neobytes/doc/tor.md

TOR SUPPORT IN BITCOIN

It is possible to run Bitcoin as a Tor hidden service, and connect to such services.

The following directions assume you have a Tor proxy running on port 9050. Many distributions default to having a SOCKS proxy listening on port 9050, but others may not. In particular, the Tor Browser Bundle defaults to listening on a random port. See Tor Project FAQ:TBBSocksPort for how to properly configure Tor.

1. Run bitcoin behind a Tor proxy

---

The first step is running Bitcoin behind a Tor proxy. This will already make all outgoing connections be anonymized, but more is possible.

-proxy=ip:port  Set the proxy server. If SOCKS5 is selected (default), this proxy
                server will be used to try to reach .onion addresses as well.

-onion=ip:port  Set the proxy server to use for tor hidden services. You do not
                need to set this if it's the same as -proxy. You can use -noonion
                to explicitly disable access to hidden service.

-listen         When using -proxy, listening is disabled by default. If you want
                to run a hidden service (see next section), you'll need to enable
                it explicitly.

-connect=X      When behind a Tor proxy, you can specify .onion addresses instead
-addnode=X      of IP addresses or hostnames in these parameters. It requires
-seednode=X     SOCKS5. In Tor mode, such addresses can also be exchanged with
                other P2P nodes.

In a typical situation, this suffices to run behind a Tor proxy:

./bitcoin -proxy=127.0.0.1:9050

2. Run a bitcoin hidden server

---

If you configure your Tor system accordingly, it is possible to make your node also reachable from the Tor network. Add these lines to your /etc/tor/torrc (or equivalent config file):

HiddenServiceDir /var/lib/tor/bitcoin-service/
HiddenServicePort 8333 127.0.0.1:8333
HiddenServicePort 18333 127.0.0.1:18333

The directory can be different of course, but (both) port numbers should be equal to your bitcoind's P2P listen port (8333 by default).

-externalip=X   You can tell bitcoin about its publicly reachable address using
                this option, and this can be a .onion address. Given the above
                configuration, you can find your onion address in
                /var/lib/tor/bitcoin-service/hostname. Onion addresses are given
                preference for your node to advertize itself with, for connections
                coming from unroutable addresses (such as 127.0.0.1, where the
                Tor proxy typically runs).

-listen         You'll need to enable listening for incoming connections, as this
                is off by default behind a proxy.

-discover       When -externalip is specified, no attempt is made to discover local
                IPv4 or IPv6 addresses. If you want to run a dual stack, reachable
                from both Tor and IPv4 (or IPv6), you'll need to either pass your
                other addresses using -externalip, or explicitly enable -discover.
                Note that both addresses of a dual-stack system may be easily
                linkable using traffic analysis.

In a typical situation, where you're only reachable via Tor, this should suffice:

./bitcoind -proxy=127.0.0.1:9050 -externalip=57qr3yd1nyntf5k.onion -listen

(obviously, replace the Onion address with your own). It should be noted that you still listen on all devices and another node could establish a clearnet connection, when knowing your address. To mitigate this, additionally bind the address of your Tor proxy:

./bitcoind ... -bind=127.0.0.1

If you don't care too much about hiding your node, and want to be reachable on IPv4 as well, use discover instead:

./bitcoind ... -discover

and open port 8333 on your firewall (or use -upnp).

If you only want to use Tor to reach onion addresses, but not use it as a proxy for normal IPv4/IPv6 communication, use:

./bitcoin -onion=127.0.0.1:9050 -externalip=57qr3yd1nyntf5k.onion -discover