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diff --git a/Feistel.hs b/Feistel.hs
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+{-# LANGUAGE UnboxedTuples #-}
+module Feistel where
+
+import qualified Data.ByteString as B
+import qualified Data.ByteString.Lazy as L
+import Data.Word
+import Data.Bits
+import Data.Binary
+import System.Endian
+
+toW32Pair :: B.ByteString -> ( Word32, Word32 )
+toW32Pair b = let (x1, x2) = B.splitAt 4 b
+                  w1 = decode32be x1
+                  w2 = decode32be x2
+              in ( w1,w2 )
+
+fromW32Pair :: (Word32, Word32) -> B.ByteString
+fromW32Pair (w1,w2)
+    = let w1' = fromIntegral w1
+          w2' = fromIntegral w2
+          w = (w1' `shiftL` 32) .|. w2'
+      in encode64be w
+
+
+decode32be :: B.ByteString -> Word32
+decode32be s = id $!
+    (fromIntegral (s `B.index` 0) `shiftL` 24) .|.
+    (fromIntegral (s `B.index` 1) `shiftL` 16) .|.
+    (fromIntegral (s `B.index` 2) `shiftL`  8) .|.
+    (fromIntegral (s `B.index` 3) )
+
+encode64be :: Word64 -> B.ByteString
+encode64be w = B.pack . map fromIntegral $
+                [ (w `shiftR` 56) .&. 0xff
+                , (w `shiftR` 48) .&. 0xff
+                , (w `shiftR` 40) .&. 0xff
+                , (w `shiftR` 32) .&. 0xff
+                , (w `shiftR` 24) .&. 0xff
+                , (w `shiftR` 16) .&. 0xff
+                , (w `shiftR` 8) .&. 0xff
+                , w .&. 0xff
+                ]
+
+splitWord32 :: Word32 -> (# Word8, Word8, Word8, Word8 #)
+splitWord32 w = (# a,b,c,d #)
+ where
+    a = fromIntegral $ w `shiftR` 24
+    b = fromIntegral $ w `shiftR` 16
+    c = fromIntegral $ w `shiftR` 8
+    d = fromIntegral $ w