Generative AI fundamentally challenges traditional written coursework in distance education, rendering conventional containment strategies ineffective. This paper presents a pedagogical framework implemented in Master's-level cyber security modules at Wilhelm Büchner Hochschule that strategically addresses AI integration through platform-based design. Using the Milanote visual workspace, the approach combines autonomous task selection from emerging topics with minimal published sources, deliberately open-ended formulations requiring explicit audience decisions, mandatory dual-board architecture separating content from reflection, multi-modal composition requirements, and evaluation criteria emphasizing curation and didactic quality over reproduction. Rather than restricting AI use, the framework explicitly encourages reflective AI integration while structurally incentivizing critical engagement through multiple decision points that complicate unreflective adoption. This design demonstrates how thoughtful pedagogical architecture can transform AI from an assessment threat into a catalyst for developing higher-order cognitive competencies essential for contemporary professional practice, while maintaining the practical constraints of distance education.

This paper addresses security vulnerabilities in Machine-to-Machine authentication for Amazon S3 object storage in industrial environments. Current AWS authentication relies on often insecurely managed symmetric keys. While Amazon's Secure Token Service with OpenID Connect authentication offers a solution in principle, most enterprise S3-compatible storage products lack STS support. We propose a security architecture combining Privileged Access Management (PAM) with OIDC authentication to abstract credentials from application code, enabling automated key rotation and centralized management. Through industrial simulation testing, we demonstrate this approach maintains production continuity while significantly improving credential security for M2M S3 access.

The evolution from traditional on-premise infrastructures to hybrid and multi-cloud architectures has transformed IT, enabling organizations to reduce vendor lock-in, optimize costs, and improve flexibility. However, managing resources across multiple clouds remains complex, especially for small and medium-sized enterprises (SMEs). This paper presents a vendor-agnostic multi-cloud framework focused on unified cost management through a standardized Cost API. The proposed architecture aims to simplify multi-cloud management, enabling more efficient and cost-effective operations. We conclude with the benefits of this approach and future research directions.

An architecture for providing multi-factor authentication as a service in a mobile environment is proposed, resting on the principle of a loose coupling and separation of duties between network entities and the end user devices. The multi-factor authentication architecture leverages Identity Federation and Single-Sign-On technologies, such as the OpenID framework, in order to provide for a modular integration of various factors of authentication. The architecture is robust and scalable in order to support any number of authentication factors, which may be executed dynamically according to service providers’ authentication policies. Additionally, the architecture provides for the mapping of defined assurance level requirements posed by service providers, to concrete authentication factors, taking into account the varied authentication capabilities of users’ devices.

A trust ecosystem for mobile devices based on trusted computing principles is presented. The trust ecosystem model from the latest PC platform provides a reference for the evolution of a trust model for the diverse mobile device market. By balancing the trusted computing burden between the mobile device and network and separating service delivery/access control decisions and error reporting from remediation, the processing in the network is hugely simplified, and efficiency in the use of network resources is increased. Additionally, certification and accreditation of the mobile device’s trust security capabilities provides a white box view into a mobile device’s security architecture and a means to gain a high level of trust assurance in the mobile device.

The establishment of trust relationships to a computing platform relies on validation processes. Validation allows an external entity to build trust in the expected behaviour of the platform based on provided evidence of the platform's configuration. In a process like remote attestation, the 'trusted' platform submits verification data created during a start up process. These data consist of hardware-protected values of platform configuration registers, containing nested measurement values, e.g., hash values, of loaded or started components. Commonly, the register values are created in linear order by a hardware secured operation. Fine-grained diagnosis of components, based on the linear order of verification data and associated measurement logs, is not optimal. We propose a method to use tree-formed verification data to validate a platform. Component measurement values represent leaves, and protected registers represent roots of a hash tree. We describe the basic mechanism of validating a platform using tree-formed measurement logs and root registers and show a logarithmic speed-up for the search of faults. Secure creation of a tree is possible using a limited number of hardware-protected registers and a single protected operation. In this way, the security of tree-formed verification data is maintained.

OpenID is a lightweight, easy to implement and deploy approach to Single Sign-On (SSO) and Identity Management (IdM), and has great potential for large scale user adoption especially for mobile applications. At the same time, Mobile Network Operators are increasingly interested in leveraging their existing infrastructure and assets for SSO and IdM. In this paper, we present the concept of Smart OpenID, an enhancement to OpenID which moves part of the OpenID authentication server functionality to the smart card of the user's device. This seamless, OpenID-conformant protocol allows for scaling security properties, and generally improves the security of OpenID by avoiding the need to send user credentials over the Internet and thus avoid phishing attacks. We also describe our implementation of the Smart OpenID protocol based on an Android phone, which interacts with OpenID-enabled web services.

Trusted computing, used as a security technology, can establish trust between multiple parties. One implementation of trusted computing technology standardised by the Trusted Computing Group is the trusted platform module (TPM). We build on the security provided by the TPM to create a trusted variant of identity management systems based on the popular OpenID protocol. We show that it is feasible to bind OpenID identities to the trustworthiness of the device. Our concept and implementation builds on previous work which showed that trusted computing can be used to create tickets. In this work, we use such tickets as a building block to establish trust in the OpenID protocol between the identity provider and the device. Furthermore, we investigate how mutual trust can be established in the communication between device and user during authentication. The concept of trust visualisation via a trusted environment and binding to user authentication are presented.

Unsolicited communication is a major issue in digital communications and hence for the networks enabling such communication. With the increasing use of IP Multimedia Subsystem (IMS) networks, protection of time-critical communication, e.g. Voice over IP, from unsolicited messages, becomes an important topic. 3GPP identified and developed various concepts to cope with unsolicited communication in IMS networks (UCI) in 3GPP TR 33.937. The Protection against UCI (PUCI) borrows concepts from traditional email SPAM filtering but needs to adapt to the nature of IMS communication being direct and time critical. In addition to the protection methods identified in TR 33.937 we present a concept which uses a secure and interoperable scorecard which is associated with the caller and the IMS communication. Depending on the outcome of the scorecard evaluation, the receiving domain can take appropriate actions such as denying or allowing a communication attempt. Scorecards are used to generate a standardized exchange format for sender and message related information. Based on 3GPP standards we present an IMS architecture with scorecard elements, including basic operating procedures for the prevention of UCI.

Efficient and seamless Single-Sign-On (SSO) access to applications is a core question for the evolution of services in wireless networks. A fundamental requirement is lightweight, secure authentication protocols and an overarching identity management framework. We review 3GPP standardisation efforts on this topic, and propose generation of identity assertions, locally at the device as an efficient and secure authentication method for mobile SSO.

Trusted Computing, used as a security technology, can establish trust between multiple parties. One implementation of Trusted Computing Technology standardized by the Trusted Computing Group is the Trusted Platform Module (TPM). We build on the security provided by the TPM to create a trusted variant of Identity Management Systems based on the popular OpenID protocol. We show that it is feasible to bind OpenID identities to the trustworthiness of the device. Our concept and implementation builds on previous work which showed that Trusted Computing can be used to create tickets. In this work, we use such tickets as a building block to establish trust in the OpenID protocol between the identity provider and the device.

Computing platforms are approaching the era of truly distributed and mobile systems. For such large scale deployments of partly autonomously communicating and connecting network elements, trust issues acquire new qualities. Remote establishment of trust and an enabling architecture to manage distributed network elements remotely become essential. Following the authors' previous analysis on trust establishment, this paper presents base concepts for platform validation and management, with scalable trust properties and flexible security. The presentation is set in context of machine-to-machine communication and intelligent gateways in mobile networks.

Machine-to-machine (M2M) communication is viewed as one of the next frontiers in wireless communications. M2M communication applications and scenarios are growing and lead the way to new business cases. Because of the nature of M2M scenarios, involving unguarded, distributed devices, new security threats emerge. The use case scenarios for M2M communication also address the new requirement on flexibility, because of deployment scenarios of the M2ME in the field. We believe that these new requirements require a paradigm shift. One important pillar of such a shift will be a new, more balanced mix of device-centric trust and traditional enforcement of security properties.

Enforcement and trust are opposite concepts in information security. This chapter reflects on the paradigm shift from traditional concepts of access control and policy enforcement toward to de-centralised methods for establishing trust between loosely connected entities. By delegating parts of enforcement tasks to trusted elements dispersed in a system, transitive trust relationships can be established. This is the most advanced evolvement of the organisational method of separation of duties within IT-security. The technological basis for trust in systems - Trusted Computing platforms - is described on conceptual levels allowing comparison with other top-level security concepts and mapping to application domains. Important applications in modern information systems and networks are e xhibited.

The Internet becomes more and more integrated into everyday life these days. Reasons may be increasing data transfer rates and decreasing connection fees. Increasing data transfer rates on the client-side cause a widespread usage of peer-to-peer techniques that balance network load between servers and clients. Especially when distributing content to a multitude of customers, usage of peer-to-peer mechanisms comes in handy. Another main impact of the Internet nowadays is an increasing appetite for on-demand content which leads to entertainment devices providing customers with on-demand media from the Internet in their living rooms. Furthermore uprising media-deployment results in an arising demand for theft-protection by the holders of copyrights. Nevertheless past showed that copyright protection methods that restrict the user in being able to playback acquired media without difficulty cause decreasing sales figures. Thus customer-friendly copyright-protection methods seem to bridge the gap between customer's and supplier's needs. Moreover one major problem in the growing usage of software implemented algorithms in embedded systems, like on-demand entertainment-devices, is the ability of customers to modify their devices in order to reveal secret data or to bypass copyrightprotection providing methods. Integrity-proving mechanisms that ensure devices are being unaltered are required accordingly. This paper presents a concept for a so called Trusted Set- Top-Box (TSTB) that will make use of peer-to-peer file sharing mechanisms to provide the customer with real-time and ondemand video streaming. To protect copyrighted video material from theft in a customer-friendly manner, novel watermarkingtechnology will be used. This allows for unproblematic playback of acquired media on distinct playback devices. The TSTB is referenced to be trusted since TPM-Technology will serve as security anchor, providing methods for attesting the devices' integrity. Through this unauthorized modification of the device will be detected.

Notwithstanding the adoption of strong cryptographic mechanisms, the anticipated degree of security in the protection and management of privacy sensitive data can only be achieved, if secret keys can be hielded adequately. In practice, most implementations are based on software tokens that shall guard the keys against eavesdropping. This fact alleviates the hardness of circumvention of used cryptographic protocols and with this the disclosure of secret keys. In this paper we propose a key management architecture which - based on the capabilities of Trusted Computing Technology - will provide a higher level of security.

Business models involving buyers of digital goods in the distribution process are called superdistribution schemes. We review the state-of-the art of research and application of superdistribution and propose a systematic approach to market mechanisms using super-distribution and technical system architectures supporting it. The limiting conditions on such markets are of economic, legal, technical, and psychological nature. Large scale applications of superdistribution such as video-on-demand and multimedia over peer-to-peer type networks pose particular requirements on security and efficiency.

Trusted Computing is a security technology which enables the establishment of trust between multiple parties. Previous work showed that Trusted Computing technology can be used to build tickets, a core concept of Identity Management Systems. Relying solely on the Trusted Platform Module we will demonstrate how this technology can be used in the context of Kerberos for an implementation variant of Identity Management.

The service oriented architectures (SOA) approach designing the interaction between various business entities leads to complex and highly automated relations between formerly separate organisations. In particular the automation of these processes demands a high level of trust of each partner in the underlying IT infrastructure and the results produced. This paper discusses the security and trust implications and shows how to utilize Trusted Computing within the SOA approach introducing means for integrity and authenticity.

In our modern society telephony has developed to an omnipresent service. People are available at anytime and anywhere. Furthermore the Internet has emerged to an important communication medium. These facts and the raising availability of broadband internet access has led to the fusion of these two services. Voice over IP or short VoIP is the keyword, that describes this combination. The advantages of VoIP in comparison to classic telephony are location independence, simplification of transport networks, ability to establish multimedia communications and the low costs. Nevertheless one can easily see, that combining two technologies, always brings up new challenges and problems that have to be solved. It is undeniable that one of the most annoying facet of the Internet nowadays is email spam. According to different sources email spam is considered to be 80 to 90 percent of the email traffic produced. Security experts suspect that this will spread out on VoIP too. The threat of so called voice spam or Spam over Internet Telephony (SPIT) is even more fatal than the threat that arose with email spam, for the annoyance and disturbance factor is much higher. As instance an email that hits the inbox at 4 p.m. is useless but will not disturb the user much. In contrast a ringing phone at 4 p.m. will lead to a much higher disturbance. From the providers point of view both email spam and voice spam produce unwanted traffic and loss of trust of customers into the service. In order to mitigate this threat different approaches from different parties have been developed. This paper focuses on state of the art anti voice spam solutions, analyses them and reveals their weak points. In the end a SPIT producing benchmark tool will be introduced, that attacks the presented anti voice spam solutions. With this tool it is possible for an administrator of a VoIP network to test how vulnerable his system is.

Business models involving buyers of digital goods in the distribution process are called superdistribution schemes. We review the state-of-the art of research and application of superdistribution and propose systematic approach to market mechanisms using super-distribution and technical system architectures supporting it. The limiting conditions on such markets are of economic, legal, technical, and psychological nature.

Security in the value creation chain hinges on many single components and their interrelations. Trusted Platforms open ways to fulfil the pertinent requirements. This chapter gives a systematic approach to the utilisation of trusted computing platforms over the whole lifecycle of multimedia products. This spans production, aggregation, (re-)distribution, consumption, and charging. Trusted Computing technology as specified by the Trusted Computing Group provides modular building blocks which can be utilized at many points in the multimedia lifecycle. We propose an according research roadmap beyond the conventional Digital Rights Management use case. Selected technical concepts illustrate the principles of Trusted Computing applications in the multimedia context.

Der Sektor mobiler Kommunikation und Dienstleistungen verändert sich rasant durch die horizontale Konvergenz von Zugangstechnologien und die zunehmende Intelligenz von Endgeräten. Neue Geschäftsmodelle in diesem Bereich brauchen neue Schutzmethoden und Vertrauensgrundlagen technischer Art. Trusted Computing (TC) in seiner Ausprägung für mobile Geräte kann diese bieten. Wir zeigen auf konzeptioneller Ebene und in konkreten Anwendungsbeispielen, wie diese Technologie nicht nur bestehende Anwendungen schützen kann sondern auch neuartige Geschäftsmodelle erst ermöglicht. Die Vorteile eines dezentralisierten Ansatzes für Identitätsmanagement basierend auf TC werden herausgestellt.

The primary goal of this paper is to design a software replacement for a Subscriber Identity Module (SIM) based on the TCG MPWG Reference Architecture in order to access a mobile cellular network and its offered services. Therefore, we introduce a virtual software SIM (vSIM) with comparable usage and security characteristics like the traditional smartcard-based solution. Additionally, running a virtual SIM as a trusted and protected software on a mobile device allow significant expansion of services by introducing new usage scenarios and business models, cost reduction and more flexibility. Our approach demonstrates the substitutability of a SIM card with an adequate trusted software module supported and protected by a trustworthy operating system. In particular we propose several methods for authentication and enrollment of a subscriber.

In its recently published TCG Mobile Reference Architecture, the TCG Mobile Phone Work Group specifies a new concept to enable trust into future mobile devices. For this purpose, the TCG devises a trusted mobile platform as a set of trusted engines on behalf of different stakeholders supported by a physical trust-anchor. In this paper, we present our perception on this emerging specification. We propose an approach for the practical design and implementation of this concept and how to deploy it to a trustworthy operating platform. In particular we propose a method for the take-ownership of a device by the user and the migration (i.e., portability) of user credentials between devices.

We propose a concept for authorisation using the location of a mobile device and the enforcement of location-based policies. Mobile devices enhanced by Trusted Computing capabilities operate an autonomous and secure location trigger and policy enforcement entity. Location determination is twotiered, integrating cell-based triggering at handover with precision location measurement by the device.

The establishment of trust relationships across multiple identifier domains in identity management architectures enables a service provider in a certain domain to trust the decisions of an identity provider located in a foreign identifier domain. As a result, users do not have to create new credentials for every identifier domain they communicate with. This trust relationship can be established by using the infrastructure provided by the Trusted Computing Group. In this paper, a concept for the establishment of this trust relationship based on trusted computing technology is developed.

We present a continuous, stochastic model - the first of its kind - for the monetary flow in multi-level markets allowing for the quantitative assessment of the incentive accruing to market participants through resales revenues. The main application of the model is for novel business models for the marketing of information goods, which purport to yield alternatives to technical copyright protection and DRM. We show analytically that within the scope of the mode free-riding can be mitigated by employing multi-level marketing, and that multi-level markets are open markets for competing information goods.

We describe a concept to employ Trusted Computing technology to secure Conditional Access Systems (CAS) for DVB. Central is the embedding of a trusted platform module (TPM) into the set-top-box or residential home gateway. Various deployment scenarios exhibit possibilities of charging co-operation with mobile network operators (MNO), or other payment providers.

We present a concept to achieve non-repudiation for natural language conversations over the Internet. The method rests on chained electronic signatures applied to pieces of packet-based, digital, voice communication. It establishes the integrity and authenticity of the bidirectional data stream and its temporal sequence and thus the security context of a conversation. The concept is close to the protocols for Voice over the Internet (VoIP), provides a high level of inherent security, and extends naturally to multilateral non-repudiation,e.g., for conferences. Signatures over conversations can become true declarations of will in analogy to electronically signed, digital documents. This enables binding verbal contracts, in principle between unacquainted speakers, and in particular without witnesses. A reference implementation of a secure VoIP archive is exhibited.

Trusted Computing is a security base technology that will perhaps be ubiquitous in a few years in personal computers and mobile devices alike. Despite its neutrality with respect to applications, it has raised some privacy concerns. We show that trusted computing can be applied for service access control in a manner protecting users' privacy. We construct a ticket system - a concept which is at the heart of Identity Management - relying solely on the capabilities of the trusted platform module and the standards specified by the Trusted Computing Group. Two examples show how it can be used for pseudonymous and protected service access.

Delivery of content to mobile devices gains increasing importance in industrial environments to support employees in the field. An important application are e-mail push services like the fashionable Blackberry. These systems are facing security challenges regarding data transport to, and storage of the data on the end user equipment. The emerging Trusted Computing technology offers new answers to these open questions.

Reputation and recommendation systems are fundamental for the formation of community market places. Yet, they are easy targets for attacks which disturb a market's equilibrium and are often based on cheap pseudonyms used to submit ratings. We present a method to price ratings using trusted computing, based on pseudonymous tickets.

We present a concept to achieve non-repudiation for natural language conversations by electronically signing packet-based, digital, voice communication. Signing a VoIP-based conversation means to protect the integrity and authenticity of the bidirectional data stream and its temporal sequence which together establish the security context of the communication. Our concept is conceptually close to the protocols that embody VoIP and provides a high level of inherent security. It enables signatures over voice as true declarations of will, in principle between unacquainted speakers. We point to trusted computing enabled devices as possible trusted signature terminals for voice communication. ACM:
C.2.0 [Computer-Communication Networks]: General - Security and protection Electronic signature; non-repudiation; voice over IP; interval signature; cryptographic chaining; natural-language communication.

A concept is proposed to extend authorised translations of documents to electronically signed, digital documents. Central element of the solution is an electronic seal, embodied as an XML data structure, which attests to the correctness of the translation and the authorisation of the translator. The seal contains a digital signature binding together original and translated document, thus enabling forensic inspection and therefore legal security in the appropriation of the translation. Organisational aspects of possible implementation variants of electronic authorised translations are discussed and a realisation as a stand-alone web-service is presented. ACM:
H.4.1 [Information Systems Applications]: Office Automation - Workflow Management;
K.6.5 [Management of Computing and Information Systems]: Security and Protection - Authentication Authorised translation; electronic signature; electronic seal.

Due to the convergence of various mobile access technologies like UMTS, WLAN, and WiMax the need for a new supporting infrastructure arises. This infrastructure should be able to support more efficient ways to authenticate users and devices, potentially enabling novel services based on the security provided by the infrastructure. In this paper we exhibit some usage scenarios from the mobile domain integrating trusted computing, which show that trusted computing offers new paradigms for implementing trust and by this enables new technical applications and business scenarios. The scenarios show how the traditional boundaries between technical and authentication domains become permeable while a high security level is maintained. ACM:
C.2.0 [Computer-Communication Networks]: General - Security and protection Trusted computing, mobile service, authentication, privacy.

An efficient archive securing the integrity of VoIP-based two-party conversations is presented. The solution is based on chains of hashes and continuously chained electronic signatures. Security is concentrated in a single, efficient component, allowing for a detailed analysis.

Convergence of access technologies potentially enables new mobile business scenarios. To enable them, trust between the stakeholders is a prerequisite, e.g., in the form of a cross-domain authentication infrastructure. Service architectures provide solutions for some of these needs. This paper proposes a use case combining the well understood techniques from the mobile domain with the upcoming new possibilities of trusted computing.

Horizontal integration of access technologies to networks and services should be accompanied by some kind of convergence of authentication technologies. The missing link for the federation of user identities across the technological boundaries separating authentication methods can be provided by trusted computing platforms. The concept of establishing transitive trust by trusted computing enables the desired crossdomain authentication functionality. The focus of target application scenarios lies in the realm of mobile networks and devices.

Identity Management is becoming more and more important in business systems as they are opened for third parties including trading partners, consumers and suppliers. This paper presents an approach to securing a system without any knowledge of its source code. The security module adds authentication and authorisation functionalities based on aspect oriented programming (AOP) and the liberty alliance identity federation framework, an upcoming industry standard providing single sign on (SSO). High modularisation is achieved through use of AspectJ, a programming language extension of Java. The security module is adapted to the host application in an intuitive, initial training phase. The use of hardware tokens and proactive computing as authorisation methods is demonstrated.

The free-rider phenomenon which impedes the marketing of information goods is conventionally countered by copyright protection regulations and technology. Alternative ways to market information goods, in particular through systems based on the super-distribution of a good from buyer to buyer, have recently raised some interest. Some of them mimic peer-to-peer file-sharing networks, while advanced ones are mechanisms falling into the category of multi-level markets. Motivated by this, the present paper develops a general model for the monetary flux in a multi-level market, quantitatively describing the incentives that buyers receive through resales revenues. Based on it, some qualitative questions pertaining to a profitable marketing of information goods are discussed. JEL: C51, C67, D4 Information good, Multi-level market, Virtual good, Incentive, Copyright protection.

As an alternative to rigid DRM measures, ways of marketing virtual goods through multi-level or networked marketing have raised some interest. This report is a first approach to multi-level markets for virtual goods from the viewpoint of theoretical economy. A generic, kinematic model for the monetary flow in multi-level markets, which quantitatively describes the incentives that buyers receive through resales revenues, is devised. Building on it, the competition of goods is examined in a dynamical, utilitytheoretic model enabling, in particular, a treatment of the free-rider problem. The most important implications for the design of multi-level market mechanisms for virtual goods, or multi-level incentive management systems, are outlined. MSC: 91B60, 90B60, 46N10 JEL: C51, C67, D4 ACM: K4.4 Multi-Level Market; Incentive; Free-Rider Problem; Competition.

Identity Management is becoming more and more important in business systems as they are opened for third parties including trading partners, consumers and suppliers. This paper presents an approach securing a system without any knowledge of the system source code. The security module adds to the existing system authentication and authorisation based on aspect oriented programming and the liberty alliance framework, an upcoming industrie standard providing single sign on. In an initial training phase the module is adapted to the application which is to be secured. Moreover the use of hardware tokens and proactive computing is demonstrated. The high modularisation is achived through use of AspectJ, a programming language extension of Java. ACM: K.6.5; D.1.5; D.2 Identity Mangement, aspect oriented programming, single sign on, liberty alliance, pro active computing, aspectj, identity federation.

Identity Management erlangt eine immer größere Bedeutung, da immer mehr Firmen ihre IT-Systeme für Partner, Lieferanten oder Kunden öffnen. Die Arbeit stellt einen Ansatz vor, durch den ein Zugriffskontroll- und Authentifikationssystem modular zu bestehenden webbasierten Systemen hinzugefügt werden kann. Das System muss hierfür nicht im Sourcecode vorliegen. In einer Trainingsphase wird das Modul an die zu schützende Applikation angepasst. Dies wird durch den Einsatz von aspektorientierter Programmierung in Form des AspectJ Frameworks erreicht. Für die Authentifikation kommt das Liberty Alliance Protokoll, ein zukünftiger Industriestandard, zum Einsatz, welches ein Single-Sign-On Protokoll unter Verwendung von Identity Federation implementiert. Eine mögliche Verwendung von Hardwaretoken in diesem Framework wird demonstriert und ein Weg vorgestellt, ein proaktives Verhalten in das Systems zu integrieren.

Umwandlungen signierter Dokumente werfen Fragen auf, die für die Anwendung erhebliche Unsicherheiten begründen. Dieser Beitrag untersucht den Themenkomplex unter rechtlichen, technischen und organisatorischen Aspekten. Es werden Grundkonzepte sicherer Transformationen erläutert, die Transformation als Prozess analysiert und Lösungsansätze präsentiert.

Transformations of signed documents raise questions of technical and organisational nature which render the legal security of the transformed document doubtful. In particular, digital signatures of originals break depriving documents of probative force. This report elucidates legal problems, and introduces fundamental concepts of legally secure document transformations in a deliberately generic, applicationindependent way. A process analysis of transformations of signed documents is carried out to elicit common security requirements. This leads to the solution approach transformation seal, a cryptographically secured container used to ensure legal security for transformed documents by securing the content's integrity, attesting a transformation's correctnes, and attributing it to a responsible party.

Umwandlungen signierter Dokumente werfen Fragen auf, die für die Anwendung erhebliche Unsicherheiten begründen. Dieser Beitrag untersucht den Themenkomplex unter rechtlichen, technischen und organisatorischen Aspekten. Es werden Grundkonzepte sicherer Transformationen erläutert, die Transformation als Prozess analysiert und Lösungsansätze präsentiert.

We introduce new subclasses of Fourier hyperfunctions of mixed type, satisfying polynomial growth conditions at infinity, and develop their sheaf and duality theory. We use Fourier transformation and duality to examine relations of these asymptotic and tempered hyperfunctions to known classes of test functions and distributions, especially the Gelfand–Shilov-Spaces. Further it is shown that the asymptotic hyperfunctions, which decay faster than any negative power, are precisely the class that allow asymptotic expansions at infinity. These asymptotic expansions are carried over to the higher-dimensional case by applying the Radon transformation for hyperfunctions. 46F15, 46F20, 30E15 Hyperfunctions, asymptotic expansions, moments, Radon transformation

TBased on the heuristics that maintaining presumptions can be beneficial in uncertain environments, we propose a set of basic axioms for learning systems to incorporate the concept of prejudice. The simplest, memoryless model of a deterministic learning rule obeying the axioms is constructed, and shown to be equivalent to the logistic map. The system's performance is analysed in an environment in which it is subject to external randomness, weighing learning defectiveness against stability gained. The corresponding random dynamical system with inhomogeneous, additive noise is studied, and shown to exhibit the phenomena of noise induced stability and stochastic bifurcations. The overall results allow for the interpretation that prejudice in uncertain environments entails a considerable portion of stubbornness as a secondary phenomenon. 91A26, 34F05 Learning, prejudice, uncertainty, noise, random dynamical system, noise induced stability, stochastic bifurcation

Large scale Digital Rights Management (DRM) systems are close to deployment in various areas. However, interoperability problems associated with DRM based content distribution systems encompassing many business models, consumer use cases, content and device types, have not been regarded in detail. On grounds of an analysis of these issues we argue that comprehensive DRM poses very special interoperability challenges, and advocate the utility of intermediary roles for viable DRM solutions.

Die besonderen Anforderungen der Planung und Durchsetzung von Sicherheitspolitiken in Telekollaborations-Umgebungen, in die verschiedene Partner unterschiedliche Sicherheitsrichtlinien einbringen, werden diskutiert. Ein durchgängiges Vorgehensmodell wird vorgestellt, dass von der Planung und Formalisierung über die formale Verifikation bis zur Implementierung der Sicherheits-Policies reicht. An einem konkreten Szenario aus der Automotive Industrie wird exemplarisch die Umsetzung des Konzepts dargestellt. Schließlich werden verbleibende Probleme diskutiert und bewertet.

We present an overview of the mathematics underlying the quantum Zeno effect. Classical, functional analytic results are put into perspective and compared with more recent ones. This yields some new insights into mathematical preconditions entailing the Zeno paradox, in particular a simplified proof of Misra's and Sudarshan's theorem. We empahsise the complex-analytic structures associated to the issue of existence of the Zeno dynamics. On grounds of the assembled material, we reason about possible future mathematical developments pertaining to the Zeno paradox and its counterpart, the anti-Zeno paradox, both of which seem to be close to complete characterisations. 46L60, 47D03, 81P15, 81R15, 82B10; 03.65.Xp, 03.65Db, 05.30.-d, 02.30.T Quantum Zeno Effect, anti-Zeno effect, measurement, Trotter's product formula, degenerate semigroup, operator algebra, modular automorphism group, KMS-state, return to equilibrium, Gibbs state

Seit fast zwei Jahren existiert mit dem XML Signaturstandard ein Format für elektronische Signatu-ren, das weit über herkömmliche Signaturformate hinausgeht. Flexibilität und Mächtigkeit des Standards bergen aber auch erhebliche Gefahren. Dieser Bei-trag untersucht, welche Risiken sich in Bezug auf das Präsentationsproblem bei der Anwendung von XML-Signaturen ergeben und welche Anforderungen sich daraus für die anwendungsspezifische Ausgestaltung und Einschränkungen des grundlegenden Standards ergeben.

Integrability conditions of type $L^p$ along straight lines within a strip in $\mathbf{C}$ are derived for holomorphic functions which are integrable over the area of the strip. 30E20, 30A10 Phragmén-Lindelöf principle, Hadamard's Three-Lines Theorem, $L^p$ bounds, $L^p$ means, convexity

We study the quantum Zeno effect in quantum statistical mechanics within the operator algebraic framework. We formulate a condition for the appearance of the effect in W*-dynamical systems, in terms of the short-time behaviour of the dynamics. Examples of quantum spin systems show that this condition can be effectively applied to quantum statistical mechanical models. Furthermore, we derive an explicit form of the Zeno generator, and use it to construct Gibbs equilibrium states for the Zeno dynamics. As a concrete example, we consider the X-Y model, for which we show that a frequent measurement at a microscopic level, e.g. a single lattice site, can produce a macroscopic effect in changing the global equilibrium. 82B10, 82C10, 81R15; 03.65.Xp, 05.30.-d, 02.30.Tb Quantum Zeno dynamics, W*-dynamical system, quantum spin systems, X-Y model, return to equilibrium

We reconsider estimates for the heat kernel on weighted graphs recently found by Metzger and Stollmann. In the case that the weights satisfy a positive lower bound as well as a finite upper bound, we obtain a specialized lower estimate and a proper generalization of a previous upper estimate. 39A12 Heat kernel, Laplace operator on graphs

The dynamical quantum Zeno effect is studied in the context of von Neumann algebras. It is shown that the Zeno dynamics coincides with the modular dynamics of a localized subalgebra. This relates the modular operator of that subalgebra to the modular operator of the original algebra by a variant of the Kato--Lie--Trotter product formula. 46L60, 81P15, 81R15; 03.65.Xp, 03.65.Db, 02.30.Tb Quantum Zeno effect, von Neumann algebra, modular group

We present a method for the construction of a Krein space completion for spaces of test functions, equipped with an indefinite inner product induced by a kernel which is more singular than a distribution of finite order. This generalizes a regularization method for infrared singularities in quantum field theory, introduced by G. Morchio and F. Strocchi, to the case of singularites of infinite order. We give conditions for the possibility of this procedure in terms of local differential operators and the Gelfand-Shilov test function spaces, as well as an abstract sufficient condition. As a model case we construct a maximally positive definite state space for the Heisenberg algebra in the presence of an infinite infrared singularity. 46C20, 46F05, 47B50, 81T05; 11.10.-z, 02.10.-v, 02.30.Tb Infrared singularity, Gelfand-Shilov space, Heisenberg algebra, indefinite inner product space, Krein space

This report combines two different threads of research: In the first chapter, we make a proposal for a mathematical model of prejudiced behaviour. The heuristic background of this is the study of agents in open marketplaces, e.g., on the internet. We derive our model from a simple outset within the framework of the general theory of learning systems and a few axiomatic assumptions. The model considered turns out to be an example of a noisy dynamical system. Systems of this type have recently attracted much attention in the physical and mathematical communities. We perform a theoretical study of our special system in chapter 2 and carry out some numerical experiments. We stress the analogy of the phenomenology of the system with phase transitions in physical systems. The results that we obtain in chapter 2 give us some insight into the qualitative behaviour that learning systems governed by our prejudiced learning rule will exhibit. Dieser Bericht führt zwei verschiedene Forschungsthemen zusammen: Im ersten Kapitel stellen wir ein mathematisches Modell für vorurteilsbehaftetes Verhalten vor. Den heuristische Hintergrund bildet hierbei die Studie des Verhaltens von Agenten in offenen Marktplätzen wie z. B. internetbasierten. Das Modell leiten wir im Rahmen einfacher Grundlagen der Theorie lernender Systeme aus wenigen axiomatischen Annahmen her. Es erweist sich als ein Beispiel für ein dynamisches System mit Rauschen. Systeme dieses Typs haben in jüngster Zeit in Mathematik und Physik einige Aufmerksamkeit erregt. Wir führen eine theoretische Studie unseres speziellen Systems in Kapitel 2 durch und sammeln empirische Daten mittels numerischer Experimente. Dabei betonen wir besonders die Analogie zum Phänomen der Phasenübergänge in physikalischen Systemen. Die Resultate, die wir erhalten ermöglichen es uns wiederum in Kapitel 2, einigen Einblick in das qualitative Verhalten das lernende Systeme, die unserer Lernregel gehorchen, zeigen werden, zu gewinnen.

Eines der gravierendsten Probleme, die sich einer breiten öffentlichen Anwendung digitaler Signaturen in den Weg stellt, ist das Problem der zurechenbaren und beweiskräftigen Präsentation signierter Dokumente. Im vorliegenden Beitrag wird untersucht, welchen Lösungsbeitrag hierzu die Extensible Markup Language (XML) als universelles Datenformat und der XML-Signaturstandard, der zurzeit vom World Wide Web Consortium (W3C) spezifiziert wird, leisten können.

Wir führen eine neue Unterklasse der Fourier Hyperfunktionen mit polynomialen Wachstumsbedingungen ein mit dem Ziel, asymptotische Entwicklungen von Hyperfunktionen studieren zu wollen, wie sie für gewisse Distributionenklassen bekannt sind. Wir entwickeln zuerst die Theorie analytischer Funktionale auf Räumen integrabler Funktionen bezüglich Maßen mit Wachstum O(|Re z|^gamma), wobei gamma in R ist, im Unendlichen. Ein an das berühmte Phragmén-Lindelöf-Prinzip erinnerndes, einfaches analytisches Resultat bildet die Basis der Dualitätstheorie dieser Räume zu Funktionen mit festgelegtem Wachstumstyp. Wir studieren diese Dualität analytischer Funktionale mit Wachstumsbedingungen und unbeschränkten Trägern gründlich in einer Dimension unter Verwendung des von den Fourier Hyperfunktionen her bekannten exponentiell abfallenden Cauchy-Hilbert-Kerns. Daraus ergeben sich Analoga zu den Theoremen von Runge und Mittag-Leffler, die die Grundlage für die Garbentheorie der Hyperfunktionen mit polynomialen Wachstumsbedingungen sind, die wir sodann entwickeln. Die für uns wichtigsten neuen Klassen von Fourier Hyperfunktionen sind die von unendlichem Typ, das heißt solche, die wie eine beliebige Potenz wachsen beziehungsweise schneller als jede Potenz abfallen. In n Dimensionen benutzen wir die Fouriertransformation und Dualität um das Verhältnis dieser temperierten beziehungsweise asymptotischen Hyperfunktionen zu bekannten Distributionenräumen zu studieren. Wir leiten Theoreme vom Paley-Wiener-Typ her, die es uns erlauben, unsere Hyperfunktionen in ein Schema zu ordnen, das Wachstumsordnung und Singularität gegenüberstellt. Wir zeigen, daß dieses Schema eine sinvolle Erweiterung des von Gelfand und Shilow zur Charakterisierung von Testfunktionenräumen eingeführten Schemas der Räume S(alpha,beta) um verallgemeinerte Funktionen ist. Schließlich zeigen wir die Nuklearität der temperierten und asymptotischen Hyperfunktionen. Wir zeigen, daß die asymptotischen Hyperfunktionen genau die Klasse bilden, die Moment-asymptotische Entwicklungen erlauben, wie sie von Estrada et al. für Distributionen betrachtet wurden. Estradas Theorie ist damit ein Spezialfall der unsrigen. Für Hyperfunktionen lassen sich aber dank des Konzeptes der standard definierenden Funktionen die Moment-asymptotischen Entwicklungen als klassische asymptotische Entwicklungen von analytischen Funktionen verstehen. Wir zeigen die einfache Beziehung zwischen der Moment-asymptotischen Entwicklung und der Taylorentwicklung der Fouriertransformierten und benutzen dann ein Resultat von Estrada, um die Vollständigkeit unseres Moment-asymptotischen Schemas abzuleiten. Wir geben genaue Bedingungen für die Moment-Folgen von Hyperfunktionen mit kompaktem Träger an, die kürzlich von Kim et al. gefunden wurden. Die asymptotischen Entwicklungen übertragen wir auf den höherdimensionalen Fall, indem wir die von Kaneko und Takiguchi eingeführte Radontransformation für Hyperfunktionen verwenden. Die wohlbekannte Beziehung zwischen Radon- und Fouriertransformation zeigt wiederum das enge Verhältnis von asymptotischer Entwicklung zur Taylorentwicklung der Fouriertransformierten. Wir benutzen Kims Resultate, um die Moment-Folgen von Hyperfunktionen zu charakterisieren, die von Kugeln mit endlichem Radius getragen werden. Schließlich verwenden wir das Träger-Theorem der Radontransformation, um ein Resultat über das Singularitätenspektrum aus Bedingungen an die Radontransformierte abzuleiten. We introduce new subclasses of Fourier hyperfunctions satisfying polynomial growth conditions at infinity with the intention to study asymptotic expansions in hyperfunction theory, which are known to hold in certain spaces of distributions. We begin by developing the theory of analytic functionals on spaces of integrable functions with respect to measures of growth O(|Re z|^gamma), where gamma is in R, at infinity. A simple analytic result for these Hardy type spaces, reminiscent of the famous Phragmén-Lindelöf principle, prepares the ground for the duality of these functions to spaces of functions of fixed polynomial growth at real infinity. We study this duality theory for analytic funcionals with growth conditions and unbounded carriers in full detail in one dimension, utilizing the exponentially decreasing Cauchy-Hilbert kernel known from the theory of Fourier hyperfunctions. We derive theorems of Runge and Mittag-Leffler type and thereby lay the grounds for a theory of hyperfunctions of the namely growth types as a flabby sheaf theory on the compactified space D, which is then exhibited. The most important new types of Fourier hyperfunctions are such with growth type ±infinity, that is, growing with arbitrary polynomial type or decaying faster than any polynomial, respectively. In higher dimensions we use Fourier transformation and duality to examine relations of these tempered and asymptotic hyperfunctions to known classes of test functions, distributions and hyperfunctions. We identify the Fourier transforms of tempered and asymptotic hyperfunctions by theorems of Paley--Wiener type which allow us to order these spaces into a scheme relating growth type to singularity. This scheme is shown to be a sensible extension to generalized functions of the scheme of spaces S(alpha,beta) which was introduced by Gelfand and Shilov to classify the spaces of test functions for distributions. Finally, we show the nuclearity of the spaces of tempered and asymptotic hyperfunctions. Further, it is shown in one dimension that the asymptotic hyperfunctions which decay faster than any negative power are precisely the class that allow moment asymptotic expansions at infinity, as were studied by Estrada et al. for distributions. We show that Estradas theory of asymptotic expansions is contained in ours. But for hyperfunctions, these asymptotic expansions can be related to the classical asymptotic expansions of analytic functions by the concept of standard defining functions. We show the simple relation of the moment asymptotic expansion of asymptotic hyperfunctions to the Taylor expansion of their Fourier transform, by which we can use a result of Estrada to show the completeness of the asymptotic scheme in our case. We cite the necessary and sufficient conditions for the moment sequences of hyperfunctions with compact support, which were recently found by Kim et al. These asymptotic expansions are carried over to the higher-dimensional case by apploying the Radon transformation for hyperfunctions, as introduced by Kaneko and Takiguchi. The well-known relation between Radon and Fourier transformation shows again the relation between the moment asymptotic expansion of hyperfunctions and the Taylor expansion of their Fourier transforms. We use Kim's result to characterize the moment sequences of hyperfunctions carried by balls with finite radius. Finally, we use the support theorem for the Radon transformation to derive a condition on the singularity spectrum of a hyperfunction by conditions on its Radon transform.

This extended write-up of my talk gives an introductory survey of mathematical problems of the quantization of gauge systems. Using the Schwinger model as an exactly tractable but nontrivial example which exhibits general features of gauge quantum field theory, I cover the following subjects: The axiomatics of quantum field theory, formulation of quantum field theory in terms of Wightman functions, reconstruction of the state space, the local formulation of gauge theories, indefiniteness of the Wightman functions in general and in the special case of the Schwinger model, the state space of the Schwinger model, special features of the model. New results are contained in the Mathematical Appendix, where I consider in an abstract setting the Pontrjagin space structure of a special class of indefinite inner product spaces --- the so called quasi--positive ones. This is motivated by the indefinite inner product space structure appearing in the above context and generalizes results of Morchio and Strocchi in [J. Math. Phys. 31 (1990) 1467] and Dubin and Tarski in [Ann.~Phys. 13 (1967) 263]. 81T13, 81-02, 81T10, 81T05 quantum field theory, Schwinger model, Krein space, Pontrjagin space

Wir geben eine in sich geschlossene Darstellung des Runge-Phänomens in der Polynominterpolation. Ausgehend von Runges Originalbeobachtung (1901) werden Bernsteins Divergenzsatz, Fabers Theorem, die Rolle der Lebesgue-Konstante im funktionalanalytischen Rahmen und die Konvergenzanalyse über Bernstein-Ellipsen entwickelt. Die Optimalität der Tschebyschow-Stützstellen wird potentialtheoretisch begründet. Abschließend untersuchen wir das Phänomen in L^p-Normen: Während bei äquidistanten Stützstellen die Divergenz in allen L^p-Normen persistiert, ergibt sich bei optimaler Stützstellenwahl eine echte Hierarchie mit dem Satz von Erdős–Turán (L²-Konvergenz) und Nevais Schwelle bei p = 4.

In this short note on my talk I want to point out the mathematical difficulties that arise in the study of the relation of Wightman and Euclidean quantum field theory, i.e., the relation between the hierarchies of Wightman and Schwinger functions. The two extreme cases where the reconstructed Wightman functions are either tempered distributions - the well-known Osterwalder-Schrader reconstruction - or modified Fourier hyperfunctions are discussed in some detail. Finally, some perpectives towards a classification of Euclidean reconstruction theorems are outlined and preliminary steps in that direction are presented.

Skript mit mathematischen Ergänzungen zur Vorlesung von Prof. Dr. F. Constantinescu, Wintersemester 1995/96. Darstellungstheorie von Lie- und assoziativen Algebren; Höchstgewichtsdarstellungen; Tensorprodukte; Clebsch-Gordan-Koeffizienten; Wigner-Eckart-Theorem; Racah-Wigner-Koeffizienten; 6j-Symbole; Invariantentheorie; Brauer-Weyl-Theorie.

Auf die Dokumentenbeschreibungssprache XML (EXtensible Markup Language) gründen sich weitreichende Hoffnungen im Hinblick auf interoperable Web-Anwendungen - XML könnte zu einer `lingua franca' des WWW werden. Das World Wide Web Consortium (W3C) entwickelt zur Zeit einen Standard zur Realisierung digitaler Signaturen in XML (XML-DSig) - ein Mosaikstein zur Einlösung dieser Hoffnungen. Nach einem Überblick über den Stand dieses Projekts werden am Beispiel des von der GMD Darmstadt entwickelten BAKO-Protokolls (S. Kolletzki, in: Computer Networks and ISDN Systems 28, 1996, S. 1891-1899, Elsevier) (zum Abschluß zweiseitiger, verbindlicher Verträge) die grundlegenden Techniken und Möglichkeiten von XML-DSig und der Zusammenhang mit anderen W3C-Standards rund um XML diskutiert. Wenn - nach EU-Richtlinie und deutschem Signaturgesetz rechtsverbindliche - Dokumente mit digitalen Signaturen in interoperablen Web-Welten breite Anwendung finden sollen, verdient das sogenannte Präsentationsproblem [U. Pordesch. DuD 2/2000. S. 89-95. A. U. Schmidt. Signiertes XML und das Präsentationsproblem. DuD 3/2000. S. 153-158.] besondere Beachtung: Wurden dem Anwender die zu signierenden Daten vollständig und unverfälscht präsentiert? Und noch wichtiger: ist dies im Streitfall gerichtlich überprüfbar? Es soll gezeigt werden, daß XML und XML-DSig einen Ansatz zu einer (wenigstens teilweisen) Lösung dieses grundlegenden Problems digitaler Signaturen bietet, und wie dies funktionieren kann. Dies weist aber zugleich auf noch offene technische, praktische und theoretische Probleme von XML-DSig hin.

Noisy alias random dynamical systems in recent years have attracted the interest of physicists and mathematicians, for two basic reasons: Physically, they add a good deal of realism to the theoretical models of many natural phenomena which were hitherto modeled by deterministic dynamical systems, since it has been realized that noise is almost ubiquitous in reality and often significantly affects the behaviour of complicated systems. Mathematically, random dynamical systems present an attractive synthesis of the fields of stochastics and general dynamical systems in which many branches of mathematical physics and pure mathematics converge and generate new insights. In both disciplines, it soon became clear that random dynamical systems possess a number of interesting new properties, most prominently the phenomena noise induced stability, on-off intermittence, and stochastic bifurcations also called noise induced (phase) transitions.

Von der klassischen zur Quantenkryptographie

Zunehmend werden zwischen Unternehmen, Behörden, Privatpersonen und auch Rechtsanwälten und Notaren elektronisch signierte Dokumente ausgetauscht. Die stetig größer werdende Vielfalt von Dokumentformaten für spezielle Anwendungsbereiche wird hierbei zum kritischen Reibungspunkt: Wird ein Dokumentenformat geändert, so bricht die ursprüngliche Signatur. Ein analoges Problem tritt beim Übergang von der Papier- in die digitale Welt auf, etwa wenn ein Krankenhaus Patientenakten und Arztbriefe in elektronische Form bringen will. In all diesen Fällen steht die rechtliche Wirksamkeit des umgewandelten, transformierten Dokuments in Frage. Auch bei der Archivierung von Dokumenten wird dieses Problem akut. Um hier langfristige Sicherheit und Lesbarkeit von Dokumenten zu garantieren, müssen Methoden zur sicheren Überführung alter Dokumentenformate in aktuelle gefunden und bei der Konzeption von Archivierungssystemen mitbedacht werden. Rechtssichere Transformationen: Das vom BMWA geförderte Verbundprojekt TransiDoc greift dieses Problem in den drei zentralen Anwendungsfeldern Medizin (Patientenakten), öffentliche Verwaltung (Bauanträge) und Notariate auf. Das Projekt verfolgt dabei einen interdisziplinären Ansatz, der die Entwicklung technischer Lösungen mit der organisatorischer Verfahren verbindet. Dabei ist der bestehende und sich entwickelnde Gesetzesrahmen genau zu berücksichtigen. Zum Projekt gehört eine gründliche Untersuchung der Eig-nung von häufig verwendeten Datenformaten bezüglich Signaturen und Transformationen, aber auch die Konzeption von Gestaltungsvorschlägen für die Rechtsentwicklung. TransiDoc zielt auf eine umfassende Methode, mit der ein breites Spektrum von Transformationen rechtssicher gestaltet werden kann, was bedeutet, dass ein transformiertes Dokument rechtlich gesehen genau so genutzt werden kann wie das ursprüngliche. Kernpunkt des Lösungsansatzes ist es, für einen späteren Begutachter nachvollziehbar und nachprüfbar zu machen, was während der Transformation mit dem Dokument geschah und wie, mit welchen Mitteln und durch wen sie ausgeführt wurde. Transformationssiegel: TransiDoc entwickelt und spezifiziert ein elektronisches Transformationssiegel, in dem die genannten Daten in vertrauenswürdiger, das heißt kryptografisch gesicherter Form vermerkt und an das transformierte Dokument gebunden werden können. In vielen Fällen kann ein mit einem Transformationssiegel versehenes Dokument das Ausgangsdokument für die praktische Verwendung komplett ersetzen. In TransiDoc werden Tools zur Erzeugung, Bearbeitung und Prüfung von Trans-formationssiegeln entwickelt. Organisatorischer Rahmen: Ein Transformationssiegel kann nur dann nützlich sein, wenn sein Zustan-dekommen auf vertrauenswürdige Weise gesichert ist. Hierzu entwickelt TransiDoc einen Organisationsrahmen, also einen Katalog von Handlungsanweisungen, Vorgehensbeschreibungen und technischen Maßgaben. Dieser flexible Rahmen kann von Anwendern auf ihre Bereiche und Anwendungsfälle angepasst werden.

Identity Management erlangt eine immer größere Bedeutung, da immer mehr Firmen ihre IT-Systeme für Partner, Lieferanten oder Kunden öffnen. Die Diplomarbeit stellt einen Ansatz vor, durch den ein Zugriffskontroll- und Authentifikationssystem modular zu bestehenden webbasierten Systemen hinzugefügt werden kann. Das System muss hierfür nicht im Sourcecode vorliegen. In einer Trainingsphase wird das Modul an die zu schützende Applikation angepasst. Dies wird durch den Einsatz von aspektorientierter Programmierung in Form des AspectJ Frameworks erreicht. Für die Authentifikation kommt das Liberty Alliance Protokoll, ein zukünftiger Industriestandard, zum Einsatz, welches ein Single-Sign-On Protokoll unter Verwendung von Identity Federation implementiert. Eine mögliche Verwendung von Hardwaretoken in diesem Framework wird demonstriert und eine Weg vorgestellt, ein proaktives Verhalten in das Systems zu integrieren. Identity Management is becoming more and more important in business systems as they are opened for third parties including trading partners, consumers and suppliers. This thesis presents an approach securing a system without any knowledge of the system source code. The security module adds to the existing system authentication and authorisation based on aspect oriented programming and the liberty alliance framework, an upcoming industrie standard providing single sign on. In an initial training phase the module is adapted to the application which is to be secured. Moreover the use of hardware tokens and proactive computing is demonstrated. The high modularisation is achived through use of AspectJ, a programming language extension of Java. Identity Mangement, aspect oriented programming, single sign on, liberty alliance, pro active computing, aspectj, identity federation

Spam stellt ein immer größeres Problem im E-Mail Verkehr dar und erfordert zunehmend den Einsatz von Spamfiltern. Die aktuell verfügbaren Spamfilter arbeiten entropiebasiert und stützen sich in der Regel auf so genannte Bayes'sche Filter, die Spam aufgrund bedingter Wahrscheinlichkeiten klassifizieren, oder auf die Markov-Diskriminierung, die Zeichenketten in den E-Mails identifiziert und zuordnet. Die bisherigen Filtermethoden liefern zwar gute Ergebnisse, es ist jedoch sinnvoll, verschiedene Verfahren zur Filterung von Spam miteinander zu kombinieren, um bessere Ergebnisse zu erzielen. Weiterhin erschwert die Kombination verschiedener Techniken das Umgehen derartiger Filter, da verschiedene Verfahren auf unterschiedliche Charakteristiken der E-Mails abstellen. Diese Arbeit behandelt die Filterung von Spam mittels eines Textanalyseverfahrens. Dazu wird zunächst der Begriff der Entropie definiert, der weiter zum Begriff des informationsbasierten Abstands zwischen Texten und zur relativen Entropie führt. Mittels dieser relativen Entropie erfolgt nun die Klassifizierung der E-Mails. Im Gegensatz zu Bayes'schen Filtern, die jedem Wort der E-Mail eine Wahrscheinlichkeit zuordnen um die Spamwahrscheinlichkeit der E-Mail zu berechnen, betrachtet die Textanalyse den Informationsgehalt, der durch die Entropie definiert wird.

Beglaubigte Übersetzungen sind zurzeit ein rein papierbasiertes Geschüft, obwohl im deutschen Rechtsraum alle rechtlichen Voraussetzungen für beglaubigte Übersetzungen von elektronischen Dokumenten gegeben sind. Diese Diplomarbeit beschreibt die digitale Nachbildung des Prozesses der beglaubigten Übersetzung. Grundlage hierfür bildet das Projekt TransiDoc - Rechtssichere Transformation signierter Dokumente [20]. Aus dem für TransiDoc zentralen Konzept des Transformationssiegels wird ein anwendungsspezifisches Übersetzungssiegel abgeleitet, das das Ausgangs- und das Zieldokument mittels einer elektronischen Signatur verbindet und weitere Daten wie z. B. den Beglaubigungsvermerk enthält.

This thesis presents a concept to achieve non-repudiation for natural language conversations by electronically signing continuous, packet-based, digital voice communication (VoIP). Signing a VoIP-based conversation means to protect the integrity and authenticity of the bidirectional data stream and its temporal sequence which together establish the security context of the communication. The solution is based on chains of hashes and continuously chained electronic signatures. The protection is provided continuously during the ongoing conversations, they are not processed at once like traditional digital documents which could be trivially signed. A possible implementation and necessary protocols are described to apply these concepts to SIP/RTP-based VoIP-communication. This provides a high level of inherent security and enables PKI-based non-reputable signatures over voice as true declarations of will, without additional witnesses and in principle between unacquainted speakers. As a demonstrator for these concepts, an efficient VoIP-archive securing the integrity of SIP-based two-party conversations was implemented.

In the context of identity management, a major research topic is the establishment of trust relationships between multiple identifier domains. Conventional approaches such as cross certification, spanning certificate authorities or mirroring of user databases result in substantial technical overhead. A possible approach is the usage of already existing architectures such as the infrastructure provided by trusted computing technology. The goal of this thesis is the development of a concept that allows a user from a certain identifier domain to access a service at a service provider belonging to a foreign identifier domain by using a ticket issued by an identity provider located in the primary identifier domain. To decide whether the foreign ticket can be accepted, the service provider first of all has to verify that the identity provider is authorized to issue tickets for the particular identifier domain. Moreover, the service provider has to validate the identity provider�s configuration and system status at the moment of the ticket issuing in order to decide whether the identity provider�s decision can be trusted. In the thesis, the realization of these requirements by using trusted computing technology is analyzed. For the authorization of the identity provider, the process of issuing attestation identifier credentials by the privacy-CA has to be adapted. If the identity provider is authorized to issue trusted tickets, the privacy-CA includes a certain key usage attribute in the certificate. In order to create the trusted tickets, SAML assertions are used to transport the status information from the identity provider to the foreign service provider. The flexible SAML framework allows the integration of the identity provider�s status information signed with the attestation identifier key in the attributes of the assertion. For the creation of information describing the platform�s current configuration and system status, the trusted computing technology offers the necessary attestation mechanisms. The developed concept and the reference implementation show that it is possible to use the trusted computing architecture for the establishment of trust relationships across multiple identifier domains in the context of identity management.

In our modern society telephony has developed to an omnipresent service. People are available at anytime and anywhere. Furthermore the Internet has emerged to an important communication medium. These facts and the raising availability of broadband internet access has led to the fusion of these two services. Voice over IP or short VoIP is the keyword, that describes this combination. The advantages of VoIP in comparison to classic telephony are location independence, simplification of transport networks, ability to establish multimedia communications and the low costs. Nevertheless one can easily see, that combining two technologies, always brings up new challenges and problems that have to be solved. It is undeniable that one of the most annoying facet of the Internet nowadays is email spam. According to different sources email spam is considered to be 80 to 90 percent of the email traffic produced. Security experts suspect that this will spread out on VoIP too. The threat of so called voice spam or Spam over Internet Telephony (SPIT) is even more fatal than the threat that arose with email spam, for the annoyance and disturbance factor is much higher. As instance an email that hits the inbox at 4 p.m. is useless but will not disturb the user much. In contrast a ringing phone at 4 p.m. will lead to a much higher disturbance. From the providers point of view both email spam and voice spam produce unwanted traffic and loss of trust of customers into the service. In order to mitigate this threat different approaches from different parties have been developed. This thesis focuses on state of the art anti voice spam solutions, analyzes them to the core and reveals their weak points. In the end a SPIT producing benchmark tool will be implemented, that attacks the presented anti voice spam solutions. With this tool it is possible for an administrator of a VoIP network to test how vulnerable his system is.