arXiv:2610.27441v1 Announce Type: new Abstract: In industries like semi-conductors and aerospace, it is common for the design company to contract out part of the testing process to a Testing-as-a-Service (TaaS) company. In such a setup, both parties want to keep their intellectual property private (i.e. unknown to the other party): namely the design and its output traces for the designer, and the detailed correctness specifications for the tester. We demonstrate a practical way for conducting provably private TaaS using a cryptographically secure multi-party computation protocol. We do so for the common setup where the specification is in Signal Temporal Logic, and testing is done using robustness-guided falsification. Our implementation carefully separates the steps of falsification, and manages to be $\textit{maximally secure}$, in the sense that the parties learn the absolutely minimum necessary for falsification. For up to a 100-dimensional input search space, the generation of one test takes less than 80 msec, and the overhead of the privacy-preserving protocol is less than 6x. These numbers mean that privacy-preserving TaaS is practical, thus enabling TaaS in security-sensitive industries.