sipa · aesedepece · Sep 12, 2017
diff --git a/ref/elixir/.gitignore b/ref/elixir/.gitignore
@@ -0,0 +1,17 @@
+# The directory Mix will write compiled artifacts to.
+/_build
+
+# If you run "mix test --cover", coverage assets end up here.
+/cover
+
+# The directory Mix downloads your dependencies sources to.
+/deps
+
+# Where 3rd-party dependencies like ExDoc output generated docs.
+/doc
+
+# If the VM crashes, it generates a dump, let's ignore it too.
+erl_crash.dump
+
+# Also ignore archive artifacts (built via "mix archive.build").
+*.ez
diff --git a/ref/elixir/README.md b/ref/elixir/README.md
@@ -0,0 +1,91 @@
+# BIP-0173 [![Build Status](https://travis-ci.org/stampery/elixir-bip0173.svg?branch=master)](https://travis-ci.org/stampery/elixir-bip0173)
+
+**Elixir implementation of Bitcoin's address format for native SegWit outputs.**
+
+Upstream GitHub repository: [stampery/elixir-bip0173](https://github.com/stampery/elixir-bip0173)
+
+## About BIP-0173 and Bech32
+
+[BIP-0173](https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki) proposes a checksummed base32 format, "Bech32", and a standard for native segregated witness output addresses using it.
+
+You can find more information in [the original proposal](https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki) by [@sipa](https://github.com/sipa) and [@gmaxwell](https://github.com/gmaxwell).
+
+## Installation
+
+  1. Add `bip0173` to your list of dependencies in `mix.exs`:
+
+```elixir
+  def deps do
+    [{:bip0173, "~> 0.1.2"}]
+  end
+```
+
+## How to use
+
+You can find the full API reference and examples in the [online documentation at Hexdocs](https://hexdocs.pm/bip0173/api-reference.html).
+
+### Bech32
+
+#### Encoding data to Bech32 string
+```elixir
+iex> Bech32.encode("bech32", [0, 1, 2])
+"bech321qpz4nc4pe"
+```
+```elixir
+iex> Bech32.encode("bc", [0, 14, 20, 15, 7, 13, 26, 0, 25, 18, 6, 11, 13,
+...> 8, 21, 4, 20, 3, 17, 2, 29, 3, 12, 29, 3, 4, 15, 24,20, 6, 14, 30, 22])
+"bc1qw508d6qejxtdg4y5r3zarvary0c5xw7kv8f3t4"
+```
+
+#### Decoding data from Bech32 string
+```elixir
+iex> Bech32.decode("bech321qpz4nc4pe")
+{:ok, {"bech32", [0, 1, 2]}}
+```
+``` elixir
+iex> Bech32.decode("bc1qw508d6qejxtdg4y5r3zarvary0c5xw7kv8f3t4")
+{:ok, {"bc", [0, 14, 20, 15, 7, 13, 26, 0, 25, 18, 6, 11, 13, 8, 21,
+  4, 20, 3, 17, 2, 29, 3, 12, 29, 3, 4, 15, 24, 20, 6, 14, 30, 22]}}
+```
+
+### SegwitAddr
+
+#### Encoding a SegWit program into BIP-0173 format
+```elixir
+iex> SegwitAddr.encode("bc", "0014751e76e8199196d454941c45d1b3a323f1433bd6")
+"bc1qw508d6qejxtdg4y5r3zarvary0c5xw7kv8f3t4"
+```
+```elixir
+iex> SegwitAddr.encode("bc", 0, [117, 30, 118, 232, 25, 145, 150, 212,
+...> 84, 148, 28, 69, 209, 179, 163, 35, 241, 67, 59, 214])
+"bc1qw508d6qejxtdg4y5r3zarvary0c5xw7kv8f3t4"
+```
+
+#### Decoding a BIP-0173 address into a SegWit program and formatting it as an hexadecimal ScriptPubKey
+```elixir
+iex> SegwitAddr.decode("bc1qw508d6qejxtdg4y5r3zarvary0c5xw7kv8f3t4")
+{:ok, {"bc", 0, [117, 30, 118, 232, 25, 145, 150, 212,
+84, 148, 28, 69, 209, 179, 163, 35, 241, 67, 59, 214]}}
+```
+```elixir
+iex> SegwitAddr.to_script_pub_key(0, [117, 30, 118, 232, 25, 145, 150,
+...> 212, 84, 148, 28, 69, 209, 179, 163, 35, 241, 67, 59, 214])
+"0014751e76e8199196d454941c45d1b3a323f1433bd6"
+```
+
+## Development
+
+### Running tests
+```bash
+$ mix deps.get
+$ mix test
+```
+
+### Running static analysis
+
+This package uses Erlang's [dialyzer](http://erlang.org/doc/man/dialyzer.html) to find software discrepancies such as definite type errors, code which has become dead or unreachable due to some programming error, unnecessary tests, etc.
+
+```bash
+$ mix deps.get
+$ mix dialyzer
+```
diff --git a/ref/elixir/lib/bech32.ex b/ref/elixir/lib/bech32.ex
@@ -0,0 +1,153 @@
+# Copyright (c) 2017 Adán Sánchez de Pedro Crespo
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+
+defmodule Bech32 do
+  use Bitwise
+
+  @moduledoc ~S"""
+  Encode and decode the Bech32 format, with checksums.
+  """
+
+  # Encoding character set. Maps data value -> char
+  @charset 'qpzry9x8gf2tvdw0s3jn54khce6mua7l'
+
+  # Human-readable part and data part separator
+  @separator 0x31
+
+  # Generator coefficients
+  @generator [0x3b6a57b2, 0x26508e6d, 0x1ea119fa, 0x3d4233dd, 0x2a1462b3]
+
+  @doc ~S"""
+  Encode a Bech32 string.
+
+  ## Examples
+
+      iex> Bech32.encode("bech32", [0, 1, 2])
+      "bech321qpz4nc4pe"
+
+      iex> Bech32.encode("bc", [0, 14, 20, 15, 7, 13, 26, 0, 25, 18, 6, 11, 13,
+      ...> 8, 21, 4, 20, 3, 17, 2, 29, 3, 12, 29, 3, 4, 15, 24,20, 6, 14, 30, 22])
+      "bc1qw508d6qejxtdg4y5r3zarvary0c5xw7kv8f3t4"
+  """
+  @spec encode(String.t, list(integer)) :: String.t
+  def encode(hrp, data) when is_list(data) do
+    checksummed = data ++ create_checksum(hrp, data)
+    dp = for (i <- checksummed), into: "", do: <<Enum.at(@charset, i)>>
+    <<hrp::binary, @separator, dp::binary>>
+  end
+
+  @spec encode(String.t, String.t) :: String.t
+  def encode(hrp, data) when is_binary(data) do
+    encode(hrp, :binary.bin_to_list(data))
+  end
+
+  @doc ~S"""
+  Decode a Bech32 string.
+
+  ## Examples
+
+      iex> Bech32.decode("bech321qpz4nc4pe")
+      {:ok, {"bech32", [0, 1, 2]}}
+
+      iex> Bech32.decode("bc1qw508d6qejxtdg4y5r3zarvary0c5xw7kv8f3t4")
+      {:ok, {"bc", [0, 14, 20, 15, 7, 13, 26, 0, 25, 18, 6, 11, 13, 8, 21,
+        4, 20, 3, 17, 2, 29, 3, 12, 29, 3, 4, 15, 24, 20, 6, 14, 30, 22]}}
+  """
+  @spec decode(String.t) :: {:ok, {String.t, list(integer)}} | {:error, String.t}
+  def decode(bech) do
+    with  {_, false}  <- {:mixed,  String.downcase(bech) != bech &&
+            String.upcase(bech) != bech},
+          bech_charlist = :binary.bin_to_list(bech),
+          {_, nil} <- {:oor, Enum.find(
+            bech_charlist,
+            fn (c) -> c < 33 || c > 126 end
+          )},
+          bech = String.downcase(bech),
+          len = Enum.count(bech_charlist),
+          pos = Enum.find_index(Enum.reverse(bech_charlist), fn (c) ->
+            c == @separator
+          end),
+          {_, true} <- {:oor_sep, pos != nil},
+          pos = len - pos - 1,
+          {_, false} <- {:empty_hrp, pos < 1},
+          {_, false, _} <- {:short_cs, pos + 7 > len, len},
+          {_, false, _} <- {:too_long, len > 90, len},
+          <<hrp::binary-size(pos), @separator, data::binary>> = bech,
+          data_charlist = (for c <- :binary.bin_to_list(data) do
+            Enum.find_index(@charset, fn (d) -> c == d end)
+          end),
+          {_, nil} <- {:oor_data, Enum.find_index(
+            data_charlist,
+            fn (c) -> c < 0 || c > 31 end
+          )},
+          {_, true} <- {:cs, verify_checksum(hrp, data_charlist)},
+          data_len = Enum.count(data_charlist),
+          data = Enum.slice(data_charlist, 0, data_len - 6)
+          do
+            {:ok, {hrp, data}}
+          else
+            {:mixed, _} -> {:error, "Mixed case"}
+            {:oor, c} -> {:error, "Character #{inspect(<<c>>)} out of range (#{c})"}
+            {:oor_sep, _} -> {:error, "No separator character"}
+            {:empty_hrp, _} -> {:error, "Empty HRP"}
+            {:short_cs, _, l} -> {:error, "Too short checksum (#{l})"}
+            {:too_long, _, l} -> {:error, "Overall max length exceeded (#{l})"}
+            {:oor_data, c} -> {:error, "Invalid data character #{inspect(<<c>>)} (#{c})}"}
+            {:cs, _} -> {:error, "Invalid checksum"}
+            _ -> {:error, "Unknown error"}
+          end
+    end
+
+  # Create a checksum.
+  defp create_checksum(hrp, data) do
+    values = expand_hrp(hrp) ++ data ++ [0, 0, 0, 0, 0, 0]
+    mod = polymod(values) ^^^ 1
+    for p <- 0..5, do: (mod >>> 5 * (5 - p)) &&& 31
+  end
+
+  # Verify a checksum.
+  defp verify_checksum(hrp, data) do
+    polymod(expand_hrp(hrp) ++ data) == 1
+  end
+
+  # Expand a HRP for use in checksum computation.
+  defp expand_hrp(hrp) do
+    hrp_charlist = :binary.bin_to_list(hrp)
+    a_values = for c <- hrp_charlist, do: c >>> 5
+    b_values = for c <- hrp_charlist, do: c &&& 31
+    a_values ++ [0] ++ b_values
+  end
+
+  # Find the polynomial with value coefficients mod the generator as 30-bit.
+  defp polymod(values) do
+    Enum.reduce(values, 1, fn (v, chk) ->
+      top = chk >>> 25
+      chk = ((chk &&& 0x1ffffff) <<< 5) ^^^ v
+      Enum.reduce((for i <- 0..4, do: i), chk, fn(i, chk) ->
+        chk ^^^ if ((top >>> i) &&& 1) != 0 do
+          Enum.at(@generator, i)
+        else
+          0
+        end
+      end)
+    end)
+  end
+
+end
diff --git a/ref/elixir/lib/segwit_addr.ex b/ref/elixir/lib/segwit_addr.ex
@@ -0,0 +1,132 @@
+# Copyright (c) 2017 Adán Sánchez de Pedro Crespo
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+
+defmodule SegwitAddr do
+  use Bitwise
+
+  @moduledoc ~S"""
+  Encode and decode BIP-0173 compliant SegWit addresses.
+  """
+
+  @doc ~S"""
+  Encode a SegWit address.
+
+  ## Examples
+
+      iex> SegwitAddr.encode("bc", "0014751e76e8199196d454941c45d1b3a323f1433bd6")
+      "bc1qw508d6qejxtdg4y5r3zarvary0c5xw7kv8f3t4"
+
+      iex> SegwitAddr.encode("bc", 0, [117, 30, 118, 232, 25, 145, 150, 212,
+      ...> 84, 148, 28, 69, 209, 179, 163, 35, 241, 67, 59, 214])
+      "bc1qw508d6qejxtdg4y5r3zarvary0c5xw7kv8f3t4"
+  """
+  @spec encode(String.t, integer, list(integer)) :: String.t
+  def encode(hrp, version, program) when is_list(program) do
+    Bech32.encode(hrp, [version] ++ convert_bits(program, 8, 5))
+  end
+
+  @spec encode(String.t, String.t) :: String.t
+  def encode(hrp, program) when is_binary(program) do
+    <<version, _size, program::binary>> = Base.decode16!(program, case: :mixed)
+    program
+      |> :binary.bin_to_list
+      |> (&(encode(hrp, version, &1))).()
+  end
+
+  @doc ~S"""
+  Decode a SegWit address.
+
+  ## Examples
+
+      iex> SegwitAddr.decode("bc1qw508d6qejxtdg4y5r3zarvary0c5xw7kv8f3t4")
+      {:ok, {"bc", 0, [117, 30, 118, 232, 25, 145, 150, 212,
+      84, 148, 28, 69, 209, 179, 163, 35, 241, 67, 59, 214]}}
+  """
+  @spec decode(String.t)
+  :: {:ok, {pos_integer, list(integer)}} | {:error,  String.t}
+  def decode(addr) do
+    case Bech32.decode(addr) do
+      {:ok, {hrp, data}} ->
+        [version | encoded] = data
+        program = convert_bits(encoded, 5, 8, false)
+        {:ok, {hrp, version, program}}
+      error -> error
+    end
+  end
+
+  @doc ~S"""
+  Encode a witness program into a hexadecimal ScriptPubKey.
+
+  ## Examples
+
+      iex> SegwitAddr.to_script_pub_key(0, [117, 30, 118, 232, 25, 145, 150,
+      ...> 212, 84, 148, 28, 69, 209, 179, 163, 35, 241, 67, 59, 214])
+      "0014751e76e8199196d454941c45d1b3a323f1433bd6"
+  """
+  @spec to_script_pub_key(pos_integer, list(integer)) :: String.t
+  def to_script_pub_key(version, program) do
+    [
+      if version == 0 do 0 else version + 0x50 end,
+      Enum.count(program) | program
+    ]
+      |> :binary.list_to_bin()
+      |> Base.encode16(case: :lower)
+  end
+
+  # General power-of-2 base conversion.
+  defp convert_bits(data, from, to, pad \\ true) do
+    max_v = (1 <<< to) - 1
+    if (Enum.find(data, fn (c) -> c < 0 || (c >>> from) != 0 end)) do
+      nil
+    else
+      {acc, bits, ret} = Enum.reduce(
+        data,
+        {0, 0, []},
+        fn (value, {acc, bits, ret}) ->
+          acc = ((acc <<< from) ||| value)
+          bits = bits + from
+          {bits, ret} = convert_bits_loop(to, max_v, acc, bits, ret)
+          {acc, bits, ret}
+        end
+      )
+      if (pad && bits > 0) do
+        ret ++ [(acc <<< (to - bits)) &&& max_v]
+      else
+        if (bits > from || ((acc <<< (to - bits)) &&& max_v) > 0) do
+          nil
+        else
+          ret
+        end
+      end
+    end
+  end
+
+  # Recursive version of the inner loop of the convert_bits function
+  defp convert_bits_loop(to, max_v, acc, bits, ret) do
+    if (bits >= to) do
+      bits = bits - to
+      ret = ret ++ [(acc >>> bits) &&& max_v]
+      convert_bits_loop(to, max_v, acc, bits, ret)
+    else
+      {bits, ret}
+    end
+  end
+
+end