def main():
text = open('ecb_text').read()
ctr = RandomAccessCTR()
ciphertext = ctr.encrypt(text)
new_ciphertext = ctr.edit(ciphertext, 0, 'a' * len(ciphertext))
keystream = util.string_xor(new_ciphertext, 'a' * len(ciphertext))
print util.string_xor(keystream, ciphertext)
def main():
text = open('ecb_text').read()
ctr = RandomAccessCTR()
ciphertext = ctr.encrypt(text)
new_ciphertext = ctr.edit(ciphertext, 0, 'a'*len(ciphertext))
keystream = util.string_xor(new_ciphertext, 'a'*len(ciphertext))
print util.string_xor(keystream, ciphertext)
def cbc_encrypt(text, key, iv):
''' CBC encrypt text with initialization vector iv and key '''
block_length = len(iv)
text = pkcs_padding(text, block_length)
blocks = util.blocks(text, block_length)
blocks[0] = util.string_xor(blocks[0], iv)
blocks[0] = util.ecb_encrypt(blocks[0], key)
for i in xrange(1, len(blocks)):
blocks[i] = util.string_xor(blocks[i], blocks[i - 1])
blocks[i] = util.ecb_encrypt(blocks[i], key)
return ''.join(blocks)
def cbc_decrypt(text, key, iv):
''' CBC decrypt text with initialization vector iv and key '''
block_length = len(iv)
blocks = util.blocks(text, block_length)
decoded_blocks = [0] * len(blocks)
decoded_blocks[0] = util.ecb_decrypt(blocks[0], key)
decoded_blocks[0] = util.string_xor(decoded_blocks[0], iv)
for i in xrange(1, len(blocks)):
decoded_blocks[i] = util.ecb_decrypt(blocks[i], key)
decoded_blocks[i] = util.string_xor(decoded_blocks[i], blocks[i - 1])
return ''.join(decoded_blocks)
def cbc_decrypt(text, key, iv):
''' CBC decrypt text with initialization vector iv and key '''
block_length = len(iv)
blocks = util.blocks(text, block_length)
decoded_blocks = [0] * len(blocks)
decoded_blocks[0] = util.ecb_decrypt(blocks[0], key)
decoded_blocks[0] = util.string_xor(decoded_blocks[0], iv)
for i in xrange(1, len(blocks)):
decoded_blocks[i] = util.ecb_decrypt(blocks[i], key)
decoded_blocks[i] = util.string_xor(decoded_blocks[i], blocks[i-1])
return ''.join(decoded_blocks)
def cbc_encrypt(text, key, iv):
''' CBC encrypt text with initialization vector iv and key '''
block_length = len(iv)
text = pkcs_padding(text, block_length)
blocks = util.blocks(text, block_length)
blocks[0] = util.string_xor(blocks[0], iv)
blocks[0] = util.ecb_encrypt(blocks[0], key)
for i in xrange(1, len(blocks)):
blocks[i] = util.string_xor(blocks[i], blocks[i-1])
blocks[i] = util.ecb_encrypt(blocks[i], key)
return ''.join(blocks)
def recover_seed(ciphertext, known_text):
known_length = len(known_text)
padding = len(ciphertext) - known_length
rounded_padding = padding % 4
if rounded_padding != 0:
rounded_padding = 4 - rounded_padding
# Start of our known text
known_start = padding + rounded_padding
known_end = padding + rounded_padding + 8
known = ciphertext[known_start:known_end]
# Convert them to numbers which were generated by rng
t = util.string_xor(known, known_text[-8:])
known_a = struct.unpack(">L", t[:4])[0]
known_b = struct.unpack(">L", t[4:])[0]
for i in xrange(65536):
update_progress(i, 65536)
mt = MersenneTwister(i)
for ignore in xrange(padding/4):
mt.next()
for check in xrange(known_length + 5):
if mt.next() == known_a:
if mt.next() == known_b:
return i
return "FAILED"
def ctr_decrypt(text, key='YELLOW SUBMARINE', nonce=0):
''' CTR decrypt a text using key and nonce '''
block_size = len(key)
blocks = util.get_blocks(text, block_size)
c = Counter()
decrypted = ''
for block in blocks:
keystring = util.ecb_encrypt(c.next(), key)
decrypted += util.string_xor(keystring, block)
return decrypted
def try_ngrams(ciphertexts, length, ngram_frequency):
''' Match most repeated ngram with most common possible
ngrams (from the list declared above), going down to least
possible occurence
'''
global trigrams
global keystream
most_common = repeated_ngrams(ciphertexts, length)
# Start with most occured ngram
for repeated_ngram in most_common:
# ngram reference frequency
for ngram in ngram_frequency:
possible_keystream = util.string_xor(repeated_ngram['content'], ngram)
start = repeated_ngram['start']
s = ''
# Go through every ciphertext, and apply keystream at that position
for ciphertext in ciphertexts:
s += util.string_xor(possible_keystream, ciphertext[start:start+length]) + '-'
if len(s.strip(allowed_letters)) == 0:
if keystream.available(start, possible_keystream):
keystream.assign(start, possible_keystream)
def main():
aes = AES()
text = 'a' * 16 * 3
encrypted = aes.encrypt(text)
blocks_encrypted = util.get_blocks(encrypted, 16)
blocks_encrypted[0] = blocks_encrypted[2] = blocks_encrypted[1]
blocks_encrypted[1] = '\0' * 16
modified_encrypted = ''.join(blocks_encrypted)
try:
decrypted = aes.decrypt(modified_encrypted)
except InvalidString as e:
decrypted = str(e)
blocks_decrypted = util.get_blocks(decrypted, 16)
print 'Recovered key/IV: ', repr(util.string_xor(blocks_decrypted[0], blocks_decrypted[2]))
def main():
aes = AES()
text = 'a' * 16 * 3
encrypted = aes.encrypt(text)
blocks_encrypted = util.get_blocks(encrypted, 16)
blocks_encrypted[0] = blocks_encrypted[2] = blocks_encrypted[1]
blocks_encrypted[1] = '\0' * 16
modified_encrypted = ''.join(blocks_encrypted)
try:
decrypted = aes.decrypt(modified_encrypted)
except InvalidString as e:
decrypted = str(e)
blocks_decrypted = util.get_blocks(decrypted, 16)
print 'Recovered key/IV: ', repr(
util.string_xor(blocks_decrypted[0], blocks_decrypted[2]))
def print_decoded(ciphertexts, keystream):
for ciphertext in ciphertexts:
print repr(util.string_xor(ciphertext, str(keystream)))