{"title":"Chained time lock puzzle with small puzzle size","authors":"Ramakant Kumar, Sahadeo Padhye","doi":"10.1016/j.ic.2025.105301","DOIUrl":"10.1016/j.ic.2025.105301","url":null,"abstract":"<div><div>A time lock puzzle (TLP) is an interesting cryptographic primitive used to lock messages for a limited time period. After the desired time interval, the puzzle solver can know the message. Chained time lock puzzle (C-TLP) is multi instance time lock puzzle where the solution of any instance depends on the previous instance. In this paper, we design a C-TLP with security relying on the integer factorization problem (IFP). The size of the output puzzle is smaller than the size in the existing C-TLPs.</div></div>","PeriodicalId":54985,"journal":{"name":"Information and Computation","volume":"304 ","pages":"Article 105301"},"PeriodicalIF":0.8,"publicationDate":"2025-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143870089","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Modules and PQ-trees in Robinson spaces","authors":"M. Carmona , V. Chepoi , G. Naves , P. Préa","doi":"10.1016/j.ic.2025.105300","DOIUrl":"10.1016/j.ic.2025.105300","url":null,"abstract":"<div><div>A Robinson space is a dissimilarity space <span><math><mo>(</mo><mi>X</mi><mo>,</mo><mi>d</mi><mo>)</mo></math></span> on <em>n</em> points for which there exists a compatible order, <em>i.e.</em> a total order < on <em>X</em> such that <span><math><mi>x</mi><mo><</mo><mi>y</mi><mo><</mo><mi>z</mi></math></span> implies that <span><math><mi>d</mi><mo>(</mo><mi>x</mi><mo>,</mo><mi>y</mi><mo>)</mo><mo>≤</mo><mi>d</mi><mo>(</mo><mi>x</mi><mo>,</mo><mi>z</mi><mo>)</mo></math></span> and <span><math><mi>d</mi><mo>(</mo><mi>y</mi><mo>,</mo><mi>z</mi><mo>)</mo><mo>≤</mo><mi>d</mi><mo>(</mo><mi>x</mi><mo>,</mo><mi>z</mi><mo>)</mo></math></span>. Recognizing whether a dissimilarity space is Robinson has numerous applications in seriation and classification. The set of all compatible orders of a Robinson space can be succintly represented by a PQ-tree, a classical data structure introduced by Booth and Lueker. An mmodule is a subset <em>M</em> of <em>X</em> which is not distinguishable from the outside of <em>M</em>, <em>i.e.</em> the distances from any point of <span><math><mi>X</mi><mo>∖</mo><mi>M</mi></math></span> to all points of <em>M</em> are the same. The hierarchical structure of mmodules can also be represented by a tree: the mmodule-tree of a dissimilarity space <span><math><mo>(</mo><mi>X</mi><mo>,</mo><mi>d</mi><mo>)</mo></math></span>.</div><div>In this paper, we establish correspondences between the PQ-trees and the mmodule-trees of Robinson spaces. More precisely, we show how to construct the mmodule-tree of a Robinson dissimilarity from its PQ-tree and <em>vice versa</em>. To establish this translation, we introduce the notions of <em>δ</em>-graph <span><math><msub><mrow><mi>G</mi></mrow><mrow><mover><mrow><mi>δ</mi></mrow><mo>‾</mo></mover></mrow></msub></math></span> of a Robinson space and of <em>δ</em>-mmodules, the connected components of <span><math><msub><mrow><mi>G</mi></mrow><mrow><mover><mrow><mi>δ</mi></mrow><mo>‾</mo></mover></mrow></msub></math></span>. It also involves the dendrogram of the subdominant ultrametric of <em>d</em>. All these results also lead to optimal <span><math><mi>O</mi><mo>(</mo><msup><mrow><mi>n</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>)</mo></math></span> time algorithms for constructing the PQ-tree and the mmodule tree of Robinson spaces.</div></div>","PeriodicalId":54985,"journal":{"name":"Information and Computation","volume":"304 ","pages":"Article 105300"},"PeriodicalIF":0.8,"publicationDate":"2025-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143826082","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shaull Almagor , Arka Ghosh , Tim Leys , Guillermo A. Pérez
{"title":"The geometry of reachability in continuous vector addition systems with states","authors":"Shaull Almagor , Arka Ghosh , Tim Leys , Guillermo A. Pérez","doi":"10.1016/j.ic.2025.105298","DOIUrl":"10.1016/j.ic.2025.105298","url":null,"abstract":"<div><div>We study the geometry of reachability sets of continuous vector addition systems with states (VASS). In particular we establish that they are “almost” Minkowski sums of convex cones and zonotopes generated by the vectors labelling the transitions of the VASS. We use the latter to prove that short so-called linear path schemes suffice as witnesses of reachability in continuous VASS. Then, we give new polynomial-time algorithms for the reachability problem for linear path schemes. Finally, we also establish that enriching the model with zero tests makes the reachability problem intractable already for linear path schemes of dimension two.</div></div>","PeriodicalId":54985,"journal":{"name":"Information and Computation","volume":"304 ","pages":"Article 105298"},"PeriodicalIF":0.8,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143747264","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Set semantics for asynchronous TeamLTL: Expressivity and complexity","authors":"Juha Kontinen , Max Sandström , Jonni Virtema","doi":"10.1016/j.ic.2025.105299","DOIUrl":"10.1016/j.ic.2025.105299","url":null,"abstract":"<div><div>We introduce and develop a set-based semantics for asynchronous TeamLTL. We consider two canonical logics in this setting: the extensions of TeamLTL by the Boolean disjunction and by the Boolean negation. We relate the new semantics with the original semantics based on multisets and establish one of the first positive complexity theoretic results in the temporal team semantics setting. In particular we show that both logics enjoy normal forms that can be utilised to obtain results related to expressivity and complexity (decidability) of the new logics.</div></div>","PeriodicalId":54985,"journal":{"name":"Information and Computation","volume":"304 ","pages":"Article 105299"},"PeriodicalIF":0.8,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143769031","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"On the data persistency of replicated erasure codes in distributed storage systems","authors":"Roy Friedman , Rafał Kapelko , Karol Marchwicki","doi":"10.1016/j.ic.2025.105297","DOIUrl":"10.1016/j.ic.2025.105297","url":null,"abstract":"<div><div>This paper studies the fundamental problem of <em>data persistency</em> for a general family of redundancy schemes, called <em>replicated erasure codes</em>. In replicated erasure codes each document is divided into <em>p</em> chunks and then encoded into <span><math><mi>p</mi><mo>+</mo><mi>q</mi></math></span> chunks. Then, each of the <span><math><mi>p</mi><mo>+</mo><mi>q</mi></math></span> chunks is replicated into <em>r</em> replicas. We analyze two strategies of replicated erasure codes distribution: <em>random</em> (all chunks are spread randomly among storage nodes) and <em>sequential</em> (the chunks are sequentially placed into storage nodes). For both strategies we derive closed-form expression and asymptotic bounds for expected data persistency of replicated erasure codes when the storage nodes leave the storage system and erase their locally stored data. We observe that the maximal expected data persistency of replicated erasure codes for both placement strategies is attained for parameter <span><math><mi>p</mi><mo>=</mo><mn>1</mn></math></span> and give formulas in terms of the beta function in this case.</div></div>","PeriodicalId":54985,"journal":{"name":"Information and Computation","volume":"304 ","pages":"Article 105297"},"PeriodicalIF":0.8,"publicationDate":"2025-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143697623","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Elastic-degenerate string comparison","authors":"Estéban Gabory , Moses Njagi Mwaniki , Nadia Pisanti , Solon P. Pissis , Jakub Radoszewski , Michelle Sweering , Wiktor Zuba","doi":"10.1016/j.ic.2025.105296","DOIUrl":"10.1016/j.ic.2025.105296","url":null,"abstract":"<div><div>An elastic-degenerate (ED) string <em>T</em> is a sequence of <em>n</em> sets <span><math><mi>T</mi><mo>[</mo><mn>1</mn><mo>]</mo><mo>,</mo><mo>…</mo><mo>,</mo><mi>T</mi><mo>[</mo><mi>n</mi><mo>]</mo></math></span> containing <em>m</em> strings in total whose cumulative length is <em>N</em>. We call <em>n</em>, <em>m</em>, and <em>N</em> the length, the cardinality and the size of <em>T</em>, respectively. The language of <em>T</em> is defined as <span><math><mi>L</mi><mo>(</mo><mi>T</mi><mo>)</mo><mo>=</mo><mo>{</mo><msub><mrow><mi>S</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>⋯</mo><msub><mrow><mi>S</mi></mrow><mrow><mi>n</mi></mrow></msub><mspace></mspace><mo>:</mo><mspace></mspace><msub><mrow><mi>S</mi></mrow><mrow><mi>i</mi></mrow></msub><mo>∈</mo><mi>T</mi><mo>[</mo><mi>i</mi><mo>]</mo><mtext> for all </mtext><mi>i</mi><mo>∈</mo><mo>[</mo><mn>1</mn><mo>,</mo><mi>n</mi><mo>]</mo><mo>}</mo></math></span>. Given two ED strings, how fast can we check whether the two languages they represent have a nonempty intersection? We call this problem the <span>ED String Intersection</span> (EDSI) problem. For two ED strings <span><math><msub><mrow><mi>T</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> and <span><math><msub><mrow><mi>T</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> of lengths <span><math><msub><mrow><mi>n</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> and <span><math><msub><mrow><mi>n</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>, cardinalities <span><math><msub><mrow><mi>m</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> and <span><math><msub><mrow><mi>m</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>, and sizes <span><math><msub><mrow><mi>N</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> and <span><math><msub><mrow><mi>N</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>, respectively, we show the following:<ul><li><span>•</span><span><div>There is no <span><math><mi>O</mi><mo>(</mo><msup><mrow><mo>(</mo><msub><mrow><mi>N</mi></mrow><mrow><mn>1</mn></mrow></msub><msub><mrow><mi>N</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>)</mo></mrow><mrow><mn>1</mn><mo>−</mo><mi>ϵ</mi></mrow></msup><mo>)</mo></math></span>-time algorithm, for any <span><math><mi>ϵ</mi><mo>></mo><mn>0</mn></math></span>, for EDSI even if <span><math><msub><mrow><mi>T</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> and <span><math><msub><mrow><mi>T</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> are over a binary alphabet, unless the Strong Exponential-Time Hypothesis is false.</div></span></li><li><span>•</span><span><div>There is no combinatorial <span><math><mi>O</mi><mo>(</mo><msup><mrow><mo>(</mo><msub><mrow><mi>N</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>+</mo><msub><mrow><mi>N</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>)</mo></mrow><mrow><mn>1.2</mn><mo>−</mo><mi>ϵ</mi></mrow></msup><mi>f</mi><mo>(</mo><msub><mrow><mi>n</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>","PeriodicalId":54985,"journal":{"name":"Information and Computation","volume":"304 ","pages":"Article 105296"},"PeriodicalIF":0.8,"publicationDate":"2025-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143697046","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Derandomization of quantum algorithm for triangle finding","authors":"Guanzhong Li , Lvzhou Li","doi":"10.1016/j.ic.2025.105295","DOIUrl":"10.1016/j.ic.2025.105295","url":null,"abstract":"<div><div>Derandomization is the process of taking a randomized algorithm and turning it into a deterministic algorithm, which has attracted great attention in classical computing. In quantum computing, it is challenging and intriguing to derandomize quantum algorithms, due to the inherent randomness of quantum mechanics. The significance of derandomizing quantum algorithms lies not only in theoretically proving that the success probability can essentially be 1 without sacrificing quantum speedups, but also in experimentally improving the success rate when the algorithm is implemented on a real quantum computer.</div><div>In this paper, we focus on derandomizing quantum algorithms for the triangle sum problem (including the famous triangle finding problem as a special case), which asks to find a triangle in an edge-weighted graph with <em>n</em> vertices, such that its edges sum up to a given weight. We show that when the graph is promised to contain at most one target triangle, there exists a deterministic quantum algorithm that either finds the triangle if it exists or outputs “no triangle” if none exists. It makes <span><math><mi>O</mi><mo>(</mo><msup><mrow><mi>n</mi></mrow><mrow><mn>9</mn><mo>/</mo><mn>7</mn></mrow></msup><mo>)</mo></math></span> queries to the edge weight matrix oracle, and thus has the same complexity as the state-of-the-art bounded-error quantum algorithm. To achieve this derandomization, we make full use of several techniques: nested quantum walk with quantum data structure, deterministic quantum search with adjustable parameters, and dimensional reduction of quantum walk search on Johnson graph.</div></div>","PeriodicalId":54985,"journal":{"name":"Information and Computation","volume":"304 ","pages":"Article 105295"},"PeriodicalIF":0.8,"publicationDate":"2025-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143621436","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Duncan Adamson , Nathan Flaherty , Igor Potapov , Paul G. Spirakis
{"title":"Collision-free Robot Scheduling","authors":"Duncan Adamson , Nathan Flaherty , Igor Potapov , Paul G. Spirakis","doi":"10.1016/j.ic.2025.105294","DOIUrl":"10.1016/j.ic.2025.105294","url":null,"abstract":"<div><div>In this paper, we investigate the problem of designing <em>schedules</em> for completing a set of tasks at fixed locations with multiple robots in a laboratory. We represent the laboratory as a graph with tasks placed on fixed vertices and robots represented as agents, with the constraint that no two robots may occupy the same vertex at any given timestep. Each schedule is partitioned into a set of timesteps, corresponding to a walk through the graph (allowing for a robot to wait at a vertex to complete a task), with each timestep taking time equal to the time for a robot to move from one vertex to another and each task taking some given number of timesteps during the completion of which a robot must stay at the vertex containing the task. The goal is to determine a set of schedules, with one schedule for each robot, minimising the number of timesteps taken by the schedule taking the greatest number of timesteps within the set of schedules. We show that this problem is NP-complete for both star graphs (for <span><math><mi>k</mi><mo>≥</mo><mn>2</mn></math></span> robots), and planar graphs (for any number of robots). Finally, we provide positive results for path, cycle, and tadpole graphs, showing that we can find an optimal set of schedules for <em>k</em> robots completing <em>m</em> tasks of equal duration of a path of length <em>n</em> in <span><math><mi>O</mi><mo>(</mo><mi>k</mi><mi>m</mi><mi>n</mi><mo>)</mo></math></span>, <span><math><mi>O</mi><mo>(</mo><mi>k</mi><mi>m</mi><msup><mrow><mi>n</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>)</mo></math></span> time, and <span><math><mi>O</mi><mo>(</mo><msup><mrow><mi>k</mi></mrow><mrow><mn>3</mn></mrow></msup><msup><mrow><mi>m</mi></mrow><mrow><mn>4</mn></mrow></msup><mi>n</mi><mo>)</mo></math></span> time respectively.</div></div>","PeriodicalId":54985,"journal":{"name":"Information and Computation","volume":"304 ","pages":"Article 105294"},"PeriodicalIF":0.8,"publicationDate":"2025-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143621435","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A dichotomy result for countably based sober spaces","authors":"Hualin Miao , Qingguo Li","doi":"10.1016/j.ic.2025.105293","DOIUrl":"10.1016/j.ic.2025.105293","url":null,"abstract":"<div><div>Cartesian closed categories have been playing fundamental roles in providing denotational semantic for higher-order programming languages. In this paper we try to identify Cartesian closed subcategories of the category <span><math><mi>C</mi><msub><mrow><mi>S</mi></mrow><mrow><mo>⊥</mo></mrow></msub></math></span> of pointed countably based sober spaces, and we present a conclusion known as the dichotomy result in the category <span><math><mi>C</mi><msub><mrow><mi>S</mi></mrow><mrow><mo>⊥</mo></mrow></msub></math></span>. This result explains that any Cartesian closed full subcategory of <span><math><mi>C</mi><msub><mrow><mi>S</mi></mrow><mrow><mo>⊥</mo></mrow></msub></math></span> is contained within either the category of weakly compact open connected spaces or that of principally connected spaces.</div><div>To prove our dichotomy theorem, we first deduce that every pointed countably based sober space <em>X</em> is locally connected, if the space of all continuous functions from <em>X</em> to <em>X</em> is locally compact. Next, we demonstrate that a function space in <span><math><mi>C</mi><msub><mrow><mi>S</mi></mrow><mrow><mo>⊥</mo></mrow></msub></math></span> is locally connected only if its input space is either weakly compact open connected or its output space is principally connected.</div></div>","PeriodicalId":54985,"journal":{"name":"Information and Computation","volume":"304 ","pages":"Article 105293"},"PeriodicalIF":0.8,"publicationDate":"2025-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143563651","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A multivariate convertible undeniable signature scheme","authors":"Satyam Omar , Sahadeo Padhye , Dhananjoy Dey , Devansh Mehrotra","doi":"10.1016/j.ic.2025.105286","DOIUrl":"10.1016/j.ic.2025.105286","url":null,"abstract":"<div><div>Digital signature is an important cryptographic primitive which can be universally verified. However, this universal verifiability can be ominous in case of e-auction, e-voting, and e-cash, where the verifiability must be restricted. Undeniable signature is a type of digital signature that is mainly used to achieve the goal of access control. In this article, we propose the first multivariate-based quantum secure undeniable signature scheme, which can also be converted into an ordinary signature. The security of this scheme relies on the hardness of multivariate quadratic problem which is computationally hard to solve when defined over any finite field. We deploy Monteiro et al.'s improvement on Sakumoto et al.'s zero-knowledge protocol for the verification process. We discuss the security properties of undeniable signature, viz., completeness, soundness, unforgeability, invisibility, and non-impersonation. Additionally, we show that the proposed undeniable signature has the smallest signature and key sizes among all the existing quantum-resistant undeniable signatures.</div></div>","PeriodicalId":54985,"journal":{"name":"Information and Computation","volume":"304 ","pages":"Article 105286"},"PeriodicalIF":0.8,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143510074","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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