Short-lived zero-knowledge proofs and signatures

We introduce the short-lived proof, a non-interactive proof of knowledge with a novel feature: after a specified period of time, the proof is no longer convincing. This time-delayed loss of soundness happens naturally without further involvement from the prover or any third party. We propose formal definitions for short-lived proofs as well as the special case of short-lived signatures. We show several practical constructions built using verifiable delay functions (VDFs). The key idea in our approach is to allow any party to forge any proof by executing a large sequential computation. Some constructions achieve a stronger property called reusable forgeability in which one sequential computation allows forging an arbitrary number of proofs of different statements. Our work also introduces two novel types of VDFs, re-randomizable VDFs and zero-knowledge VDFs, which may be of independent interest

SECURE REAL-TIME SMART GRID COMMUNICATIONS: A MICROGRID PERSPECTIVE

Microgrids are a key component in the evolution of the power grid. Microgrids are required to operate in both grid connected and standalone island mode using local sources of power. A major challenge in implementing microgrids is the communications and control to support transition from grid connected mode and operation in island mode. In this dissertation we propose a distributed control architecture to govern the operation of a microgrid. The func- tional communication requirements of primary, secondary and tertiary microgrid controls are considered. Communication technology media and protocols are laid out and a worst-case availability and latency analysis is provided. Cyber Security challenges to microgrids are ex- amined and we propose a secure communication architecture to support microgrid operation and control. A security model, including network, data, and attack models, is defined and a security protocol to address the real-time communication needs of microgrids is proposed. We propose a novel security protocol that is custom tailored to meet those challenges. The chosen solution is discussed in the context of other security options available in the liter- ature. We build and develop a microgrid co-simulation model of both the power system and communication networks, that is used to simulate the two fundamental microgrid power transition functions - transition from island to grid connected mode, and grid connected to island mode. The proposed distributed control and security architectures are analyzed in terms of performance. We further characterize the response of the power and communication subsystems in emergency situations: forced islanding and forced grid modes. Based on our findings, we generalize the results to the smart grid