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|
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
-- |
-- Module : Crypto.Random.ChaChaDRG
-- License : BSD-style
-- Maintainer : Vincent Hanquez <vincent@snarc.org>
-- Stability : stable
-- Portability : good
module Crypto.Random.ChaChaDRG (
ChaChaDRG,
initialize,
initializeWords,
) where
import Crypto.Internal.ByteArray (
ByteArray,
ByteArrayAccess,
ScrubbedBytes,
)
import qualified Crypto.Internal.ByteArray as B
import Crypto.Internal.Imports
import Crypto.Random.Types
import Foreign.Storable (pokeElemOff)
import qualified Crypto.Cipher.ChaCha as C
instance DRG ChaChaDRG where
randomBytesGenerate = generate
-- | ChaCha Deterministic Random Generator
newtype ChaChaDRG = ChaChaDRG C.StateSimple
deriving (NFData)
-- | Initialize a new ChaCha context with the number of rounds,
-- the key and the nonce associated.
initialize
:: ByteArrayAccess seed
=> seed
-- ^ 40 bytes of seed
-> ChaChaDRG
-- ^ the initial ChaCha state
initialize seed = ChaChaDRG $ C.initializeSimple seed
-- | Initialize a new ChaCha context from 5-tuple of words64.
-- This interface is useful when creating a RNG out of tests generators (e.g. QuickCheck).
initializeWords :: (Word64, Word64, Word64, Word64, Word64) -> ChaChaDRG
initializeWords (a, b, c, d, e) = initialize (B.allocAndFreeze 40 fill :: ScrubbedBytes)
where
fill s = mapM_ (uncurry (pokeElemOff s)) [(0, a), (1, b), (2, c), (3, d), (4, e)]
generate :: ByteArray output => Int -> ChaChaDRG -> (output, ChaChaDRG)
generate nbBytes st@(ChaChaDRG prevSt)
| nbBytes <= 0 = (B.empty, st)
| otherwise =
let (output, newSt) = C.generateSimple prevSt nbBytes
in (output, ChaChaDRG newSt)
|
