Wyniki wyszukiwania - BazTech

1

Notary-based self-healing mechanism for centralized peer-to-peer infrastructures

Oryńczak G., Kotulski Z.

Annales Universitatis Mariae Curie-Skłodowska. Sectio AI, Informatica

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2012

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Vol. 12, no. 4

97--112

EN

Centralized architecture, due to its simplicity, fast and reliable user management mechanism (authorization, authentication and lookup) and O(1) searching capability, is still a preferable choice for many P2P-based services. However, it suffers from a “single point of failure” vulnerability, so networks based on this topology are highly vulnerable to DoS attacks or other blocking attempts. This paper describes a new mechanism that can be used for centralized P2P networks to prevent a P2P service unavailability after central server failure. High security level is obtained by using notary servers which track server public key changes and collect social feedback from users. This allows not only to detect popular attacks (like man-in-the middle) but also to assess whether the Central Server (CS) behaves properly. In the case of central server failure or when server becomes compromised, decentralized Condorcet voting is preformed and new CS is selected. Additionally, by incorporating a reputation mechanism which uses two kinds of scores respectively for providing good service and fair evaluation of other peers, the best candidates for a new Central Server can be chosen. Valuable data which is used to rebuild user database in new CS is stored in the encrypted form in peers and updated during the user-peer authorization process. The decryption key is divided between peers using the threshold secret sharing method.

2

Non-cryptographic methods for improving real time transmission security and integrity

Oryńczak G., Kotulski Z.

Annales Universitatis Mariae Curie-Skłodowska. Sectio AI, Informatica

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2011

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Vol. 11, no. 3

71--86

EN

In this paper we present a few non cryptographic methods for improving the security, integrity and reliability of real time services. The methods presented in this paper apply to real time transmitting systems, which are based on the Peer-to-Peer (P2P) model. A basic idea of the first technique is to use agents for detecting steganographic content in packet headers, so packets with suspicious entries in the IP header fields will be blocked or the fields will be erased. The two other presented techniques are based on reputation and trust systems, so trust and reputation basic definitions, types and modelling methods are shown. Also a simple design scheme of using these mechanisms in a P2P real-time data transmitting infrastructure is presented. Additionally, we describe an idea of path selecting technique, which can be used to avoid paths that are susceptible to eavesdropping.

3

Agent based infrastructure for real-time applications

Oryńczak G., Kotulski Z.

Annales Universitatis Mariae Curie-Skłodowska. Sectio AI, Informatica

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2011

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Vol. 11, no. 4

33--47

EN

In this paper we propose a new infrastructure for real-time applications. As a preliminary, we describe basic characteristics of the most popular real-time services like VoIP, videoconferencing, live media streaming, and network multiplayer games. We focus on the end-to-end latency, bandwidth and efficient transmission methods. Next, we present our project concepts, infrastructure model, details of implementation and our testing environment which was designed for testing many aspects of real-time services. The system combines mechanisms for ensuring best possible connection quality (QoS), load balance of servers in infrastructure and gives control over the packet routing decisions. Additionally, provided security mechanisms make it a good choice even in the environment where a high security level is required. The system is based on the Peer-to-Peer (P2P) model and data between users is routed over an overlay network, consisting of all participating peers as network nodes. This overlay can by used for application level multicast or live media stream. In the logging process each user is assigned to a specific node (based on his geographic location and nodes load). Because nodes are participating in data transmission, we have control over the data flow route. It is possible to specify the desired route, so, regardless of the external routing protocol, we can avoid paths that are susceptible to eavesdropping. Another feature of the presented system is usage of agents. Each agent acts within the single node. Its main task is to constantly control the quality of transmission. It analyzes such parameters like link bandwidth use, number of lost packets, time interval between each packet etc. The information collected by the agents from all nodes allows to build a dynamic routing table. Every node uses the Dijkstra's algorithm to find the best at the moment route to all other nodes. The routes are constantly modified as a consequence of changes found by agents or updates sent by other nodes. In VoD services agents also analyze popularity of streamed media, which helps build intelligent video cache. To ensure greater security and high reliability of the system, we have provided a reputation mechanism. It is used during bringing up to date the information about possible routes and their quality, given by other nodes. Owing to this solution nodes and routes which are more reliable get higher priority.

4

Agent based VoIP Application with Reputation Mechanisms

Oryńczak G., Kotulski Z.

Advances in Electronics and Telecommunications

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2011

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Vol. 2, no. 3

88--92

EN

In this paper we introduce our new VoIP model the aim of which is to meet the challenges of modern telephony. We present project concepts, details of implementation and our testing environment which was designed for testing many aspects of VoIP based systems. Our system combines mechanisms for ensuring best possible connection quality (QoS), load balance of servers in infrastructure, providing security mechanisms and giving control over the packet routing decisions. The system is based on Peer-to-Peer (P2P) model and data between users are routed over an overlay network, consisting of all participating peers as network nodes. In the logging process, each user is assigned to a specific node (based on his/her geographic location and nodes load). Every node also has a built-in mechanism allowing to mediate between the user and the main server (e.g. in logging process). Besides that, because nodes are participating in data transmission, we have control over the data flow route. It is possible to specify the desired route, so, regardless of the external routing protocol, we can avoid paths that are susceptible to eavesdropping. Another feature of presented system is usage of agents. Each agent acts with a single node. Its main task is to constantly control the quality of transmission. It analyzes such parameters like link bandwidth use, number of lost packets, time interval between each packets etc. The information collected by the agents from all nodes allows to built a dynamic routing table. Every node uses Dijkstra’s algorithm to find the best at the moment route to all other nodes. The routes are constantly modified as a consequence of changes found by agents or updates sent by other nodes. To ensure greater security and high reliability of the system, we have provided a reputation mechanism. It is used during updating of the information about possible routes and their quality, given by other nodes. Owing to this solution nodes and routes which are more reliable get higher priority.

5

Type-2 fuzzy logic controller for a mobile robot

Oryńczak G., Martyna J.

Studia Informatica

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2009

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Vol. 30, nr 2A

121-129

EN

In this paper, we present a new reasoning system based on type-2 fuzzy logic applied to mobile robot controlling. Our system allows for the processing of imprecise and uncertain variables. It has been shown that this approach indicates the imprecision better than type-1 fuzzy logic system, especially where uncertainties are great or are of a linguistic nature. It has been also seen that the prepared type-2 fuzzy inference system allows us to fit our application in navigation in real-time.

PL

W pracy przedstawiono zastosowanie zbiorów rozmytych typu 2 dla budowy sterownika ruchomego robota. Na podstawie opracowanego procesu wnioskowania w systemach przedziałowych wyrażono stopień aktywacji reguły ze sporządzonej uprzednio bazy reguł rozmytych, co umożliwia sterowanie szybkością i kierunkiem ruchu robota.