tor/doc/tor.1.in

.TH TOR 1 "May 2005" "TOR"
.SH NAME
tor \- The second-generation onion router
.SH SYNOPSIS
.B tor
[\fIOPTION value\fR]...
.SH DESCRIPTION
.I tor
is a connection-oriented anonymizing communication
service. Users choose a source-routed path through a set of nodes, and
negotiate a "virtual circuit" through the network, in which each node
knows its predecessor and successor, but no others. Traffic flowing down
the circuit is unwrapped by a symmetric key at each node, which reveals
the downstream node.
.PP
Basically \fItor\fR provides a distributed network of servers ("onion
routers"). Users bounce their TCP streams -- web traffic, ftp, ssh, etc --
around the routers, and recipients, observers, and even the routers
themselves have difficulty tracking the source of the stream.
.SH OPTIONS
\fB-h, -help\fP
Display a short help message and exit.
.TP
\fB-f \fR\fIFILE\fP
FILE contains further "option value" pairs. (Default: @CONFDIR@/torrc)
.TP
Other options can be specified either on the command-line (\fI--option
value\fR), or in the configuration file (\fIoption value\fR).
Options are case-insensitive.
.TP
\fBBandwidthRate \fR\fIN\fR \fBbytes\fR|\fBKB\fR|\fBMB\fR|\fBGB\fR|\fBTB\fP
A token bucket limits the average incoming bandwidth on this node to
the specified number of bytes per second. (Default: 2 MB)
.TP
\fBBandwidthBurst \fR\fIN\fR \fBbytes\fR|\fBKB\fR|\fBMB\fR|\fBGB\fR|\fBTB\fP
Limit the maximum token bucket size (also known as the burst) to the given number of bytes. (Default: 5 MB)
.TP
\fBMaxAdvertisedBandwidth \fR\fIN\fR \fBbytes\fR|\fBKB\fR|\fBMB\fR|\fBGB\fR|\fBTB\fP
If set, we will not advertise more than this amount of bandwidth for our
BandwidthRate. Server operators who want to reduce the number of clients
who ask to build circuits through them (since this is proportional to
advertised bandwidth rate) can thus reduce the CPU demands on their
server without impacting network performance.
.TP
\fBControlPort \fR\fIPort\fP
If set, Tor will accept connections from the same machine (localhost only) on
this port, and allow those connections to control the Tor process using the
Tor Control Protocol (described in control-spec.txt).  Note: unless you also
specify one of \fBHashedControlPassword\fP or \fBCookieAuthentication\fP,
setting this option will cause Tor to allow any process on the local host to
control it.
.TP
\fBHashedControlPassword \fR\fIhashed_password\fP
Don't allow any connections on the control port except when the other process
knows the password whose one-way hash is \fIhashed_password\fP.  You can
compute the hash of a password by running "tor --hash-password
\fIpassword\fP".
.TP
\fBCookieAuthentication \fR\fB0\fR|\fB1\fP
If this option is set to 1, don't allow any connections on the control port
except when the connecting process knows the contents of a file named
"control_auth_cookie", which Tor will create in its data directory.  This
authentication methods should only be used on systems with good filesystem
security. (Default: 0)
.TP
\fBDataDirectory \fR\fIDIR\fP
Store working data in DIR (Default: @LOCALSTATEDIR@/lib/tor)
.TP
\fBDirFetchPeriod \fR\fIN\fR \fBseconds\fR|\fBminutes\fR|\fBhours\fR|\fBdays\fR|\fBweeks\fP
Every time the specified period elapses, Tor downloads a directory.
A directory contains a signed list of all known servers as well as
their current liveness status. A value of "0 seconds" tells Tor to choose an
appropriate default. (Default: 1 hour for clients, 20 minutes for servers)
.TP
\fBDirServer \fR\fIaddress:port fingerprint\fP
Use a nonstandard authoritative directory server at the provided
address and port, with the specified key fingerprint.  This option can
be repeated many times, for multiple authoritative directory
servers. If no \fBdirserver\fP line is given, Tor will use the default
directory servers: moria1, moria2, and tor26.
.TP
\fBGroup \fR\fIGID\fP
On startup, setgid to this user.
.TP
\fBHttpProxy\fR \fIhost\fR[:\fIport\fR]\fP
Tor will make all its directory requests through this host:port
(or host:80 if port is not specified),
rather than connecting directly to any directory servers.
.TP
\fBHttpProxyAuthenticator\fR \fIusername:password\fP
If defined, Tor will use this username:password for Basic Http proxy
authentication, as in RFC 2617. This is currently the only form of
Http proxy authentication that Tor supports; feel free to submit a
patch if you want it to support others.
.TP
\fBHttpsProxy\fR \fIhost\fR[:\fIport\fR]\fP
Tor will make all its OR (SSL) connections through this host:port
(or host:443 if port is not specified), via HTTP CONNECT rather than
connecting directly to servers.  You may want to set \fBFascistFirewall\fR
to restrict the set of ports you might try to connect to, if your Https
proxy only allows connecting to certain ports.
.TP
\fBHttpsProxyAuthenticator\fR \fIusername:password\fP
If defined, Tor will use this username:password for Basic Https proxy
authentication, as in RFC 2617. This is currently the only form of
Https proxy authentication that Tor supports; feel free to submit a
patch if you want it to support others.
.TP
\fBKeepalivePeriod \fR\fINUM\fP
To keep firewalls from expiring connections, send a padding keepalive
cell every NUM seconds on open connections that are in use. If the
connection has no open circuits, it will instead be closed after NUM
seconds of idleness. (Default: 5 minutes)
.TP
\fBLog \fR\fIminSeverity\fR[-\fImaxSeverity\fR] \fBstderr\fR|\fBstdout\fR|\fBsyslog\fR\fP
Send all messages between \fIminSeverity\fR and \fImaxSeverity\fR to
the standard output stream, the standard error stream, or to the system
log. (The "syslog" value is only supported on Unix.)  Recognized
severity levels are debug, info, notice, warn, and err.  If only one
severity level is given, all messages of that level or higher will be
sent to the listed destination.
.TP
\fBLog \fR\fIminSeverity\fR[-\fImaxSeverity\fR] \fBfile\fR \fIFILENAME\fP
As above, but send log messages to the listed filename.  The "Log"
option may appear more than once in a configuration file.  Messages
are sent to all the logs that match their severity level.
.TP
\fBMaxConn \fR\fINUM\fP
Maximum number of simultaneous sockets allowed.  You probably don't need
to adjust this. (Default: 1024)
.TP
\fBOutboundBindAddress \fR\fIIP\fP
Make all outbound connections originate from the IP address specified.  This
is only useful when you have multiple network interfaces, and you want all
of Tor's outgoing connections to use a single one.
.TP
\fBPIDFile \fR\fIFILE\fP
On startup, write our PID to FILE. On clean shutdown, remove FILE.
.TP
\fBRunAsDaemon \fR\fB0\fR|\fB1\fR\fP
If 1, Tor forks and daemonizes to the background. (Default: 0)
.TP
\fBSafeLogging \fR\fB0\fR|\fB1\fP
If 1, Tor replaces potentially sensitive strings in the logs
(e.g. addresses) with the string [scrubbed]. This way logs can still be
useful, but they don't leave behind personally identifying information
about what sites a user might have visited. (Default: 1)
.TP
\fBStatusFetchPeriod \fR\fIN\fR \fBseconds\fR|\fBminutes\fR|\fBhours\fR|\fBdays\fR|\fBweeks\fP
Every time the specified period elapses, Tor downloads signed status
information about the current state of known servers.  A value of
"0 seconds" tells Tor to choose an appropriate default. (Default: 30
minutes for clients, 15 minutes for servers)
.TP
\fBUser \fR\fIUID\fP
On startup, setuid to this user.

.SH CLIENT OPTIONS
.PP
The following options are useful only for clients (that is, if \fBSOCKSPort\fP is non-zero):
.TP
\fBAllowUnverifiedNodes\fR \fBentry\fR|\fBexit\fR|\fBmiddle\fR|\fBintroduction\fR|\fBrendezvous\fR|...\fP
Where on our circuits should we allow Tor servers that the directory
servers haven't authenticated as "verified"?  (Default: middle,rendezvous)
.TP
\fBClientOnly \fR\fB0\fR|\fB1\fR\fP
If set to 1, Tor will under no circumstances run as a server. The default
is to run as a client unless ORPort is configured.  (Usually,
you don't need to set this; Tor is pretty smart at figuring out whether
you are reliable and high-bandwidth enough to be a useful server.)

This option will likely be deprecated in the future; see the NoPublish
option below. (Default: 0)
.TP
\fBEntryNodes \fR\fInickname\fR,\fInickname\fR,\fI...\fP
A list of preferred nodes to use for the first hop in the circuit, if possible.
.TP
\fBExitNodes \fR\fInickname\fR,\fInickname\fR,\fI...\fP
A list of preferred nodes to use for the last hop in the circuit, if possible.
.TP
\fBExcludeNodes \fR\fInickname\fR,\fInickname\fR,\fI...\fP
A list of nodes to never use when building a circuit.
.TP
\fBStrictExitNodes \fR\fB0\fR|\fB1\fR\fP
If 1, Tor will never use any nodes besides those listed in "exitnodes" for
the last hop of a circuit.
.TP
\fBStrictEntryNodes \fR\fB0\fR|\fB1\fR\fP
If 1, Tor will never use any nodes besides those listed in "entrynodes" for
the first hop of a circuit.
.TP
\fBFascistFirewall \fR\fB0\fR|\fB1\fR\fP
If 1, Tor will only create outgoing connections to ORs running on ports that
your firewall allows (defaults to 80 and 443; see \fBFirewallPorts\fR).  This will
allow you to run Tor as a client behind a firewall with restrictive policies,
but will not allow you to run as a server behind such a firewall.
.TP
\fBFirewallPorts \fR\fIPORTS\fP
A list of ports that your firewall allows you to connect to.  Only used when
\fBFascistFirewall\fR is set. (Default: 80, 443)
.TP
\fBLongLivedPorts \fR\fIPORTS\fP
A list of ports for services that tend to have long-running connections
(e.g. chat and interactive shells). Circuits for streams that use these
ports will contain only high-uptime nodes, to reduce the chance that a
node will go down before the stream is finished. (Default: 21, 22, 706, 1863, 5050, 
5190, 5222, 5223, 6667, 8300, 8888)
.TP
\fBMapAddress\fR \fIaddress\fR \fInewaddress\fR
When a request for address arrives to Tor, it will rewrite it to newaddress before 
processing it. For example, if you always want connections to www.indymedia.org to 
exit via \fItorserver\fR (where \fItorserver\fR is the nickname of the server), 
use "MapAddress www.indymedia.org www.indymedia.org.torserver.exit".
.TP
\fBNewCircuitPeriod \fR\fINUM\fP
Every NUM seconds consider whether to build a new circuit. (Default: 30 seconds)
.TP
\fBMaxCircuitDirtiness \fR\fINUM\fP
Feel free to reuse a circuit that was first used at most NUM seconds
ago, but never attach a new stream to a circuit that is too old. (Default: 10 minutes)
.TP
\fBNodeFamily \fR\fInickname\fR,\fInickname\fR,\fI...\fP
The named Tor servers constitute a "family" of similar or co-administered
servers, so never use any two of them in the same circuit. Defining a
NodeFamily is only needed when a server doesn't list the family itself
(with MyFamily). This option can be used multiple times.
.TP
.\" \fBPathlenCoinWeight \fR\fI0.0-1.0\fP
.\" Paths are 3 hops plus a geometric distribution centered around this coinweight. 
.\" Must be >=0.0 and <1.0. (Default: 0.3) NOT USED CURRENTLY
.\" .TP
\fBRendNodes \fR\fInickname\fR,\fInickname\fR,\fI...\fP
A list of preferred nodes to use for the rendezvous point, if possible.
.TP
\fBRendExcludeNodes \fR\fInickname\fR,\fInickname\fR,\fI...\fP
A list of nodes to never use when choosing a rendezvous point.
.TP
\fBSOCKSPort \fR\fIPORT\fP
Advertise this port to listen for connections from SOCKS-speaking
applications.  Set this to 0 if you don't want to allow application
connections. (Default: 9050)
.TP
\fBSOCKSBindAddress \fR\fIIP\fR[:\fIPORT\fR]\fP
Bind to this address to listen for connections from SOCKS-speaking
applications. (Default: 127.0.0.1) You can also specify a port
(e.g. 192.168.0.1:9100). This directive can be specified multiple times
to bind to multiple addresses/ports.
.TP
\fBSOCKSPolicy \fR\fIpolicy\fR,\fIpolicy\fR,\fI...\fP
Set an entrance policy for this server, to limit who can connect to the SOCKS ports. 
The policies have the same form as exit policies below.
.TP
\fBTrackHostExits \fR\fIhost\fR,\fI.domain\fR,\fI...\fR\fP
For each value in the comma separated list, Tor will track recent connections
to hosts that match this value and attempt to
reuse the same exit node for each. If the value is prepended with a '.', it is
treated as matching an entire domain. If one of the values is just a '.', it
means match everything. This option is useful if you frequently connect to
sites that will expire all your authentication cookies (ie log you out) if
your IP address changes. Note that this option does have the disadvantage of
making it more clear that a given history is
associated with a single user. However, most people who would wish to observe
this will observe it through cookies or other protocol-specific means anyhow.
.TP
\fBTrackHostExitsExpire \fR\fINUM\fP
Since exit servers go up and down, it is desirable to expire the association
between host and exit server after NUM seconds of inactivity. The default
is 1800 seconds (30 minutes).

.SH SERVER OPTIONS
.PP
The following options are useful only for servers (that is, if \fBORPort\fP is non-zero):
.TP
\fBAddress \fR\fIaddress\fP
The IP or fqdn of this server (e.g. moria.mit.edu). You can leave this
unset, and Tor will guess your IP.
.TP
\fBContactInfo \fR\fIemail_address\fP
Administrative contact information for server.
.TP
\fBExitPolicy \fR\fIpolicy\fR,\fIpolicy\fR,\fI...\fP
Set an exit policy for this server. Each policy is of the form
"\fBaccept\fP|\fBreject\fP \fIADDR\fP[\fB/\fP\fIMASK\fP]\fB[:\fP\fIPORT\fP]".
If \fB/\fP\fIMASK\fP is omitted then this policy just applies to the host
given.  Instead of giving a host or network you can also use "\fB*\fP" to
denote the universe (0.0.0.0/0).  \fIPORT\fP can be a single port number,
an interval of ports "\fIFROM_PORT\fP\fB-\fP\fITO_PORT\fP", or "\fB*\fP".
If \fiPORT\fP is omitted, that means "\fB*\fP".

For example, "reject 127.0.0.1:*,reject 192.168.1.0/24:*,accept *:*" would
reject any traffic destined for localhost and any 192.168.1.* address, but
accept anything else.

This directive can be specified multiple times so you don't have to put
it all on one line.

See RFC 3330 for more details about internal and reserved IP address
space. Policies are considered first to last, and the first match wins. If
you want to _replace_ the default exit policy, end your exit policy with
either a reject *:* or an accept *:*. Otherwise, you're _augmenting_
(prepending to) the default exit policy. The default exit policy is:
.PD 0
.RS 12
.IP "reject 0.0.0.0/8" 0
.IP "reject 169.254.0.0/16" 4
.IP "reject 127.0.0.0/8"
.IP "reject 192.168.0.0/16"
.IP "reject 10.0.0.0/8"
.IP "reject 172.16.0.0/12"
.IP "reject *:25"
.IP "reject *:119"
.IP "reject *:135-139"
.IP "reject *:445"
.IP "reject *:1214"
.IP "reject *:4661-4666"
.IP "reject *:6346-6429"
.IP "reject *:6699"
.IP "reject *:6881-6999"
.IP "accept *:*"
.RE
.PD
.TP
\fBMaxOnionsPending \fR\fINUM\fP
If you have more than this number of onionskins queued for decrypt, reject new ones. (Default: 100)
.TP
\fBMyFamily \fR\fInickname\fR,\fInickname\fR,\fI...\fP
Declare that this Tor server is controlled or administered by a group
or organization identical or similar to that of the other named servers.
When two servers both declare that they are in the same 'family', Tor clients
will not use them in the same circuit.  (Each server only needs to list the
other servers in its family; it doesn't need to list itself, but it won't hurt.)
.TP
\fBNickname \fR\fIname\fP
Set the server's nickname to 'name'.
.TP
\fBNoPublish \fR\fB0\fR|\fB1\fR\fP
If you set NoPublish 1, Tor will act as a server if you have an ORPort
defined, but it will not publish its descriptor to the dirservers. This
option is useful if you're testing out your server, or if you're using
alternate dirservers (e.g. for other Tor networks such as Blossom).
(Default: 0)
.TP
\fBNumCPUs \fR\fInum\fP
How many processes to use at once for decrypting onionskins. (Default: 1)
.TP
\fBORPort \fR\fIPORT\fP
Advertise this port to listen for connections from Tor clients and servers.
.TP
\fBORBindAddress \fR\fIIP\fR[:\fIPORT\fR]\fP
Bind to this IP address to listen for connections from Tor clients and
servers. If you specify a port, bind to this port rather than the one
specified in ORPort. (Default: 0.0.0.0)
.TP
\fBRedirectExit \fR\fIpattern target\fP
Whenever an outgoing connection tries to connect to one of a given set
of addresses, connect to \fItarget\fP (an \fIaddress:port\fP pair) instead.
The address
pattern is given in the same format as for an exit policy.  The
address translation applies after exit policies are applied.  Multiple
\fBRedirectExit\fP options can be used: once any one has matched
successfully, no subsequent rules are considered.  You can specify that no
redirection is to be performed on a given set of addresses by using the
special target string "pass", which prevents subsequent rules from being
considered.
.TP
\fBShutdownWaitLength\fR\fINUM\fP
When we get a SIGINT and we're a server, we begin shutting down: we close
listeners and start refusing new circuits. After \fBNUM\fP seconds,
we exit. If we get a second SIGINT, we exit immediately.  (Default:
30 seconds)
.TP
\fBDirPostPeriod \fR\fIN\fR \fBseconds\fR|\fBminutes\fR|\fBhours\fR|\fBdays\fR|\fBweeks\fP
Every time the specified period elapses, Tor uploads its server
descriptors to the directory servers.  This information is also
uploaded whenever it changes.  (Default: 20 minutes)
.TP
\fBAccountingMax \fR\fIN\fR \fBbytes\fR|\fBKB\fR|\fBMB\fR|\fBGB\fR|\fBTB\fP
Never send more than the specified number of bytes in a given
accounting period, or receive more than that number in the period.
For example, with AccountingMax set to 1 GB, a server could send 900 MB
and receive 800 MB and continue running. It will only hibernate once one
of the two reaches 1 GB.
When the number of bytes is exhausted, Tor will hibernate until some
time in the next accounting period.  To prevent all servers from
waking at the same time, Tor will also wait until a random point in
each period before waking up.  If you have bandwidth cost issues,
enabling hibernation is preferable to setting a low bandwidth, since it
provides users with a collection of fast servers that are up some of
the time, which is more useful than a set of slow servers that are
always "available".
.TP
\fBAccountingStart \fR\fBday\fR|\fBweek\fR|\fBmonth\fR [\fIday\fR] \fIHH:MM\fR\fP
Specify how long accounting periods last.  If \fBmonth\fP is given,
each accounting period runs from the time \fIHH:MM\fR on the
\fIday\fRth day of one month to the same day and time of the next.
(The day must be between 1 and 28.)  If \fBweek\fP is given, each
accounting period runs from the time \fIHH:MM\fR of the \fIday\fRth
day of one week to the same day and time of the next week, with Monday
as day 1 and Sunday as day 7.  If \fBday\fR is given, each accounting
period runs from the time \fIHH:MM\fR each day to the same time on the
next day.  All times are local, and given in 24-hour time.  (Defaults to
"month 1 0:00".)

.SH DIRECTORY SERVER OPTIONS
.PP
The following options are useful only for directory servers (that is, if \fBDirPort\fP is non-zero):
.TP
\fBAuthoritativeDirectory \fR\fB0\fR|\fB1\fR\fP
When this option is set to 1, Tor operates as an authoritative
directory server.  Instead of caching the directory, it generates its
own list of good servers, signs it, and sends that to the clients.
Unless the clients already have you listed as a trusted directory, you
probably do not want to set this option.  Please coordinate with the other
admins at tor-ops@freehaven.net if you think you should be a directory.
.TP
\fBDirPort \fR\fIPORT\fP
Advertise the directory service on this port.
.TP
\fBDirBindAddress \fR\fIIP\fR[:\fIPORT\fR]\fP
Bind the directory service to this address. If you specify a port, bind
to this port rather than the one specified in DirPort. (Default: 0.0.0.0)
.TP
\fBDirPolicy \fR\fIpolicy\fR,\fIpolicy\fR,\fI...\fP
Set an entrance policy for this server, to limit who can connect to the directory ports. 
The policies have the same form as exit policies above.
.TP
\fBRecommendedVersions \fR\fISTRING\fP
STRING is a command-separated list of Tor versions currently believed
to be safe. The list is included in each directory, and nodes which
pull down the directory learn whether they need to upgrade.  This
option can appear multiple times: the values from multiple lines are
spliced together.
.TP
\fBDirAllowPrivateAddresses \fR\fB0\fR|\fB1\fR\fP
If set to 1, Tor will accept router descriptors with arbitrary "Address"
elements. Otherwise, if the address is not an IP or is a private IP,
it will reject the router descriptor. Defaults to 0.
.TP
\fBRunTesting \fR\fB0\fR|\fB1\fR\fP
If set to 1, Tor tries to build circuits through all of the servers it
knows about, so it can tell which are up and which are down.  This
option is only useful for authoritative directories, so you probably
don't want to use it.

.SH HIDDEN SERVICE OPTIONS
.PP
The following options are used to configure a hidden service.
.TP
\fBHiddenServiceDir \fR\fIDIRECTORY\fP
Store data files for a hidden service in DIRECTORY.  Every hidden
service must have a separate directory.  You may use this option multiple
times to specify multiple services.
.TP
\fBHiddenServicePort \fR\fIVIRTPORT \fR[\fITARGET\fR]\fP
Configure a virtual port VIRTPORT for a hidden service.  You may use this
option multiple times; each time applies to the service using the most recent
hiddenservicedir.  By default, this option maps the virtual port to the
same port on 127.0.0.1.  You may override the target port, address, or both
by specifying a target of addr, port, or addr:port.
.TP
\fBHiddenServiceNodes \fR\fInickname\fR,\fInickname\fR,\fI...\fP
If possible, use the specified nodes as introduction points for the hidden
service. If this is left unset, Tor will be smart and pick some reasonable
ones; most people can leave this unset.
.TP
\fBHiddenServiceExcludeNodes \fR\fInickname\fR,\fInickname\fR,\fI...\fP
Do not use the specified nodes as introduction points for the hidden
service. In normal use there is no reason to set this.
.TP
\fBRendPostPeriod \fR\fIN\fR \fBseconds\fR|\fBminutes\fR|\fBhours\fR|\fBdays\fR|\fBweeks\fP
Every time the specified period elapses, Tor uploads any rendezvous
service descriptors to the directory servers.  This information is also
uploaded whenever it changes.  (Default: 20 minutes)

.\" UNDOCUMENTED
.\" ignoreversion

.SH SIGNALS
Tor catches the following signals:
.TP
\fBSIGTERM\fR
Tor will catch this, clean up and sync to disk if necessary, and exit.
.TP
\fBSIGINT\fR
Tor clients behave as with SIGTERM; but Tor servers will do a controlled
slow shutdown, closing listeners and waiting 30 seconds before exiting.
(The delay can be configured with the ShutdownWaitLength config option.)
.TP
\fBSIGHUP\fR
The signal instructs Tor to reload its configuration (including closing
and reopening logs), fetch a new directory, and kill and restart its
helper processes if applicable.
.TP
\fBSIGUSR1\fR
Log statistics about current connections, past connections, and
throughput.
.TP
\fBSIGUSR2\fR
Switch all logs to loglevel debug. You can go back to the old loglevels
by sending a SIGHUP.
.TP
\fBSIGCHLD\fR
Tor receives this signal when one of its helper processes has exited,
so it can clean up.
.TP
\fBSIGPIPE\fR
Tor catches this signal and ignores it.
.TP
\fBSIGXFSZ\fR
If this signal exists on your platform, Tor catches and ignores it.

.SH FILES
.TP
.I @CONFDIR@/torrc
The configuration file, which contains "option value" pairs.
.TP
.I @LOCALSTATEDIR@/lib/tor/
The tor process stores keys and other data here.

.SH SEE ALSO
.BR privoxy (1),
.BR tsocks (1),
.BR torify (1)

.BR http://tor.eff.org/

.SH BUGS
Plenty, probably. Tor is still in development. Please report them.
.SH AUTHORS
Roger Dingledine <arma@mit.edu>, Nick Mathewson <nickm@alum.mit.edu>.