Bitcoin Address

This is a demo repository that presents implementations in Elixir for
generating a Bitcoin address from a private key.

The following implementations are currently supplied:

• Pure Elixir, using bitcoin-elixir for converting public keys into
  Bitcoin addresses.
• Python, using Export to interface with pybitcointools libraries.
• C++, using Cure to interface with libbitcoin libraries.

Installation

The following instructions will focus on installation for MacOS.

Dependencies

Use Homebrew to install Bitcoin packages needed for non-Elixir code:

• libbitcoin: Various Bitcoin-related helper functions.
• gcc: Needed to compile the C++ files into the priv/ directory
• python: Needed to run Python files in the priv/ directory.
  Install either via brew or via a version control manager like asdf.

Install brew packages (includes the C++ libraries):

brew install bitcoin gcc [python]

Since Pybitcointools is not maintained any more, in order to get things working,
the library has to be installed using pip at the specific commit hash before
the entire repository was deleted:

pip install git+https://github.com/vbuterin/pybitcointools.git@aeb0a2bbb8bbfe421432d776c649650eaeb882a5

Repository

git clone git@github.com:paulfioravanti/bitcoin_address.git
cd bitcoin_address
mix deps.get

Run the Code

Open up an iex terminal and confirm that each implementation gives you the
same result for a given private key:

iex -S mix
iex(1)> private_key = BitcoinAddress.Secp256k1.generate_private_key()
"66f08a4c251147c0f9f39881e4b8290bc60f398aa1c5335f60359d1d90d123c7"
iex(2)> BitcoinAddress.Elixir.generate(private_key)
Private key: "66f08a4c251147c0f9f39881e4b8290bc60f398aa1c5335f60359d1d90d123c7"
Public key: "0266321e7bcdf4b912104401202d674954a64679eec11f18e766199f4744bc0b51"
Bitcoin address: "1FXpStf9Ma2Wxe6QrwjZCHnG9SvwGCEPJf"
"1FXpStf9Ma2Wxe6QrwjZCHnG9SvwGCEPJf"
iex(3)> BitcoinAddress.Python.generate(private_key)
Private key: "66f08a4c251147c0f9f39881e4b8290bc60f398aa1c5335f60359d1d90d123c7"
Public key: "0266321e7bcdf4b912104401202d674954a64679eec11f18e766199f4744bc0b51"
Bitcoin address: "1FXpStf9Ma2Wxe6QrwjZCHnG9SvwGCEPJf"
"1FXpStf9Ma2Wxe6QrwjZCHnG9SvwGCEPJf"
iex(4)> BitcoinAddress.CPlusPlus.generate(private_key)
Private key: "66f08a4c251147c0f9f39881e4b8290bc60f398aa1c5335f60359d1d90d123c7"
Public key: "0266321e7bcdf4b912104401202d674954a64679eec11f18e766199f4744bc0b51"
Bitcoin address: "1FXpStf9Ma2Wxe6QrwjZCHnG9SvwGCEPJf"
"1FXpStf9Ma2Wxe6QrwjZCHnG9SvwGCEPJf"

For each of the different implementations, rather than create your own private
key manually, you can:

• get the function to generate one for you, or
• use a static pre-generated one as a :test

iex(5)> BitcoinAddress.Elixir.generate()
Private key: "d11d04584bd82b6a7b290b86b88070391149ab44a446a49b92c0ac40b80ab430"
Public key: "027af4aef662ba5aa1fc100105db5160e70b8d05ffd9eda96b3e308a98e0d9c6ce"
Bitcoin address: "1C14kvagjp1Rvu1PAN5uxija6cR128yEaG"
"1C14kvagjp1Rvu1PAN5uxija6cR128yEaG"
iex(6)> BitcoinAddress.Elixir.generate(:test)
Private key: "038109007313a5807b2eccc082c8c3fbb988a973cacf1a7df9ce725c31b14776"
Public key: "0202a406624211f2abbdc68da3df929f938c3399dd79fac1b51b0e4ad1d26a47aa"
Bitcoin address: "1PRTTaJesdNovgne6Ehcdu1fpEdX7913CK"
"1PRTTaJesdNovgne6Ehcdu1fpEdX7913CK"

Tests

Each of the implementations has a sanity test check to just make sure it works,
and continues to work as expected.

Run the test suite

mix test

mix test.watch is included in this project, and hence all the tests,
as well as Credo and Dogma checks, can be continuously run when file
changes are made:

mix test.watch

Generate Documentation

This project uses ExDoc to generate HTML documentation.
Generate the documentation with the following command:

mix docs

Helpful Resources

Code

• Mastering Bitcoin repo: Code samples from
  Mastering Bitcoin 2nd Edition that I ported over to Elixir, using similar
  techniques as this repo.

Blog Posts

• Using Python's Bitcoin libraries in Elixir
• Using C++ Bitcoin libraries in Elixir

These are blog posts I wrote documenting the things I needed to do to get
Elixir communicating with Python and C++.

Presentation

I did a talk about this project at the Elixir Sydney Meetup on
7 Feb 2018 (slide deck).

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