A reliable source of randomness is not only an essential building block in various cryptographic, security, and distributed systems protocols, but also plays an integral part in the design of many new blockchain proposals. Consequently, the topic of publicly-verifiable, bias-resistant and unpredictable randomness has recently enjoyed increased attention. In particular random beacon protocols, aimed at continuous operation, can be a vital component for current Proof-of-Stake based distributed ledger proposals. We improve upon previous random beacon approaches with HydRand, a novel distributed protocol based on publicly-verifiable secret sharing (PVSS) to ensure unpredictability, bias-resistance, and public-verifiability of a continuous sequence of random beacon values. Furthermore, HydRand provides guaranteed output delivery of randomness at regular and predictable intervals in the presence of adversarial behavior and does not rely on a trusted dealer for the initial setup. Compared to existing PVSS based approaches that strive to achieve similar properties, our solution improves scalability by lowering the communication complexity from $\mathcal{O}\left( {{n^3}} \right)$ to $\mathcal{O}\left( {{n^2}} \right)$ . Furthermore, we are the first to present a detailed comparison of recently described schemes and protocols that can be used for implementing random beacons.

Blockchain has been hailed as an emerging technology with the potential to cause significant impact in a variety of fields. One domain is an application in cyber-physical systems (CPSs), e.g., as a building block for the (Industrial) Internet of Things (IIoT) and Industry 4.0. In this regard, various use cases and designs have been proposed that seek to leverage the desirable properties blockchain technologies seem to offer. While many of the principles behind blockchain have actually been studied under the veil of Byzantine fault tolerance for decades, some approaches, such as relying on game-theoretic incentives and proof-of-work (PoW), are not yet fully understood. This knowledge gap can leave both practitioners and researchers in a difficult position regarding a possible application of such technologies, as it is often unclear what guarantees and characteristics a particular blockchain design actually achieves. This work-in-progress paper provides an overview of blockchain security research, outlines system designs that are likely to exhibit vulnerabilities, and provides examples of potentially insecure proposals in the field of CPSs that employ such designs.