cryptopals

Matasano's cryptopals challenges (cryptopals.com).
git clone git://git.jtobin.io/cryptopals.git
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Tools.hs (596B)

      1 module Cryptopals.Block.Tools (
      2     Mode(..)
      3 
      4   , detectMode
      5   ) where
      6 
      7 import qualified Data.ByteString as BS
      8 import qualified Data.Set as S
      9 
     10 data Mode =
     11     ECB
     12   | CBC
     13   deriving (Eq, Show)
     14 
     15 -- Assuming the ciphertext could only have been produced by AES
     16 -- operating in ECB or CBC mode, guess the mode that was used.
     17 detectMode :: BS.ByteString -> Mode
     18 detectMode = loop mempty where
     19   loop !acc bs
     20     | BS.null bs = CBC
     21     | otherwise  =
     22         let (block, rest) = BS.splitAt 16 bs
     23         in  if   S.member block acc
     24             then ECB
     25             else loop (S.insert block acc) rest
     26