[wip] generating keypair with ec_utils copied from zx's github

2022-12-20 20:58:21 -07:00
parent 8cc46b6ac9
commit cbe487618c
8 changed files with 657 additions and 10 deletions
@@ -0,0 +1,53 @@
+%%% File        : ecu_misc.erl
+%%% Author      : Hans Svensson
+%%% Description : Misc. functionality
+%%% Created     : 13 Jan 2022 by Hans Svensson
+-module(ecu_misc).
+-vsn("1.0.0").
+
+-export([eea/2, exp_mod/3,
+         hex_to_bin/1, bin_to_hex/1,
+         pcomp/1]).
+
+%% A^B mod P
+exp_mod(_A, 0, _P) -> 1;
+exp_mod(A, B, P) when A > 0 ->
+  binary:decode_unsigned(crypto:mod_pow(A, B, P));
+exp_mod(A, B, P) ->
+  X = exp_mod(-A, B, P),
+  case B rem 2 == 0 orelse X == 0 of
+    true  -> X;
+    false -> P - X
+  end.
+
+%% Extended Euclidean Algorithm
+eea(A, B) when ((A < 1) or (B < 1)) ->
+    undefined;
+eea(A, B) ->
+    eea(A, 1, 0, B, 0, 1).
+
+eea(G, S, T, 0, _, _) ->
+    {G, S, T};
+eea(G0, S0, T0, G1, S1, T1) ->
+    Q = G0 div G1,
+    eea(G1, S1, T1, G0 - (Q * G1), S0 - (Q * S1), T0 - (Q * T1)).
+
+%% Very rudimentary parallel computation...
+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)]).