pinecone/core-2020-05-10-deduplication huggingface dataset:
Separate, Measure and Conquer: faster polynomial-space algorithms for Max 2-CSP and counting dominating sets

We show a method resulting in the improvement of several polynomial-space, exponential-time algorithms. The method capitalizes on the existence of small balanced separators for sparse graphs, which can be exploited for branching to disconnect an instance into independent components. For this algorithm design paradigm, the challenge to date has been to obtain improvements in worst-case analyses of algorithms, compared with algorithms that are analyzed with advanced methods, such as Measure and Conquer. Our contribution is the design of a general method to integrate the advantage from the separator-branching into Measure and Conquer, for an improved running time analysis.  We illustrate the method with improved algorithms for Max (r,2) -CSP and #Dominating Set. For Max (r,2) -CSP instances with domain size r and m constraints, the running time improves from r m/6   to r m/7.5   for cubic instances and from r 0.19⋅m   to r 0.18⋅m   for general instances, omitting subexponential factors. For #Dominating Set instances with n vertices, the running time improves from 1.4143 n   to 1.2458 n   for cubic instances and from 1.5673 n   to 1.5183 n   for general instances. It is likely that other algorithms relying on local transformations can be improved using our method, which exploits a non-local property of graphs
Ground state connectivity of local Hamiltonians

The study of ground state energies of local Hamiltonians has played a
fundamental role in quantum complexity theory. In this paper, we take a new
direction by introducing the physically motivated notion of "ground state
connectivity" of local Hamiltonians, which captures problems in areas ranging
from quantum stabilizer codes to quantum memories. Roughly, "ground state
connectivity" corresponds to the natural question: Given two ground states
|{\psi}> and |{\phi}> of a local Hamiltonian H, is there an "energy barrier"
(with respect to H) along any sequence of local operations mapping |{\psi}> to
|{\phi}>? We show that the complexity of this question can range from
QCMA-complete to PSPACE-complete, as well as NEXP-complete for an appropriately
defined "succinct" version of the problem. As a result, we obtain a natural
QCMA-complete problem, a goal which has generally proven difficult since the
conception of QCMA over a decade ago. Our proofs rely on a new technical tool,
the Traversal Lemma, which analyzes the Hilbert space a local unitary evolution
must traverse under certain conditions. We show that this lemma is essentially
tight with respect to the length of the unitary evolution in question.Comment: 31 pages; v3 is published journal version. Various minor updates over
  v2, including observing that our QCMA-hardness result actually also holds for
  frustration-free Hamiltonians (FF-GSCON). Thank you to anonymous referees for
  their feedbac
Improved Algorithms for Decremental Single-Source Reachability on
  Directed Graphs

Recently we presented the first algorithm for maintaining the set of nodes
reachable from a source node in a directed graph that is modified by edge
deletions with $o(mn)$ total update time, where $m$ is the number of edges and
$n$ is the number of nodes in the graph [Henzinger et al. STOC 2014]. The
algorithm is a combination of several different algorithms, each for a
different $m$ vs. $n$ trade-off. For the case of $m = \Theta(n^{1.5})$ the
running time is $O(n^{2.47})$, just barely below $mn = \Theta(n^{2.5})$. In
this paper we simplify the previous algorithm using new algorithmic ideas and
achieve an improved running time of $\tilde O(\min(m^{7/6} n^{2/3}, m^{3/4}
n^{5/4 + o(1)}, m^{2/3} n^{4/3+o(1)} + m^{3/7} n^{12/7+o(1)}))$. This gives,
e.g., $O(n^{2.36})$ for the notorious case $m = \Theta(n^{1.5})$. We obtain the
same upper bounds for the problem of maintaining the strongly connected
components of a directed graph undergoing edge deletions. Our algorithms are
correct with high probabililty against an oblivious adversary.Comment: This paper was presented at the International Colloquium on Automata,
  Languages and Programming (ICALP) 2015. A full version combining the findings
  of this paper and its predecessor [Henzinger et al. STOC 2014] is available
  at arXiv:1504.0795
Algebraic Properties of Valued Constraint Satisfaction Problem

The paper presents an algebraic framework for optimization problems
expressible as Valued Constraint Satisfaction Problems. Our results generalize
the algebraic framework for the decision version (CSPs) provided by Bulatov et
al. [SICOMP 2005]. We introduce the notions of weighted algebras and varieties
and use the Galois connection due to Cohen et al. [SICOMP 2013] to link VCSP
languages to weighted algebras. We show that the difficulty of VCSP depends
only on the weighted variety generated by the associated weighted algebra.
Paralleling the results for CSPs we exhibit a reduction to cores and rigid
cores which allows us to focus on idempotent weighted varieties. Further, we
propose an analogue of the Algebraic CSP Dichotomy Conjecture; prove the
hardness direction and verify that it agrees with known results for VCSPs on
two-element sets [Cohen et al. 2006], finite-valued VCSPs [Thapper and Zivny
2013] and conservative VCSPs [Kolmogorov and Zivny 2013].Comment: arXiv admin note: text overlap with arXiv:1207.6692 by other author
Sherali-Adams relaxations for valued CSPs

We consider Sherali-Adams linear programming relaxations for solving valued
constraint satisfaction problems to optimality. The utility of linear
programming relaxations in this context have previously been demonstrated using
the lowest possible level of this hierarchy under the name of the basic linear
programming relaxation (BLP). It has been shown that valued constraint
languages containing only finite-valued weighted relations are tractable if,
and only if, the integrality gap of the BLP is 1. In this paper, we demonstrate
that almost all of the known tractable languages with arbitrary weighted
relations have an integrality gap 1 for the Sherali-Adams relaxation with
parameters (2,3). The result is closely connected to the notion of bounded
relational width for the ordinary constraint satisfaction problem and its
recent characterisation
Parametric polymorphism - universally

In the 1980s, John Reynolds postulated that a parametrically polymorphic function is an ad-hoc polymorphic function satisfying a uniformity principle. This allowed him to prove that his set-theoretic semantics has a relational lifting which satisfies the Identity Extension Lemma and the Abstraction Theorem. However, his definition (and subsequent variants) have only been given for specific models. In contrast, we give a model-independent axiomatic treatment by characterising Reynolds' definition via a universal property, and show that the above results follow from this universal property in the axiomatic setting
Articulating personal pedagogies through learning ecologies

The digital revolution enabled by social and ubiquitous technologies is constantly transforming macro and micro levels of society including industry, organizations and government as well as ways in which we communicate, we work, and we carry on our daily lives. Education is therefore also being challenged to respond to evolving societal demands by supporting the development of competent and engaged citizens. In this context, individuals’ capability to get involved and exploit the affordances of networked environments for learning and development may condition their opportunities to cope with societal and labor demands. In this chapter, the metaphor of learning ecologies is proposed to provide a framework from which to analyze interactions between individuals and their environment, and the way their experiences across different contexts throughout life promote and shape learning processes. Learning ecologies allow us to explore frontier pedagogies connecting formal, non-formal and informal educational contexts, acting as personal strategies that may orchestrate life-long, life-wide and life-deep learning. We start by defining and framing learning ecologies, providing the theoretical roots and reviewing some recent studies in the field. Next, we propose constructs and models but also strategies and tools that may be of help to enhance and support personal ecologies for learning. Finally, the concept of personal pedagogies is proposed to refer to a set of autonomy and agency skills and attitudes that can be dynamically integrated by individuals to support an ecology for self-development and personal learning. We articulate from this perspective several trends in the area of self-directed learning located in the technological and pedagogical intersection: MOOCs, current awareness, e-portfolios and social networks
Paying the guard: An entry-guard-based payment system for Tor

When choosing the three relays that compose a circuit, Tor selects the first hop among a restricted number of relays called entry guards, pre-selected by the user himself. The reduced number of entry guards, that until recently was fixed to three, helps in mitigating the effects of several traffic analysis attacks. However, recent literature indicates that the number should be further reduced, and the time during which the user keeps the relays as guards increased. Therefore, developers of Tor recently proposed selecting only one entry guard, which is to be used by the user for all circuits and for a prolonged period of time (nine months). While this design choice was made to increase the security of the protocol, it also opens an unprecedented opportunity for a market mechanism where relays get paid for traffic by the users. In this paper, we propose to use the entry guard as the point-of-sale: users subscribe to their entry guard of choice, and deposit an amount that will be used for paying for the circuits. From the entry guard, income is then distributed to the other relays included in circuits through an inter-relay accounting system. While the user may pay the entry guard using BitCoins, or any other anonymous payment system, the relays exchange I Owe You (IOU) certificates during communication, and settle their balances only at synchronized, later points in time. This novel deferred payment approach overcomes the weaknesses of the previously proposed Tor payment mechanisms: we separate the user’s payment from the inter-relay payments, and we effectively unlink both from the chosen path, thus preserving the secrecy of the circuit
Protecting encrypted cookies from compression side-channel attacks

Compression is desirable for network applications as it saves bandwidth; however, when data is compressed before being encrypted, the amount of compression leaks information about the amount of redundancy in the plaintext. This side channel has led to successful CRIME and BREACH attacks on web traffic protected by the Transport Layer Security (TLS) protocol. The general guidance in light of these attacks has been to disable compression, preserving confidentiality but sacrificing bandwidth. In this paper, we examine two techniques - heuristic separation of secrets and fixed-dictionary compression|for enabling compression while protecting high-value secrets, such as cookies, from attack. We model the security offered by these techniques and report on the amount of compressibility that they can achieve
Programmable Hash Functions go Private: constructions and applications to (Homomorphic) signatures with shorter public keys

We introduce the notion of asymmetric programmable hash functions (APHFs, for short), which adapts Programmable Hash Functions, introduced by Hofheinz and Kiltz at Crypto 2008, with two main differences. First, an APHF works over bilinear groups, and it is asymmetric in the sense that, while only {em secretly} computable, it admits an isomorphic copy which is publicly computable. Second, in addition to the usual programmability, APHFs may have an alternative property that we call programmable pseudorandomness. In a nutshell, this property states that it is possible to embed a pseudorandom value as part of the function's output, akin to a random oracle. In spite of the apparent limitation of being only secretly computable, APHFs turn out to be surprisingly powerful objects. We show that they can be used to generically implement both regular and linearly-homomorphic signature schemes in a simple and elegant way. More importantly, when instantiating these generic constructions with our concrete realizations of APHFs, we obtain: (1) the first linearly-homomorphic signature (in the standard model) whose public key is sub-linear in both the dataset size and the dimension of the signed vectors; (2) short signatures (in the standard model) whose public key is shorter than those by Hofheinz-Jager-Kiltz from Asiacrypt 2011, and essentially the same as those by Yamada, Hannoka, Kunihiro, (CT-RSA 2012)
Short Group Signatures via Structure-Preserving Signatures: Standard Model Security from Simple Assumptions

International audienceGroup signatures are a central cryptographic primitive which allows users to sign messages while hiding their identity within a crowd of group members. In the standard model (without the random oracle idealization), the most efficient constructions rely on the Groth-Sahai proof systems (Euro-crypt'08). The structure-preserving signatures of Abe et al. (Asiacrypt'12) make it possible to design group signatures based on well-established, constant-size number theoretic assumptions (a.k.a. " simple assumptions ") like the Symmetric eXternal Diffie-Hellman or Decision Linear assumptions. While much more efficient than group signatures built on general assumptions, these constructions incur a significant overhead w.r.t. constructions secure in the idealized random oracle model. Indeed, the best known solution based on simple assumptions requires 2.8 kB per signature for currently recommended parameters. Reducing this size and presenting techniques for shorter signatures are thus natural questions. In this paper, our first contribution is to significantly reduce this overhead. Namely, we obtain the first fully anonymous group signatures based on simple assumptions with signatures shorter than 2 kB at the 128-bit security level. In dynamic (resp. static) groups, our signature length drops to 1.8 kB (resp. 1 kB). This improvement is enabled by two technical tools. As a result of independent interest, we first construct a new structure-preserving signature based on simple assumptions which shortens the best previous scheme by 25%. Our second tool is a new method for attaining anonymity in the strongest sense using a new CCA2-secure encryption scheme which is simultaneously a Groth-Sahai commitment
Predicate Encryption for Circuits from LWE

In predicate encryption, a ciphertext is associated with descriptive attribute values x in addition to a plaintext μ, and a secret key is associated with a predicate f. Decryption returns plaintext μ if and only if f(x)=1. Moreover, security of predicate encryption guarantees that an adversary learns nothing about the attribute x or the plaintext μ from a ciphertext, given arbitrary many secret keys that are not authorized to decrypt the ciphertext individually.
We construct a leveled predicate encryption scheme for all circuits, assuming the hardness of the subexponential learning with errors (LWE) problem. That is, for any polynomial function d=d(λ), we construct a predicate encryption scheme for the class of all circuits with depth bounded by d(λ), where λ is the security parameter.Microsoft Corporation (PhD Fellowship)Northrop Grumman Cybersecurity Research ConsortiumUnited States. Defense Advanced Research Projects Agency (Grant FA8750-11-2-0225)National Science Foundation (U.S.) (Awards CNS-1350619)National Science Foundation (U.S.) (Awards CNS-1413920)Alfred P. Sloan Foundation (Fellowship)Microsoft (Faculty Fellowship
On Vulnerabilities of the Security Association in the IEEE 802.15.6
  Standard

Wireless Body Area Networks (WBAN) support a variety of real-time health
monitoring and consumer electronics applications. The latest international
standard for WBAN is the IEEE 802.15.6. The security association in this
standard includes four elliptic curve-based key agreement protocols that are
used for generating a master key. In this paper, we challenge the security of
the IEEE 802.15.6 standard by showing vulnerabilities of those four protocols
to several attacks. We perform a security analysis on the protocols, and show
that they all have security problems, and are vulnerable to different attacks
Efficient algorithm for computing all low s-t edge connectivities in directed graphs

LNCS v. 9235 entitled: Mathematical Foundations of Computer Science 2015: 40th International Symposium, MFCS 2015, Milan, Italy, August 24-28, 2015, Proceedings, Part 2Given a directed graph with n nodes and m edges, the (strong) edge connectivity λ (u; v) between two nodes u and v is the minimum number of edges whose deletion makes u and v not strongly connected. The problem of computing the edge connectivities between all pairs of nodes of a directed graph can be done in O(m ω) time by Cheung, Lau and Leung (FOCS 2011), where ω is the matrix multiplication factor (≈ 2:373), or in Õ (mn1:5) time using O(n) computations of max-flows by Cheng and Hu (IPCO 1990).
We consider in this paper the “low edge connectivity” problem, which aims at computing the edge connectivities for the pairs of nodes (u; v) such that λ (u; v) ≤ k. While the undirected version of this problem was considered by Hariharan, Kavitha and Panigrahi (SODA 2007), who presented an algorithm with expected running time Õ (m+nk3), no algorithm better than computing all-pairs edge connectivities was proposed for directed graphs. We provide an algorithm that computes all low edge connectivities in O(kmn) time, improving the previous best result of O (min(m ω, mn1:5)) when k ≤ √ n. Our algorithm also computes a minimum u-v cut for each pair of nodes (u; v) with λ (u; v) ≤ k.postprin
Bounding the clique-width of H-free chordal graphs.

A graph is H-free if it has no induced subgraph isomorphic to H. Brandstädt, Engelfriet, Le and Lozin proved that the class of chordal graphs with independence number at most 3 has unbounded clique-width. Brandstädt, Le and Mosca erroneously claimed that the gem and the co-gem are the only two 1-vertex P4-extensions H for which the class of H-free chordal graphs has bounded clique-width. In fact we prove that bull-free chordal and co-chair-free chordal graphs have clique-width at most 3 and 4, respectively. In particular, we prove that the clique-width is:\ud
(i)\ud
bounded for four classes of H-free chordal graphs;\ud
 \ud
(ii)\ud
unbounded for three subclasses of split graphs.\ud
 \ud
Our main result, obtained by combining new and known results, provides a classification of all but two stubborn cases, that is, with two potential exceptions we determine all graphs H for which the class of H-free chordal graphs has bounded clique-width. We illustrate the usefulness of this classification for classifying other types of graph classes by proving that the class of (2P1+P3,K4)-free graphs has bounded clique-width via a reduction to K4-free chordal graphs. Finally, we give a complete classification of the (un)boundedness of clique-width of H-free weakly chordal graphs
The price of connectivity for cycle transversals.

For a family of graphs F, an F-transversal of a graph G is a subset S⊆V(G) that intersects every subset of V(G) that induces a subgraph isomorphic to a graph in F. Let tF(G) be the minimum size of an F-transversal of G, and ctF(G) be the minimum size of an F-transversal of G that induces a connected graph. For a class of connected graphs G, the price of connectivity for F-transversals is the supremum of the ratios ctF(G)/tF(G) over all G∈G. We perform an in-depth study into the price of connectivity for various well-known graph families F that contain an infinite number of cycles and that, in addition, may contain one or more anticycles or short paths. For each of these families we study the price of connectivity for classes of graphs characterized by one forbidden induced subgraph H. We determine exactly those classes of H-free graphs for which this graph parameter is bounded by a multiplicative constant, bounded by an additive constant, or equal to 1. In particular, our tetrachotomies extend known results of Belmonte et al. (EuroComb 2012, MFCS 2013) for the case when F is the family of all cycles
Synchronizing Automata with Extremal Properties

We present a few classes of synchronizing automata exhibiting certain
extremal properties with regard to synchronization. The first is a series of
automata with subsets whose shortest extending words are of length
$\varTheta(n^2)$, where $n$ is the number of states of the automaton. This
disproves a conjecture that every subset in a strongly connected synchronizing
automaton is $cn$-extendable, for some constant $c$, and in particular, shows
that the cubic upper bound on the length of the shortest reset words cannot be
improved generally by means of the extension method. A detailed analysis shows
that the automata in the series have subsets that require words as long as
$n^2/4+O(n)$ in order to be extended by at least one element.
  We also discuss possible relaxations of the conjecture, and propose the
image-extension conjecture, which would lead to a quadratic upper bound on the
length of the shortest reset words. In this regard we present another class of
automata, which turn out to be counterexamples to a key claim in a recent
attempt to improve the Pin-Frankl bound for reset words.
  Finally, we present two new series of slowly irreducibly synchronizing
automata over a ternary alphabet, whose lengths of the shortest reset words are
$n^2-3n+3$ and $n^2-3n+2$, respectively. These are the first examples of such
series of automata for alphabets of size larger than two.Comment: The final publication is available at Springer via doi below. arXiv
  admin note: text overlap with arXiv:1404.331
Moody Scheduling for Speculative Parallelization

Producción CientíficaScheduling is one of the factors that most directly affect performance in Thread-Level Speculation (TLS). Since loops may present dependences that cannot be predicted before runtime, Finding a good chunk size is not a simple task. The most used mechanism, Fixed-Size Chunking (FSC), requires many \dry-runs" to set the optimal chunk size. If the loop does not present dependence violations at runtime, scheduling only needs to deal with load balancing issues. For loops where the general pattern of dependences is known, as is the case with Randomized Incremental Algorithms, specialized mechanisms have been designed to maximize performance. To make TLS available to a wider community, a general scheduling algorithm that does not require a-priori knowledge of the expected pattern of dependences nor previous dry-runs to adjust any parameter is needed. In this paper, we present an algorithm that estimates at runtime the best size of the next chunk to be scheduled.
This algorithm takes advantage of our previous knowledge in the design and test of other scheduling mechanisms, and it has a solid mathematical basis. The result is a method that, using information of the execution of the previous chunks, decides the size of the next chunk to be scheduled. Our experimental results show that the use of the proposed scheduling
function compares or even increases the performance that can be obtained by FSC, greatly reducing the need of a a costly and careful search for the best fixed chunk size.Castilla-Leon (VA172A12- 2), MICINN (Spain) and the European Union FEDER (MOGECOPP project TIN2011-25639, HomProg-HetSys project, TIN2014-58876-P, CAPAP-H5 net- work TIN2014-53522-REDT), Madrid Regional Government through the TIGRE5- CM program (S2013/ICE-2919), and by the MICINN Project MTM2011-22792. Belen Palop is partially supported by MINECO MTM2012-30951