Merge pull request #145 from tdietert/tutorial

Tutorial Improvement

Crypto/Tutorial.hs

@@ -1,34 +1,65 @@
-{-# OPTIONS_GHC -fno-warn-unused-imports #-}
-{-# LANGUAGE OverloadedStrings #-}
 
-{-| How to use @cryptonite@
+{- How to use @cryptonite@ with symmetric block ciphers 
 
-> -- | Beware MUST BE 256bits as we use AES256
-> import Data.ByteString (ByteString)
-> import Crypto.Cipher.AES (AES256)
-> import Crypto.Cipher.Types (BlockCipher(..), Cipher(..),nullIV)
-> import Crypto.Error (CryptoFailable(..))
->
-> secretKey :: ByteString
-> secretKey = "012-456-89A-CDE-012-456-89A-CDE-"
->
-> encrypt :: ByteString -> ByteString -> ByteString
-> encrypt secret = ctrCombine ctx nullIV
->   where
->     ctx = cipherInitNoErr (cipherMakeKey (undefined :: AES256) secret)
->     cipherInitNoErr :: BlockCipher c => Key c -> c
->     cipherInitNoErr (Key k) = case cipherInit k of
->       CryptoPassed a -> a
->       CryptoFailed e -> error (show e)
->     cipherMakeKey :: Cipher cipher => cipher -> ByteString -> Key cipher
->     cipherMakeKey _ = Key -- Yeah Lazyness!!!!!!
->
->
-> decrypt :: ByteString -> ByteString -> ByteString
+> {-# LANGUAGE OverloadedStrings #-}
+> {-# LANGUAGE ScopedTypeVariables #-}
+> {-# LANGUAGE GADTs #-}
+> 
+> import           Crypto.Cipher.AES (AES256)
+> import           Crypto.Cipher.Types (BlockCipher(..), Cipher(..), nullIV, KeySizeSpecifier(..), IV, makeIV)
+> import           Crypto.Error (CryptoFailable(..), CryptoError(..))
+> 
+> import qualified Crypto.Random.Types as CRT
+> 
+> import           Data.ByteArray (ByteArray)
+> import           Data.ByteString (ByteString)
+> 
+> -- | Not required, but most general implementation
+> data Key c a where
+>   Key :: (BlockCipher c, ByteArray a) => a -> Key c a 
+> 
+> -- | Generates a string of bytes (key) of a specific length for a given block cipher 
+> genSecretKey :: forall m c a. (CRT.MonadRandom m, BlockCipher c, ByteArray a) => c -> Int -> m (Key c a) 
+> genSecretKey _ = fmap Key . CRT.getRandomBytes 
+>   
+> -- | Generate a random initialization vector for a given block cipher
+> genRandomIV :: forall m c. (CRT.MonadRandom m, BlockCipher c) => c -> m (Maybe (IV c)) 
+> genRandomIV _ = do
+>   bytes :: ByteString <- CRT.getRandomBytes $ blockSize (undefined :: c) 
+>   return $ makeIV bytes 
+> 
+> -- | Initialize a block cipher
+> initCipher :: (BlockCipher c, ByteArray a) => Key c a -> Either CryptoError c
+> initCipher (Key k) = case cipherInit k of
+>   CryptoFailed e -> Left e
+>   CryptoPassed a -> Right a
+> 
+> encrypt :: (BlockCipher c, ByteArray a) => Key c a -> IV c -> a -> Either CryptoError a
+> encrypt secretKey initIV msg = 
+>   case initCipher secretKey of
+>     Left e -> Left e
+>     Right c -> Right $ ctrCombine c initIV msg
+>     
+> decrypt :: (BlockCipher c, ByteArray a) => Key c a -> IV c -> a -> Either CryptoError a 
 > decrypt = encrypt
+> 
+> exampleAES256 :: ByteString -> IO ()
+> exampleAES256 msg = do
+>   -- secret key needs 256 bits (32 * 8) 
+>   secretKey <- genSecretKey (undefined :: AES256) 32
+>   mInitIV <- genRandomIV (undefined :: AES256) 
+>   case mInitIV of
+>     Nothing -> error "Failed to generate and initialization vector."
+>     Just initIV -> do
+>       let encryptedMsg = encrypt secretKey initIV msg
+>           decryptedMsg = decrypt secretKey initIV =<< encryptedMsg
+>       case (,) <$> encryptedMsg <*> decryptedMsg of
+>         Left err -> error $ show err
+>         Right (eMsg, dMsg) -> do
+>           putStrLn $ "Original Message: " ++ show msg
+>           putStrLn $ "Message after encryption: " ++ show eMsg 
+>           putStrLn $ "Message after decryption: " ++ show dMsg
 
 |-}
 
-module Crypto.Tutorial () where
-
-import Crypto.Cipher.Types
+module Crypto.Tutorial where