oneTimePad.py

#!/usr/bin/env python
# coding=utf-8

from os import urandom

def process(m, k):
    tmp = m ^ k
    res = 0
    for i in bin(tmp)[2:]:
        res = res << 1;
        if (int(i)):
            res = res ^ tmp
        if (res >> 256):
            res = res ^ P
    return res

def keygen(seed):
    key = str2num(urandom(32))
    while True:
        yield key
        key = process(key, seed)

def str2num(s):
    return int(s.encode('hex'), 16)

P = 0x10000000000000000000000000000000000000000000000000000000000000425L

true_secret = open('flag.txt').read()[:32]
assert len(true_secret) == 32
print 'flag{%s}' % true_secret
fake_secret1 = "I_am_not_a_secret_so_you_know_me"
fake_secret2 = "feeddeadbeefcafefeeddeadbeefcafe"
secret = str2num(urandom(32))

generator = keygen(secret)
ctxt1 = hex(str2num(true_secret) ^ generator.next())[2:-1]
ctxt2 = hex(str2num(fake_secret1) ^ generator.next())[2:-1]
ctxt3 = hex(str2num(fake_secret2) ^ generator.next())[2:-1]
f = open('ciphertext', 'w')
f.write(ctxt1+'\n')
f.write(ctxt2+'\n')
f.write(ctxt3+'\n')
f.close()