#
# One-Time (or Two-Time) Padding Code
#

### This is "super secure"!  We need a good cryptographic PRNG.
from Crypto.Random import random

###
### Some routines for manipulating bits
###

BITS = ('0', '1')

def display_bits(b):
    """converts list of {0, 1}* to string"""
    return ''.join([BITS[e] for e in b])

def seq_to_bits(seq):
    return [0 if b == '0' else 1 for b in seq]

def convert_to_bits(n, pad): 
    result = []
    while n > 0:
        result = [n % 2] + result
        n = n / 2
    while len(result) < pad: result = [0] + result
    return result

def string_to_bits(s):
    def chr_to_bit(c): return convert_to_bits(ord(c), 7)
    return [b for group in map(chr_to_bit, s) for b in group]

def bits_to_char(b):
    assert len(b) == 7
    value = 0
    for e in b: value = (value * 2) + e
    return chr(value)

def list_to_string(p):
    return ''.join(p)

def bits_to_string(b):
    return ''.join([bits_to_char(b[i:i + 7]) 
                    for i in range(0, len(b), 7)])

def random_sequence(n):
    return map(lambda x: random.choice([0, 1]), range(n))

### One-Time Pad - just XOR all message bits with corresponding key bits.

def otp(m, k):
    assert len(m) == len(k)
    return [(mm + kk) % 2 for mm, kk in zip(m, k)]