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Getting values out of types at runtime
{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE ScopedTypeVariables #-}
module Key (Key, makeKey) where
import Data.ByteString (ByteString)
import qualified Data.ByteString as B
import Data.Proxy
import GHC.TypeLits
newtype Key (size :: Nat) = Key ByteString
deriving (Show)
makeKey :: forall size. KnownNat size => ByteString -> Maybe (Key size)
makeKey s | B.length s == (keyLength `div` 8) = Just (Key s)
| otherwise = Nothing
where
keyLength = fromInteger $ natVal (Proxy :: Proxy size)
--encrypt :: Key 96 -> Key 256 -> String -> String
--encrypt (Key nonce) (Key cipherKey) plaintext = undefined
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