#!/usr/bin/env python

def bbs_gen(n, seed):
    """Blum Blum Shub PRNG"""
    x = pow(seed, 2, n)
    while True:
        yield x % 256
        x = pow(x, 2, n)

def xor_cipher(text, n, seed):
    """Uses Blum Blum Shub generator to en/decipher text via XOR"""
    bbs = bbs_gen(n, seed)
    return ''.join(chr(x) for x in (ord(t) ^ next(bbs) for t in text))

if __name__ == "__main__":
    P, Q, S = 983, 991, 17
    PLAIN = "PROGRAMMING PRAXIS"
    CIPHER = xor_cipher(PLAIN, P * Q, S)
    print CIPHER
    print xor_cipher(CIPHER, P * Q, S)

def encypher(n, s, text):
bbs = blum_blum_shub(n, s)
return [ord(c)^bbs.next() for c in text]

def decypher (n, s, lst):
bbs = blum_blum_shub(n, s)
return ”.join([chr(i^bbs.next()) for i in lst])

decypher(974153, 17, encypher (974153, 17, “PROGRAMMING PRAXIS”))

import Data.Bits
import Data.Char

rng :: Int -> Int -> [Int]
rng m = map (.&. 7) . tail . iterate (\n -> mod (n ^ 2) m)

cipher :: Int -> Int -> Int -> String -> String
cipher s p q = map chr . zipWith xor (rng (p * q) s) . map ord

main :: IO ()
main = do print $ cipher 3 11 19 "Bonsai Code"
          print . cipher 3 11 19 $ cipher 3 11 19 "Bonsai Code"