arXiv subjects

Florian Wohner

Publications and source records attributed to Florian Wohner.

4 recordsLinked to original sources

arXiv2026

Privacy-Preserving Distributed Optimization Under Time Constraints Using Secure Multi-Party Computation and Evolutionary Algorithms

In distributed optimization, multiple parties collaborate to find an optimal solution to a problem. Privacy-preserving distributed optimization uses techniques, such as secure multi-party computation (MPC), to protect the private inputs of each party. In time-critical settings, the runtime overhead introduced by privacy-preserving computations may prevent the optimization from finishing within the deadline. This paper presents an approach for privacy-preserving distributed optimization in time-critical settings that combines evolutionary algorithms for solution search and MPC for the evaluation of solutions. The approach reduces the impact of privacy-preserving computations on runtime and allows to return solution within the deadline. Obfuscation of evaluation results provides additional protection for private inputs from an honest-but-curious platform provider, but introduces a potential trade-off between protection and solution quality. This trade-off is investigated in experiments using a genetic algorithm for both the single-objective assignment problem and the traveling salesperson problem, as well as NSGA-II for the multi-objective assignment problem.

cs.NE↗

arXiv2026

Topology-Hiding Path Validation for Large-Scale Quantum Key Distribution Networks

Secure long-distance communication in quantum key distribution (QKD) networks depends on trusted repeater nodes along the entire transmission path. Consequently, these nodes will be subject to strict auditing and certification in future large-scale QKD deployments. However, trust must also extend to the network operator, who is responsible for fulfilling contractual obligations -- such as ensuring certified devices are used and transmission paths remain disjoint where required. In this work, we present a path validation protocol specifically designed for QKD networks. It enables the receiver to verify compliance with agreed-upon policies. At the same time, the protocol preserves the operator's confidentiality by ensuring that no sensitive information about the network topology is revealed to users. We provide a formal model and a provably secure generic construction of the protocol, along with a concrete instantiation. For long-distance communication involving 100 nodes, the protocol has a computational cost of 1-2.5s depending on the machine, and a communication overhead of less than 70kB - demonstrating the efficiency of our approach.

quant-ph↗

arXiv2022

A Verifiable Multiparty Computation Solver for the Assignment Problem and Applications to Air Traffic Management

The assignment problem is an essential problem in many application fields and frequently used to optimize resource usage. The problem is well understood and various efficient algorithms exist to solve the problem. However, it was unclear what practical performance could be achieved for privacy preserving implementations based on multiparty computation (MPC) by leveraging more efficient solution strategies than MPC based simplex solvers for linear programs. We solve this question by implementing and comparing different optimized MPC algorithms to solve the assignment problem for reasonable problem sizes. Our empirical approach revealed various insights to MPC based optimization and we measured a significant (50x) speedup compared to the known simplex based approach. Furthermore, we also study the overhead introduced by making the results publicly verifiable by means of non-interactive zero-knowledge proofs. By leveraging modern proof systems we also achieve significant speedup for proof and verification times compared to the previously proposed approaches as well as compact proof sizes.

cs.CR↗

arXiv2021

Towards a Performance Model for Byzantine Fault Tolerant (Storage) Services

Byzantine fault-tolerant systems have been researched for more than four decades, and although shown possible early, the solutions were impractical for a long time. With PBFT the first practical solution was proposed in 1999 and spawned new research which culminated in novel applications using it today. Although the safety and liveness properties of PBFT-type protocols have been rigorously analyzed, when it comes to practical performance only empirical results - often in artificial settings - are known and imperfections on the communication channels are not specifically considered. In this work we present the first performance model for PBFT specifically considering the impact of unreliable channels and the use of different transport protocols over them. We also did extensive simulations to verify the model and to gain more insight on the impact of deployment parameters on the overall transaction time. We show that the usage of UDP can lead to significant speedup for PBFT protocols compared to TCP when tuned accordingly even over lossy channels. Finally, we compared the simulation to a real implementation and measure the benefits of a developed improvement directly. We found that the impact on the design of the network layer has been overlooked in the past but offers some additional room for improvement when it comes to practical performance. In this work we are focusing on the optimistic case with no node failures, as this is hopefully the most relevant situation.

cs.DC↗