def hmac_sha1(key, message):
if len(key) > block_size:
key = sha1(key).digest()
if len(key) < block_size:
key += (block_size - len(key)) * b'\x00'
o_key_pad = fixed_xor(key, b'\x5c' * block_size)
i_key_pad = fixed_xor(key, b'\x36' * block_size)
return sha1(o_key_pad + sha1(i_key_pad + message).digest()).digest()
def modify_ciphertext_ctr(ciphertext):
_, plaintext = authenticate(ciphertext)
print_split_blocks(plaintext)
# This is the ciphertext xor-red with the plaintext
# plaintext = ciphertext ^ keystream
# ciphertext = plaintext ^ keystream
# comment1=cooking|%20MCs;userdata=|hacker;comment2=|%20like%20a%20po|und%20of%20bacon
# print(len(plaintext), len(ciphertext))
keystream = fixed_xor(ciphertext, plaintext)
# print(keystream)
# print(len(keystream))
new_plaintext = bytearray(plaintext)
new_plaintext[32:48] = b'a;admin=true;c2='
new_plaintext = bytes(new_plaintext)
new_ciphertext = fixed_xor(new_plaintext, keystream)
return new_ciphertext
def modify_ciphertext(ciphertext):
# if we modify a certain block, it will be xor-ed with the ciphertext in the block after.
new_ciphertext = bytearray(ciphertext)
# this gives us the plaintext "comment1=whatever;userdata=hacker;commment2=whatever"
block_print() # keep stdout clean
_, plaintext = authenticate(ciphertext)
enable_print()
# b'comment1=cooking|%20MCs;userdata=|hacker;comment2=|%20like%20a%20po|und%20of%20bacon'
# Unchanged Unchanged Scrambled We Control Unchanged
to_xor = fixed_xor(plaintext[48:64], b'a;admin=true;ab=')
to_xor = pack('16B', *to_xor)
new_ciphertext[32:48] = fixed_xor(new_ciphertext[32:48], to_xor)
print_split_blocks_hex(ciphertext)
print_split_blocks_hex(new_ciphertext)
# we know that the plaintext
return bytes(new_ciphertext)
def aes_ctr_crypt(text, key, nonce):
othertext = bytearray()
counter = 0
aes = AES.new(key)
for block in split_blocks(text):
encrypted = aes.encrypt(pack('<qq', nonce, counter))
othertext += fixed_xor(encrypted[:len(block)], block)
counter += 1
return bytes(othertext)
def repeating_key(binary_string, binary_key):
binary_list = list(binary_string) # "Burning 'em" -> ["B", "u", ...]
key_list = repeat_to_length(binary_key, len(binary_list))
result = []
for a,b in zip(binary_list, key_list):
result.append(challenge2.fixed_xor(a,b))
return ''.join(map(str,result))
def test_set2(self):
text = fixed_xor('1c0111001f010100061a024b53535009181c',
'686974207468652062756c6c277320657965')
self.assertEqual(text, '0x746865206b696420646f6e277420706c6179')
def single_xor(binary, ascii_code): return challenge2.fixed_xor(binary, chr(ascii_code) * len(binary))
def crypt_mtr(text, seed):
mt = MersenneTwister()
mt.seed_mt(seed)
keystream = b''.join(
[struct.pack('I', mt.extract_number()) for _ in range(len(text))])
return fixed_xor(text, keystream, True)
import challenge3, challenge2
import sys
f = open("/Users/jacobhammontree/Projects/cryptopals/set1/challenge4.data",
"r")
lines = []
for l in f:
lines.append((l[0:len(l) - 1]))
lowest_score = sys.maxsize
results = {}
for l in lines:
analysis = challenge3.freq_analysis_get_key(l)
key = analysis[0] * (len(l) // 2)
pt_candidate = challenge2.fixed_xor(l, key)
pt_chunked = [
pt_candidate[i:i + 2] for i in range(0, len(pt_candidate), 2)
]
stringed = ""
for c in pt_chunked:
stringed += chr(int(c, 16))
results[analysis[1]] = stringed
print(results[min(results.keys())], min(results.keys()))
print(sorted(results.keys()))
