diff --git a/Crypto/Cipher/DES/Serialization.hs b/Crypto/Cipher/DES/Serialization.hs
--- a/Crypto/Cipher/DES/Serialization.hs
+++ b/Crypto/Cipher/DES/Serialization.hs
@@ -15,40 +15,47 @@
     , unblockify
     ) where
 
-import Data.Word (Word64)
 import qualified Data.ByteString as B
 import Crypto.Cipher.DES.Primitive (Block(..))
 
 #ifdef ARCH_IS_LITTLE_ENDIAN
+import Data.Word (Word64)
 import Data.Byteable (withBytePtr)
 import qualified Data.ByteString.Internal as B (inlinePerformIO, unsafeCreate)
 import Foreign.Storable
 import Foreign.Ptr (castPtr, plusPtr, Ptr)
+import Data.Bits (shiftL, shiftR, (.|.), (.&.))
 #else
 import Data.Bits (shiftL, shiftR, (.|.))
 #endif
 
 #ifdef ARCH_IS_LITTLE_ENDIAN
--- | convert a 8 byte bytestring to a little endian word64
+-- | convert a 8 byte bytestring big endian to a host one
 toW64 :: B.ByteString -> Block
-toW64 b = Block $ B.inlinePerformIO $ withBytePtr b $ \ptr -> peek (castPtr ptr)
+toW64 b = Block $ B.inlinePerformIO $ withBytePtr b $ \ptr -> (be64 `fmap` peek (castPtr ptr))
 
--- | convert a word64 to a bytestring in little endian format
+-- | convert a word64 to a bytestring in big endian format
 toBS :: Block -> B.ByteString
-toBS (Block w) = B.unsafeCreate 8 $ \ptr -> poke (castPtr ptr) w
+toBS (Block w) = B.unsafeCreate 8 $ \ptr -> poke (castPtr ptr) (be64 w)
 
 -- | Create a strict bytestring out of DES blocks
 unblockify :: [Block] -> B.ByteString
 unblockify blocks = B.unsafeCreate (nbBlocks * 8) $ \initPtr -> pokeTo (castPtr initPtr) blocks
   where nbBlocks = length blocks
         pokeTo :: Ptr Word64 -> [Block] -> IO ()
-        pokeTo _   []     = return ()
-        pokeTo ptr (Block x:xs) = poke ptr x >> pokeTo (ptr `plusPtr` 8) xs
+        pokeTo _   []           = return ()
+        pokeTo ptr (Block x:xs) = poke ptr (be64 x) >> pokeTo (ptr `plusPtr` 8) xs
 
+be64 :: Word64 -> Word64
+be64 w =
+        (w `shiftR` 56)                  .|. (w `shiftL` 56)
+    .|. ((w `shiftR` 40) .&. 0xff00)     .|. ((w .&. 0xff00) `shiftL` 40)
+    .|. ((w `shiftR` 24) .&. 0xff0000)   .|. ((w .&. 0xff0000) `shiftL` 24)
+    .|. ((w `shiftR` 8)  .&. 0xff000000) .|. ((w .&. 0xff000000) `shiftL` 8)
 #else
 -- | convert a 8 byte bytestring to a little endian word64
 toW64 :: B.ByteString -> Block
-toW64 b = Block $ case B.unpack b of
+toW64 bs = Block $ case B.unpack bs of
             [a,b,c,d,e,f,g,h] -> shl h 0  .|. shl g 8 .|. shl f 16 .|. shl e 24 .|.
                                  shl d 32 .|. shl c 40 .|. shl b 48 .|. shl a 56
             _                 -> 0
@@ -56,7 +63,7 @@
 
 -- | convert a word64 to a bytestring in little endian format
 toBS :: Block -> B.ByteString
-toBS (Block w) = B.pack $ map (shr w) [56,48,40,32,24,16,8,0]
+toBS (Block b) = B.pack $ map (shr b) [56,48,40,32,24,16,8,0]
   where shr w n = fromIntegral (w `shiftR` n)
 
 -- | Create a strict bytestring out of DES blocks
diff --git a/cipher-des.cabal b/cipher-des.cabal
--- a/cipher-des.cabal
+++ b/cipher-des.cabal
@@ -1,5 +1,5 @@
 Name:                cipher-des
-Version:             0.0.2
+Version:             0.0.3
 Description:         DES and 3DES primitives
 License:             BSD3
 License-file:        LICENSE