from multiprocessing import Process

def encrypt(key, msg):
    key = list(key)
    msg = list(msg)
    for char_key in key:
        for i in range(len(msg)):
            if i == 0:
                tmp = ord(msg[i]) + ord(char_key) + ord(msg[-1])
            else:
                tmp = ord(msg[i]) + ord(char_key) + ord(msg[i-1])

            while tmp > 255:
                tmp -= 256
            msg[i] = chr(tmp)
    return ''.join(msg)

def decrypt(key, msg):
    key = list(key)
    msg = list(msg)
    for char_key in reversed(key):
        for i in reversed(range(len(msg))):
            if i == 0:
                tmp = ord(msg[i]) - (ord(char_key) + ord(msg[-1]))
            else:
                tmp = ord(msg[i]) - (ord(char_key) + ord(msg[i-1]))
            while tmp < 0:
                tmp += 256
            msg[i] = chr(tmp)
    return ''.join(msg)

def is_ascii(txt, prc = 0.6):
    tot = len(txt)
    num_ascii = 0
    for c in txt:
        if ord(c) < 128:
            num_ascii += 1
    return (num_ascii / tot) >= prc

def are_there_some_spaces(txt, some = 5):
    tot = len(txt)
    num_spaces = 0
    for c in txt:
        if ord(c) == 0x20: # space hex code
            num_spaces += 1
    return num_spaces >= some

def brute_force_job(words, start, end, job):
    print('I am job #{0}, trying from {1} to {2}...'.format(job, start, end))
    enc_file = open('ciphertext', 'rb')
    enc_text = enc_file.read()
    for index in range(start, end):
        key = words[index].strip()
        dec = decrypt(key, enc_text)
        try:
            # dec_text = dec.decode()
            if are_there_some_spaces(dec, 5):
                print('Found Key: {0}'.format(key))
                print('Found Txt: {0}'.format(dec))
        except:
            continue

def brute_force(wordlist_path, cpu = 8):
    wordlist = open(wordlist_path, 'r')
    words = wordlist.readlines()
    chunk_size = len(words) / cpu
    curr_start = 0
    curr_end = curr_start + chunk_size
    for c in range(cpu):
        if c == cpu - 1:
            curr_end = len(words)
        p = Process(target=brute_force_job, args=(words, curr_start, curr_end, c))
        p.start()
        curr_start = curr_end
        curr_end = curr_end + chunk_size


if __name__ == '__main__':
    brute_force('/usr/share/wordlists/rockyou.txt', 8)