Decode CTX1 encoding

DecodeCTX1.hs

module Main where

import Data.Char
import Data.Word
import Data.Bits
import qualified Data.Text as T
import qualified Data.Text.Encoding as E
import Data.ByteString as B
import Data.ByteString.Char8 as BC

decodeCTX1 :: [Word8] -> [Word8]
decodeCTX1 (c1:c2:cs) = toEnum ((fromEnum c1 - fromEnum 'A') * 16 + (fromEnum c2 - fromEnum 'A')) : decodeCTX1 cs
decodeCTX1 _ = []

applyXor :: Word8 -> [Word8] -> [Word8]
applyXor seed = go 0
    where go s (c:cs) = let c' = c `xor` seed `xor` s in c' : go c cs
          go _ [] = []

main :: IO()
main = B.interact $
    -- BC.pack . show . 
    E.encodeUtf8 . E.decodeUtf16LE . B.pack .    
        applyXor 0xA5 . decodeCTX1 . B.unpack