137 research outputs found

    LIPIcs, Volume 251, ITCS 2023, Complete Volume

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    LIPIcs, Volume 251, ITCS 2023, Complete Volum

    LIPIcs, Volume 261, ICALP 2023, Complete Volume

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    LIPIcs, Volume 261, ICALP 2023, Complete Volum

    Low Power Memory/Memristor Devices and Systems

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    This reprint focusses on achieving low-power computation using memristive devices. The topic was designed as a convenient reference point: it contains a mix of techniques starting from the fundamental manufacturing of memristive devices all the way to applications such as physically unclonable functions, and also covers perspectives on, e.g., in-memory computing, which is inextricably linked with emerging memory devices such as memristors. Finally, the reprint contains a few articles representing how other communities (from typical CMOS design to photonics) are fighting on their own fronts in the quest towards low-power computation, as a comparison with the memristor literature. We hope that readers will enjoy discovering the articles within

    Minimizing Hitting Time between Disparate Groups with Shortcut Edges

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    Structural bias or segregation of networks refers to situations where two or more disparate groups are present in the network, so that the groups are highly connected internally, but loosely connected to each other. In many cases it is of interest to increase the connectivity of disparate groups so as to, e.g., minimize social friction, or expose individuals to diverse viewpoints. A commonly-used mechanism for increasing the network connectivity is to add edge shortcuts between pairs of nodes. In many applications of interest, edge shortcuts typically translate to recommendations, e.g., what video to watch, or what news article to read next. The problem of reducing structural bias or segregation via edge shortcuts has recently been studied in the literature, and random walks have been an essential tool for modeling navigation and connectivity in the underlying networks. Existing methods, however, either do not offer approximation guarantees, or engineer the objective so that it satisfies certain desirable properties that simplify the optimization~task. In this paper we address the problem of adding a given number of shortcut edges in the network so as to directly minimize the average hitting time and the maximum hitting time between two disparate groups. Our algorithm for minimizing average hitting time is a greedy bicriteria that relies on supermodularity. In contrast, maximum hitting time is not supermodular. Despite, we develop an approximation algorithm for that objective as well, by leveraging connections with average hitting time and the asymmetric k-center problem.Comment: To appear in KDD 202

    LIPIcs, Volume 274, ESA 2023, Complete Volume

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    LIPIcs, Volume 274, ESA 2023, Complete Volum

    LIPIcs, Volume 258, SoCG 2023, Complete Volume

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    LIPIcs, Volume 258, SoCG 2023, Complete Volum

    On Time-Space Lower Bounds for Finding Short Collisions in Sponge Hash Functions

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    Sponge paradigm, used in the design of SHA-3, is an alternative hashing technique to the popular Merkle-Damgård paradigm. We revisit the problem of finding BB-block-long collisions in sponge hash functions in the auxiliary-input random permutation model, in which an attacker gets a piece of SS-bit advice about the random permutation and makes TT (forward or inverse) oracle queries to the random permutation. Recently, significant progress has been made in the Merkle-Damgård setting and optimal bounds are known for a large range of parameters, including all constant values of BB. However, the sponge setting is widely open: there exist significant gaps between known attacks and security bounds even for B=1B=1. Freitag, Ghoshal and Komargodski (CRYPTO 2022) showed a novel attack for B=1B=1 that takes advantage of the inverse queries and achieves advantage Ω~(min(S2T2/22c\tilde{\Omega}(\min(S^2T^2/2^{2c}, (S2T/22c)2/3)+T2/2r) (S^2T/2^{2c})^{2/3})+T^2/2^r), where rr is bit-rate and cc is the capacity of the random permutation. However, they only showed an O~(ST/2c+T2/2r)\tilde{O}(ST/2^c+T^2/2^r) security bound, leaving open an intriguing quadratic gap. For B=2B=2, they beat the general security bound by Coretti, Dodis, Guo (CRYPTO 2018) for arbitrary values of BB. However, their highly non-trivial argument is quite laborious, and no better (than the general) bounds are known for B3B\geq 3. In this work, we study the possibility of proving better security bounds in the sponge setting. To this end, - For B=1B=1, we prove an improved O~(S2T2/22c+S/2c+T/2c+T2/2r)\tilde{O}(S^2T^2/2^{2c}+S/2^c+T/2^c+T^2/2^r) bound. Our bound strictly improves the bound by Freitag et al., and is optimal for ST22cST^2\leq 2^c. - For B=2B=2, we give a considerably simpler and more modular proof, recovering the bound obtained by Freitag et al. - We obtain our bounds by adapting the recent multi-instance technique of Akshima, Guo and Liu (CRYPTO 2022) which bypasses the limitations of prior techniques in the Merkle-Damgård setting. To complement our results, we provably show that the recent multi-instance technique cannot further improve our bounds for B=1,2B=1,2, and the general bound by Correti et al., for B3B\geq 3. Overall, our results yield state-of-the-art security bounds for finding short collisions and fully characterize the power of the multi-instance technique in the sponge setting

    Communication Complexity of Inner Product in Symmetric Normed Spaces

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