Computer Engineering / Bilgisayar Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/10

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End date: 2009Publication Index: search.filters.publicationIndex.Scopus

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Now showing 1 - 10 of 57
  • Conference Object
    Duyarga Ağları için Bir Γ Eşuyumcusu Tasarım ve Uygulaması
    (IEEE, 2008) Özsoyeller, Deniz; Erciyeş, Kayhan; Dağdeviren, Orhan
    Implementation of synchronous algorithms in distributed systems in general is less troublesome than the implementation of asynchronous algorithms. Synchronizers provide synchronous execution of an asynchronous algorithm in distributed systems. In this study, we propose a gamma synchronizer for Wireless Sensor Networks (WSNs). This synchronizer consists of a and beta synchronizers. In our work, the WSN is first divided into clusters and then these clusters are connected using a ring protocol. Synchronization is provided using the beta synchronizer in the cluster and a synchronizer among the clusters. We describe the clustering algorithm and the ring formation algorithm for the WSNs and give the results obtained so far.
  • Conference Object
    Citation - Scopus: 15
    Gezgin Tasarsız Ağlar için Taşırma Tabanlı Yönlendirme Yordamı
    (IEEE, 2008) Çokuslu, Deniz; Erciyeş, Kayhan
    Mobile Ad Hoc Networks (MANETs) are videly in use in rescue, military operations, scientific and business areas. Many studies are addressed in MANETs because of their need to long lasting liveness, fault tolerance, dynamic addressing, collusion prevention, mobility management and security. Especially, self clustering, backbone construction and routing are the most interesting academic and industrial research areas in MANETs. A wide range of studies addressed the routing problem in MANETs. Many previous studies address the clustering and routing problems as seperate subjects. However, rowing approaches which are specific to the clustering methodologies may have many advantages in terms of efficiency and availability. In this study, a flooding based routing algorithm is proposed. First, a detailed description of the algorithm is explained, then the analysis and test results using the ns2 simulator are given which show that the designed algorithm is scalable and has favorable performance.
  • Conference Object
    Citation - Scopus: 4
    Test Case Generation for Firewall Implementation Testing Using Software Testing Techniques
    (Tafford Publishing, 2008) Tuğlular, Tuğkan
    The firewall implementation testing approach checks actions performed by the firewall with respect to corresponding firewall rules. This type of firewall testing can be implemented by developing test cases from firewall rule sequence, generating test packets using those test cases and injecting those test packets into the firewall. Although this method has been already defined in the academic world, an approach to generate test cases does not exist in the literature. In this work, a test case generation approach is developed using software testing techniques. © 2008 Atilla Elçi.
  • Conference Object
    The Performance Results of Ecdsa Implementation on Different Coordinate Systems
    (Tafford Publishing, 2008) Atay, Serap
    Elliptic Curve Cryptography has a high computational cost due to arithmetic operations of point addition and point doubling. But the cost can be reduced if different coordinate systems utilized. This paper shows that the performance of an elliptic curve digital signature algorithm (ECDSA) can be significantly increased by using different coordinate systems.
  • Conference Object
    On Ntru and Its Performance
    (Tafford Publishing, 2008) Mersin, Ali; Beyazıt, Mutlu
    Hardness of lattice problems has introduced a new candidate for public key cryptosystems. NTRU is one of such cryptosystems. The fact that it works with small integers and that the complexities of key generation, encryption and decryption are relatively small leads to good overall performance when compared to the other public key cryptosystems. The aim of this study is to make a theoretical to practical introduction to NTRU and investigate how it performs against popular public key cryptosystems such as RSA and, especially, ECC. © 2008 Atilla Elçi.
  • Conference Object
    A Memory Management Model for Cryptographic Software Libraries
    (Tafford Publishing, 2008) Mersin, Ali; Beyazıt, Mutlu
    Cryptographic protocols are implemented on the abstraction of multiple precision number libraries in which the dominant design criterion mostly turns out to be the maximization of the system performance. In contrast, each protocol may have its own memory usage pattern. In general case, the memory allocation and release routines are frequently called during the runtime. For this reason, an improper memory management strategy may yield an inefficient implementation. In this paper, we propose a memory management technique which is constructed under the consideration of the context of high level cryptographic software running on multi-programmed environments. Also, we show the implementation results of our approach and discuss with respect to the common static and dynamic memory allocation strategies. © 2008 Atilla Elçi.
  • Conference Object
    Monitoring of Policy Operations in a Distributed Firewall Environment
    (2008) Çakı, Oğuzhan; Tuğlular, Tuğkan; Çetin, Füsun
    Distributed firewalls concept has been introduced to overcome some drawbacks of traditional firewalls. Distributed firewall approach is based on the idea of enforcing policy rules at the intermediate and end points rather than a single entry point to the network. Management of policy rules in a distributed firewall environment requires surveillance of policy operations performed on each firewall. With this paper, we propose a monitoring architecture and its application prototype for distributed firewalls to keep track of actions, such as create, read, update, and delete, carried out on policy rule sets. We performed some emulation and laboratory experiments to obtain operational values of the proposed architecture. ©2008 by Bo?aziçi University.
  • Conference Object
    Citation - Scopus: 2
    Telsiz Duyarga Ağlarında Hızlı Hareket Eden Hedefler için Küme Tabanlı Hedef İzleme Algoritması
    (Institute of Electrical and Electronics Engineers Inc., 2009) Alaybeyoğlu, Ayşegül; Dağdeviren, Orhan; Kantarcı, Aylin; Erciyes, Kayhan
    Kablosuz iletişim teknolojilerindeki ilerlemelerle birlikte telsiz duyarga ağları (TDA) birçok sivil ve askeri uygulamalarda özellikle de hareketli hedefin takibi gibi konularda yaygın olarak kullanılmaya başlanmıştır. Bu çalışmada da TDA’da hızlı hareket eden nesneler için küme tabanlı bir hedef izleme algoritması önerilmiştir. Literatürde bulunan mevcut çalışmalarda lider düğüm, hedefin sadece t+1 anında yaklaşacağı konumu tahminleyerek bu konuma en yakın düğümü uyandırır. Hedefin çok hızlı hareket etmesi durumunda ise hedefin kısa süre içerisinde bir grup düğümün yakınlarından algılanmadan geçip gitmesi söz konusudur. Önermiş olduğumuz algoritma ile hedefin hızına bağlı olarak, hedefin tahmini gideceği yöndeki düğümler önceden uyandırılarak, kümeler önceden oluşturulmaktadır. Böylece hedefin ani hızlanması durumunda, önceden oluşturmuş olduğumuz kümeler sayesinde hedefin kaybolma riskini azaltmış bulunmaktayız.
  • Article
    Citation - WoS: 4
    Citation - Scopus: 5
    Query optimization: Mobile agents versus accuracy of the cost estimation
    (CRL Publishing, 2005) Özakar, Belgin; Morvan, F.; Hameurlaint, A.
    Since an increasing number of diverse sources of data and information become available through World Wide Web, the field of distributed heterogeneous query processing attracts attention of the researchers. One of the main concerns is to reduce the amount of communication and the volume of data transferred in terms of query optimization where it is a real challenge to have the statistics of the resources predictable and up-to-date. Autonomy, proactivity and mobility features of mobile agents seem promising under some conditions. In this paper we are interested in the study of the efficiency of the mobile agents in relation with the approach of the cost model used during the optimization process. We present an execution model based on mobile agents. Performance evaluation shows the efficiency intervals of the execution model according to the estimation errors and the current state of the system. The major contribution of this paper is to point out the effective use of an execution model based on mobile agents in relation with the approach of the cost model and with the query type. © 2005 CRL Publishing Ltd.
  • Conference Object
    Citation - Scopus: 1
    A Semantic Based Certification and Access Control Approach Using Security Patterns on Seagent
    (Knowledge Systems Institute, 2008) Tekbacak, Fatih; Tuğlular, Tuğkan; Dikenelli, Oğuz
    In this paper, we propose a security infrastructure for communication between agents adaptable to FIPA security specifications by employing security patterns and semantic based policy descriptions. Security patterns are used as a generalized approach for generating security based services. This paper analyzes the authentication and semantic based access control among agents by using the security patterns.