1,721,206 research outputs found
Introduction: no justice, no ecological peace: the groundings of ecological reparation
Full text linkIntroduction: no justice, no ecological peace: the groundings of ecological reparation
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
VEX : a zkRollup architecture for verifiable exchange systems
No full textNon-custodial on-chain trading platforms are foundational to decentralized finance (DeFi), enabling transparent and verifiable asset exchanges while allowing users to retain direct control over their funds. However, scalability limitations on Layer 1 (L1) blockchains have driven the adoption of Layer 2 (L2) solutions, with zero-knowledge rollups (zkRollups) emerging as a prominent approach. Although zkRollups address scalability challenges, they encounter significant computational bottlenecks during proof generation, leading to elevated hardware requirements and extended proving times. This thesis presents VEX, an application-specific zkRollup architecture for verifiable exchange systems. To mitigate prover inefficiencies, two key optimizations are introduced: (1) Adopting PLONK with Segment Lookup for Branching Logic, which dynamically activates transaction-specific sub-circuits based on batch inputs, ensuring that prover costs scale quasi-linearly with the number of active sub-circuits; and (2) Shared Logic Separation, which precomputes and independently proves shared operations, such as signature verification and hashing, reducing segment lookup overhead and enabling tailored optimizations. The proof components for shared and transaction-specific logic are aggregated through an AND composition of CP-SNARKs. A Link Protocol with universal setup is proposed, ensuring constant proof size and verification time for CP-PLONK compositions. Additionally, cross-framework composition between PLONK with Segment Lookup and Groth16 is facilitated through an intermediate PLONK circuit. Experimental evaluations demonstrate that VEX achieves a throughput of 11 transactions per second (TPS) on a budget machine with four physical cores and a batch size of 1024. Transaction-specific logic proving is 43 times faster than that of monolithic designs. These results highlight the potential of VEX to deliver significantly higher throughput with improved hardware configurations, positioning it as a scalable solution for verifiable exchange systems.</p
Pigeon : a space-efficient zkSNARK with optimal proving time
No full textWe present Pigeon, the first space-efficient zkSNARK for the correct computation of layered data- parallel arithmetic circuits with asymptotically optimal prover time. More precisely, for any layered data-parallel arithmetic circuit C, Pigeon has proving complexity of O( field/group operations, proof size and verification time of O(√ while the space complexity is O( + √ + Seval), where Seval << ← is the space needed to evaluate the circuit. Pigeon is built upon a novel space-efficient sumcheck protocol for inner products that rely on folding schemes for sumcheck instances and achieves linear proving time—a logarithmic improvement over the state of the art. We then use it to instantiate a space-efficient variant of the GKR protocol. Finally, we compile our modified GKR using two space-efficient Polynomial commitment schemes. The first uses the Kopis scheme while the second relies on the Brakedown scheme along with additional optimizations concretely reducing its proof size. By doing so, we obtain two instantiations of Pigeon with different performance and security guarantees. In particular, the first has a small proof size and verification times, while the sec- ond enjoys a considerably faster prover and is post-quantum. Our experimental results for three use cases (arbitrary data parallel circuits, multiplication trees, batch SHA256 hashing) indicate Pigeon outperforms the prior state-of-the-art space-efficient SNARK for arithmetic circuits Gemini (Bootle et al., EUROCRYPT’22) by 4-128× in prover space and 5.6-27.6× in prover time. Even more interestingly, compared to standard GKR-based zkSNARKs, uses 32-1000×← less space while having no more than 2× proving overhead.</p
Secure and practical search over dynamic encrypted datasets
No full textThis thesis studies the problem of dynamic symmetric searchable encryption (DSE) where one or more data owners store their encrypted data on an untrusted remote server, and wishes to efficiently search on it (or allow other users to access it). This is a heavily studied problem in literature and the specific focus of this thesis is on dynamic schemes, i.e., with efficient support for data insertion, deletion, and modification. In particular, it is crucial to minimize the information revealed to the server as a result of not only search queries, but also updates. We present schemes that achieve the two strongest privacy notions for DSE: forward and backward privacy. The first makes it hard for the server to link an update operation with previous queries, while the second limits what the server can learn about entries that were deleted from the database, from queries that happen after the deletion. Our results improve the state-of-the-art in this area across multiple aspects, as we describe next. First, we introduce novel constructions that are extremely lightweight while also achieving stronger backward privacy notions than existing ones. Our first scheme Mitra achieves Type-II backward privacy and is, to the best of our knowledge, the fastest and easiest to implement DSE scheme to date. Our second scheme Orion achieves even stronger Type-I backward privacy and is the only implemented scheme in the literature of its kind. Finally, our third scheme Horus improves the second one by reducing the number of communication roundtrips during queries, but reveals slightly more information to the server (Type-III backward privacy). Second, we explicitly focus on DSE with efficient (optimal/quasi-optimal) search in the presence of deletions, i.e., constructions where the search overhead is within a polylogarithmic multiplicative factor of the theoretical optimal (i.e., the result size of a search). This property is achieved by our schemes Orion and Horus but we next aim at much more practically efficient schemes. Towards that end, we first propose OSSE, the first DSE scheme that can achieve asymptotically optimal search time, improving the previous state-of-the-art by a multiplicative logarithmic factor. We also propose an alternative scheme LLSE, that achieves a sublogarithmic search overhead compared to the optimal. While this is slightly worse than the previous scheme, it still outperforms all prior works, while also achieving faster deletions and smaller server storage. Third, we shift our attention to the problem of multi-user dynamic searchable symmetric encryption (DMUSSE) where some of the users may be colluding with the server to extract additional information about the dataset, besides what the owner is willing to server with them. We provide the first formal security and forward/backward privacy definitions for the dynamic multi-user setting. We then propose μSE, the first provably secure DMUSSE scheme under our definition and instantiate it in two versions, with different performance trade-offs. Furthermore, we extend μSE to support verifiability of results by adopting a blockchain-based approach for the digests’ dissemination. Finally, we prototype all our schemes and open-source their code. We evaluate their performance for different datasets and queryloads, experimentally compare them with prior state-of-the-art DSE schemes, and report the results.</p
An integrated system for privacy-preserving, and auditable transactions on hyperledger fabric
No full textThe banking industry is considering adopting permissioned blockchain technology to improve security and reconcile transactions efficiently. The financial institutions are determined to demonstrate their compliance, but the banks are reluctant to have the ledgers transparent to the other network participants as it might leak trading strategy. In this thesis, we provide an integrated system for privacy-preserving, and auditable decentralized transaction system on Hyperledger Fabric with zkLedger. Through literature review, prototype design, and experimentation, the study identifies the challenges and bottlenecks in implementing the zkLedger design on Hyperledger Fabric, particularly regarding transaction security and concurrency. Two approaches are proposed as trade-offs between security and efficiency: the first provides complete security properties but requires serial transaction processing, while the second allows concurrent transactions with delayed Proof of Assets, offering increased practicality at the cost of reduced security. The research contributes to the understanding of auditable privacy-preserving transactions on blockchain and presents a novel approach to implementing zkLedger with enhanced concurrency, improving the overall efficiency and scalability of the system.</p
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