Intro

Notbit is a minimal client for the Bitmessage network. It is designed to work as a daemon with no UI. The idea is that it will store messages in the standard maildir format and accept new messages via a process like sendmail. That way it can be used with any compliant mail program such as Evolution or Mutt.

Notbit is a work in progress and currently has some limitations. It can already send and receive messages to regular addresses but it doesn't yet support channels or broadcasts.

Disclaimer

I am not a cryptography expert and I don't know whether Notbit or the Bitmessage protocol is actually safe for secure communications. I wouldn't recommend using for anything highly sensitive.

Dependencies

Notbit requires a modern Unix such as Linux. It also requires libcrypto with support for elliptic-curve cryptography. Unfortunately if you are building on Fedora you will need to build libcrypto from source because they don't ship ECC due to patent concerns.

Building

First you will need to install the build dependencies for your system. The main one to install is libopenssl-devel to get libcrypto. If you are building from the git repo you will also need the standard autotools such as automake and autoconf.

Now you can run the following commands to build Notbit:

git clone https://github.com/bpeel/notbit.git
cd notbit
./autogen.sh --prefix=$HOME
make
make install

This will install Notbit into your home directory. The executable will be in ~/bin which is typically already in your search path.

Running Notbit

Once notbit is built you can run it by just typing notbit. By default this will output logging messages to stdout. It will immediately try to connect to the network and start downloading messages. If instead you want to run notbit in the background you can type notbit -d which will launch it as a daemon. In that case you can see the logging messages by typing:

tail -f ~/.local/share/notbit/notbit.log

If you want to exit the daemon you can type killall notbit. This will do a graceful shutdown.

Creating an address

Once Notbit is running you can type notbit-keygen to create a new address. The new address will be printed on the standard out. The private keys for the address are saved in notbit's config files so you can immediately start receiving messages to this address. If you want to spend a bit of extra processing time in order to get a shorter address you can also pass the -z option to notbit-keygen. The -l <label> option can be used to specify a label for the key. There are also other less useful options which can be seen in the help by typing notbit-keygen -h.

Importing addresses

If you already have some addresses from the official PyBitmessage client you can import these directly by copying over the keys.dat. file. To do this, make sure Notbit is not currently running and then type:

cp ~/.config/PyBitmessage/keys.dat ~/.local/share/notbit/

Reading messages

If Notbit receives a message for one of the addresses in keys.dat it will write it out in maildir format. maildir is a standard format which can be read by most mail programs such as mutt. By default the maildir will be ~/.maildir. You can change this with the -m option.

Sending messages

You can send messages by running the notbit-sendmail command. This takes a message formatted as RFC5322 mail message on the standard input. This is the same format as used by sendmail so you can use notbit-sendmail as a drop-in replacement to send messages from almost any mail client. The addresses used can not be real email addresses but instead they must be of the form <bitmessage-address>@bitmessage. For example, you could type the following to create a new address and use it to send a message to the echo server to test it:

echo -e "From: "`notbit-keygen`"@bitmessage\\n"\
"To: BM-orkCbppXWSqPpAxnz6jnfTZ2djb5pJKDb@bitmessage\\n"\
"\\n"\
"Hello from Notbit\\x21" | notbit-sendmail

Note that any messages you send must have the content type set to text/plain and can't contain any attachments. This means that HTML messages won't work. They must use either the us-ascii encoding or UTF-8.

Integrating with a mail client

Notbit can be used with any mail client that supports maildir and local delivery via sendmail. For example, to configure an account with Evolution you would do the following:

• Click the ‘New’ → ‘Mail account’ menu
• In the email address field, type an address generated using notbit-keygen. Don't forget to add ‘@bitmessage’ on the end to make it look like an email address.
• For the ‘server type’ select ‘Maildir-format mail directories’
• Select the .maildir folder as the ‘Mail Directory’. Note that you may have to right-click and select ‘show hidden files’ in order to see this. Alternatively you can make Notbit use a different directory by passing the -m option when you run it.
• Under the ‘Sending E-mail’ settings, select ‘Sendmail’ as the server type.
• Tick the ‘Use custom binary’ option and type /home/<you>/bin/notbit-sendmail as the binary, where is your username.
• The rest of the settings can be left at the default.

You should now be able to send a Bitmessage using Evolution. Just remember to add ‘@bitmessage’ to any address you send to and make sure you select ‘Plain text’ as the format (HTML emails and attachments aren't supported by Bitmessage). Don't worry if your name appears in the From box next to your address as this information won't be sent over Bitmessage. Only the subject and the body of the mail are sent.

Using with Tor

You can tell Notbit to connect via a Tor server running on the local machine by passing the -T option. This will also disable the DNS bootstrapping and won't open any listening ports. The -T option is a convienence option which is equivalent to -r 127.0.0.1:9050 -B -i. The -B option disables DNS bootstrapping and the -i argument disables listening ports. If you are running the Tor server on a different address you can specify these three options explicitly using the correct address.

Options

Notbit has some command line options to configure it. These are listed below:

 -h                    Show a help message
 -p <port>             Specifies a port to listen on.
                       Equivalent to -a [::]:port.
 -a <address[:port]>   Add an address to listen on. Can be
                       specified multiple times. Defaults to
                       [::] to listen on port 8444
 -P <address[:port]>   Add to the list of initial peers that
                       might be connected to.
 -e                    Only connect to peers specified by -P
 -l <file>             Specify the pathname for the log file
                       Defaults to stdout or
                       $XDG_DATA_HOME/notbit/notbit.log if -d is used
 -d                    Fork and detach from terminal after
                       creating listen socket. (Daemonize)
 -T                    Use a local Tor server. Equivalent to
                       -r 127.0.0.1:9050 -B -i
 -r <address[:port]>   Specify a SOCKSv5 proxy to use for
                       outgoing connections.
 -u <user>             Specify a user to run as. Used to drop
                       privileges.
 -g <group>            Specify a group to run as.
 -D <datadir>          Specify an alternate location for the
                       object store. Defaults to $XDG_DATA_HOME/notbit
 -m <maildir>          Specify the maildir to save messages to.
                       Defaults to $HOME/.maildir
 -L                    Allow private addresses for peers
 -b                    Don't bootstrap with default peers.
                       Useful for creating your own private
                       network. Note that this requires all
                       nodes to be trustworthy
 -B                    Don't bootstrap with DNS. Useful if
                       running under Tor.
 -i                    Don't listen for incoming connections.