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Update tutorial based on suggestions

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tdietert 2017-03-26 00:47:02 +00:00
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Crypto/Tutorial.hs
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@ -1,12 +1,12 @@
{- How to use @cryptonite@ with symmetric block ciphers
{- How to use @cryptonite@ with symmetric block ciphers
> {-# LANGUAGE OverloadedStrings #-}
> {-# LANGUAGE ScopedTypeVariables #-}
> {-# LANGUAGE GADTs #-}
>
> import Crypto.Cipher.AES (AES256)
> import Crypto.Cipher.Types (BlockCipher(..), Cipher(..), nullIV, KeySizeSpecifier(..))
> import Crypto.Cipher.Types (BlockCipher(..), Cipher(..), nullIV, KeySizeSpecifier(..), IV, makeIV)
> import Crypto.Error (CryptoFailable(..), CryptoError(..))
>
> import qualified Crypto.Random.Types as CRT
@ -18,40 +18,47 @@
> data Key c a where
> Key :: (BlockCipher c, ByteArray a) => a -> Key c a
>
> genPrivateKey :: forall m c a. (CRT.MonadRandom m, BlockCipher c, ByteArray a)
> => c -> m (Key c a)
> genPrivateKey _ = fmap Key $ CRT.getRandomBytes $
> case cipherKeySize (undefined :: c) of
> KeySizeRange _ maxSize -> maxSize
> KeySizeFixed ks -> ks
> KeySizeEnum [] -> error "No key size specified"
> KeySizeEnum kss -> last kss -- largest key size
>
> -- | 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 -> a -> Either CryptoError a
> encrypt privKey msg =
> case initCipher privKey of
> 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 nullIV msg
> Right c -> Right $ ctrCombine c initIV msg
>
> decrypt :: (BlockCipher c, ByteArray a) => Key c a -> a -> Either CryptoError a
> decrypt :: (BlockCipher c, ByteArray a) => Key c a -> IV c -> a -> Either CryptoError a
> decrypt = encrypt
>
> exampleAES256 :: ByteString -> IO ()
> exampleAES256 msg = do
> privKey <- genPrivateKey (undefined :: AES256)
> let eMsg = encrypt privKey msg >>= decrypt privKey
> case eMsg of
> Left err -> error $ show err
> Right msg' -> do
> putStrLn $ "Original Message: " ++ show msg
> putStrLn $ "Message after encryption & decryption: " ++ show msg'
>
> -- | More Examples... ?
> -- 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
|-}