-- | -- Module : Crypto.MAC.HMAC -- License : BSD-style -- Maintainer : Vincent Hanquez <vincent@snarc.org> -- Stability : experimental -- Portability : unknown -- -- provide the HMAC (Hash based Message Authentification Code) base algorithm. -- <http://en.wikipedia.org/wiki/HMAC> -- module Crypto.MAC.HMAC ( hmac ) where import Data.ByteString (ByteString) import qualified Data.ByteString as B import Data.Bits (xor) -- | compute a MAC using the supplied hashing function -- -- An incremental API can be found in the module "Crypto.Hash". -- hmac :: (ByteString -> ByteString) -- ^ hash function -> Int -- ^ block size -> ByteString -- ^ secret -> ByteString -- ^ message -> ByteString hmac hashF blockSize secret msg = hashF $ B.append opad (hashF $ B.append ipad msg) where opad = B.map (xor 0x5c) k' ipad = B.map (xor 0x36) k' k' = B.append kt pad kt = if B.length secret > fromIntegral blockSize then hashF secret else secret pad = B.replicate (fromIntegral blockSize - B.length kt) 0