some cleanups, and cite SS03

% XXX Cite SS03

\documentclass[times,10pt,twocolumn]{article}

\usepackage{latex8}

or rotated its keys.  In Tor, clients negotiate {\it rendezvous points}

to connect with hidden servers; reply onions are no longer required.

Unlike Freedom~\cite{freedom2-arch}, Tor does not require OS kernel

patches or network stack support.  This prevents us from anonymizing

non-TCP protocols, but has greatly helped our portability and

deployability.

Unlike Freedom~\cite{freedom2-arch}, Tor does not anonymize

non-TCP protocols---not requiring patches (or built-in support) in an

operating system's network stack has been valuable to Tor's

portability and deployability.

%Unlike Freedom~\cite{freedom2-arch}, Tor only anonymizes

%TCP-based protocols---not requiring patches (or built-in support) in an

%operating system's network stack has been valuable to Tor's

%portability and deployability.

We have implemented all of the above features except rendezvous

points. Our source code is

We have deployed a wide-area alpha network

to test the design, to get more experience with usability

and users, and to provide a research platform for experimentation.

As of this writing, the network stands at sixteen nodes in thirteen

As of this writing, the network stands at eighteen nodes in thirteen

distinct administrative domains on two continents.

We review previous work in Section~\ref{sec:related-work}, describe

involve many packets that must be delivered quickly, it is

difficult for them to prevent an attacker who can eavesdrop both ends of the

communication from correlating the timing and volume

of traffic entering the anonymity network with traffic leaving it.  These

of traffic entering the anonymity network with traffic leaving it \cite{SS03}.

These

protocols are similarly vulnerable to an active adversary who introduces

timing patterns into traffic entering the network and looks

for correlated patterns among exiting traffic.

\Section{Early experiences: Tor in the Wild}

\label{sec:in-the-wild}

As of mid-January 2004, the Tor network consists of 17 nodes

(15 in the US, 2 in Europe), and more are joining each week as the code

As of mid-January 2004, the Tor network consists of 18 nodes

(16 in the US, 2 in Europe), and more are joining each week as the code

matures.\footnote{For comparison, the current remailer network

has about 30 reliable nodes. We haven't asked PlanetLab to provide

Tor nodes, since their AUP wouldn't allow exit nodes (see