We analyzed two non-repudiation protocols and found some new attacks on the fairness and termination property of these protocols. Our attacks are enabled by several inherent design weaknesses, which also apply to other non-repudiation protocols. To prevent these attacks, we propose generic countermeasures that considerably strengthen the design and implementation of non-repudiation protocols. The application of these countermeasures is finally shown by our construction of a new fair non-repudiation protocol

Abstract. The requirement for higher security and dependability of systems is continuously increasing even in domains not traditionally deeply involved in such issues. Yet, evolution of embedded systems towards devices connected via Internet, wireless communication or other interfaces requires a reconsideration of secure and trusted embedded systems engineering processes. In this paper, we propose an approach that associates model driven engineering (MDE) and formal validation to build security and dependability (S&D) patterns for trusted RCES applications. The contribution of this work is twofold. On the one hand, we use model-based techniques to capture a set of artifacts to encode S&D patterns. On the other hand, we introduce a set of artifacts for the formal validation of these patterns in order to guarantee their correctness. The formal validation in turn follows the the MDE process and thus links concrete validation results to the S&D requirements identified at higher levels of abstraction.

Abstract. The Trusted Platform Module TPM is a basic but nevertheless very complex security component that can provide the foundations and the root of security for a variety of applications. In contrast to the TPM, other basic security mechanisms like cryptographic algorithms or security protocols have frequently been subject to thorough security analysis and formal verification. This paper presents a first methodic security analysis of a large part of the TPM specification. A formal automata model based on asynchronous product automata APA and a finite state verification tool SHVT are used to emulate a TPM within an executable model. On this basis four different generic scenarios were analysed with respect to security and practicability: secure boot, secure storage, remote attestation and data migration. A variety of security problems and inconsistencies was found. Subsequently, the TPM specification was adapted to overcome the problems identified. In this paper, the analysis of the remote attestation scenario and some of the problems found are explained in more detail.

Abstract.Historically, various different notions of trust can be found, each addressing particular aspects of ICT systems, e.g. trust in electronic commerce systems based on reputation and recommendation, or trust in public key infrastructures. While these notions support the understanding of trust establishment and degrees of trustworthiness in their respective application domains, they are insufficient for the more general notion of trust needed when reasoning about security in ICT systems. In this paper we present a formal definition of trust to be able to exactly express trust requirements from the view of different entities involved in the system and to support formal reasoning such that security requirements, security and trust mechanisms and underlying trust assumptions can be formally linked and made explicit. Integrated in our Security Modeling Framework this formal definition of trust can support security engineering processes and formal validation and verification by enabling reasoning about security properties w.r.t. trust.

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