Add keymaster

ebin/hakuzaru.app

@@ -4,5 +4,5 @@
               {applications,[stdlib,kernel]},
               {description,"Gajumaru interoperation library"},
               {vsn,"0.6.0"},
-              {modules,[hakuzaru,hz,hz_fetcher,hz_man,hz_sup]},
+              {modules,[hakuzaru,hz,hz_fetcher,hz_grids,hz_man,hz_sup]},
               {mod,{hakuzaru,[]}}]}.

src/hz_key_master.erl

@@ -0,0 +1,164 @@
+%%% @doc
+%%% Key functions
+%%%
+%%% The main reason this is a module of its own is that in the original architecture
+%%% it was a process rather than just a library of functions. Now that it exists, though,
+%%% there is little motivation to cram everything here into the controller process's
+%%% code.
+%%% @end
+
+-module(hz_key_master).
+-vsn("0.6.0").
+
+
+-export([make_key/2, encode/1, decode/1]).
+-export([lcg/1]).
+-include("gd.hrl").
+
+
+make_key("", <<>>) ->
+    Pair = #{public := Public} = ecu_eddsa:sign_keypair(),
+    ID = gmser_api_encoder:encode(account_pubkey, Public),
+    Name = binary_to_list(ID),
+    #key{name = Name, id = ID, pair = Pair};
+make_key("", Seed) ->
+    Pair = #{public := Public} = ecu_eddsa:sign_seed_keypair(Seed),
+    ID = gmser_api_encoder:encode(account_pubkey, Public),
+    Name = binary_to_list(ID),
+    #key{name = Name, id = ID, pair = Pair};
+make_key(Name, <<>>) ->
+    Pair = #{public := Public} = ecu_eddsa:sign_keypair(),
+    ID = gmser_api_encoder:encode(account_pubkey, Public),
+    #key{name = Name, id = ID, pair = Pair};
+make_key(Name, Seed) ->
+    Pair = #{public := Public} = ecu_eddsa:sign_seed_keypair(Seed),
+    ID = gmser_api_encoder:encode(account_pubkey, Public),
+    #key{name = Name, id = ID, pair = Pair}.
+
+
+-spec encode(Secret) -> Phrase
+    when Secret :: binary(),
+         Phrase :: string().
+%% @doc
+%% The encoding and decoding procesures are written to be able to handle any
+%% width of bitstring or binary and a variable size dictionary. The magic numbers
+%% 32, 4096 and 12 have been dropped in because currently these are known, but that
+%% will change in the future if the key size or type changes.
+
+encode(Bin) ->
+    <<Number:(32 * 8)>> = Bin,
+    DictSize = 4096,
+    Words = read_words(),
+%   Width = chunksize(DictSize - 1, 2),
+    Width = 12,
+    Chunks = chunksize(Number, DictSize),
+    Binary = <<Number:(Chunks * Width)>>,
+    encode(Width, Binary, Words).
+
+encode(Width, Bits, Words) ->
+    CheckSum = checksum(Width, Bits),
+    encode(Width, <<CheckSum:Width, Bits/bitstring>>, Words, []).
+
+encode(_, <<>>, _, Acc) ->
+    unicode:characters_to_list(lists:join(" ", lists:reverse(Acc)));
+encode(Width, Bits, Words, Acc) ->
+    <<I:Width, Rest/bitstring>> = Bits,
+    Word = lists:nth(I + 1, Words),
+    encode(Width, Rest, Words, [Word | Acc]).
+
+
+-spec decode(Phrase) -> {ok, Secret} | {error, Reason}
+    when Phrase :: string(),
+         Secret :: binary(),
+         Reason :: bad_phrase | bad_word.
+%% @doc
+%% Reverses the encoded secret string back into its binary representation.
+
+decode(Encoded) ->
+    DictSize = 4096,
+    Words = read_words(),
+    Width = chunksize(DictSize - 1, 2),
+    decode(Width, Words, Encoded).
+
+decode(Width, Words, Encoded) when is_list(Encoded) ->
+    decode(Width, Words, list_to_binary(Encoded));
+decode(Width, Words, Encoded) ->
+    Split = string:lexemes(Encoded, " "),
+    decode(Width, Words, Split, <<>>).
+
+decode(Width, Words, [Word | Rest], Acc) ->
+    case find(Word, Words) of
+        {ok, N} -> decode(Width, Words, Rest, <<Acc/bitstring, N:Width>>);
+        Error   -> Error
+    end;
+decode(Width, _, [], Acc) ->
+    sumcheck(Width, Acc).
+
+
+chunksize(N, C) ->
+    chunksize(N, C, 0).
+
+chunksize(0, _, A) -> A;
+chunksize(N, C, A) -> chunksize(N div C, C, A + 1).
+
+
+read_words() ->
+    Path = filename:join([zx:get_home(), "priv", "words4096.txt"]),
+    {ok, Bin} = file:read_file(Path),
+    string:lexemes(Bin, "\n").
+
+
+find(Word, Words) ->
+    find(Word, Words, 0).
+
+find(Word, [Word | _], N) -> {ok, N};
+find(Word, [_ | Rest], N) -> find(Word, Rest, N + 1);
+find(Word, [], _)         -> {error, {bad_word, Word}}.
+
+
+checksum(Width, Bits) ->
+    checksum(Width, Bits, 0).
+
+checksum(_, <<>>, Sum) ->
+    Sum;
+checksum(Width, Bits, Sum) ->
+    <<N:Width, Rest/bitstring>> = Bits,
+    checksum(Width, Rest, N bxor Sum).
+
+
+sumcheck(Width, Bits) ->
+    <<CheckSum:Width, Binary/bitstring>> = Bits,
+    case checksum(Width, Binary) =:= CheckSum of
+        true ->
+            <<N:(bit_size(Binary))>> = Binary,
+            {ok, <<N:(32 * 8)>>};
+        false ->
+            {error, bad_phrase}
+    end.
+
+
+
+-spec lcg(integer()) -> integer().
+%% A simple PRNG that fits into 32 bits and is easy to implement anywhere (Kotlin).
+%% Specifically, it is a "linear congruential generator" of the Lehmer variety.
+%% The constants used are based on recommendations from Park, Miller and Stockmeyer:
+%% https://www.firstpr.com.au/dsp/rand31/p105-crawford.pdf#page=4
+%%
+%% The input value should be between 1 and 2^31-1.
+%%
+%% The purpose of this PRNG is for password-based dictionary shuffling.
+
+lcg(N) ->
+    M = 16#7FFFFFFF,
+    A = 48271,
+    Q = 44488,  %  M div A
+    R = 3399,   %  M rem A
+    Div = N div Q,
+    Rem = N rem Q,
+    S = Rem * A,
+    T = Div * R,
+    Result = S - T,
+    case Result < 0 of
+        false -> Result;
+        true  -> Result + M
+    end.