double_key.hs

-- implementing a simple 2 key encrypt/decrypt
-- assuming a n-vector p (message)
-- generate a random n-vector v1 (key1)
-- and n-vector v2 (via subtract v1 from p)

subV :: Integer -> Integer -> Integer
subV x y | x == y = 0
         | otherwise = 1

encode :: [Integer] -> [Integer] -> [Integer]
encode [] _ = []
encode (p:ps) (v1:v1s) = [subV p v1] ++ encode ps v1s

-- e.g.
-- Prelude> let p = [1,0,1,0,1,1,1]
-- Prelude> let v1 = [0,0,0,1,0,1,0]
-- Prelude> let v2 = encode p v1
-- Prelude> v2
-- [1,0,1,1,1,0,1]
-- Prelude> p == encode v2 v1
-- True