248 research outputs found
Online Multi-Coloring with Advice
We consider the problem of online graph multi-coloring with advice.
Multi-coloring is often used to model frequency allocation in cellular
networks. We give several nearly tight upper and lower bounds for the most
standard topologies of cellular networks, paths and hexagonal graphs. For the
path, negative results trivially carry over to bipartite graphs, and our
positive results are also valid for bipartite graphs. The advice given
represents information that is likely to be available, studying for instance
the data from earlier similar periods of time.Comment: IMADA-preprint-c
Adding Isolated Vertices Makes some Online Algorithms Optimal
An unexpected difference between online and offline algorithms is observed.
The natural greedy algorithms are shown to be worst case online optimal for
Online Independent Set and Online Vertex Cover on graphs with 'enough' isolated
vertices, Freckle Graphs. For Online Dominating Set, the greedy algorithm is
shown to be worst case online optimal on graphs with at least one isolated
vertex. These algorithms are not online optimal in general. The online
optimality results for these greedy algorithms imply optimality according to
various worst case performance measures, such as the competitive ratio. It is
also shown that, despite this worst case optimality, there are Freckle graphs
where the greedy independent set algorithm is objectively less good than
another algorithm. It is shown that it is NP-hard to determine any of the
following for a given graph: the online independence number, the online vertex
cover number, and the online domination number.Comment: A footnote in the .tex file didn't show up in the last version. This
was fixe
Lower bounds for several online variants of bin packing
We consider several previously studied online variants of bin packing and
prove new and improved lower bounds on the asymptotic competitive ratios for
them. For that, we use a method of fully adaptive constructions. In particular,
we improve the lower bound for the asymptotic competitive ratio of online
square packing significantly, raising it from roughly 1.68 to above 1.75.Comment: WAOA 201
Implementing Grover Oracles for Quantum Key Search on AES and LowMC
Grover's search algorithm gives a quantum attack against block ciphers by
searching for a key that matches a small number of plaintext-ciphertext pairs.
This attack uses calls to the cipher to search a key space of
size . Previous work in the specific case of AES derived the full gate cost
by analyzing quantum circuits for the cipher, but focused on minimizing the
number of qubits. In contrast, we study the cost of quantum key search attacks
under a depth restriction and introduce techniques that reduce the oracle
depth, even if it requires more qubits. As cases in point, we design quantum
circuits for the block ciphers AES and LowMC. Our circuits give a lower overall
attack cost in both the gate count and depth-times-width cost models. In NIST's
post-quantum cryptography standardization process, security categories are
defined based on the concrete cost of quantum key search against AES. We
present new, lower cost estimates for each category, so our work has immediate
implications for the security assessment of post-quantum cryptography. As part
of this work, we release Q# implementations of the full Grover oracle for
AES-128, -192, -256 and for the three LowMC instantiations used in Picnic,
including unit tests and code to reproduce our quantum resource estimates. To
the best of our knowledge, these are the first two such full implementations
and automatic resource estimations.Comment: 36 pages, 8 figures, 14 table
Quantum Algorithms for the Most Frequently String Search, Intersection of Two String Sequences and Sorting of Strings Problems
We study algorithms for solving three problems on strings. The first one is
the Most Frequently String Search Problem. The problem is the following. Assume
that we have a sequence of strings of length . The problem is finding
the string that occurs in the sequence most often. We propose a quantum
algorithm that has a query complexity . This algorithm
shows speed-up comparing with the deterministic algorithm that requires
queries. The second one is searching intersection of two sequences
of strings. All strings have the same length . The size of the first set is
and the size of the second set is . We propose a quantum algorithm that
has a query complexity . This algorithm shows
speed-up comparing with the deterministic algorithm that requires
queries. The third problem is sorting of strings of length
. On the one hand, it is known that quantum algorithms cannot sort objects
asymptotically faster than classical ones. On the other hand, we focus on
sorting strings that are not arbitrary objects. We propose a quantum algorithm
that has a query complexity . This algorithm shows
speed-up comparing with the deterministic algorithm (radix sort) that requires
queries, where is a size of the alphabet.Comment: THe paper was presented on TPNC 201
Age before stage: insulin resistance rises before the onset of puberty: a 9-year longitudinal study (EarlyBird 26).
OBJECTIVE: Insulin resistance (IR) is associated with diabetes. IR is higher during puberty in both sexes, with some studies showing the increase to be independent of changes in adiposity. Few longitudinal studies have reported on children, and it remains unclear when the rise in IR that is often attributed to puberty really begins. We sought to establish from longitudinal data its relationship to pubertal onset, and interactions with age, sex, adiposity, and IGF-1. RESEARCH DESIGN AND METHODS: The EarlyBird Diabetes study is a longitudinal prospective cohort study of healthy children aged 5-14 years. Homeostasis model assessment (HOMA-IR), skinfolds (SSF), adiposity (percent fat, measured by dual-energy X-ray absorptiometry), serum leptin, and IGF-1 were measured annually in 235 children (134 boys). Pubertal onset was adduced from Tanner stage (TS) and from the age at which luteinizing hormone (LH) first became serially detectable (≥0.2 international units/L). RESULTS: IR rose progressively from age 7 years, 3-4 years before TS2 was reached or LH became detectable. Rising adiposity and IGF-1 together explained 34% of the variance in IR in boys and 35% in girls (both P < 0.001) over the 3 years preceding pubertal onset. The contribution of IGF-1 to IR was greater in boys, despite their comparatively lower IGF-1 levels. CONCLUSIONS: IR starts to rise in mid-childhood, some years before puberty. Its emergence relates more to the age of the child than to pubertal onset. More than 60% of the variation in IR prior to puberty was unexplained. The demography of childhood diabetes is changing, and prepubertal IR may be important
A cross-national study on the antecedents of work–life balance from the fit and balance perspective
Drawing on the perceived work–family fit and balance perspective, this study investigates demands and resources as antecedents of work–life balance (WLB) across four countries (New Zealand, France, Italy and Spain), so as to provide empirical cross-national evidence. Using structural equation modelling analysis on a sample of 870 full time employees, we found that work demands, hours worked and family demands were negatively related to WLB, while job autonomy and supervisor support were positively related to WLB. We also found evidence that resources (job autonomy and supervisor support) moderated the relationships between demands and work–life balance, with high resources consistently buffering any detrimental influence of demands on WLB. Furthermore, our study identified additional predictors of WLB that were unique to some national contexts. For example, in France and Italy, overtime hours worked were negatively associated with WLB, while parental status was positively associated with WLB. Overall, the implications for theory and practice are discussed.Peer ReviewedPostprint (author's final draft
Tight Private Circuits: Achieving Probing Security with the Least Refreshing
Masking is a common countermeasure to secure implementations against side-channel attacks. In 2003, Ishai, Sahai, and Wagner introduced a formal security model, named t-probing model, which is now widely used to theoretically reason on the security of masked implementations. While many works have provided security proofs for small masked components, called gadgets, within this model, no formal method allowed to securely compose gadgets with a tight number of shares (namely, t + 1) until recently. In 2016, Barthe et al. filled this gap with maskComp, a tool checking the security of masking schemes composed of several gadgets. This tool can achieve provable security with tight number of shares by inserting mask-refreshing gadgets at carefully selected locations. However the method is not tight in the sense that there exists some compositions of gadgets for which it cannot exhibit a flaw nor prove the security. As a result, it is overconservative and might insert more refresh gadgets than actually needed to ensure t-probing security. In this paper, we exhibit the first tool, referred to as tightPROVE, able to clearly state whether a shared circuit composed of standard gadgets (addition, multiplication, and refresh) is t-probing secure or not. Given such a composition, our tool either produces a probing-security proof (valid at any order) or exhibits a security flaw that directly implies a probing attack at a given order. Compared to maskComp, tightPROVE can drastically reduce the number of required refresh gadgets to get a probing security proof, and thus the randomness requirement for some secure shared circuits. We apply our method to a recent AES implementation secured with higher-order masking in bitslice and we show that we can save all the refresh gadgets involved in the s-box layer, which results in an significant performance gain
LNCS
We extend a commitment scheme based on the learning with errors over rings (RLWE) problem, and present efficient companion zeroknowledge proofs of knowledge. Our scheme maps elements from the ring (or equivalently, n elements fro
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