def hmac(key, message):
if (len(key) > BLOCKSIZE):
key = bytearray(sha1(key).decode(
'hex')) # keys longer than BLOCKSIZE are shortened
if (len(key) < BLOCKSIZE):
# keys shorter than BLOCKSIZE are zero-padded (where + is concatenation)
key = key + bytearray([0x00] *
(BLOCKSIZE - len(key))) # Where * is repetition.
o_key_pad = xor(bytearray([0x5c] * BLOCKSIZE), key)
i_key_pad = xor(bytearray([0x36] * BLOCKSIZE), key)
h1 = sha1(i_key_pad + string_to_bytearray(message))
return sha1(o_key_pad + hexstr2bytearray(h1))
def find_x_mod_r(h, r, m, tag):
for i in range(0, r):
k = pow(h, i, p)
key = bytearray(sha1(str(k)).decode('hex'))[:16]
if hmac(key, m) == tag:
return i
raise Exception('x mod r not found!!!')
def mitm_attack_3():
p = int(
"ffffffffffffffffc90fdaa22168c234c4c6628b80dc1cd129024"
"e088a67cc74020bbea63b139b22514a08798e3404ddef9519b3cd"
"3a431b302b0a6df25f14374fe1356d6d51c245e485b576625e7ec"
"6f44c42e9a637ed6b0bff5cb6f406b7edee386bfb5a899fa5ae9f"
"24117c4b1fe649286651ece45b3dc2007cb8a163bf0598da48361"
"c55d39a69163fa8fd24cf5f83655d23dca3ad961c62f356208552"
"bb9ed529077096966d670c354e4abc9804f1746c08ca237327fff"
"fffffffffffff", 16)
g = 2
# initial phase
alice = HonestCryptographer(p, g)
alice.generate_keys()
bob = HonestCryptographer(1, 1) # inactive party with dummy params
# 1st message
message_type = 'p, g'
message = (alice.p, alice.g)
for_bob = send_A_to_B(alice, bob, message_type, message,
active_adversary_g_p_minus_1)
bob.p = for_bob[0]
bob.g = for_bob[1]
bob.generate_keys()
# 2nd mesage
message_type = 'ACK'
message = 'ACK'
_ = send_B_to_A(alice, bob, message_type, message,
active_adversary_g_p_minus_1)
print(f"Bob params: p = {bob.p}, g = {bob.g}")
# 3rd message
message_type = 'A'
message = alice.public_key
for_bob = send_A_to_B(alice, bob, message_type, message,
active_adversary_g_p_minus_1)
bob.compute_shared_secret(for_bob)
print(f'Bob shared secret: {bob.shared_secret}')
# 4th message
message_type = 'B'
message = bob.public_key
for_alice = send_A_to_B(alice, bob, message_type, message,
active_adversary_g_p_minus_1)
alice.compute_shared_secret(for_alice)
print(f'Alice shared secret: {alice.shared_secret}')
# 5th message
message_type = 'A->B message'
message = alice.send_encrypted_message(s2b('YELLOW SUBMARINE'))
for_bob = send_A_to_B(alice, bob, message_type, message,
active_adversary_g_p_minus_1)
print(
f'\nReceived by Bob: {bob.receive_encrypted_message(for_bob[0], for_bob[1])}'
)
key = key = hex_string_to_bytearray(sha1(s2b('1')))[:16]
decrypted = decrypt_aes_cbc(for_bob[0], key, for_bob[1])
print(f'Decrypted by Mallory: {decrypted}')
win_condition_1 = decrypted == b'YELLOW SUBMARINE'
key = hex_string_to_bytearray(sha1(s2b(str(ADVERSARY_STATE_3['p'] -
1))))[:16]
decrypted = decrypt_aes_cbc(for_bob[0], key, for_bob[1])
print(f'Decrypted by Mallory: {decrypted}')
win_condition_2 = decrypted == b'YELLOW SUBMARINE'
# 6th message
message_type = 'B->A message'
message = bob.send_encrypted_message(s2b('SATOSHI NAKAMOTO'))
for_alice = send_A_to_B(alice, bob, message_type, message,
active_adversary_g_p_minus_1)
print(
f'\nReceived by Alice: {alice.receive_encrypted_message(for_alice[0], for_alice[1])}'
)
return win_condition_1 or win_condition_2
def hkdf(self):
ss = string_to_bytearray(str(self.shared_secret))
return hex_string_to_bytearray(sha1(ss))[:16]