{-# LANGUAGE LambdaCase, ScopedTypeVariables #-}
{-
Example of using PBKDF2 to seed the TF (ThreeFish) random number
generator with a string.

Copyright 2015 Ken Takusagawa

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at
your option) any later version.

This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
-}

module Main(main) where {
import qualified System.Random.TF.Instances as TF;
import Data.ByteString (ByteString);
import qualified Data.Binary as Binary;
import Crypto.PBKDF.ByteString(sha512PBKDF2);
import Data.Text.Encoding(encodeUtf8);
import qualified Data.Text as Text;
import qualified Data.ByteString.Lazy as Lazy;
import System.Random.TF.Gen(TFGen, seedTFGen);
import Data.Word;

main :: IO ();
main = do {
let { gen :: TFGen ; gen = seedTFGen $ Binary.decode $ Lazy.fromStrict $ sha512PBKDF2 (string2bs mypassphrase) (string2bs salt) (fromIntegral iterations_pbkdf2) (fromIntegral keylength_bytes) };
mapM_ print (TF.randoms gen :: [Word8]);
};

-- world's most famous password
mypassphrase :: String;
mypassphrase = "ACollectionOfDiplomaticHistorySince_1966_ToThe_PresentDay#";

salt::String;
salt = "mysalt98754321";

string2bs :: String -> ByteString;
string2bs = encodeUtf8 . Text.pack;

keylength_bytes :: Integer;
keylength_bytes = 4 * div 64 8;  -- 4-tuple of Word64

{- On one hand, quoting the documentation: "it has not been designed
with cryptographic applications in mind."  On the other hand, I see no
reason (other than side channel attacks) why the stream is not
cryptographically secure, so use a crytographically secure number of
rounds in the KDF as well.-}

iterations_pbkdf2 :: Integer;
iterations_pbkdf2 = 100000;

} -- end