Add Litecoin support

README.md

@@ -93,6 +93,13 @@ path = "M/44'/0'/0'"
 xpub = BlockKeys.CKD.derive(root_key, path)
 ```
 
+### Litecoin
+
+```
+path = "M/44'/2'/0'"
+xpub = BlockKeys.CKD.derive(root_key, path)
+```
+
 ### Ethereum
 
 ```
@@ -120,6 +127,13 @@ path = "M/0/0"
 address = BlockKeys.Bitcoin.address(xpub, path)
 ```
 
+### Litecoin
+
+```
+path = "M/0/0"
+address = BlockKeys.Litecoin.address(xpub, path)
+```
+
 ### Ethereum
 
 ```

lib/block_keys/litecoin/address.ex

@@ -0,0 +1,22 @@
+defmodule BlockKeys.Litecoin.Address do
+  @moduledoc """
+  Converts a public extended key into a Litecoin Address
+  """
+
+  alias BlockKeys.{Crypto, Encoding}
+
+  def from_xpub(xpub) do
+    xpub
+    |> maybe_decode()
+    |> Crypto.hash160()
+    |> Encoding.base58_encode(<<48>>)
+  end
+
+  defp maybe_decode(<<"xpub", _rest::binary>> = encoded_key) do
+    encoded_key
+    |> Encoding.decode_extended_key()
+    |> Map.fetch!(:key)
+  end
+
+  defp maybe_decode(key), do: key
+end

lib/block_keys/litecoin/litecoin.ex

@@ -0,0 +1,13 @@
+defmodule BlockKeys.Litecoin do
+  @moduledoc """
+  Helper module to derive and convert to a Litecoin Address
+  """
+
+  alias BlockKeys.Litecoin.Address
+  alias BlockKeys.CKD
+
+  def address(key, path) do
+    CKD.derive(key, path)
+    |> Address.from_xpub()
+  end
+end

test/block_keys/litecoin/address_test.exs

@@ -0,0 +1,24 @@
+defmodule LitecoinAddressTest do
+  use ExUnit.Case, async: true
+
+  alias BlockKeys.Litecoin.Address
+  alias BlockKeys.CKD
+
+  test "generate address from public key" do
+    xpub =
+      "xpub6C35qtG2zHpXwVKjpEmTjam5igvoQh2bYkPNdYrCekv44W3ioNi8DJ7zAXTuWgYCbm57ZZRhgiwC56dCYvzfur7pxwKQhcgqga7fafdeH4q"
+
+    assert Address.from_xpub(xpub) == "LaFTXS4cTPZGRf2ie6wDsG7S6RVuXYSW9A"
+  end
+
+  test "generates the first address for BIP44 path" do
+    path = "M/44'/2'/0'/0/0"
+
+    xprv =
+      "xprv9s21ZrQH143K4RdNK1f51Rdeu4XRG8q2cgzeh7ejtzgYpdZcHpNb1MJ2DdBa4iX6NVoZZajsC4gr26mLFaHGBrrtvGkxwhGh6ng8HVZRSeV"
+
+    xpub = CKD.derive(xprv, path)
+
+    assert Address.from_xpub(xpub) == "LdWaYyadtKgZmfg5tf1fPj9m5FQq3Hdc1K"
+  end
+end