Norbert Luttenberger

SOA and Web Services: New Technologies, New Standards - New Attacks

Being regarded as the new paradigm for Internet communication, Web Services have introduced a large number of new standards and technologies. Though founding on decades of networking experience, Web Services are not more resistant to security attacks than other open network systems. Quite the opposite is true: Web Services are exposed to attacks well-known from common Internet protocols and additionally to new kinds of attacks targeting Web Services in particular. Along with their severe impact, most of these attacks can be performed with minimum effort from the attackers side. In this paper we present a list of vulnerabilities in the context of Web Services. To proof the practical relevance of the threats, we performed exemplary attacks on widespread Web Service implementations. Further, general countermeasures for prevention and mitigation of such attacks are discussed.

Protecting Web Services from DoS Attacks by SOAP Message Validation

Though Web Services become more and more popular, not only inside closed intranets but also for inter-enterprise communications, few efforts have been made so far to secure a Web Service’s availability. Existing security standards like e.g. WS-Security only address message integrity and confidentiality, and user authentication and authorization. In this article we present a system for protecting Web Services from Denial-of-Service (DoS) attacks. DoS attacks often rely on misformed and/or overly long messages that engage a server in resource-consuming computations. Therefore, a suitable means to prevent such kinds of attacks is the full grammatical validation of messages by an application level gateway before forwarding them to the server. We discuss specific kinds of DoS attacks against Web Services, show how message grammars can automatically be derived from formal Web Service descriptions (written in the Web Service Description Language), and present an application level gateway solution called “Checkway” that uses these grammars to filter Web service messages. The paper closes by giving some performance figures for full grammatical validation.

The Impact of Flooding Attacks on Network-based Services

One of the most severe threats to Internet security are Denial of Service attacks. Intended to annihilate the availability of a network-based service, this kind of attack troubles all service providers. In this paper we focus on a special type of Denial of Service attacks that relies on message flooding techniques, overloading the victims service with invalid requests. We describe some well- known and some rather new attacks, discuss commonalities and approaches for countermeasures. A main focus of this paper is directed towards Denial of Service attacks on Web Services and Web Service Compositions. We resume these threats by illustrating some possible attacks, and we relate our experimental results to the well-known attack impact of the TCP SYN Flooding attack.

Fast in-place sorting with CUDA based on bitonic sort

State of the art graphics processors provide high processing power and furthermore, the high programmability of GPUs offered by frameworks like CUDA increases their usability as high-performance coprocessors for general-purpose computing. Sorting is well-investigated in Computer Science in general, but (because of this new field of application for GPUs) there is a demand for high-performance parallel sorting algorithms that fit to the characteristics of modern GPU-architecture. We present a high-performance in-place implementation of Batchers bitonic sorting networks for CUDA-enabled GPUs. We adapted bitonic sort for arbitrary input length and assigned compare/exchange-operations to threads in a way that decreases low-performance global-memory access and thereby greatly increases the performance of the implementation.

Server-Side Streaming Processing of WS-Security

With SOAP-based web services leaving the stadium of being an explorative set of new technologies and entering the stage of mature and fundamental building blocks for service-driven business processes-and in some cases even for mission-critical systems-the demand for nonfunctional requirements including efficiency as well as security and dependability commonly increases rapidly. Although web services are capable of coupling heterogeneous information systems in a flexible and cost-efficient way, the processing efficiency and robustness against certain attacks do not fulfill industry-strength requirements. In this paper, a comprehensive stream-based WS-Security processing system is introduced, which enables a more efficient processing in service computing and increases the robustness against different types of Denial-of-Service (DoS) attacks. The introduced engine is capable of processing all standard-conforming applications of WS-Security in a streaming manner. It can handle, e.g., any order, number, and nesting degree of signature and encryption operations, closing the gap toward more efficient and dependable web services.

Minimal transmission power as distance estimation for precise localization in sensor networks

Positioning sensor nodes requires distance information to reference points. Due to resource limitations in sensor networks, distance determination in low-cost sensor nodes without additional hardware is difficult. Known techniques such as distance estimation based on received signal strength (RSSI) are mostly inaccurate or have limitations. We propose a new method to measure the distance between a transmitting node and a receiving node using the minimal transmission power. The determined distance is more precise than RSSI, has a low variance and is therefore particularly suitable for positioning. Finally, we implemented a demonstrator application using weighted centroid localization to show the practical implementation.

A Novel Sorting Algorithm for Many-core Architectures Based on Adaptive Bitonic Sort

Adaptive bitonic sort is a well known merge-based parallel sorting algorithm. It achieves optimal complexity using a complex tree-like data structure called a bitonic tree. Due to this, using adaptive bitonic sort together with other algorithms usually implies converting bitonic trees to arrays and vice versa. This makes adaptive bitonic sort inappropriate in the context of hybrid sorting algorithms where frequent switches between algorithms are performed. In this article we present a novel optimal sorting algorithm that is based on an approach similar to adaptive bitonic sort. Our approach does not use bitonic trees but uses the input array together with some additional information. Using this approach it is trivial to switch between adaptive bitonic sort and other algorithms. We present an implementation of a hybrid algorithm for GPUs based on bitonic sort and our novel algorithm. This implementation turns out to be the fastest comparison-based sorting algorithm for GPUs found in literature.

From UML to OWL 2

In this paper we present a transformation between UML class diagrams and OWL 2 ontologies. We specify the transformation on the M2 level using the QVT transformation language and the meta-models of UML and OWL 2. For this purpose we analyze similarities and differences between UML and OWL 2 and identify incompatible language features.

Fast in-place, comparison-based sorting with CUDA: a study with bitonic sort

State‐of‐the‐art graphics processors provide high processing power and furthermore, the high programmability of GPUs offered by frameworks like CUDA (Compute Unified Device Architecture) increases their usability as high‐performance co‐processors for general‐purpose computing. Sorting is well investigated in Computer Science in general, but (because of this new field of application for GPUs) there is a demand for high‐performance parallel sorting algorithms that fit with the characteristics of the modern GPU‐architecture. We present a high‐performance in‐place implementation of Batchers bitonic sorting networks for CUDA‐enabled GPUs. Therefore, we assigned compare/exchange operations to threads in a way that decreases low‐performance global‐memory access and makes efficient use of high‐performance shared memory. This greatly increases the performance of this in‐place, comparison‐based sorting algorithm. Our implementation outperforms all other algorithms in our tests when sorting 64‐bit keys. It is the fastest comparison‐based GPU sorting algorithm for 32‐bit keys, being only outperformed by (non‐comparison‐based) radix sort when sorting sequences larger than 223. Copyright

Graph-based mobility model for urban areas fueled with real world datasets

Mobile ad-hoc networks (MANETs) and especially mobile Wireless Sensor Networks (mWSNs) are embedded in the environment and therefore stand under strong influence of its specific characteristics. Beside e.g. sensor input, nodes motion patterns are supposed to be a very basic factor regarding performance. Hence simulations may need to account scenario specific mobility patterns while keeping the tradeoff related to simulation complexity in mind. This contribution proposes a graph based mobility model, designed to resemble probabilistic node movements according to real world node paths like they may be induced by road grids. The model is presented along with a real world mWSN sample deployment from which the paths are extracted and against which the simulation fine-tuned.