184 research outputs found

    Sharp: Short Relaxed Range Proofs

    Get PDF

    РОЛЬ РОДИНИ ЛЕВИЦЬКИХ У РОЗВИТКУ ОСВІТИ І КУЛЬТУРИ ПРИОРІЛЛЯ (КІНЕЦЬ ХVIII – ПОЧАТОК ХХ СТ.)

    Get PDF
    У історії України мало знайдеться родин, які б впродовж більше 300 років так плідно працювали на ниві культури і освіти, як це було з родиною Левиць-ких. Корені роду Левицьких знаходяться на Волині А на Приоріллі його предста-вники з’явилися у другій половині ХVII ст. в період «Руїни», коли правобережні українські землі були перетворені на пустку [12, c. 553]. Уряд гетьмана Самой-ловича охоче надав правобережні поорільські землі для розселення втікачам з Правобережної України, маючи на меті їх руками освоїти ці тоді ще малозаселені землі і водночас перетворити містечка Нехворощу, Маячку, Китайгород, Царичанку на оборонні пункти від набігів орд кримських татар та своєї експансії на лівобережні поорільські землі , які запорозькі козаки вважали своєю територією [3, c. 414-415]. Саме в цей час Кирило Степанович Левицький стає в містечку Маячці священиком місцевої Михайлівської церкви , поклавши цим самим поча- ток цьому славетному роду і місцевій священицькій діяльності [3, c. 416]

    The Influence of Climatic Seasonality on the Diversity of Different Tropical Pollinator Groups

    Get PDF
    Tropical South America is rich in different groups of pollinators, but the biotic and abiotic factors determining the geographical distribution of their species richness are poorly understood. We analyzed the species richness of three groups of pollinators (bees and wasps, butterflies, hummingbirds) in six tropical forests in the Bolivian lowlands along a gradient of climatic seasonality and precipitation ranging from 410 mm to 6250 mm. At each site, we sampled the three pollinator groups and their food plants twice for 16 days in both the dry and rainy seasons. The richness of the pollinator groups was related to climatic factors by linear regressions. Differences in species numbers between pollinator groups were analyzed by Wilcoxon tests for matched pairs and the proportion in species numbers between pollinator groups by correlation analyses. Species richness of hummingbirds was most closely correlated to the continuous availability of food, that of bees and wasps to the number of food plant species and flowers, and that of butterflies to air temperature. Only the species number of butterflies differed significantly between seasons. We were not able to find shifts in the proportion of species numbers of the different groups of pollinators along the study gradient. Thus, we conclude that the diversity of pollinator guilds is determined by group-specific factors and that the constant proportions in species numbers of the different pollinator groups constitute a general pattern

    Hermes: I/O-Efficient Forward-Secure Searchable Symmetric Encryption

    Get PDF
    Dynamic Symmetric Searchable Encryption (SSE) enables a user to outsource the storage of an encrypted database to an untrusted server, while retaining the ability to privately search and update the outsourced database. The performance bottleneck of SSE schemes typically comes from their I/O efficiency. Over the last few years, a line of work has substantially improved that bottleneck. However, all existing I/O-efficient SSE schemes have a common limitation: they are not forward-secure. Since the seminal work of Bost at CCS 2016, forward security has become a de facto standard in SSE. In the same article, Bost conjectures that forward security and I/O efficiency are incompatible. This explains the current status quo, where users are forced to make a difficult choice between security and efficiency. The central contribution of this paper it to show that, contrary to what the status quo suggests, forward security and I/O efficiency can be realized simultaneously. This result is enabled by two new key techniques. First, we make use of a controlled amount of client buffering, combined with a deterministic update schedule. Second, we introduce the notion of SSE supporting dummy updates. In combination, those two techniques offer a new path to realizing forward security, which is compatible with I/O efficiency. Our new SSE scheme, Hermes, achieves sublogarithmic I/O efficiency O(loglogNp)O(\log\log \frac{N}{p}), storage efficiency O(1)O(1), with standard leakage, as well as backward and forward security. Practical experiments confirm that Hermes achieves excellent performance

    Practical Round-Optimal Blind Signatures in the ROM from Standard Assumptions

    Get PDF
    Blind signatures serve as a foundational tool for privacy-preserving applications and have recently seen renewed interest due to new applications in blockchains and privacy-authentication tokens. With this, constructing practical round-optimal (i.e., signing consists of the minimum two rounds) blind signatures in the random oracle model (ROM) has been an active area of research, where several impossibility results indicate that either the ROM or a trusted setup is inherent. In this work, we present two round-optimal blind signatures under standard assumptions in the ROM with different approaches: one achieves the smallest sum of the signature and communication sizes, while the other achieves the smallest signature size. Both of our instantiations are based on standard assumptions over asymmetric pairing groups, i.e., CDH, DDH, and/or SXDH. Our first construction is a highly optimized variant of the generic blind signature construction by Fischlin (CRYPTO\u2706) and has signature and communication sizes 447 B and 303 B, respectively. We progressively weaken the building blocks required by Fischlin and we result in the first blind signature where the sum of the signature and communication sizes fit below 1 KB based on standard assumptions. Our second construction is a semi-generic construction from a specific class of randomizable signature schemes that admits an all-but-one reduction. The signature size is only 96 B while the communication size is 2.2 KB. This matches the previously known smallest signature size while improving the communication size by several orders of magnitude. Finally, both of our constructions rely on a (non-black box) fine-grained analysis of the forking lemma that may be of independent interest

    Pairing-Free Blind Signatures from Standard Assumptions in the ROM

    Get PDF
    Blind Signatures are a useful primitive for privacy preserving applications such as electronic payments, e-voting, anonymous credentials, and more. However, existing practical blind signature schemes based on standard assumptions require either pairings or lattices. We present the first construction of a round-optimal blind signature in the random oracle model based on standard assumptions without resorting to pairings or lattices. In particular, our construction is secure under the strong RSA assumption and DDH (in pairing-free groups). For our construction, we provide a NIZK-friendly signature based on strong RSA, and efficiently instantiate Fischlin\u27s generic framework (CRYPTO\u2706). Our Blind Signature scheme has signatures of size 4.28 KB and communication cost 62.19 KB. On the way, we develop techniques that might be of independent interest. In particular, we provide efficient relaxed range-proofs with subversion zero-knowledge and compact commitments to elements of arbitrary groups

    Breaking Parallel ROS: Implication for Isogeny and Lattice-based Blind Signatures

    Get PDF
    Many of the three-round blind signatures based on identification protocols are only proven to be \ell-concurrently unforgeable for =polylog(λ)\ell = \mathsf{polylog}(\lambda). It was only recently shown in a seminal work by Benhamouda et al. (EUROCRYPT\u2721) that this is not just a limitation of the proof technique. They proposed an elegant polynomial time attack against the \ell-concurrently unforgeability of the classical blind Schnorr protocol for =poly(λ)\ell = \mathsf{poly}(\lambda). However, there are still many blind signatures following a similar recipe to blind Schnorr where the attack by Benhamouda et al. does not apply. This includes for instance the isogeny-based blind signature CSI-Otter by Katsumata et al (CRYPTO\u2723), the lattice-based blind signatures Blaze+ by Alkeilani et al. (ACISP\u2720) and BlindOR by Alkeilani et al. (CANS\u2720). In this work, we provide a simple and novel attack on blind signatures based on identification protocols performing parallel repetition to reduce the soundness error. Our attack translates to a polynomial time break for the \ell-concurrent unforgeability of CSI-Otter, Blaze+, and BlindOR for =poly(λ)\ell = \mathsf{poly}(\lambda). More formally, we define an intermediate problem called Parallel Random inhomogeneities in an Overdetermined Solvable system of linear equations (pROS) problem and show that an attack against pROS implies an attack to the above blind signatures. One takeaway of our finding is that while parallel repetition allows to exponentially reduce the soundness error of an identification protocol, this has minimal effect on the resulting blind signature. Our attack is concretely very efficient and for instance breaks 44-concurrent unforgeability of CSI-Otter in time roughly 2342^{34} hash computations

    Dehorning the Darwinian Dilemma for Normative Realism

    Get PDF
    Normative realists tend to consider evolutionary debunking arguments as posing epistemological challenges to their view. By understanding Sharon Street's 'Darwinian dilemma' argument in this way, they have overlooked and left unanswered her unique scientific challenge to normative realism. This paper counters Street's scientific challenge and shows that normative realism is compatible with evolutionary views of human evaluative judgment. After presenting several problems that her Adaptive Link Account (ALA) of evaluative judgments faces, I outline and defend an evolutionary byproduct perspective on evaluative judgment. I then argue that a consideration of levels of analysis in biological-behavioral explanation suggests that the realist who adopts the byproduct perspective I outline is not at a prima facie disadvantage to the normative anti-realist on grounds of parsimony. This perspective, I suggest, can enable normative realists to answer evolutionary challenges to their view

    An Adaptation Reasoning Approach for Large Scale Component-based Applications

    Get PDF
    There is a growing demand for context-aware applications that can dynamically adapt to their run-time environment. An application offers a collection of functionalities that can be realized through a composition of software components and/or services that are made available at runtime. With the availability of alternative variants of such components and/or services that provide the basic functionalities, while differ in extra-functional characteristics, characterized by quality of services (QoS), an unforeseen number of application variants can be created. The variant that best fits the current context is selected through adaptation reasoning, which can suffer from the processing capabilities of resource-scarce mobile devices, especially when a huge number of application variants needs to be reason about. In this paper, we present a reasoning approach, which provides a meaningful adaptation decision for adaptive applications having a large number of variants within a reasonable time frame. The approach is validated through two arbitrary applications with large number of variants. Keywords: self-adaptation, ubiquitous computing, adaptation reasoning, variability, scalability, utility functio

    SSE and SSD: Page-Efficient Searchable Symmetric Encryption

    Get PDF
    International audienceSearchable Symmetric Encryption (SSE) enables a client to outsource a database to an untrusted server, while retaining the ability to securely search the data. The performance bottleneck of classic SSE schemes typically does not come from their fast, symmetric cryptographic operations, but rather from the cost of memory accesses. To address this issue, many works in the literature have considered the notion of locality, a simple design criterion that helps capture the cost of memory accesses in traditional storage media, such as Hard Disk Drives. A common thread among many SSE schemes aiming to improve locality is that they are built on top of new memory allocation schemes, which form the technical core of the constructions. The starting observation of this work is that for newer storage media such as Solid State Drives (SSDs), which have become increasingly common, locality is not a good predictor of practical performance. Instead, SSD performance mainly depends on page efficiency, that is, reading as few pages as possible. We define this notion, and identify a simple memory allocation problem, Data-Independent Packing (DIP), that captures the main technical challenge required to build page-efficient SSE. As our main result, we build a page-efficient and storage-efficient data-independent packing scheme, and deduce the Tethys SSE scheme, the first SSE scheme to achieve at once O(1) page efficiency and O(1) storage efficiency. The technical core of the result is a new generalization of cuckoo hashing to items of variable size. Practical experiments show that this new approach achieves excellent performance
    corecore