{-| Maintainer: Thomas.DuBuisson@gmail.com Stability: beta Portability: portable -} module Crypto.HMAC ( hmac , hmac' , MacKey(..) ) where import qualified Data.ByteString as B import qualified Data.ByteString.Lazy as L import Crypto.Classes import Data.Serialize (encode) import Data.Bits (xor) -- | A key carrying phantom types @c@ and @d@, forcing the key data to only be used -- by particular hash algorithms. newtype MacKey c d = MacKey B.ByteString deriving (Eq, Ord, Show) -- |Message authentication code calculation for lazy bytestrings. -- @hmac k msg@ will compute an authentication code for @msg@ using key @k@ hmac :: (Hash c d) => MacKey c d -> L.ByteString -> d hmac (MacKey k) msg = res where res = hash' . B.append ko . encode . f . L.append ki $ msg f = hashFunc res keylen = B.length k blen = blockLength .::. res `div` 8 k' = case compare keylen blen of GT -> B.append (encode . f . fc $ k) (B.replicate (blen - (outputLength .::. res `div` 8) ) 0x00) EQ -> k LT -> B.append k (B.replicate (blen - keylen) 0x00) ko = B.map (`xor` 0x5c) k' ki = fc $ B.map (`xor` 0x36) k' fc = L.fromChunks . (\x -> [x]) -- | @hmac k msg@ will compute an authentication code for @msg@ using key @k@ hmac' :: (Hash c d) => MacKey c d -> B.ByteString -> d hmac' k = hmac k . L.fromChunks . return