Tight reduction for generic construction of certificateless signature and its instantiation from DDH assumption

Certificateless signature was proposed by Al-Riyami and Paterson to eliminate the certificate management in the public-key infrastructures and solve the key escrow problem in the identity-based signature. In 2007, Hu et al. proposed a generic construction of certificateless signature. They construct certificateless signature scheme from any standard identity-based signature and signature scheme.However, their security reduction is loose; the security of the constructed scheme depends on the number of users. In this paper, we give the tight reduction for their construction and instantiate a tightly-secure certificateless signature scheme without pairing from DDH assumption. Best of our knowledge, this scheme is the first tightly-secure certificateless signature scheme

Critical Perspectives on Provable Security: Fifteen Years of Another Look Papers

We give an overview of our critiques of “proofs” of security and a guide to our papers on the subject that have appeared over the past decade and a half. We also provide numerous additional examples and a few updates and errata

Biometric Cryptosystems : Authentication, Encryption and Signature for Biometric Identities

Biometrics have been used for secure identification and authentication for more than two decades since biometric data is unique, non-transferable, unforgettable, and always with us. Recently, biometrics has pervaded other aspects of security applications that can be listed under the topic of ``Biometric Cryptosystems''. Although the security of some of these systems is questionable when they are utilized alone, integration with other technologies such as digital signatures or Identity Based Encryption (IBE) schemes results in cryptographically secure applications of biometrics. It is exactly this field of biometric cryptosystems that we focused in this thesis. In particular, our goal is to design cryptographic protocols for biometrics in the framework of a realistic security model with a security reduction. Our protocols are designed for biometric based encryption, signature and remote authentication. We first analyze the recently introduced biometric remote authentication schemes designed according to the security model of Bringer et al.. In this model, we show that one can improve the database storage cost significantly by designing a new architecture, which is a two-factor authentication protocol. This construction is also secure against the new attacks we present, which disprove the claimed security of remote authentication schemes, in particular the ones requiring a secure sketch. Thus, we introduce a new notion called ``Weak-identity Privacy'' and propose a new construction by combining cancelable biometrics and distributed remote authentication in order to obtain a highly secure biometric authentication system. We continue our research on biometric remote authentication by analyzing the security issues of multi-factor biometric authentication (MFBA). We formally describe the security model for MFBA that captures simultaneous attacks against these systems and define the notion of user privacy, where the goal of the adversary is to impersonate a client to the server. We design a new protocol by combining bipartite biotokens, homomorphic encryption and zero-knowledge proofs and provide a security reduction to achieve user privacy. The main difference of this MFBA protocol is that the server-side computations are performed in the encrypted domain but without requiring a decryption key for the authentication decision of the server. Thus, leakage of the secret key of any system component does not affect the security of the scheme as opposed to the current biometric systems involving cryptographic techniques. We also show that there is a tradeoff between the security level the scheme achieves and the requirement for making the authentication decision without using any secret key. In the second part of the thesis, we delve into biometric-based signature and encryption schemes. We start by designing a new biometric IBS system that is based on the currently most efficient pairing based signature scheme in the literature. We prove the security of our new scheme in the framework of a stronger model compared to existing adversarial models for fuzzy IBS, which basically simulates the leakage of partial secret key components of the challenge identity. In accordance with the novel features of this scheme, we describe a new biometric IBE system called as BIO-IBE. BIO-IBE differs from the current fuzzy systems with its key generation method that not only allows for a larger set of encryption systems to function for biometric identities, but also provides a better accuracy/identification of the users in the system. In this context, BIO-IBE is the first scheme that allows for the use of multi-modal biometrics to avoid collision attacks. Finally, BIO-IBE outperforms the current schemes and for small-universe of attributes, it is secure in the standard model with a better efficiency compared to its counterpart. Another contribution of this thesis is the design of biometric IBE systems without using pairings. In fact, current fuzzy IBE schemes are secure under (stronger) bilinear assumptions and the decryption of each message requires pairing computations almost equal to the number of attributes defining the user. Thus, fuzzy IBE makes error-tolerant encryption possible at the expense of efficiency and security. Hence, we design a completely new construction for biometric IBE based on error-correcting codes, generic conversion schemes and weakly secure anonymous IBE schemes that encrypt a message bit by bit. The resulting scheme is anonymous, highly secure and more efficient compared to pairing-based biometric IBE, especially for the decryption phase. The security of our generic construction is reduced to the security of the anonymous IBE scheme, which is based on the Quadratic Residuosity assumption. The binding of biometric features to the user's identity is achieved similar to BIO-IBE, thus, preserving the advantages of its key generation procedure

Faculty Publications and Creative Works 2005

Faculty Publications & Creative Works is an annual compendium of scholarly and creative activities of University of New Mexico faculty during the noted calendar year. Published by the Office of the Vice President for Research and Economic Development, it serves to illustrate the robust and active intellectual pursuits conducted by the faculty in support of teaching and research at UNM. In 2005, UNM faculty produced over 1,887 works, including 1,887 scholarly papers and articles, 57 books, 127 book chapters, 58 reviews, 68 creative works and 4 patented works. We are proud of the accomplishments of our faculty which are in part reflected in this book, which illustrates the diversity of intellectual pursuits in support of research and education at the University of New Mexico

Conservative management of retinoblastoma : Challenging orthodoxy without compromising the state of metastatic grace. "Alive, with good vision and no comorbidity"

Correction: Volume: 78 Article Number: 100857 DOI: 10.1016/j.preteyeres.2020.100857 Published: SEP 2020Retinoblastoma is lethal by metastasis if left untreated, so the primary goal of therapy is to preserve life, with ocular survival, visual preservation and quality of life as secondary aims. Historically, enucleation was the first successful therapeutic approach to decrease mortality, followed over 100 years ago by the first eye salvage attempts with radiotherapy. This led to the empiric delineation of a window for conservative management subject to a "state of metastatic grace" never to be violated. Over the last two decades, conservative management of retinoblastoma witnessed an impressive acceleration of improvements, culminating in two major paradigm shifts in therapeutic strategy. Firstly, the introduction of systemic chemotherapy and focal treatments in the late 1990s enabled radiotherapy to be progressively abandoned. Around 10 years later, the advent of chemotherapy in situ, with the capitalization of new routes of targeted drug delivery, namely intra-arterial, intravitreal and now intracameral injections, allowed significant increase in eye preservation rate, definitive eradication of radiotherapy and reduction of systemic chemotherapy. Here we intend to review the relevant knowledge susceptible to improve the conservative management of retinoblastoma in compliance with the "state of metastatic grace", with particular attention to (i) reviewing how new imaging modalities impact the frontiers of conservative management, (ii) dissecting retinoblastoma genesis, growth patterns, and intraocular routes of tumor propagation, (iii) assessing major therapeutic changes and trends, (iv) proposing a classification of relapsing retinoblastoma, (v) examining treatable/preventable disease-related or treatment-induced complications, and (vi) appraising new therapeutic targets and concepts, as well as liquid biopsy potentiality.Peer reviewe

Determinants of incentive-based forest governance in the Amazon : Evidence from Ecuador, Peru, and Brazil

Command-and-control policies are often criticized as insufficient to tackle tropical deforestation. Over the past two decades, both academics and policy-makers have promoted incentive-based policies, such as payments for environmental services, as attractive alternatives to curb forest loss, while also potentially contributing to poverty reduction of forest-dwelling populations. Many science-based recommendations on how to design effective incentive-based policies have, however, not found much resonance within policy circles. To understand the gap between recommendations and practice, it is important to understand why political decision-makers adopt incentive-based forest conservation schemes and what determines how these schemes are designed towards achieving environmental and non-environmental outcomes. To this end, we analyzed the governance dynamics of three government-led incentive schemes in the Amazon regions of Brazil, Ecuador, and Peru. We adopt a theoretical framework based on public policy theories, specifically on agenda-setting and policy instruments design. We find that environmental concerns are not always the prime motives for PES programs, as political and institutional contexts limit environmental policy-makers' actions. Yet, policy choice processes become less constrained when environmental issues are closer to a government's priorities. Electoral interests and bureaucratic politics exert pressure on policy design teams, who then trade off long-term societal efficiency concerns against short-term administrative goals. Lessons from other jurisdictions will often be drawn, as they may help in reaching acceptable policy proposals in a shorter time-frame. Priority is sometimes given to non-environmental concerns due to perceptions of political feasibility, to the influence of non-environmental agencies within governments, to beliefs in what role governments should take and how populations respond to proposed policies. These findings are especially relevant for scholars studying the processes and impacts of incentive-based conservation policies and for practitioners aiming to enhance policy efficiency.Politische Instrumente zur Überwachung und Bestrafung von illegaler Endwaldung (Command-and Control Policies) werden häufig als unzureichend kritisiert, um tropische Regenwälder effektiv und nachhaltig zu schützen. In diesem Kontext wurden in den letzten zwei Jahrzehnten sowohl von Wissenschaftlern als auch von politischen Entscheidungsträgern anreizorientierte Politikinstrumente beworben, um den Verlust der Regenwälder einzudämmen. Solche Instrumente umfassen beispielsweise Zahlungen für Umweltdienstleistungen, die zusätzlich die Armut der Bevölkerung in den Waldregionen mindern können. Dennoch fanden viele wissenschaftliche Empfehlungen für die Entwicklung effektiver, anreizorientierter Methoden wenig Resonanz in den politischen Kreisen. Um die Diskrepanz zwischen wissenschaftlichen Empfehlungen und der praktischen Umsetzung nachvollziehen zu können, ist es zunächst wichtig zu verstehen, warum anreizorientierte Instrumente überhaupt von den Politikern implementiert werden. Ferner ist es wichtig zu verstehen, welche Faktoren Einfluss auf das Politikdesign haben, dass die umweltspezifischen und umweltunspezifischen Ziele der Programme vorgibt. Zu diesem Zweck haben wir drei staatlich getragene Governance-Prozesse in Brasilien, Peru und Ecuador analysiert. Für unsere Studie benutzen wir ein theoretisches Gerüst, welches auf Theorien zur Staatstätigkeit (Public Policy) basiert, im Besonderen in den Bereichen des Agenda-Settings und der Entwicklung politischer Maßnahmen. Unsere Ergebnisse zeigen, dass umweltspezifische Ziele nicht immer der Hauptbeweggrund für die Entwicklung von Politiken zur Förderung von Umweltdienstleistung sind, da der politische und institutionelle Kontext häufig den Handlungsspielraum der verantwortlichen Politiker einschränkt. In diesem Kontext kann jedoch festgehalten werden, dass politische Entscheidungen immer dann ein geringeres Maß an Restriktionen erfahren, wenn der Umweltschutz allgemein einen hohen Stellenwert bei der verantwortlichen Regierung genießt. Wahltaktische und bürokratische Rahmenbedingungen beeinflussen zudem die politischen Gestalter, die langfristige gesellschaftliche Interessen und kurzfristige Regierungsziele gegeneinander ausbalancieren müssen. Dabei spielen auch immer die bisherigen Erfahrungen mit anderen Gesetzvorhaben eine große Rolle, da sie eine zeitnahe Ausarbeitung geeigneter politischer Konzepte ermöglichen. Desweiteren können umweltunspezifische Ziele denn Vorrang erhalten, wenn deren politische Durchsetzbarkeit einfacher erscheint. Ebenso kann die Priorisierung umweltunspezifischer Ziele auch durch den politischen Einfluss von Nichtregierungsorganisationen bestärkt werden, sowie durch politische Überzeugungen der gesetzesgebenden Akteure, zur Rolle des Staates allgemein und zu möglichen Reaktionen der Bevölkerung auf die Gesetzesvorhaben. Unsere Ergebnisse sind vor allem für Wissenschaftler relevant, die anreizorientierte Umweltschutzpolitiken erforschen und für Fachleute, die die Effektivität der Umweltpolitik verbessern möchten

Sustainability in fashion supply chains: Examining the dynamics of small and medium enterprise sustainability in fashion industry multitier supply chains

Sustainability in supply chain management (SSCM) has become established in both academia and increasingly in practice (Fraser, Müller and Schwarzkopf, 2020). As stakeholders continue to require organisations to take more responsibility for their entire supply chains, this has led to the development of multitier SSCM. Despite small and medium enterprises’ (SMEs’) pivotal impact on the global economy, environmental and social responsibility commitments and SSCM have been largely overlooked (Chow et al., 2017). Little attention has been paid to the convergence of sustainability dimensions in SMEs. This thesis examines how sustainability-inspired SMEs in the fashion industry in Scotland implement sustainability and diffuse sustainability across the diverse supply chain. This leads to an investigation of the factors that influence sustainability practices along the supply chain and practices adopted to verify sustainability in the supply chain, with an overall view to improving multidimensional performance. This research adopts an exploratory multiple case study approach that combines multiple data sources: semi-structured interviews, observation, and secondary data analysis. The empirical study includes two SME fashion retailers registered in Scotland and their respective supply chain partners. This thesis contributes to SSCM research in SMEs by exploring from both the conceptual and empirical points of view, investigating fashion SMEs’ sustainability and SSCM and developing a conceptual sustainability performance rating model. This conceptual model uses multidimensional sustainability measurement criteria derived from the literature to determine sustainability performance levels from the farm to the retailer. Evaluation of the supply chain is likely to aid supplier selection, sustainability comparison and transparency. The investigated fashion SMEs and their supply chains are used to exemplify the usefulness of the proposed conceptual sustainability performance model. Based on the supply chains investigated, both retailers’ sustainability performances are similar, while one supply chain outperformed the other. In addition, the research findings show that SME retailers face the greatest challenge in managing supply chain sustainability, while the most influential suppliers can develop creative approaches to diffuse sustainability within the supply chain. This thesis suggests that there is considerable need for further qualitative research and the proposed model perhaps needs to be implemented in various business models to evaluate its validity