Added compact signature support.

lib/ex_web3_ec_recover/compact_signature.ex

@@ -0,0 +1,37 @@
+defmodule ExWeb3EcRecover.CompactSignature do
+  @moduledoc false
+  @enforce_keys [:r, :y_parity_and_s]
+  defstruct @enforce_keys
+
+  @type t :: %__MODULE__{
+          r: binary(),
+          y_parity_and_s: binary()
+        }
+
+  @spec from_hexstring(binary()) :: ExWeb3EcRecover.CompactSignature.t()
+  def from_hexstring("0x" <> signature) when byte_size(signature) == 64 do
+    <<r::binary-size(256), y_parity_and_s::binary-size(256)>> = Base.decode16!(signature)
+
+    %__MODULE__{
+      r: r,
+      y_parity_and_s: y_parity_and_s
+    }
+  end
+
+  @spec from_canonical(ExWeb3EcRecover.Signature.t()) :: ExWeb3EcRecover.CompactSignature.t()
+  def from_canonical(%ExWeb3EcRecover.Signature{} = sig) do
+    y_parity = sig.v_num
+    <<s::size(256)>> = sig.s
+    y_parity_and_s = Bitwise.bor(Bitwise.bsl(y_parity, 255), s)
+
+    %__MODULE__{
+      r: sig.r,
+      y_parity_and_s: <<y_parity_and_s::size(256)>>
+    }
+  end
+
+  @spec serialize(__MODULE__.t()) :: binary()
+  def serialize(%__MODULE__{} = cs) do
+    cs.r <> cs.y_parity_and_s
+  end
+end

lib/ex_web3_ec_recover/signature.ex

@@ -3,6 +3,12 @@ defmodule ExWeb3EcRecover.Signature do
   @enforce_keys [:r, :s, :v_num]
   defstruct @enforce_keys
 
+  @type t :: %__MODULE__{
+    r: binary(),
+    s: binary(),
+    v_num: 0 | 1
+  }
+
   def from_hexstring("0x" <> signature) when byte_size(signature) == 130 do
     # 65 bytes of data, each byte takes two bytes in hexstring
     sig_binary = Base.decode16!(signature, case: :lower)

test/compact_signature_test.exs

@@ -0,0 +1,33 @@
+defmodule ExWeb3EcRecover.CompactSignatureTest do
+  @moduledoc false
+  # Test data provided by https://eips.ethereum.org/EIPS/eip-2098#example-implementation-in-python
+  use ExUnit.Case, async: true
+
+  test "parity 0" do
+    sig =
+      "0x68a020a209d3d56c46f38cc50a33f704f4a9a10a59377f8dd762ac66910e9b907e865ad05c4035ab5792787d4a0297a43617ae897930a6fe4d822b8faea520641b"
+
+    canon = ExWeb3EcRecover.Signature.from_hexstring(sig)
+    result = ExWeb3EcRecover.CompactSignature.from_canonical(canon)
+
+    assert Base.encode16(result.r, case: :lower) ==
+             "68a020a209d3d56c46f38cc50a33f704f4a9a10a59377f8dd762ac66910e9b90"
+
+    assert Base.encode16(result.y_parity_and_s, case: :lower) ==
+             "7e865ad05c4035ab5792787d4a0297a43617ae897930a6fe4d822b8faea52064"
+  end
+
+  test "parity 1" do
+    sig =
+      "0x9328da16089fcba9bececa81663203989f2df5fe1faa6291a45381c81bd17f76139c6d6b623b42da56557e5e734a43dc83345ddfadec52cbe24d0cc64f5507931c"
+
+    canon = ExWeb3EcRecover.Signature.from_hexstring(sig)
+    result = ExWeb3EcRecover.CompactSignature.from_canonical(canon)
+
+    assert Base.encode16(result.r, case: :lower) ==
+             "9328da16089fcba9bececa81663203989f2df5fe1faa6291a45381c81bd17f76"
+
+    assert Base.encode16(result.y_parity_and_s, case: :lower) ==
+             "939c6d6b623b42da56557e5e734a43dc83345ddfadec52cbe24d0cc64f550793"
+  end
+end

test/signed_type_test.exs

@@ -59,7 +59,7 @@ defmodule ExWeb3EcRecover.SignedTypeTest do
       types = %{
         "Message" => [
           %{"name" => "data1", "type" => "int256"},
-          %{"name" => "data2", "type" => "uint256"},
+          %{"name" => "data2", "type" => "uint256"}
         ]
       }