def forward_and_decrypt(self, key: bytes) -> bytes:
key = SHA1(key).digest()[:16]
iv = self.received_cyphertext[-16:]
message = de_pkcs7(decrypt_aes_cbc(key, iv,
self.received_cyphertext[:-16]))
self.peer.receive_message(self.received_cyphertext)
return message
def main() -> None:
with open("data/10.txt", "r") as data:
cyphertext = b64decode(data.read())
key = b"YELLOW SUBMARINE"
iv = bytes(len(key))
plaintext = de_pkcs7(decrypt_aes_cbc(key, iv, cyphertext))
print(plaintext.decode())
def break_ecb(oracle: Callable[[bytes], bytes]) -> bytes:
bs = blocksize(oracle)
l = len(oracle(b""))
string_length = len_string(oracle)
plaintext = b""
prefix = (l + bs - 1) * b"A"
while len(plaintext) <= string_length:
oracle_prefix = oracle(prefix)
for i in range(127):
test = prefix + plaintext + bytes([i])
if oracle(test)[l:l + bs] == oracle_prefix[l:l + bs]:
prefix = prefix[1:]
plaintext += bytes([i])
break
return de_pkcs7(plaintext)
def break_ecb(oracle: Callable[[bytes], bytes]) -> bytes:
bs = blocksize(oracle)
l = len(oracle(b""))
prefix_length = len_prefix(oracle)
string_length = len_string(oracle) - prefix_length
plaintext = b""
uc = (l + bs - prefix_length - 1) * b"A"
while len(plaintext) <= string_length:
oracle_input = oracle(uc)
for i in range(127):
test = uc + plaintext + bytes([i])
if oracle(test)[l:l + bs] == oracle_input[l:l + bs]:
uc = uc[1:]
plaintext += bytes([i])
break
return de_pkcs7(plaintext)
def break_ecb(oracle):
bs = blocksize(oracle)
l = len(oracle())
string_length = len_string(oracle)
prefix_length = len_prefix(oracle)
plaintext = b''
uc = (l + bs - len_prefix(oracle) - 1) * b'A'
while len(plaintext) <= string_length:
oracle_input = oracle(uc)
for i in range(127):
test = uc + plaintext + bytes([i])
if oracle(test)[l:l + bs] == oracle_input[l:l + bs]:
uc = uc[1:]
plaintext += bytes([i])
#print(chr(i), end = "", flush = True)
break
return de_pkcs7(plaintext)
def break_ecb(oracle):
bs = blocksize(oracle)
l = len(oracle())
string_length = len_string(oracle)
plaintext = b''
prefix = (l + bs - 1) * b'A'
while len(plaintext) <= string_length:
oracle_prefix = oracle(prefix)
for i in range(127):
test = prefix + plaintext + bytes([i])
if oracle(test)[l:l + bs] == oracle_prefix[l:l + bs]:
#if i < 10: # hack to break if non-
# return plaintext # printable padding found
prefix = prefix[1:]
plaintext += bytes([i])
#print(chr(i), end = "", flush = True)
break
return de_pkcs7(plaintext)
def decrypt(cyphertext):
cypher = AES.new(RANDOM_KEY, AES.MODE_ECB)
return de_pkcs7(cypher.decrypt(cyphertext))
def receive_message(self, cyphertext: bytes) -> None:
self.received_cyphertext = cyphertext
iv = cyphertext[-16:]
message = de_pkcs7(decrypt_aes_cbc(self._aes_key(), iv,
cyphertext[:-16]))
self.received_message = message
def decrypt_oracle(profile: bytes) -> dict[str, str]:
cypher = AES.new(RANDOM_KEY, AES.MODE_ECB)
profile = de_pkcs7(cypher.decrypt(profile))
return parse(profile.decode())
def decrypt_oracle(profile):
cypher = AES.new(RANDOM_KEY, AES.MODE_ECB)
profile = de_pkcs7(cypher.decrypt(profile))
return parse(profile.decode())
def decrypt(cyphertext: bytes) -> bytes:
cypher = AES.new(RANDOM_KEY, AES.MODE_ECB)
return de_pkcs7(cypher.decrypt(cyphertext))
for block in blocks:
block = fixed_xor(block, vector)
block = cypher.encrypt(block)
cyphertext += block
vector = block
return cyphertext
def decrypt_aes_cbc(cyphertext, key, iv):
cypher = AES.new(key, AES.MODE_ECB)
blocks = [cyphertext[i:i + len(key)] for i in range(0, len(cyphertext), len(key))]
vector = iv
plaintext = b''
for aesblock in blocks:
block = cypher.decrypt(aesblock)
plaintext += fixed_xor(block, vector)
vector = aesblock
return plaintext
if __name__ == "__main__":
cyphertext = b64decode(open("data/10.txt", "r").read())
key = bytes("YELLOW SUBMARINE", "utf8")
iv = bytes(len(key))
plaintext = de_pkcs7(decrypt_aes_cbc(cyphertext, key, iv))
print(plaintext.decode())
def decrypt(self, cyphertext: bytes = None) -> bytes:
cyphertext = cyphertext or self._message_buffer.pop()
iv = cyphertext[-16:]
message = de_pkcs7(
decrypt_aes_cbc(self._aes_key(), iv, cyphertext[:-16]))
return message
