Add some Ethereum crypto functionality

src/ecu_crypto.erl

@@ -0,0 +1,60 @@
+%%% File        : ecu_crypto.erl
+%%% Author      : Hans Svensson
+%%% Description :
+%%% Created     : 13 Jan 2022 by Hans Svensson
+-module(ecu_crypto).
+
+-export([private_to_short/2, public_to_short/2,
+         eth_sign/2, eth_recover/2, eth_verify/3, eth_msg_hash/1,
+         keccak256/1]).
+
+private_to_short(bitcoin, PrivateKey) ->
+  public_to_short(bitcoin, aeu_ecdsa:private_to_public(secp256k1, PrivateKey));
+private_to_short(ethereum, <<PrivateKey:256>>) ->
+  public_to_short(ethereum, ecu_secp256k1:scalar_mul_base(PrivateKey)).
+
+public_to_short(bitcoin, PubKey = <<_:33/bytes>>) ->
+  crypto:hash(ripemd160, crypto:hash(sha256, PubKey));
+public_to_short(bitcoin, PubKey) ->
+  crypto:hash(ripemd160, crypto:hash(sha256, ecu_secp256k1:compress(PubKey)));
+public_to_short(ethereum, PubKey) ->
+  case PubKey of
+    <<_:33/bytes>> -> public_to_short(ethereum, ecu_secp256k1:decompress(PubKey));
+    <<4:8, X:256, Y:256>> -> public_to_short(ethereum, {X, Y});
+    {X, Y} ->
+      <<_:12/bytes, ShortPub:20/bytes>> = keccak256(<<X:256, Y:256>>),
+      ShortPub
+  end.
+
+eth_sign(Msg, PrivateKey = <<_:32/bytes>>) ->
+  {BaseSig, YVal} = ecu_ecdsa:sign_secp256k1(eth_msg_hash(Msg), PrivateKey),
+  V = if YVal rem 2 == 0 -> 27;
+         true            -> 28
+      end,
+  <<V:8, BaseSig/bytes>>.
+
+eth_recover(Msg, Sig = <<_:65/bytes>>) ->
+  MsgHash = eth_msg_hash(Msg),
+  <<E:256>> = MsgHash,
+  <<V:8, R:256, S:256>> = Sig,
+  Z = E rem ecu_secp256k1:n(),
+  RInv = ecu_secp256k1:s_inv(R),
+  Rd = ecu_secp256k1:decompress(<<(V - 27 + 2):8, R:256>>),
+  [P1, P2] =
+    ecu_misc:pcomp(
+      [fun() -> ecu_secp256k1:scalar_mul(ecu_secp256k1:s_mul(RInv, S), Rd) end,
+       fun() -> ecu_secp256k1:scalar_mul_base(ecu_secp256k1:s_mul(RInv,Z)) end]),
+
+  {X, Y} = ecu_secp256k1:p_add(P1, ecu_secp256k1:p_neg(P2)),
+  <<_:12/bytes, RPub:20/bytes>> = keccak256(<<X:256, Y:256>>),
+  RPub.
+
+eth_verify(Msg, PublicKey, Sig) ->
+  PublicKey == eth_recover(Msg, Sig).
+
+eth_msg_hash(Msg0) ->
+  Msg = ["\x19Ethereum Signed Message:\n", integer_to_list(byte_size(Msg0)), Msg0],
+  keccak256(iolist_to_binary(Msg)).
+
+keccak256(Bin) ->
+  sha3:hash(256, Bin).

src/ecu_misc.erl

@@ -4,7 +4,9 @@
 %%% Created     : 13 Jan 2022 by Hans Svensson
 -module(ecu_misc).
 
--export([eea/2, pcomp/1]).
+-export([eea/2,
+         hex_to_bin/1, bin_to_hex/1,
+         pcomp/1]).
 
 %% Extended Euclidean Algorithm
 eea(A, B) when ((A < 1) or (B < 1)) ->
@@ -23,3 +25,17 @@ pcomp(Fs) ->
   Parent = self(),
   Pids = [ spawn(fun() -> Parent ! {self(), F()} end) || F <- Fs ],
   [ receive {Pid, X} -> X after 500 -> error(timeout) end || Pid <- Pids ].
+
+%% Hex encode/decode
+-spec hex_to_bin(Input :: string()) -> binary().
+hex_to_bin(S) ->
+  hex_to_bin(S, []).
+hex_to_bin([], Acc) ->
+  list_to_binary(lists:reverse(Acc));
+hex_to_bin([X,Y|T], Acc) ->
+  {ok, [V], []} = io_lib:fread("~16u", [X,Y]),
+  hex_to_bin(T, [V | Acc]).
+
+-spec bin_to_hex(Input :: binary()) -> string().
+bin_to_hex(Bin) ->
+  lists:flatten([io_lib:format("~2.16.0B", [X]) || X <- binary_to_list(Bin)]).