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In the past several years, we have witnessed unprecedented political, racial, economic, and health-related ruptures in society. The resulting turmoil has had an inevitable and negative impact on students, teachers, the profession of education, and especially marginalized and vulnerable populations. Academics and policymakers have had their say on how to address today's volatile issues, but teachers and other practitioners closest to students have not had the same visibility or access. This volume is an attempt to remedy that absence, resulting in a compelling picture of education today. Chapters highlight essays written by a diverse group of K-12 classroom teachers who share their visions for education and describe their empowering classroom practices. At times hopeful and full of joy, at other times angry and full of frustration, these essays speak to what classrooms and schools based on social justice might mean for our nation. "Teachers Speak Up!" presents a bold vision of what education could be if teachers were to have a more direct influence on the purpose and aims of learning and teaching. This book: (1) offers grounded accounts about creating classrooms filled with hope and promise amid the many challenges to everyday practice; (2) addresses the harm done by universal school closures due to the pandemic, growing political divisions, the ugly specter of racism, book bans, and more; (3) gives voice to classroom teachers who describe their vision for education, as well as their successful practice teaching diverse students; and (4) includes chapter authors who are diverse in their identities, the subject matter they teach, and their time in the profession.

A must read for new teachers and seasoned practitioners, this unique book presents Sonia Nieto and Alicia López, mother and daughter writing about the trajectories, vision, and values that brought them to teaching, including the ups and downs they have experienced and the reasons why they have stubbornly remained in one of the oldest, most difficult, and most rewarding of professions. Drawing on their extensive experience as educators in school and university classrooms, they reflect on what it means to teach young people, prospective teachers, and future academics in our complex, dynamic, and multicultural society. "Teaching, A Life's Work" is at once theoretical and practical, reflective and critical, personal, professional, and political. Nieto and López document their reasons for becoming teachers and share some of the most important lessons they have learned along the way. Using journals, blogs, current writings, and their research, they explore how their views on curriculum, pedagogy, and the field of education itself have evolved over the years. The book features: (1) Experiences and insights from elementary, secondary, and post-secondary education; (2) Ideas from authors who have been at the forefront of progressive movements in public and private education in the United States; (3) An accessible text that includes both theoretical concepts about teaching and practical examples of curriculum and pedagogy; and (4) A chapter based on a dialogue similar to the "talking book" created by Ira Shor and Paulo Freire (1987).

In "Brooklyn Dreams," Sonia Nieto--one of the leading authors and teachers in the field of multicultural education--looks back on her formative experiences as a student, activist, and educator, and shows how they reflect and illuminate the themes of her life's work. Nieto offers a poignant account of her childhood and the complexities of navigating the boundaries between the rich culture of her working-class Puerto Rican family and the world of school. "Brooklyn Dreams" also chronicles her experiences as a fledgling teacher at the first bilingual public school in New York City--in the midst of the Ocean Hill-Brownsville strike--and the heady days of activism during the founding of the bilingual education program at Brooklyn College and later in establishing and running an alternative multicultural school in Amherst, Massachusetts. Along the way, Nieto reflects on the ideas and individuals who influenced her work, from Jonathan Kozol to Paulo Freire, and talks frankly about the limits of activism, the failures of school reform, and the joys and challenges of working with preservice and in-service educators to deepen their appreciation of diversity. "Brooklyn Dreams" is an intimate account of an educator's life lived with zest, generosity, and warmth. An index is included.

This book examines what can be learned from veteran teachers who not only continue to teach but also manage to remain enthusiastic about it despite deprivation and challenges. Nine chapters are: (1) "Teaching as Evolution" (e.g., lessons learned along the way and the promise of multicultural education); (2) "Teaching as Autobiography" (teacher autobiographies and a response from the editor); (3) "Teaching as Love" (e.g. effective urban school teachers and respecting and affirming students' identities); (4) "Teaching as Hope and Possibility" (e.g., the promise of public education and faith in their own abilities as teachers); (5) "Teaching as Anger and Desperation" (e.g., bureaucratic restructuring and indignity at the lack of respect); (6) "Teaching as Intellectual Work" (e.g., the need for adult conversations and sustaining community in teaching); (7) "Teaching as Democratic Practice" (the struggle for equal education and racism in schools and society); (8) "Teaching as Shaping Futures" (the power of teachers' words and teachers changing lives forever); and (9) "Final Thoughts: What Keeps Teachers Going in Spite of Everything?" (lessons from teachers' work, rethinking professional development, restructuring schools, and developing new national priorities for teaching). (Contains approximately 150 references.) (SM)

This book examines the meaning, necessity for, and benefits of multicultural education for students of all backgrounds, providing a conceptual framework and suggestions for implementing multicultural education in today's classrooms. It presents case studies, in the words of students from a variety of backgrounds, about home, school, and community experiences and how they influence school achievement. There are 11 chapters in three parts. Part 1, "Setting the Stage: Approaches and Definitions," includes: (1) "Why the Case Study Approach?" and (2) "About Terminology." Part 2, "Multicultural Education in a Sociopolitical Context: Developing a Contextual Framework," includes: (3) "Racism, Discrimination, and Expectations of Students' Achievement"; (4) "Structural and Organizational Issues in Schools"; (5) "Culture, Identity, and Learning"; (6) "Linguistic Diversity in Multicultural Classrooms"; and (7) "Toward an Understanding of School Achievement." Part 3, "Implications of Diversity for Teaching and Learning in a Multicultural Society," includes: (8) "Learning from Students"; (9) "Multicultural Education and School Reform"; (10) "Affirming Diversity: Implications for Teachers, Schools, and Families"; and (11) "Multicultural Education in Practice." An appendix presents resources for collaboration and educational transformation. (Contains approximately 360 bibliographic references.) (SM)

This collection of papers presents scholarly writings and personal reflections on Puerto Rican students in American schools. Following "Introduction and Overview" (Sonia Nieto), there are 12 chapters in five parts. Part 1, "Historical and Sociopolitical Context," includes: (1) "Puerto Rican Students in U.S. Schools: A Brief History" (Sonia Nieto); (2) "Return Migrant Students: Yankee Go Home?" (Xae Alicia Reyes); and (3) "Educational Leadership, Educational Change: A Puerto Rican Perspective" (Luis O. Reyes). It also includes an essay, "Moving Around and Moving On" (Gillian Rivera). Part 2, "Identity: Culture, Race, Language, and Gender," includes an essay, "A Strong Sense of Self Is Crucial for Success" (Hipolito Baez) and (4) "The Struggle of 'Imagined Communities' in School: Identification, Survival, and Belonging for Puerto Ricans" (Catherine E. Walsh); (5) "Puerto Rican Identity: What's Language Got To Do with It?" (Maria V. Zavala); an essay entitled "Black Pearl Unnoticed" (Carols Mills De Jesus, Jr.); (6) "Puerto Rican Female Narratives about Self, School, and Success" (Carmen A. Rolon); and (7) "Puerto Rican Mothering Strategies: The Role of Mothers and Grandmothers in Promoting School Success" (Nitza M. Hidalgo). Part 3, "Social Activism, Community Involvement, and Policy Implications," includes an essay, "A Different Kind of School" (Alicia Lopez); (8) "The Puerto Rican/Latino Education Roundtable: Seeking Unity in Vision and Organizing for Educational Change" (Diana Caballero); and (9) "The Spirit of Transformation: An Education Reform Movement in a New York City Latino/a Community" (Melissa Rivera and Pedro Pedraza). Part 4, "Classroom and School Studies," includes an essay, "The Counselor" (Jaime Flores) and (10) "Social Action Projects: Apprenticeships for Change in School and Community" (Milga Morales and Elvira R. Tarr); an essay, "Teachers Don't Care" (Jose Manuel Caraballo); (11) "Puerto Rican/Latino Student Voices: Stand and Deliver" (Maria E. Torres-Guzman and Yvonne Martinez Thorne); an essay, "Teachers Who Made a Difference" (Elizabeth Capifali); and (12) "Student Agency through Collaborative Research in Puerto Rican Communities" (Carmen I. Mercado and Luis C. Moll). Part 5, "Directions for the Future," presents "Afterword" (Janice Petrovich Beiso). (SM)

This book focuses on ways teachers can modify their teaching in order to increase the academic achievement of students from the racial and ethnic groups that are experiencing massive failure in U.S. schools, and consequently in society. Modifying instruction to improve the academic achievement of African American and Latino students will benefit all students because underachievement exists within all segments of the school population. The chapters are: (1) "Learning, the Social Context, and Multicultural Education"; (2) "Learning and Inequality"; (3) "Culture and Learning"; (4) "Who Does the Accommodating? Institutional Transformation To Promote Learning"; (5) "Critical Pedagogy, Empowerment, and Learning"; (6) "The Personal and Collective Transformation of Teachers"; and (7)"Creating Learning Communities: Implications for Multicultural Education." (Contains multiple references.) (SLD)

The Latino population is the largest racial and ethnic minority group in Massachusetts. In the 1980s, the poverty rate of Latinos in the state was twice that of Blacks and six times that of Whites. With Latino children dropping out of school at a rate three times that of white children, the economic future of this population is bleak. The following chapters address economic and educational issues and suggest strategies for empowerment of Latinos: (1) "The Status of Latino Students in Massachusetts Public Schools" (Anne Wheelock); (2) "Entitlements of Latino Students and Parents: Some Legal Policy Considerations" (Jose Javier Colon-Morera, and others); (3) "Bilingual Education: Perspectives on Research and Other Issues" (Diana Lam); (4) "Barriers to Latino Parental Involvement in the Boston Public Schools" (Ralph Rivera); (5) "Latinos and Educational Reform: The Privatization of Chelsea Public Schools" (Glenn Jacobs); (6) "Latino Experiences in Vocational Technical Education: Implications for Educational Policy and Reform in Massachusetts" (James Jennings); (7) "What Do Latino Children Need to Succeed in School? A Study of Four Boston Public Schools" (Antonia Darder and Carole Christoff Upshur); (8) "I Was an Outsider: An Exploratory Study of Dropping Out among Puerto Rican Youths in Holyoke, Massachusetts" (Manuel Frau-Ramos and Sonia Nieto); (9) "Academic Costs of Social Marginalization: An Analysis of the Perceptions of Latino Students at a Boston High School" (Virginia Vogel Zanger); (10) "Poverty, Resilience, and Academic Achievement among Latino College Students and High School Dropouts" (Castellano B. Turner, and others); (11) "The Effects of the Schooling Processes and Practices on Potential At-Risk Latino High School Students" (Martha Montero-Sieburth); and (12) "Creating Possibilities: Educating Latino Students in Massachusetts" (Sonia Nieto). (SLD)

This book explores the meaning, necessity, and benefits of multicultural education for students from all cultural backgrounds. The constant and complex interplay and interactions among personal, social, political, and educational factors in exploring the success or failure of students in schools and the benefits of multicultural education are considered. In Part I, the author develops a conceptual framework for multicultural education in the sociopolitical context and emphasizes structural and cultural factors in schooling as well as individual and group responses to education. This section focuses on understanding the myriad forces that may affect the school achievement of students. Case studies appear throughout to highlight salient issues. Part II focuses on the implications of the case studies for teaching and learning. Using the definition of multicultural education developed in the first section, the author presents a rationale for multicultural education as a way of equalizing educational experiences. This section also explores school and home life and conflicting expectations, collaboration for positive student achievement, ways to remove barriers that inhibit learning, suggestions for developing environments that foster high-quality education, multicultural education as a process, and a model of multicultural education that affirms all students. (Contains 366 references.) (JB)

Authors of these books spend little energy on defending multiculturalism and instead focus on specific programs, strategies, and outcomes of multicultural teaching practices in higher education. Two of the books focus on the challenges of teacher education in the face of growing diversity; the third concerns multicultural teaching at the university. (SLD)

This paper deals with the study of the influence of shear rate and surfactant concentration on the transient flow of a lamellar liquid crystal. A polyethylene glycol (EO=10) nonylphenyl ether has been used. Rheological studies have been carried out with a rotational viscometer, using a Mooney-Ewart sensor system. Shear rate ranged between 0.3 and 18 s−1. All measurements were made at 20°C. A stress overshoot can be observed in transient flow. Time at the overshoot decreases as shear rate or surfactant concentration increases. A power law equation can be used to fit the experimental results of peak and equilibrium viscosities vs shear rate. Shear rate has much more influence on peak than on equilibrium viscosity. The amount of overshoot decreases as shear rate increases. This decay is more significant for systems with less surfactant content. Time-dependent stress decay and fall in viscosity with shear rate have been related to the orientation of crystallites. The decrease of the amount of overshoot with shear rate indicates the formation of metastable defects that lead to an increase in viscosity with rate and shear time. [ABSTRACT FROM AUTHOR]

This is a survey of some recent developments on the so called "Perfectly Matched Layer" (PML) method. We take as model the scattering problems in linear acoustics. First, the Cartesian PML equations are described in the time domain for the split Berenger and the unsplit Zhao-Cangellaris formulations. The energy estimates existing in the literature are revised, and the coupled fluid/PML problem is introduced. Next, the pressure formulation of the Cartesian PML model is derived in the frequency domain. We show that a PML method based on a non-integrable absorbing function allows recovering the exact solution in the physical domain of interest, in the framework of plane waves with oblique incidence. We revise the theoretical results that state the well-posedness of the continuous model for the acoustic scattering problem. Finally, we illustrate with some numerical results the efficiency and accuracy of the Cartesian PML approach and compare different absorbing profiles. Finally, we introduce the pressure formulation of the radial PML model in the frequency domain and revise the theoretical results that assess the accuracy of this technique in the continuous model. Under convenient assumptions, we show its convergence when the thickness of the PML becomes larger and its exactness when a non-integrable absorbing function is used. The numerical accuracy of this approach is also illustrated. [ABSTRACT FROM AUTHOR]

This is a survey of numerical methods to compute a particular fluid-solid interaction: the so called "elastoacoustic problem". It concerns the determination of the motion of an elastic structure in contact with a compressible fluid. In this case displacements are small and, then, we can assume a linear response of the structure.We neglect gravity effects and consider a homogeneous fluid for which its reference density is constant. Other usual simplifications for this kind of problems are that viscous effects are not relevant in the fluid and that velocities are small enough for convective effects to be neglected. We review several alternative formulations of the elastoacoustic vibration problem, which differ from each other in the variables used to describe the fluid: pressure, a displacement potential or both. In all these cases, standard Lagrange finite elements are used for the discretization. We compare the results obtained with all these methods and with the pure displacement formulation, which has to be discretized by Raviart-Thomas elements. Next, we show how to apply a modal synthesis approach based on the displacement potential formulation. Finally, we report how the pure displacement formulation can be used to deal with thin layers of interface acoustic damping material and to solve the elastoacoustic problem in the time-domain. [ABSTRACT FROM AUTHOR]

In this work we study high order finite volume methods by state reconstructions. We apply it to beload sediment transport problems. For the hydrodynamical component we consider Shallow Water Equations, for the morphodynamical component we consider a continuity equation [ABSTRACT FROM AUTHOR]

This paper presents a new hybrid intelligent system that solves the Bin Packing Problem. The methodology involves the fusion of Soft Computing by means a genetic algorithm and Hard Computing using limits criterion and deterministic strategies. The innovative proposal inverts minimum computational resources expressed in generations with a high level quality solution and shows the algorithm performance with statistical methods. The average theoretical ratio for 1370 standard instances was 1.002 and the best known solution was achieved in 83.72% of the cases. As future work, an exhaustive analysis of characteristics of the hardest instances is proposed; the purpose is to find new hybrid methods. [ABSTRACT FROM AUTHOR]

In this work different numerical models related with the sediment transport process are presented. Two kinds of models are presented: the first one uses a continuity equation for the sediment layer in order to study bed-load sediment transport phenomena. The second one is a model for submarine avalanches. [ABSTRACT FROM AUTHOR]

Texture is a quality attribute that is critical in determining the acceptability of raw and processed fruits, so it is of primary concern in product development and/or preservation techniques design. Texture is a sensory attribute that can only be sensed by people. Perceived texture results from an array of sensory inputs, arising before and during consumption (Jack et al., 1995). As a rule, one texture property is based on various physical properties. However, product texture is closely related with product rheology, and this is one of the most obvious reasons for studying fruit rheology. Mechanical properties of biologic tissues depend on contributions from the different levels of structure: the molecular level (i.e., the chemicals and interactions between the constituting polymers), the cellular level (i.e., the architecture of the tissue cells and their interaction) and the organ level (i.e., the arrangement of cells into tissues and their chemical and physical interactions) (Ilker and Szczesniak, 1990; Waldron et al., 1997; Jackman and Stanley, 1995a; Alzamora et al., 2000). Fruits are composite materials and consist of various structural elements with different mechanical properties. The edible portion of most plant foods is predominantly composed of parenchymatous tissue. The parenchyma cells, approximately 50-500µm across and polyhedral or spherical in shape, show, from out to inner, the middle lamella that glue adjacent cells; the primary cell wall with the plasmodesmata; the plasma membrane; a thin layer of parietal cytoplasm containing different organelles (mitochondrias, spherosomes, plastids, chloroplasts, endoplasmic reticulum, nucleus and so on); and, bound by the tonoplast membrane, one or more vacuoles that contain a watery solution of organic acids, salts, pigments, and flavors that are responsible for the osmotic potential of the cell. Cells and intercellular spaces are arranged into tissues, and these last into the final organ (Brett and Waldron, 1996). This chapter is part of a comprehensive study on the relationship between structure, rheology and texture of raw and minimally processed fruit. With this aim, this chapter is intended to explore the correlation between the linear viscoelastic (oscillatory shear and creep) properties and the microstructure/ultrastructure of selected fruits (melon, apple), as affected by osmotic dehydration and/or calcium incorporation. [ABSTRACT FROM AUTHOR]

This paper presents the remote sensing techniques of measuring sea states, currents and bathymetry by using an X-band nautical radar. It briefly describes the fundamental methods to infer sea state information (e.g. ocean wave and current parameters) from nautical radar imagery. In addition, this work describes in detail the performance of the Wave Monitoring System WaMoS II (a commercial system for real-time monitoring of wave fields based on nautical radar technology). Two examples of nautical radar applications are presented: the first application is an example of the standard WaMoS II installation for sea state measurements, and the second application shows results of a research project aiming at the determination of shallow water bathymetry by means of nautical radar imagery. [ABSTRACT FROM AUTHOR]

Recently, we have introduced a new procedure to automatically generate students' conceptual models to assist teachers in finding out their students' main misconceptions and lack of concepts, from their interaction with an automatic and adaptive free-text scoring system. In this paper, we present an improvement of this procedure: the models can be built from the students' answers in plain text and they refer not only to one particular student but to the whole class. We also introduce a new tool called COMOV (COnceptual MOdels Viewer) to display the models as concept maps, tables, bar charts or text summaries. Finally, we provide an evaluation of this new approach. [ABSTRACT FROM AUTHOR]

We introduce the notion of security-mediated certificateless (SMC) cryptography. This allows more lightweight versions of mediated cryptography while maintaining the ability for instantaneous revocation of keys. Moreover, our solutions avoid key escrow, which has been used in all previous mediated cryptography algorithms. We provide a model of security against a fully-adaptive chosen ciphertext attacker, who may be a rogue key generation centre or any coalition of rogue users. We present a generic construction and also a concrete algorithm based on bilinear pairings. Our concrete scheme is more efficient than the identity-based mediated encryption scheme of Baek and Zheng in PKC 2004 which is provably secure in a comparable security model. In addition, our proposals can be easily extended to support distributed security mediators. Keywords: security-mediated cryptography, certificateless cryptography. [ABSTRACT FROM AUTHOR]

Voice pathologies have become a social concern, as voice and speech play an important role in certain professions, and in the general population quality of life. In these last years emphasis has been placed in early pathology detection, for which classical perturbation measurements (jitter, shimmer, HNR, etc.) have been used. Going one step ahead the present work is aimed to estimate the values of the biomechanical parameters of the vocal fold system, as mass, stiffness and losses by the inversion of the vocal fold structure, which could help non only in pathology detection, but in classifying the specific patient's pathology as well. The model structure of the vocal cord will be presented, and a method to estimate the biomechanical parameters of the cord body structure will be described. From these, deviations from normophonic cases, and unbalance between cords may be extracted to serve as pathology correlates. The relevance of deviations and unbalance in Pathology Detection is shown through Principal Component Analysis. Results for normal and pathological cases will be presented and discussed. [ABSTRACT FROM AUTHOR]

We analyse some questions concerning splitting solution techniques of non-hydrostatic models with atmospheric forcing. We prove that at the free surface the dynamic pressure must exactly vanish. We also analyse a linearised model of free surface and give simple rules to construct stable pairs of (horizontal velocities, free surfaces) for mixed discretizations. [ABSTRACT FROM AUTHOR]

This paper is concerned with the numerical approximation of bed-load sediment transport due to water evolution. We introduce an unified formulation for several bed-load models. Some numerical simulations are presented.4 [ABSTRACT FROM AUTHOR]

The recent H.264 video coding standard has been developed to increase video coding efficiency, achieving better Rate-Distortion results than any other standard. This is mainly due to the new features included at the motion estimation process, as tree structured motion compensation and multiple reference frames. However, the motion estimation stage is the most expensive part of a video encoder, and these improvements greatly intensify this computational load. To solve this situation, in this paper we propose a fast mode decision scheme, that analyses the activity between frames and classify the picture into active and non-active areas. This classification is performed with and adaptive thresholding technique that minimizes the area set as active and the activity energy of the area set as non-active. For each macroblock, a sub-set of inter-prediction alternatives is selected according to the amount of active and non-active area inside it. Results show motion estimation time reduction of 38% to 51% while achieving Rate-Distortion values very similar to the ones obtained with the complete analysis of inter-prediction alternatives. [ABSTRACT FROM AUTHOR]

Formal system development needs expressive specification languages, but also calls for highly automated tools. These two goals are not easy to reconcile, especially if one also aims at high assurances for correctness. In this paper, we describe a combination of Isabelle/HOL with a proof-producing SMT (Satisfiability Modulo Theories) solver that contains a SAT engine and a decision procedure for quantifier-free first-order logic with equality. As a result, a user benefits from the expressiveness of Isabelle/HOL when modeling a system, but obtains much better automation for those fragments of the proofs that fall within the scope of the (automatic) SMT solver. Soundness is not compromised because all proofs are submitted to the trusted kernel of Isabelle for certification. This architecture is straightforward to extend for other interactive proof assistants and proof-producing reasoners. [ABSTRACT FROM AUTHOR]

We analyze the problem of storing contextual information across a set of distributed heterogeneous mobile devices. These devices form a Mobile Ad Hoc Network (MANET) interconnected to Internet, in which partitions may eventually happen due to mobility. We present a new mechanism called Contextual Hash Table (CHT), which uses the semantic of the contextual information to select which nodes will store that information. Unlike previous general-purpose data replication algoritms, CHT manages to store information in the area of the network in which that information is most likely needed by neighboring nodes. [ABSTRACT FROM AUTHOR]

Two methods to implement privacy in network communication, anonymity and DCSC (data confidentiality and secure computation) are analysed and compared in regard to privacy in mobile agent applications. It is illustrated that privacy through DCSC is more suitable in mobile agent applications. To support this conclusion, privacy is concretely implemented in a bidding mobile agent scheme in this paper. Success of this example demonstrates that privacy can be practically achieved in mobile agent applications through DCSC without compromising the advantage of mobile agent. Keywords: Mobile agent, privacy, DCSC, secure computation. [ABSTRACT FROM AUTHOR]

In this paper we investigate several issues for equivalence classes of Boolean functions which are interesting for cryptology. As well as reviewing the established concepts, we present three new applications of these ideas. Firstly we propose a novel yet natural extension to the existing transform based equivalence class distinguishing algorithm, which can provide improved performance. Secondly, making novel use of the class graph notion, we completely explain the required conditions for high nonlinearity in the concatenation construction of Boolean functions. Finally, we use the linear class graph to comment on algebraic attacks by defining all the equivalence classes possible for the important set of annihilating functions. This approach provides a new solution to the problem of finding (and avoiding) low degree annihilators. [ABSTRACT FROM AUTHOR]

The PCBC block cipher mode of operation has many variants, of which one, due to Meyer and Matyas, dates back over 20 years. Whilst a particularly simple variant of PCBC has long been known to be very weak when used for data integrity protection, the Meyer-Matyas variant has not previously been attacked. In this paper we cryptanalyse this mode, and show that it possesses a serious weakness when used for data integrity protection. Specifically, we show how to construct an existential forgery using only a single known ciphertext message and a modest amount of known plaintext (this could be as little as three plaintext blocks). We also describe a ciphertext-only existential forgery attack against another, recently proposed, PCBC-variant called M-PCBC. [ABSTRACT FROM AUTHOR]

Mobile and ad-hoc networks allow businesses to provide a new range of applications and services and at the same time they introduce new constraints that have important effects on the way in which security primitives must be designed. This is challenging because it translates to a demand of richer and more flexible security primitives that often need to satisfy stricter requirements than traditional wired network scenarios. In this paper we focus on one of this primitive, namely security credentials. We present a solution that extends the existing protocols used to implement off-line credentials such that, not only abuses can be detected but they can also be counted. Our solution addresses the problem of 1-time and 2-times credentials and we will conclude by discussing the challenges that need to be solved to generalize the primitive to k=n. [ABSTRACT FROM AUTHOR]

Anonymous credentials are an important privacy-enhancing technique that allows users to convince a service provider of their legitimacy for service accesses in an anonymous manner. Among others, a fundamental feature of anonymous credentials is unlinkability, that is, multiple showings of the same credential should not be linked by the service providers, the issuing organization, or the coalition of the two. Recently, Persiano et. al. proposed an interesting anonymous credential system, which was claimed to be unlinkable. In this paper, we prove that their unlinkability claim is false. In particular, we show that the issuing organization can easily relate two showings of the same credential, point out the flaw in their original security proof and present a fix to avoid our attack. [ABSTRACT FROM AUTHOR]

We have seen an explosion in the number of: conferences and workshops on all aspects of information security, topics studied in this field, and papers published. At the same time we have only seen a few widely deployed applications of this research. Meanwhile, computers are becoming less secure and criminals are exploiting new tricks. So, there is clearly a gap between theory and practice in information security. In this paper we analyze it and discuss the potential impacts of this gap. [ABSTRACT FROM AUTHOR]

Multivariate public-key cryptosystems (sometimes polynomial-based PKC's or just multivariates) handle polynomials of many variables over relatively small fields instead of elements of a large ring or group. The "tame-like" or "sparse" class of multivariates are distinguished by the relatively few terms that they have per central equation. We explain how they differ from the "big-field" type of multivariates, represented by derivatives of C∗ and HFE, how they are better, and give basic security criteria for them. The last is shown to be satisfied by efficient schemes called "Enhanced TTS" which is built on a combination of the Oil-and-Vinegar and Triangular ideas. Their security levels are estimated. In this process we summarize and in some cases, improve rank-based attacks, which seek linear combinations of certain matrices at given ranks. These attacks are responsible for breaking many prior multivariate designs. [ABSTRACT FROM AUTHOR]

In ICICS 2004, Gonzalez-Deleito, Markowitch and Dall'Olio proposed an efficient strong key-insulated signature scheme. They claimed that it is (N-1,N)-key-insulated, i.e., the compromise of the secret keys for even N-1 time periods does not expose the secret keys for the remaining time period. But in this paper, we demonstrate an attack and show that an adversary armed with the signing keys for any two time periods can derive the signing key for any of the remaining time periods with high probability. In a second attack, the adversary may be able to forge signatures for many remaining time periods without computing the corresponding signing keys. A variant forward-secure signature scheme was also presented in ICICS 2004 and claimed more robust than traditional forward-secure signature schemes. But we find that the scheme has two similar weaknesses. We give the way how to repair the two schemes in this paper. [ABSTRACT FROM AUTHOR]

In this paper we present an efficient ID-based authenticated key agreement (AKA) protocol by using bilinear maps, especially well suited to unbalanced computing environments : an ID-based AKA protocol for Server and Client. Particularly, considering low-power clients' devices, we remove expensive operations such as bilinear maps from a client side. To achieve our goal we combine two notions, key agreement and ID-based authenticryption in which only designated verifier (or Sever) can verify the validity of a given transcript. We prove the security of our ID-based AKA protocols in the random oracle model. [ABSTRACT FROM AUTHOR]

The Host Identity Protocol (HIP) is an Internet security and multi-addressing mechanism specified by the IETF. HIP introduces a new layer between the transport and network layers of the TCP/IP stack that maps host identifiers to network locations, thus separating the two conflicting roles that IP addresses have in the current Internet. This paper analyzes the security and functionality of the HIP base exchange, which is a classic key exchange protocol with some novel features for authentication and DoS protection. The base exchange is the most stable part of the HIP specification with multiple existing implementations. We point out several security issues in the current protocol and propose changes that are compatible with the goals of HIP. [ABSTRACT FROM AUTHOR]

We present the first group signature scheme with provable security and signature size O(λ) bits where the group manager, the group members, and the Open Authority (OA) are all identity-based. We use the security model of Bellare, Shi, and Zhang [3], except to add three identity managers for manager, members, and OA respectively, and we discard the Open Oracle (${\mathcal O} {\mathcal O}$). Our construction uses identity-based signatures summarized in Bellare, Namprempre, and Neven [2] for manager, Boneh and Franklin's IBE [7] for OA, and we extend Bellare et al.[3]'s group signature construction by verifiably encrypt an image of the member public key, instead of the public key itself. The last innovation is crucial in our efficiency; otherwise, Camenisch and Damgard[9]'s verifiable encryption would have to be used resulting in lower efficiency. [ABSTRACT FROM AUTHOR]

We propose a new group signature scheme which is secure if we assume the Decision Diffie-Hellman assumption, the q-Strong Diffie-Hellman assumption, and the existence of random oracles. The proposed scheme is the most efficient among the all previous group signature schemes in signature length and in computational complexity. [ABSTRACT FROM AUTHOR]

Group signature schemes with membership revocation have been intensively researched. However, signing and/or verification of some existing schemes have computational costs of O(R), where R is the number of revoked members. Existing schemes using a dynamic accumulator or a similar technique have efficient signing and verifications with O(1) complexity. However, before signing, the signer has to modify his secret key with O(N) or O(R) complexity, where N is the group size. Therefore, for larger groups, signers suffer from enormous costs. On the other hand, an efficient scheme for middle-scale groups with about 1,000 members is previously proposed, where the signer need not modify his secret key. However this scheme also suffers from heavy signing/verification costs for larger groups. In this paper, we adapt the middle-scale scheme to the larger groups. At the sacrifice of the group manager's cost, our signing/verification has only O(1) complexity. [ABSTRACT FROM AUTHOR]

We observe that the definitions of security in the computational complexity proof models of Bellare & Rogaway (1993) and Canetti & Krawczyk (2001) require two partners in the presence of a malicious adversary to accept the same session key, which we term a key sharing requirement. We then revisit the Bellare-Rogaway three-party key distribution (3PKD) protocol and the Jeong-Katz-Lee two-party authenticated key exchange protocol $\mathcal{TS}2$, which carry claimed proofs of security in the Canetti & Krawczyk (2001) model and the Bellare & Rogaway (1993) model respectively. We reveal previously unpublished flaws in these protocols where we demonstrate that both protocols fail to satisfy the definition of security in the respective models. We present a new 3PKD protocol as an improvement with a proof of security in the Canetti & Krawczyk (2001) model and a simple fix to the specification of protocol $\mathcal{TS}2$. We also identify several variants of the key sharing requirement and present a brief discussion. [ABSTRACT FROM AUTHOR]

A secure roaming protocol involves three parties: a roaming user, a visiting foreign server and the user's home server. The protocol allows the user and the foreign server to establish a session key and carry out mutual authentication with the help of the home server. In the mutual authentication, user authentication is generally done in two steps. First, the user claims that a particular server is his home server. Second, that particular server is called in by the foreign server for providing a ‘credential' which testifies the user's claim. We present a new attacking technique which allows a malicious server to modify the user's claim in the first step without being detected and provide a fake credential to the foreign server in the second step in such a way that the foreign server believes that the malicious server is the user's home server. We give some examples to explain why it is undesirable in practice if a roaming protocol is vulnerable to this attack. We also show that there are three roaming protocols proposed previously which are vulnerable to this attack. [ABSTRACT FROM AUTHOR]

In CRYPTO2002, Bresson, Stern, and Szydlo proposed a threshold ring signature scheme. Their scheme uses the notion of fair partition and is provably secure in the random oracle model. Their scheme is efficient when the number t of signers is small compared with the number n of group members, i.e., $t={\mathcal O}(\log{n})$ (we call this scheme BSS scheme). However, it is inefficient when t is ω(logn). In this paper, we propose a new threshold ring signature scheme which is efficient when the number of signers is large compared with the number n of group members, i.e., when the number t of non-signers in the group members is small compared with n. This scheme is very efficient when $t={\mathcal O}(\log{n})$. This scheme has a kind of dual structure of BSS scheme which is inefficient when the number of signers is large compared with the number of group members. In order to construct our scheme, we modify the trap-door one-way permutations in the ring signature scheme, and use the combinatorial notion of fair partition. This scheme is provably secure in the random oracle model. [ABSTRACT FROM AUTHOR]

We present protocols for threshold decryption and threshold key generation in the GBD public-key cryptosystem in the "honest-but-curious" setting. These allow GBD computations to be performed in a distributed manner during both key generation and decryption, without revealing the private key to any party. GBD threshold decryption is similar to El-Gamal threshold decryption. GBD threshold key generation is based on adaptations of protocols for RSA key generation by Boneh and Franklin, and Catalano et al, and includes a new protocol for efficiently computing the inverse of a shared secret modulo another shared secret. We also show an application of GBD threshold cryptography to RSA key recovery, and point out two open problems in this application. [ABSTRACT FROM AUTHOR]

Several threshold RSA signature schemes have been proposed, in particular the schemes [4,8] and [20]. Recent research has shown that the earlier schemes [4,8] may be in some cases more "efficient" than these later schemes. Here we describe efficient implementations of threshold RSA schemes as well as further enhancements to improve performance of the Desmedt-Frankel scheme. Our conclusion is that if memory is not an issue there will be situations, for example if one can expect shareholders know who will be participating in the signature generation, that the Desmedt-Frankel scheme is very efficient. [ABSTRACT FROM AUTHOR]

In this paper we analyze the access control requirements of the dynamic virtual organization in grid environment and define an absolutely decentralized access control mechanism for the dynamic coalition characteristic of virtual organization. The access control framework in the paper combines the threshold BLS signature schema and the role based access control mechanism to provide a flexible and decentralized mechanism for the VO-based grid applications. [ABSTRACT FROM AUTHOR]

Role Based Access Control (RBAC) [6] is a popular approach to specify and enforce security policies in organizations. In RBAC, users are not directly assigned permission but with the use of roles as the intermediary. Role activation is one important component in RBAC. A user may activate a subset of his/her assigned roles to exercise the associated permission. This paper proposes a number of ways in which the role activation constraints can be specified and enforced in the enterprise environment. Also, an access control model and an authorization process are proposed to support the specification and enforcement of dynamic separation of duty constraints in a decentralized manner. Key words: Role Based Access Control, Security Management, Role Activation, Dynamic Separation of Duty [ABSTRACT FROM AUTHOR]

There are now more than 7 million internet banking users in Australia. Despite this substantial uptake in Australia, Australian banks continue to concentrate their respective security efforts upon internal mechanisms. Education of bank customers has not for the most part solved the fundamental flaws existent in internet banking. It is widely accepted that the weakest link in internet banking facilities is not with the banks' internal mechanisms but with customer PC. This paper analyses the research opportunities available to improve internet banking in Australia, which research could be exported to other jurisdictions where internet banking is available. [ABSTRACT FROM AUTHOR]