Features: Adds Signer behaviour.

config/config.exs

@@ -10,4 +10,5 @@ config :tt_eth,
     secondary: "0xe2187dc017e880dded10c403f7c0d397afb11736ac027c1202e318b0dd345086",
     ternary: "0xfa015243f2e6d8694ab037a7987dc73b1630fc8cb1ce82860344684c15d24026"
   ],
-  transaction_module: TTEth.Transactions.LegacyTransaction
+  transaction_module: TTEth.Transactions.LegacyTransaction,
+  signer_module: TTEth.Secp256k1

lib/tt_eth.ex

@@ -123,6 +123,10 @@ defmodule TTEth do
   def transaction_module(),
     do: :tt_eth |> get_env(:transaction_module, TTEth.Transactions.EIP1559Transaction)
 
+  @spec signer_module() :: module
+  def signer_module(),
+    do: :tt_eth |> get_env(:signer_module, TTEth.Secp256k1)
+
   ## Mocks related stuff.
 
   @doc false

lib/tt_eth/behaviours/signer.ex

@@ -0,0 +1,9 @@
+defmodule TTEth.Behaviours.Signer do
+  @moduledoc """
+  Defines a behaviour to encapsulate a signer.
+  """
+
+  @callback sign_transaction(transaction :: binary(), private_key :: binary()) ::
+              {:ok, {r_s :: binary(), v :: non_neg_integer()}}
+              | {:error, term()}
+end

lib/tt_eth/secp256k1.ex

@@ -3,6 +3,12 @@ defmodule TTEth.Secp256k1 do
   Wrapper around `ExSecp256k1` functions.
   """
 
+  @behaviour TTEth.Behaviours.Signer
+
+  @impl TTEth.Behaviours.Signer
+  def sign_transaction(transaction, private_key),
+    do: ecdsa_sign_compact(transaction, private_key)
+
   @doc """
   Delegates to `ExSecp256k1.recover_compact/3` with guards around the `recovery_id` value.
   """

lib/tt_eth/transactions/eip1559_transaction.ex

@@ -4,9 +4,10 @@ defmodule TTEth.Transactions.EIP1559Transaction do
 
   SEE: https://eips.ethereum.org/EIPS/eip-1559
   """
-  alias TTEth.{BitHelper, Secp256k1}
+  alias TTEth.BitHelper
   alias TTEth.Behaviours.Transaction
   import BitHelper, only: [encode_unsigned: 1]
+  import TTEth, only: [signer_module: 0]
 
   @behaviour Transaction
 
@@ -89,7 +90,8 @@ defmodule TTEth.Transactions.EIP1559Transaction do
   Returns a ECDSA signature (v,r,s) for a given hashed value.
   """
   def sign_hash(hash, private_key) do
-    {:ok, {<<r::size(256), s::size(256)>>, v}} = Secp256k1.ecdsa_sign_compact(hash, private_key)
+    {:ok, {<<r::size(256), s::size(256)>>, v}} =
+      signer_module().sign_transaction(hash, private_key)
 
     {v, r, s}
   end