{-# LANGUAGE ConstraintKinds             #-}
{-# LANGUAGE MultiParamTypeClasses       #-}
{-# LANGUAGE FlexibleInstances           #-}
{-# LANGUAGE FlexibleContexts            #-}
{-# LANGUAGE TypeFamilies                #-}

-- | Implementation of stream ciphers. Since encryption/decryption is
-- done by typically xoring the keystream witht he data, the have two
-- property.
--
-- 1. Using the same key stream can compromise the safety so typically these
--    primitives take, apart from the key a nounce that needs to be distinct.
--    It is the key nounce pair that should not be reused.
--
-- 2. They usually can rewind/advace/skip input and perform
--    encryption/decryption.
--

signature Implementation where

import Raaz.Core

-- | The primitive
data Prim

-- | The internal memory used by the implementation.
data Internals
instance Memory Internals

instance Initialisable Internals (Key Prim)
instance Initialisable Internals (Nounce Prim)
instance Initialisable Internals (BlockCount Prim) -- To restore/advance
                                               -- to a particular
                                               -- block in the stream

instance Extractable Internals (BlockCount Prim)   -- To query the position