Where's Alice?

Abstract

In this short paper, we revisit the celebrated Naor?Naor?Reingold (NNR) protocol for ?[convincing] people you know where Waldo is without revealing information about his location?. We observe that, despite oft-repeated claims to the contrary, the NNR protocol is neither zero-knowledge nor a proof of knowledge. We propose a slightly more elaborate version that is both of these things?but still eminently suitable for children?s playdates (and the classroom).