137 research outputs found
LIPIcs, Volume 251, ITCS 2023, Complete Volume
LIPIcs, Volume 251, ITCS 2023, Complete Volum
LIPIcs, Volume 261, ICALP 2023, Complete Volume
LIPIcs, Volume 261, ICALP 2023, Complete Volum
Low Power Memory/Memristor Devices and Systems
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
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
LIPIcs, Volume 274, ESA 2023, Complete Volum
LIPIcs, Volume 258, SoCG 2023, Complete Volume
LIPIcs, Volume 258, SoCG 2023, Complete Volum
On Time-Space Lower Bounds for Finding Short Collisions in Sponge Hash Functions
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 -block-long collisions in sponge hash functions in the auxiliary-input random permutation model, in which an attacker gets a piece of -bit advice about the random permutation and makes (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 . However, the sponge setting is widely open: there exist significant gaps between known attacks and security bounds even for .
Freitag, Ghoshal and Komargodski (CRYPTO 2022) showed a novel attack for that takes advantage of the inverse queries and achieves advantage , , where is bit-rate and is the capacity of the random permutation. However, they only showed an security bound, leaving open an intriguing quadratic gap. For , they beat the general security bound
by Coretti, Dodis,
Guo (CRYPTO 2018) for arbitrary values of . However, their highly non-trivial argument is quite laborious, and no better (than the general) bounds are known for .
In this work, we study the possibility of proving better security bounds in the sponge setting. To this end,
- For , we prove an improved bound. Our bound strictly improves the bound by Freitag et al.,
and is optimal for .
- For , 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 , and the general bound by Correti et al., for .
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
Recommended from our members
Examining university student satisfaction and barriers to taking online remote exams
Recent years have seen a surge in the popularity of online exams at universities, due to the greater convenience and flexibility they offer both students and institutions. Driven by the dearth of empirical data on distance learning students' satisfaction levels and the difficulties they face when taking online exams, a survey with 562 students at The Open University (UK) was conducted to gain insights into their experiences with this type of exam. Satisfaction was reported with the environment and exams, while work commitments and technical difficulties presented the greatest barriers. Gender, race and disability were also associated with different levels of satisfaction and barriers. This study adds to the increasing number of studies into online exams, demonstrating how this type of exam can still have a substantial effect on students experienced in online learning systems and
technologies
- …