This book constitutes the refereed proceedings of the 23rd International Symposium on Algorithms and Computation, ISAAC 2012, held in Taipei, Taiwan, in December 2012. The 68 revised full papers presented together with three invited talks were carefully reviewed and selected from 174 submissions for inclusion in the book. This volume contains topics such as graph algorithms; online and streaming algorithms; combinatorial optimization; computational complexity; computational geometry; string algorithms; approximation algorithms; graph drawing; data structures; randomized algorithms; and algorithmic game theory.

The 11th Information Security Conference (ISC 2008) was held in Taipei, T- wan, September 15-18,2008. ISC is an annual international conference covering researchintheoryandapplicationsofinformationsecurity.Itwas?rstinitiatedas a workshop(ISW) in Japan in 1997.This was followed by ISW 1999 in Malaysia and ISW 2000 in Australia. ISW became ISC when it was held in Spain in 2001 (ISC2001).ThelatestconferenceswereheldinBrazil(ISC2002), UK(ISC2003), USA(ISC2004), Singapore(ISC2005), Greece(ISC2006), andChile(ISC2007). ThisyeartheeventwassponsoredbytheChineseCryptologyandInformation- curity Association (Taiwan), the Taiwan Information Security Center of the - searchCenterforITInnovation(AcademiaSinica, Taiwan), theNationalTaiwan UniversityofScience andTechnology(Taiwan), the NTUCenterfor Information and Electronics Technologies(Taiwan), Academia Sinica (Taiwan), the National ScienceCouncil(Taiwan), the MinistryofEducation(Taiwan), the TaipeiCh- terofthe IEEEComputerSociety (Taiwan), BankProE-serviceTechnologyCo., Ltd.(Taiwan), ExsiorData &InformationTechnology, Inc.(Taiwan), Giga-Byte EducationFoundation(Taiwan), Hewlett-PackardTaiwan, HivocalTechnologies, Co., Ltd.(Taiwan), MicrosoftTaiwan, PaysecureTechnologyCo., Ltd.(Taiwan), Symlink(Taiwan), and Yahoo TaiwanHoldingsLimited(TaiwanBranch). In order to cover the conference's broad scope, this year's main Program Committee consisted of 61 experts from 22 countries. Additionally, the c- ference also featured a special AES Subcommittee, chaired by Vincent Rijmen (Graz University of Technology, Austria). Theconferencereceived134submissions from31countries,33(including 4 in the AES special session) of which were selected by the committee members for presentation at the conference, based on quality, originality and relevance. Each paperwasanonymouslyreviewedbyatleastthreecommitteemembers.Inorderto encourageandpromotestudentparticipation, theISC2008ProgramCommittee selected three student-coauthored papers for the Best Student Paper award, one fromeachregion: Asia, Europe, andtheAmericas.Thepaperswere, respectively, "Deterministic Constructions of 21-Step Collisions for the SHA-2 Hash Family," bySomitraSanadhyaandPalashSarkar(IndianStatisticalInstitute, India),"C- lisions for RC4-Hash," by Sebastiaan Indesteege and Bart Preneel (Katholieke UniversiteitLeuven, Belgium), and"ProxyRe-signaturesintheStandardModel," byShermanS.M. Chow(New YorkUniversity, USA) andRaphaelPhan(Lou- borough University, UK). The program also included invited speeches by Doug Tygar(UC Berkeley, USA) andTatsuakiOkamoto(NTT, Japan). Many people helped to make ISC 2008 successful. We would like to thank all thosewhocontributedtothetechnicalprogramandtoorganizingtheconference.

Voronoi diagrams partition space according to the influence certain sites exert on their environment. Since the 17th century, such structures play an important role in many areas like Astronomy, Physics, Chemistry, Biology, Ecology, Economics, Mathematics and Computer Science. They help to describe zones of political influence, to determine the hospital nearest to an accident site, to compute collision-free paths for mobile robots, to reconstruct curves and surfaces from sample points, to refine triangular meshes, and to design location strategies for competing markets. This unique book offers a state-of-the-art view of Voronoi diagrams and their structure, and it provides efficient algorithms towards their computation. Readers with an entry-level background in algorithms can enjoy a guided tour of gently increasing difficulty through a fascinating area. Lecturers might find this volume a welcome source for their courses on computational geometry. Experts are offered a broader view, including many alternative solutions, and up-to-date references to the existing literature; they might benefit in their own research or application development.