A secure mobile agent system

Hareketli etmen mimarisi istemci-sunucu çalışma modeline karşın dağıtık işlemeye farklı bir yaklaşım sunmaktadır. Kodun hareketliliğine dayanan hareketli etmen sistemlerinde, güvenlik düşünülmesi gereken önemli bir unsurdur; çünkü artık durağan bir yazılım parçası değil, kodunu ve verisini uzak düğümlere taşıyabilen yazılımlar, yani etmenler söz konusudur. Bu türden hareketli yazılımların hem kodunun hem de verisinin izlenme veya değiştirilmesi gibi yeni güvenlik risklerinin ortaya çıkması kaçınılmazdır. Birbirleri ile haberleşebilen etmenlerin mesajlaşmaları sırasında da aynı tehlikeler söz konusudur. Daha da önemlisi, güvenlik riskleri ile karşı karşıya olan sadece etmenler değildir, etmenleri üzerlerinde çalıştıran düğümler de aynı ölçüde risk altındadırlar. Bu yazıda, hareketli etmen sistemlerindeki mevcut güvenlik tehlikelerini ortadan kaldıracak yeni bir mimarinin tasarım ve gerçeklenme ayrıntıları incelenmiştir. Geliştirilen güvenli etmen sistemi, hem etmenlerin güvenlik gereksinimlerine yanıt vermek, hem de kolay kullanımlı ve esnek bir çalışma ortamı sunmak üzere tasarlanmış ve gerçeklenmiştir. Gelişmiş güvenlik özellikleri yanında sistem, değişen güvenlik ihtiyaçlarına kolay ve anında uyum sağlayabilmek için güvenlik politikalarını kullanmaktadır. Güvenlik politikaları, değişen güvenlik ihtiyaçlarına, hızlı ve etmenin yeniden programlanmasını gerektirmeden cevap verebilmeyi sağlar. Sistem ayrıca sadece etmenlerin değil, etmenlere çalışma ortamı sunan düğümlerin güvenliği için de gerekli mekanizmaları sunmaktadır. Geliştirilmiş olan hareketli etmen sistemi, güçlü bir mesajlaşma altyapısı sunmasının yanında, izlenilebilirlik, yönetilebilirlik ve süreklilik için de esnek arayüzler barındırmaktadır. Sistem katmanlı bir mimariye sahiptir ve geliştirilmeye açıktır. Anahtar Kelimeler: Etmen, hareketli etmen sistemleri, hareketli etmen sistemlerinde güvenlik.According to the accepted definition, an agent is a small application with some special features. Being autonomous, capable of adapting itself to its environment, communicating with other agents for coordination or cooperation, intelligence, ability to clone itself and ability to make decisions are the features that can distinguish an agent from ordinary software. Even though mobility, ability to migrate from one host to another host, is not a required feature, agents with this ability have advantages especially in terms of distributed data processing. A mobile agent is not restricted to the node where it is running and can migrate to anywhere on the network of its own accord. While moving from one host to another, not only the agent's executable code is transferred, but also data that the agent has collected or constructed are transferred as well. Thus, the agent can preserve its state even when it is mobile. The execution framework necessary for a mobile agent is provided by a mobile agent system. This framework simply provides the basic agent related tasks and functions such as agent creation, activation, migration, communication, cloning and destruction. The competence and power of a mobile agent system depends on the flexibility of these functions. Even though using mobile agent technologies provides potential benefits to applications, an agent's ability to move introduces significant security risks. Mobile agents are under security threats during their life times. Since the code is mobile, it can be stolen or altered by a third party. The same danger is present for the messages agents send to each other and for the data that determines the agent's state. Furthermore, not only the agents but also hosts are also under many security risks in mobile agent systems. Several mobile agent systems have been proposed and developed up to now. They all have their software agent specific features. Although most of them have enough features for mobile agents to communicate with each other and migrate to remote hosts, agent security related tasks are not available in most of them. Some provide limited security for agents, but do not provide any features to protect hosts. Most of these mobile agent systems leave the security to agent programmer or to the traditional net work security solutions which may be very difficult and inefficient to implement or integrate. The mobile agent system is expected to include all necessary security mechanisms for both agents and computers hosting mobile agents. The scope of this paper is the design and implementation of a new, secure, flexible, highly available and fast mobile agent system (SECMAP). The architecture of the system is especially designed for security purposes, and requirements not only for agent security but also for host security are also provided. Besides ensuring security of both agents and hosts, SECMAP also presents a very flexible agent programming interface. Naturally, these features play an important role on the usability and popularity of the system. SECMAP also presents a policy based management framework to protect system-level resources and agents against unauthorized access, as well. The policy architecture allows for dynamic manipulation of policy content, which results in an adaptive and flexible framework that eliminates the reprogramming of the agents on changing conditions. Logging and monitoring of the basic agent activities are also possible. Availability is very important for the collaborating agents. For this reason, a mobile agent system should be up and running even only one host in the system is active. When necessary the system should be able to transfer the duties of a dead host to another one in the system. SECMAP includes very powerful algorithms to ensure the availability of the overall system. It accomplishes this by assigning special working modes to different agent servers in the system. Another important feature is that the system and agents can be managed and monitored from a browser in the network. All agents present in the system can be monitored from a single window. Any module of the system can also be managed by a browser from remote hosts. SECMAP is worth being used not only for the security features it presents for agents and hosts, but also for its flexibility and powerful agent programming interface. The system has a layered architecture and is open to be improved with more powerful features. Keywords: Agents, Mobile agent systems, Security in mobile agent systems

An Autonomic Cross-Platform Operating Environment for On-Demand Internet Computing

The Internet has evolved into a global and ubiquitous communication medium interconnecting powerful application servers, diverse desktop computers and mobile notebooks. Along with recent developments in computer technology, such as the convergence of computing and communication devices, the way how people use computers and the Internet has changed people´s working habits and has led to new application scenarios. On the one hand, pervasive computing, ubiquitous computing and nomadic computing become more and more important since different computing devices like PDAs and notebooks may be used concurrently and alternately, e.g. while the user is on the move. On the other hand, the ubiquitous availability and pervasive interconnection of computing systems have fostered various trends towards the dynamic utilization and spontaneous collaboration of available remote computing resources, which are addressed by approaches like utility computing, grid computing, cloud computing and public computing. From a general point of view, the common objective of this development is the use of Internet applications on demand, i.e. applications that are not installed in advance by a platform administrator but are dynamically deployed and run as they are requested by the application user. The heterogeneous and unmanaged nature of the Internet represents a major challenge for the on demand use of custom Internet applications across heterogeneous hardware platforms, operating systems and network environments. Promising remedies are autonomic computing systems that are supposed to maintain themselves without particular user or application intervention. In this thesis, an Autonomic Cross-Platform Operating Environment (ACOE) is presented that supports On Demand Internet Computing (ODIC), such as dynamic application composition and ad hoc execution migration. The approach is based on an integration middleware called crossware that does not replace existing middleware but operates as a self-managing mediator between diverse application requirements and heterogeneous platform configurations. A Java implementation of the Crossware Development Kit (XDK) is presented, followed by the description of the On Demand Internet Computing System (ODIX). The feasibility of the approach is shown by the implementation of an Internet Application Workbench, an Internet Application Factory and an Internet Peer Federation. They illustrate the use of ODIX to support local, remote and distributed ODIC, respectively. Finally, the suitability of the approach is discussed with respect to the support of ODIC

Supporting policy-based contextual reconfiguration and adaptation in ubiquitous computing

In order for pervasive computing systems to be able to perform tasks which support us in everyday life without requiring attention from the users of the environment, they need to adapt themselves in response to context. This makes context-awareness in general, and context-aware adaptation in particular, an essential requirement for pervasive computing systems. Two of the features of context-awareness are: contextual reconfiguration and contextual adaptation in which applications adapt their behaviour in response to context. We combine both these features of context-awareness to provide a broad scope of adaptation and put forward a system, called Policy-Based Contextual Reconfiguration and Adaptation (PCRA) that provides runtime support for both. The combination of both context-aware reconfiguration and context-aware adaptation provides a broad scope of adaptation and hence allows the development of diverse adaptive context-aware applications. However, another important issue is the choice of an effective means for developing, modifying and extending such applications. The main argument forming the basis of this thesis is that we advocate the use of a policy-based programming model and argue that it provides more effective means for developing, modifying and extending such applications. This thesis addresses other important surrounding issues which are associated with adaptive context-aware applications. These include the management of invalid bindings and the provision of seamless caching support for remote services involved in bindings for improved performance. The bindings may become invalid due to failure conditions that can arise due to network problems or migration of software components, causing bindings between the application component and remote service to become invalid. We have integrated reconfiguration support to manage bindings, and seamless caching support for remote services in PCRA. This thesis also describes the design and implementation of PCRA, which enables development of adaptive context-aware applications using policy specifications. Within PCRA, adaptive context-aware applications are modelled by specifying binding policies and adaptation policies. The use of policies within PCRA simplifies the development task because policies are expressed at a high-level of abstraction, and are expressed independently of each other. PCRA also allows the dynamic modification of applications since policies are independent units of execution and can be dynamically loaded and removed from the system. This is a powerful and useful capability as applications may evolve over time, i.e. the user needs and preferences may change, but re-starting is undesirable. We evaluate PCRA by comparing its features to other systems in the literature, and by performance measures

Policy-Based Dynamic Reconfiguration of Mobile-Code Applications

Code mobility enables dynamic customization and configuration of ubiquitous Internet applications. Mobile applications can transfer the execution of software components from one device to another depending on resource availability. They can also adapt functionality according to user needs and device characteristics. Thus, the authors have developed a policy-based approach to mobility programming that expresses and controls reconfiguration strategies at a high level of abstraction, separate from the application's functionality

Policy-based Dynamic Reconfiguration of Mobile Code Applications

Policy-Enabled Mobile Applications (Poema) is a policy-based approach to mobility programming that expresses and controls reconfiguration strategies at a high level of abstraction, separate from the application's functionality. It provides an integrated environment for developing applications that can change both their functionality and layout at runtime in response to environment conditions