Anomaly detection is a crucial task in complex distributed systems. A thorough understanding of the requirements and challenges of anomaly detection is pivotal to the security of such systems, especially for real-world deployment. While there are many works and application domains that deal with this problem, few have attempted to provide an in-depth look at such systems. In this survey, we explore the potentials of graph-based algorithms to identify anomalies in distributed systems. These systems can be heterogeneous or homogeneous, which can result in distinct requirements. One of our objectives is to provide an in-depth look at graph-based approaches to conceptually analyze their capability to handle real-world challenges such as heterogeneity and dynamic structure. This study gives an overview of the State-of-the-Art (SotA) research articles in the field and compare and contrast their characteristics. To facilitate a more comprehensive understanding, we present three systems with varying abstractions as use cases. We examine the specific challenges involved in anomaly detection within such systems. Subsequently, we elucidate the efficacy of graphs in such systems and explicate their advantages. We then delve into the SotA methods and highlight their strength and weaknesses, pointing out the areas for possible improvements and future works.

Authentication of participants is fundamental for secure communication systems. Many traditional systems rely on central components (like certification authorities). These have to be powerful and well-protected, making them expensive, and require trust in a central authority. Conventional decentralized solutions based on local trust between participants only (like PGP) are cheaper but either must be supported by central components, or they are prone to e.g. Sybil attacks. We present a decentralized solution without any trusted central components for finding paths of trust between arbitrary participants in an unstructured network: In an initialization phase a hierarchical overlay structure is constructed, providing each participant with certificate chains to predefined reference nodes. These certificate chains can be used later to find short trust chains between nodes. Monte-Carlo simulations clearly demonstrate the feasibility and efficiency of our approach for social networks. Further features like merging of networks, limited trust relationships between participants and revocation of trust can be integrated easily.

In this paper we describe a new algorithm to prevent fault attacks on RSA signature algorithms using the Chinese Remainder Theorem (CRT-RSA). This variant of the RSA signature algorithm is widely used on smartcards. Smartcards on the other hand are particularly susceptible to fault attacks like the one described in [7]. Recent results have shown that fault attacks are practical and easy to accomplish ([21], [17]).Therefore, they establish a practical need for fault attack protected CRT-RSA schemes. Starting from a careful derivation and classification of fault models, we describe a new variant of the CRT-RSA algorithm. For the most realistic fault model described, we rigorously analyze the success probability of an adversary against our new CRT-RSA algorithm. Thereby, we prove that our new algorithm is secure against the Bellcore attack.