation mechanisms, overcoming the main obstacle to the deployment of this primitive in practical applications. We then focus on P-homomorphic signatures that make it possible to modify a signed message in a controlled way. In particular, we propose new mechanisms providing structure-preserving linearly homomorphic signatures, from which we build the first constant-size non-malleable commitments compatible with standard proof systems, as well as a generalization of this construction into a generic transformation. Finally we further investigate the unexpected applications of this kind of malleable signatures to non-malleable cryptography. This leads us to new proof systems for linear languages which in turn provide the most efficient publicly verifiable CCA-secure threshold encryption to date, and other new extensions.
A new signature scheme based solely on the MQ-problem is presented,which satisfies the following properties:(1)Forward security,which means that a compromise of a key now does not necessarily expose old traffic.(2)Backward security,which means that a compromise of a key now does not necessarily expose future traffic.We do not have to revoke our public key and re-issue a new key system everytime we detect a key leak.We use two fundamental tools,such as zero knowledge proof and mulitivariate public crypto.Our basic model is Koichi Sakumoto's identifcation scheme which is transformed by parallel processing and Fiat-Shamir transforming.What is novel about our approach is the key updating algortithm,which makes our scheme preserve backward security besides the forward property.Finally,we prove that our scheme satisfies the security under the random oracle model.
Abstract. We consider the following problem: Assuming that Alice and Bob have an integer interval [a, e] and an integer b respectively, for a commitment c to b, Alice and Bob jointly check whether b is within [a, e] without revealing their inputs, where either party may behave malicious-ly. A special case of the problem is the secure integer comparison in the malicious model. This problem mainly arises from location-based access control systems where one party needs to assure to the other party that its location is within some definite area. Our main result is a constant-round protocol that exhibit the square of log e communication and the square of log e exponentiations with simulation-based security. At the heart of the construction is perfec-t k-ary index and corresponding zero-knowledge proof techniques. We consider a more general case of the problem where the interval is substi-tuted by a union of intervals.
One of the central problems in the development of distributed systems is the design of cryptographic protocols that meet specified functional requirements and preserve user privacy. Methods of conventional encryption algorithms typically use PKI. In this paper we presented a method based on other approach. The authors have developed a cryptographic framework for access control, ensured the confidentiality of social relations, secrecy of resources and anonymity of users in social networks. The implementation of the protocols in the framework is combination of zero-knowledge proof and signature schemes Camenisch-Lysyanskaya.
Rafail Ostrovsky, Giuseppe Persiano, Ivan Visconti
In [AGP14] Ananth et al. showed that continual leakage-resilient non-transferable interactive proofs exist when a leak-free input-encoding phase is allowed and a common reference string is available. They left open the problem of removing the need of a common reference string. In [BGJK12] Boyle et al. showed that for some interesting functionalities continual leakage-resilient secure computation is possible when leak-free interactive preprocessing and input-encoding phases are allowed. They left open the problem of removing the interactive pre-processing. In this work we study the above questions. Our main contribution shows that leakage-resilient black-box zero-knowledge is impossible when relying on a leak-free input-encoding phase only (i.e., without CRS/preprocessing). Additionally, we also show that leakage-resilient multi-party computation for all functionalities is impossible (regardless of the number of players assuming just one corrupted player) when relying only on a leak-free input-encoding phase (i.e., without CRS/preprocessing). Our results are achieved by extending a technique of [NVZ13] to prove lower bounds for leakage-resilient security. Indeed as in [NVZ13] we use leakage queries to run an execution of a communication-efficient protocol in the head of the adversary. Moreover, to defeat the black-box simulator we connect the above technique for leakage resilience to security against reset attacks.
Abstract. We construct O(log 1+ɛ n)-round public-coin concurrent zero knowledge arguments for NP from standard (against any polynomial-time adversary) collision-resistant hash functions for arbitrarily small constant ɛ. Our construction is straight-line simulatable. This is the first public-coin concurrent zero knowledge protocol based on standard/long-studied assumption that (almost) achieves the best known round-complexity of its private-coin counterpart [Prabhakaran et al., FOCS 02]. Previously, such publiccoin constructions require either polynomial number of rounds [Goyal, STOC 13], newly-introduced assumptions [Chung et al., FOCS 13], or stronger model [Canetti et al., TCC 13]. This result has strong consequences: it yields the first (almost) logarithmic round simultaneously resettable arguments for NP and the first (almost) logarithmic round concurrent multi-party computation in the single input setting. These results significantly improve over the polynomial round-complexity of the best known protocols based on standard assumptions in both cases. Our technical contribution is two-fold. First, we introduce a simulation strategy called clearance that yields a simulation tree of very special combinatorial structure and enables us to instantiate Barak’s protocol [Barak, FOCS 01] using the recent Ben-Sasson et al.’s quasi-linear construction of PCP system [Ben-Sasson et al., STOC 13] to obtain logarithmic round-complexity; secondly, we show how to modify Barak’s protocol such that the soundness of overall construction does not rely on the (implicit/explicit) proof of knowledge property of the underlying universal argument/PCP system, which in turn allows us to benefit from progress on short PCP system of more general types without assuming stronger/superpolynomial hardness. 1