feat(plugins): added required crypto and did stuff for ucan build

lib/ex_ucan/plugins/ed25519/crypto.ex

@@ -0,0 +1,20 @@
+defmodule ExUcan.Plugins.Ed25519.Crypto do
+  @moduledoc """
+  Crypto functions related to `ExUcan.Plugins.Ed25519.Keypair`
+  """
+  alias ExUcan.Plugins.Utils
+
+  @edwards_did_prefix <<0xED, 0x01>>
+
+  # TODO: doc
+  @spec did_to_publickey(did :: String.t()) :: binary()
+  def did_to_publickey(did) do
+    Utils.key_bytes_from_did(did, @edwards_did_prefix)
+  end
+
+  # TODO: doc
+  @spec publickey_to_did(pubkey :: binary()) :: String.t()
+  def publickey_to_did(pubkey) do
+    Utils.did_from_key_bytes(pubkey, @edwards_did_prefix)
+  end
+end

lib/ex_ucan/plugins/ed25519/keypair.ex

@@ -2,15 +2,16 @@ defmodule ExUcan.Plugins.Ed25519.Keypair do
   @moduledoc """
   Encapsulates Ed25519 Keypair generation and other utilities
   """
+  alias ExUcan.Plugins.Ed25519.Crypto
   # TODO: more doc..
 
   # TODO: Need type doc
   @type t :: %__MODULE__{
-    jwt_alg: String.t(),
-    secret_key: binary(),
-    public_key: binary(),
-    exportable: boolean()
-  }
+          jwt_alg: String.t(),
+          secret_key: binary(),
+          public_key: binary(),
+          exportable: boolean()
+        }
 
   defstruct(
     jwt_alg: "EdDSA",
@@ -19,10 +20,12 @@ defmodule ExUcan.Plugins.Ed25519.Keypair do
     exportable: false
   )
 
-
   @spec create(boolean()) :: __MODULE__.t()
+  def create(exportable? \\ true)
+
   def create(exportable?) do
     {pub, priv} = :crypto.generate_key(:eddsa, :ed25519)
+
     __MODULE__.__struct__(
       jwt_alg: "EdDSA",
       secret_key: priv,
@@ -31,9 +34,8 @@ defmodule ExUcan.Plugins.Ed25519.Keypair do
     )
   end
 
-  # @spec
-  def did() do
-
+  @spec did(__MODULE__.t()) :: String.t()
+  def did(keypair) do
+    Crypto.publickey_to_did(keypair.public_key)
   end
-
 end

lib/ex_ucan/plugins/utils.ex

@@ -0,0 +1,31 @@
+defmodule ExUcan.Plugins.Utils do
+  @moduledoc """
+  Utilites related to plugins
+  """
+
+  @base58_did_prefix "did:key:z"
+
+  # TODO: docs
+  @spec did_from_key_bytes(publickey_bytes :: binary(), prefix :: binary()) :: String.t()
+  def did_from_key_bytes(publickey_bytes, prefix) do
+    bytes = <<prefix::binary, publickey_bytes::binary>>
+    base58key = Base58.encode(bytes)
+    @base58_did_prefix <> base58key
+  end
+
+  # TODO: docs
+  @spec key_bytes_from_did(String.t(), binary()) :: {:ok, binary()} | {:error, String.t()}
+  def key_bytes_from_did("did:key:z" <> non_prefix_did, expected_prefix) do
+    bytes = Base58.decode(non_prefix_did)
+    <<a::size(8), b::size(8), pub::binary>> = bytes
+
+    if <<a, b>> == expected_prefix do
+      {:ok, pub}
+    else
+      {:error, "Expected prefix #{inspect(expected_prefix)}"}
+    end
+  end
+
+  def key_bytes_from_did(_did, _expected_prefix),
+    do: {:error, "Please use a base58-encoded DID formatted `did:key:z..."}
+end

mix.exs

@@ -22,7 +22,8 @@ defmodule ExUcan.MixProject do
   defp deps do
     [
       {:rustler, "~> 0.30.0", runtime: false},
-      {:credo, "~> 1.7", only: [:dev, :test], runtime: false}
+      {:credo, "~> 1.7", only: [:dev, :test], runtime: false},
+      {:b58, "~> 1.0.2"}
       # {:dep_from_hexpm, "~> 0.3.0"},
       # {:dep_from_git, git: "https://github.com/elixir-lang/my_dep.git", tag: "0.1.0"}
     ]

mix.lock

@@ -1,4 +1,5 @@
 %{
+  "b58": {:hex, :b58, "1.0.3", "d300d6ae5a3de956a54b9e8220e924e4fee1a349de983df2340fe61e0e464202", [:mix], [], "hexpm", "af62a98a8661fd89978cf3a3a4b5b2ebe82209de6ac6164f0b112e36af72fc59"},
   "bunt": {:hex, :bunt, "0.2.1", "e2d4792f7bc0ced7583ab54922808919518d0e57ee162901a16a1b6664ef3b14", [:mix], [], "hexpm", "a330bfb4245239787b15005e66ae6845c9cd524a288f0d141c148b02603777a5"},
   "credo": {:hex, :credo, "1.7.1", "6e26bbcc9e22eefbff7e43188e69924e78818e2fe6282487d0703652bc20fd62", [:mix], [{:bunt, "~> 0.2.1", [hex: :bunt, repo: "hexpm", optional: false]}, {:file_system, "~> 0.2.8", [hex: :file_system, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "e9871c6095a4c0381c89b6aa98bc6260a8ba6addccf7f6a53da8849c748a58a2"},
   "file_system": {:hex, :file_system, "0.2.10", "fb082005a9cd1711c05b5248710f8826b02d7d1784e7c3451f9c1231d4fc162d", [:mix], [], "hexpm", "41195edbfb562a593726eda3b3e8b103a309b733ad25f3d642ba49696bf715dc"},