Bitmsg is a utility to publish and receive encrypted messages via the Bitcoin network. No proof of work is necessary due to the fact that publishing messages requires payment to the network, i.e., sacrifice.

Bitmsg is only tested on Windows using Python 3.3 32-bit. You need A copy of libeay32.dll (obtained from the OpenSSL packages for Windows or built yourself).

The code has very few dependencies so should be trivial to port to Linux, MacOS, etc.

There are two programs of note: buildmessage.py and msgwatch.py. The rest of the files in this archive are support modules for Bitcoin and related code.

Run "python buildmessage.py" and provide the information asked of you.

The program msgwatch.py is used to connect to the Bitcoin network and monitor transactions that are floating around. The arguments to pass to msgwatch.py will help determine which messages you are able to receive.

• -p : This will listen on the network for unencrypted, public messages.
• -w key : This will listen on the network for encrypted (RC4) messages. You can specify '-w' multiple times.
• -a key : This will listen on the network for encrypted (AES-128) messages. You can specify '-a' multiple times. AES-128 keys must be 16 bytes in length.
• -b key : This will listen on the network for encrypted (AES-256) messages. You can specify '-b' multiple times. AES-256 keys must be 32 bytes in length.
• -r file.key : This will listen on the network for encrypted (RSA + AES-256) messages. You can specify '-r' multiple times. RSA key files can be of any size.

For example, "python msgwatch.py -p -w general -a mysecretkeyhello -r mykey.key" will listen for messages that are encrypted with RC4 using the phrase "general", with AES-128 using mysecretkeyhello, or messages delivered to the RSA public key associated with file.key.

Some important tasks left to be done include:

• Proper internet message formatting
• Parsing blocks and blockchain for transactions that were missed while offline
  • This requires keeping track of the where you are at in the blockchain download
• Relaying blocks and transactions
• More configurable things such as the amount to sacrifice
• Zero-bitcoin outputs (but this creates non-standard txns)
• I would like all coins to be sacrificed (except change) to miners instead of throwing away a Satoshi for each output
• Obscure the fact the transactions are messages by changing the trigger addressed based on the encryption key as well as use less predictable amounts for the outputs
• ECC encryption (using Bitcoin pub/priv keypairs)
• Change to the m-of-n multisig embedding by making each of the pubkeys valid secp256k1 keys (use arbitrary data for the X coord, compute the Y coord)
• A GUI to collect and save messages in a local db (in progress)