On Sat, Sep 22, 2007 at 03:51:07PM -0400, Anthony DiPierro wrote: > > If the user started churning through circuits at five times the current > > rate, we may end up forced to move the "10 minute" value back even farther > > to compensate, resulting in even more user connections becoming linkable. > > > Why does new circuit creation use up so much CPU? Are you spawning a > new thread for each circuit, or something? If so, maybe there's a way > to be more efficient instead?
It's because of the crypto. Each server on the path needs to do two public key operations for each new circuit -- one to ensure perfect forward secrecy, and the other for authentication. See e.g. https://tor.eff.org/svn/trunk/doc/design-paper/tor-design.html#subsec:circuits or Section 5.1 of https://tor.eff.org/svn/trunk/doc/spec/tor-spec.txt If you still want to read after those, also see http://freehaven.net/anonbib/#overlier-pet2007 and http://freehaven.net/anonbib/full/date.html#kate-pet2007 --Roger
