ExperimenTor: A Testbed for Safe and Realistic Tor Experimentation.

Tor is one of the most widely-used privacy enhancing technologies for achieving online anonymity and resisting censorship. Simultaneously, Tor is also an evolving research network on which investigators perform experiments to improve the network's resilience to attacks and enhance its performance. Existing methods for studying Tor have included analytical modeling, simulations, small-scale network emulations, small-scale PlanetLab deployments, and measurement and analysis of the live Tor network. Despite the growing body of work concerning Tor, there is no widely accepted methodology for conducting Tor research in a manner that preserves realism while protecting live users' privacy. In an effort to propose a standard, rigorous experimental framework for conducting Tor research in a way that ensures safety and realism, we present the design of ExperimenTor, a large-scale Tor network emulation toolkit and testbed. We also report our early experiences with prototype testbeds currently deployed at four research institutions.