"What makes Tor different from the usual thesaurus-full of government projects is that Tor is essentially a very elaborate math trick, using layers of math puzzles to create a network-within-the-network. That math is being implemented in front of a global audience of millions of sophisticated watchers. It is likely the most examined codebase in the world. It has been subjected to multiple public audits. The math, well known and widely standardized, will work for everyone, or it will not, whoever pays the bills."

from https://pando.com/2014/12/09/clearing-the-air-around-tor/