**Journal & Conference Papers**

M. Chroni, S.D. Nikolopoulos, and L. Palios , Encoding Watermark Numbers as Reducible Permutation Graphs using Self-inverting Permutations,**Discrete Applied Mathematics**(accepted)A.L. Konstantinidis, S.D. Nikolopoulos, and C. Papadopoulos , Strong Triadic Closure in Cographs and Graphs of Low Maximum Degree,**Theoretical Computer Science**2018S.D. Nikolopoulos and I. Polenakis , Preventing Malware Pandemics in Mobile Devices by Establishing Response-time Bounds,**Journal of Information Security and Applications**, 2017S.D. Nikolopoulos and I. Polenakis , A Graph-based Model for Malware Detection and Classification using System-call Groups,**Journal of Computer Virology and Hacking Techniques**, 2017A. Konstantinidis, S.D. Nikolopoulos, and Ch. Papadopoulos , Strong Triadic Closure in Cographs and Graphs of Low Maximum Degree,**23rd International Computing and Combinatorics Conference (COCOON'17)**, LNCS Proceedings, 2017A. Mpanti, S.D. Nikolopoulos, and M. Rini , Experimental Study of the Resilience of a Graph-based Watermarking System under Edge Modifications,**21st Panhellenic Conference on Info (PCI'17)**, ACM ICPS Proceedings, 2017A. Mpanti, S.D. Nikolopoulos, and Iosif Polenakis , Defending Hardware-based Attacks on Trusted Computing using a Hardware-Integrity Attestation Protocol,**18th Int'l Conference on Computer Systems and Technologies (CompSysTech'17)**, ACM ICPS Proceedings, 2017M. Chroni, S.D. Nikolopoulos and L. Palios , Encoding Watermark Numbers as Reducible Permutation Graphs using Self-inverting Permutations,**CoRR abs/1712.08482**, Dec 2017.S.D. Nikolopoulos and I. Polenakis , A Model for Establishing Response-time Bounds to Prevent Malware Pandemics in Mobile Devices,**17th Int'l Conference on Computer Systems and Technologies (CompSysTech'16)**, ACM ICPS Proceedings, 2016A. Mpanti and S.D. Nikolopoulos , Graph-structured Watermarking using Bitonic Sequences of Self-inverting Permutations,**20th Panhellenic Conference on Info (PCI'16)**, ACM ICPS Proceedings, 2016S.D. Nikolopoulos and I. Polenakis , Preventing Malware Pandemics in Mobile Devices by Establishing Response-time Bounds,**CoRR abs/1607.00827**, July 2016.A. Mpanti and S.D. Nikolopoulos , Two RPG Flow-graphs for Software Watermarking using Bitonic Sequences of Self-inverting Permutations,**CoRR abs/1607.02281**, July 2016.

S.D. Nikolopoulos and I. Polenakis , A Graph-based Model for Malicious Code Detection Exploiting Dependencies of System-call Groups,**16th Int'l Conference on Computer Systems and Technologies (CompSysTech'15)**, ACM ICPS Proceedings, 2015S.D. Nikolopoulos and I. Polenakis , Malicious software classification based on relations of system-call groups,**19th Panhellenic Conference on Informatics (PCI'15)**, ACM ICPS Proceedings, 2015M. Chroni and S.D. Nikolopoulos , Encoding numbers into reducible permutation graphs using heap-ordered trees,**19th Panhellenic Conference on Informatics (PCI'15)**, ACM ICPS Proceedings, 2015M. Chroni and S.D. Nikolopoulos , Watermarking PDF documents using various representations of self-inverting permutations,**11th Int'l Conference on Web Information Systems and Technologies (WEBIST'15)**, SciTePress Digital Library, 2015M. Chroni and S.D. Nikolopoulos , Watermarking PDF Documents using Various Representations of Self-inverting Permutations,**CoRR abs/1501.02686**, Jan 2015.

L. Georgiadis, S.D. Nikolopoulos, and L. Palios , Join-reachability problems in directed graphs,**Theory of Computing Systems**, 2014S.D. Nikolopoulos, L. Palios, and C. Papadopoulos , Counting spanning trees using modular decomposition,**Theoretical Computer Science**, 2014M. Chroni, A. Fylakis, and S.D. Nikolopoulos , Watermarking Digital Images in the Frequency Domain: Performance and Attack Issues,**Book LNBIP 189, Chapter No 5**, 2014M. Chroni, A. Fylakis, and S.D. Nikolopoulos , From image to audio watermarking using self-inverting permutations,**10th Int'l Conference on Web Information Systems and Technologies (WEBIST'14)**, SciTePress Digital Library, 2014S.D. Nikolopoulos and Iosif Polenakis , Detecting malicious code by exploiting dependencies of system-call groups ,**CoRR abs/1412.8712**, Dec. 2014.I. Chionis, M. Chroni, and S.D. Nikolopoulos , WaterRPG: A graph-based dynamic watermarking model for software protection,**CoRR abs/1403.6658**, March 2014.

M. Chroni, A. Fylakis, and S.D. Nikolopoulos, Watermarking images in the frequency domain by exploiting self-inverting permutations,

**Journal of Information Security**, 2013K. Ioannidou and S.D. Nikolopoulos , The longest path problem is polynomial on cocomparability graphs,**Algorithmica**, 2013E. Lappas, S.D. Nikolopoulos, and L. Palios , An O(n)-time algorithm for the paired-domination problem on permutation graphs,**European Journal of Combinatorics**, 2013I. Chionis, M. Chroni, and S.D. Nikolopoulos , A dynamic watermarking model for embedding reducible permutation graphs into software,**10th Int'l Conference on Security and Cryptography (SECRYPT'13)**, SciTePress Digital Library, 2013M. Chroni and S.D. Nikolopoulos , Design and evaluation of a graph codec system for software watermarking,**2nd Int'l Conference on Data Management Technologies and Applications (DATA'13)**, SciTePress Digital Library, 2013M. Chroni, A. Fylakis, and S.D. Nikolopoulos , Watermarking images in the frequency domain by exploiting self-inverting permutations,**9th Int'l Conference on Web Information Systems and Technologies (WEBIST'13)**, SciTePress Digital Library, 2013 (Best Student Paper Award)I. Chionis, M. Chroni, and S.D. Nikolopoulos , Watermarking Java application programs using the WaterRpg dynamic model,**14th Int'l Conference on Computer Systems and Technologies (CompSysTech'13)**, ACM ICPS Proceedings, 2013 (Best Paper Award)I. Chionis, M. Chroni, and S.D. Nikolopoulos , Evaluating the WaterRpg software watermarking model on Java application programs,**17th Panhellenic Conference on Informatics (PCI'13)**, ACM ICPS Proceedings, 2013

S.D. Nikolopoulos and L. Palios , An O(nm)-time certifying algorithm for recognizing HHD-free graphs,**Theoretical Computer Science**, 2012S.D. Nikolopoulos, L. Palios, and C. Papadopoulos , A fully dynamic algorithm for the recognition of P4-sparse graphs,**Theoretical Computer Science**, 2012M. Chroni and S.D. Nikolopoulos , Multiple encoding of a watermark number into reducible permutation graphs using cotrees,**13th Int'l Conference on Computer Systems and Technologies (CompSysTech'12)**, ACM ICPS Proceedings, 2012M. Chroni and S.D. Nikolopoulos , An efficient graph codec system for software watermarking,**36th Int'l Conference on Computers, Software, and Applications (COMPSAC'12); Workshop STPSA'12**, IEEE Proceedings, 2012M. Chroni, A. Fylakis, and S.D. Nikolopoulos , A watermarking system for teaching intellectual property rights: implementation and performance,**11th Int'l Conference on Information Technology Based Higher Education and Training (ITHET'12)**, IEEE Proceedings, 2012M. Chroni and S.D. Nikolopoulos , An embedding graph-based model for software watermarking,**8th Int'l Conference on Intelligent Information Hiding and Multimedia Signal Processing (IIH-MSP'12)**, IEEE Proceedings, 2012M. Chroni, A. Fylakis, and S.D. Nikolopoulos , Watermarking images using 2D representations of self-inverting permutations,**8th Int'l Conference on Web Information Systems and Technologies (WEBIST'12)**, SciTePress Digital Library, 2012M. Chroni, A. Fylakis, and S.D. Nikolopoulos , A watermarking system for teaching students to respect intellectual property rights,**4th Int'l Conference on Computer Supported Education (CSEDU'12)**, Poster paper, 2012

K. Ioannidou, G.B. Mertzios, and S.D. Nikolopoulos , The longest path problem has a polynomial solution on interval graphs,**Algorithmica**, 2011S.D. Nikolopoulos and C. Papadopoulos , A simple linear-time recognition algorithm for weakly quasi-threshold graphs,**Graphs and Combinatorics**, 2011L. Georgiadis, S.D. Nikolopoulos, and L. Palios , Join-reachability problems in directed graphs,**6th Int'l Computer Science Symposium in Russia (CSR'11)**, LNCS 6651, 2011M. Chroni and S.D. Nikolopoulos , Encoding watermark numbers as cographs using self-inverting permutations,**12th Int'l Conference on Computer Systems and Technologies (CompSysTech'11)**, ACM ICPS 578, 2011 (Best Paper Award)S.D. Nikolopoulos, L. Palios, and C. Papadopoulos , Counting spanning trees in graphs using modular decomposition,**5th Int'l Workshop on Algorithms and Computation (WALCOM'11)**, LNCS 6552, 2011

K. Asdre and S.D. Nikolopoulos , The 1-fixed-endpoint path cover problem is polynomial on interval graphs,**Algorithmica**, 2010K. Asdre and S.D. Nikolopoulos , A polynomial solution to the k-fixed-endpoint path cover problem on proper interval graphs,**Theoretical Computer Science**, 2010M. Chroni and S.D. Nikolopoulos , Encoding watermark integers as self-inverting permutations,**11th Int'l Conference on Computer Systems and Technologies (CompSysTech'10)**, ACM ICPS 471, 2010K. Ioannidou and S.D. Nikolopoulos , The longest path problem is polynomial on cocomparability graphs,**36th Int'l Workshop on Graph-Theoretic Concepts in Computer Science (WG'10)**, LNCS 6410, 2010K. Ioannidou and S.D. Nikolopoulos , Harmonious coloring on subclasses of colinear graphs,**4th Int'l Workshop on Algorithms and Computation (WALCOM'10)**, LNCS 5942, 2010

S.D. Nikolopoulos, L. Palios, and C. Papadopoulos , Maximizing the number of spanning trees in Kn-complements of asteroidal graphs,**Discrete Mathematics**, 2009S.D. Nikolopoulos and C. Papadopoulos , Counting spanning trees in cographs: an algorithmic approach,**Ars Combinatoria**, 2009K. Ioannidou, G.B. Mertzios, and S.D. Nikolopoulos , The longest path problem is polynomial on interval graphs,**34th Int'l Symposium on Mathematical Foundations of Computer Science (MFCS'09)**, LNCS 5734, 2009E. Lappas, S.D. Nikolopoulos, and L. Palios , An O(n)-time algorithm for the paired-domination problem on permutation graphs,**20th Int'l Workshop on Combinatorial Algorithms (IWOCA'09)**, LNCS 5874, 2009K. Ioannidou and S.D. Nikolopoulos , Colinear coloring on graphs,**3rd Int'l Workshop on Algorithms and Computation (WALCOM'09)**, LNCS 5431, 2009

D. Koukopoulos, S.D. Nikolopoulos, L. Palios, and P.G. Spirakis , Optimal algorithms for detecting network stability,**2ed Int'l Workshop on Algorithms and Computation (WALCOM'08)**, LNCS 4921, 2008K. Asdre and S.D. Nikolopoulos , The 2-terminal-set path cover problem and its polynomial solution on cographs,**2nd Int'l Frontiers of Algorithmics Workshop (FAW'08)**, LNCS 5059, 2008

K. Asdre, K. Ioannidou, and S.D. Nikolopoulos , The Harmonious coloring problem is NP-complete for interval and permutation graphs,**Discrete Applied Mathematics**, 2007K. Asdre and S.D. Nikolopoulos , NP-completeness results for some problems on subclasses of bipartite and chordal graphs,**Theoretical Computer Science**, 2007K. Asdre and S.D. Nikolopoulos , A linear-time algorithm for the k-fixed-endpoint path cover problem on cographs,**Networks**, 2007S.D. Nikolopoulos and L. Palios , On the parallel computation of the biconnected and strongly connected co-components of graphs,**Discrete Applied Mathematics**, 2007K. Asdre, S.D. Nikolopoulos, and C. Papadopoulos , An optimal parallel solution for the path cover problem on P4-sparse graphs,**J. Parallel and Distributed Computing**, 2007S.D. Nikolopoulos and L. Palios , Detecting holes and antiholes in graphs,**Algorithmica**, 2007K. Asdre and S.D. Nikolopoulos , A polynomial solution for the k-fixed-endpoint path cover problem on proper interval graphs,**18th Int'l Workshop on Combinatorial Algorithms (IWOCA'07)**, College Publications, Texts in Algorithmics Vol. 10, 2007S.D. Nikolopoulos and L. Palios , An O(nm)-time certifying algorithm for recognizing HHDfree graphs,**1st Int'l Frontiers in Algorithmics Workshop (FAW'07)**, LNCS 4613, 2007M. Chroni, D. Koukopoulos, and S.D. Nikolopoulos , An experimental study of stability in heterogenous networks,**6th Workshop on Experimental Algorithms (WEA'07)**, LNCS 4525, 2007

S.D. Nikolopoulos and C. Papadopoulos , On the number of spanning trees of Kn +/- G graphs,**Discrete Mathematics and Theoretical Computer Science**, 2006K. Asdre and S.D. Nikolopoulos , P-tree structures and event horizon: efficient event-set implementations,**J. Computer Science and Technology**, 2006S.D. Nikolopoulos and L. Palios , Minimal separators in P4-sparse graphs,**Discrete Mathematics**, 2006S.D. Nikolopoulos and L. Palios , Recognizing HH-free, HHD-free and Welsh-Powell opposition graphs,**Discrete Mathematics and Theoretical Computer Science**, 2006S.D. Nikolopoulos, L. Palios, and C. Papadopoulos , A fully dynamic algorithm for the recognition of P4-sparse graphs,**32nd Int'l Workshop on Graph-Theoretic Concepts in Computer Science (WG'06)**, LNCS 4271, 2006D. Koukopoulos and S.D. Nikolopoulos , Heterogenous networks can be unstable at arbitrarily low injection rates,**6th Conference on Algorithms and Complexity (CIAC'06)**, LNCS 3998, 2006

S.D. Nikolopoulos and L. Palios , Efficient parallel recognition of cographs,**Discrete Applied Mathematics**, 2005S.D. Nikolopoulos and L. Palios , On the recognition of bipolarizable and P4-simplicial graphs,**Discrete Mathematics and Theoretical Computer Science**, 2005P. Fragopoulou, S.D. Nikolopoulos, and L. Palios , Multi-source trees: algorithms for minimizing eccentricity metrics,**16th Int'l Symposium on Algorithms and Computation (ISAAC'05)**, LNCS 3827, 2005S.D. Nikolopoulos and L. Palios , Maximum-size subgraphs of P4-sparse graphs admitting a perfect matching,**10th Panhellenic Conference on Informatics (PCI'05)**, LNCS 3746, 2005S.D. Nikolopoulos and L. Palios , Recognizing HHDS-free graphs,**31st Int'l Workshop on Graph-Theoretic Concepts in Computer Science (WG'05)**, LNCS 3787, 2005S.D. Nikolopoulos and L. Palios , Adding an edge in a cograph,**31st Int'l Workshop on Graph-Theoretic Concepts in Computer Science (WG'05)**, LNCS 3787, 2005

S.D. Nikolopoulos, C. Nomikos, and P. Rondogiannis , A limit characterization for the number of spanning trees of graphs,**Information Processing Letters**, 2004S.D. Nikolopoulos and L. Palios , Parallel algorithms for P4-comparability graphs,**J. Algorithms**, 2004S.D. Nikolopoulos and L. Palios , Parallel algorithms for recognizing P5-free and coP5-free weakly chordal graphs,**Parallel Processing Letters**, 2004S.D. Nikolopoulos and L. Palios , Algorithms for P4-comparability graph recognition and acyclic P4-transitive orientation,**Algorithmica**, 2004S.D. Nikolopoulos and C. Papadopoulos , The number of spanning trees in Kn-complements of quasi-threshold graphs,**Graphs and Combinatorics**, 2004S.D. Nikolopoulos , Parallel algorithms for Hamiltonian problems on quasi-threshold graphs,**J. Parallel and Distributed Computing**, 2004K.W. Chong, S.D. Nikolopoulos, and L. Palios , An optimal parallel co-connectivity algorithm,**Theory of Computing Systems**, 2004S.D. Nikolopoulos and L. Palios , Recognizing HHD-free and Welsh-Powell opposition graphs,**30th Int'l Workshop on Graph-Theoretic Concepts in Computer Science (WG'04)**, LNCS 3353, 2004S.D. Nikolopoulos and L. Palios , Hole and antihole detection in graphs,**15th ACM-SIAM Symposium on Discrete Algorithms (SODA'04)**, Vol. 1, 2004

S.D. Nikolopoulos and L. Palios , Recognizing bipolarizable and P4-simplicial graphs,**29th Int'l Workshop on Graph-Theoretic Concepts in Computer Science (WG'03)**, LNCS 2880, 2003

S.D. Nikolopoulos , Coloring permutation graphs in parallel,**Discrete Applied Mathematics**, 2002S.D. Nikolopoulos and L. Palios , On the recognition of P4-comparability graphs,**28th Int'l Workshop on Graph-Theoretic Concepts in Computer Science (WG'02)**, LNCS 2573, 2002

S.D. Nikolopoulos , Optimal Gray-code labeling and recognition algorithms for hypercubes,**Information Sciences**, 2001S.D. Nikolopoulos and L. Palios , Recognition and orientation algorithms for P4-comparability graphs,**12th Int'l Symposium on Algorithms and Computation (ISAAC'01)**, LNCS 2223, 2001

S.D. Nikolopoulos and C. Papadopoulos , On the performance of the First-Fit coloring algorithm on permutation graphs,**Information Processing Letters**, 2000S.D. Nikolopoulos , Recognizing cographs and threshold graphs through a classification of their edges,**Information Processing Letters**, 2000

M. Andreou and S.D. Nikolopoulos , NC coloring algorithms for permutation graphs,**Nordic J. Computing**, 1999S.D. Nikolopoulos and P. Rondogiannis , On the number of spanning trees of multi-star related graphs,**Information Processing Letters**, 1998F. Harary and S.D. Nikolopoulos , On complete systems of invariants for small graphs,**Intern. J. Computer Mathematics**, 1997S.D. Nikolopoulos and G. Samaras , Sub-optimal solutions to track detection problem using graph theoretic concepts,**J. Systems Architecture**, 1997S.D. Nikolopoulos , Parallel block-finding using distance matrices,**J. Parallel Algorithms and Applications**, 1996S.D. Nikolopoulos , Constant-time parallel recognition of split graphs,**Information Processing Letters**, 1995S.D. Nikolopoulos and S.D. Danielopoulos , Parallel computation of perfect elimination schemes using partition techniques on triangulated graphs,**Computers and Mathematics with Applications**, 1995S.D. Nikolopoulos and S.D. Danielopoulos , On the parallel evaluation of DWBA integrals,**Intern. J. Computer Mathematics**, 1994S.D. Nikolopoulos and S.D. Danielopoulos , Odd-even, compare-exchange parallel sorting,**Microprocessing and Microprogramming**, 1994S.D. Nikolopoulos and S.D. Danielopoulos , Fast parallel algorithms for finding cutpoints and bridges of undirected graphs,**J. Parallel Algorithms and Applications**, 1994S.D. Nikolopoulos and R. MacLeod , An experimental analysis of event set algorithms for discrete event simulation,**Microprocessing and Microprogramming**, 1993

S.D. Nikolopoulos, A. Pitsillides, and D. Tipper , Addressing network survivability issues by finding the K-best paths through a trellis graph,**16th IEEE Conference on Computer Communications (INFOCOM'97)**, IEEE Proceedings, 1997G. Samaras, S.D. Nikolopoulos, K. Britton, and A. Cirton , Managing transaction identifiers in the Peer-to-Peer distributed transactional environment,**9th Int'l Conference on Parallel and Distributed Computing Systems (PDCS'96)**, Vol. 2, 1996S.D. Nikolopoulos and G. Samaras , Sub-optimal approach to track detection for real-time systems,**21st Euromicro Conference on Design of Hardware and Software Systems (EUROMICRO'95)**, Vol. 1, 1995F. Harary and S.D. Nikolopoulos , Graph isomorphism problem for small graphs,**2nd Int'l Conference on Digital Signal Processing (DSP'95)**, Vol. 1, 1995S.D. Nikolopoulos , Parallel recognition and location algorithms for chordal graphs using distance matrices,**3rd Int'l Conference on Parallel and Vector Processing (CONPAR'94)**, LNCS 854, 1994

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