Hello everyone,
Today I am trying to resolve an AES incompatibility with Python. I am
using CFB Mode. I use the same base64 key and iv on both and I printed out
the bytes and they are the same.
I load in the same key/iv into both of them. When I print out the bytes
they are different.
This *encrypt_aes* is returning a string, I'm concerned maybe there is a
string conversion when decoding UTF-8/ASCII or something like that, so I
want to first do just raw bytes encryption, not a string ?
Question is how do I change the encrypt_aes to return a byte* rather than
string ?
std::string encrypt_aes(std::string message, SecByteBlock key, SecByteBlock
iv) {
try {
CFB_Mode<AES>::Encryption e;
std::string cipher;
e.SetKeyWithIV(key, key.size(), iv);
StringSource ss(message, true, new StreamTransformationFilter(e, new
StringSink(cipher)));
return cipher;
}
catch (CryptoPP::Exception e) {
std::cerr << e.what() << std::endl;
return "";
}
}
class AESModeOfOperationCFB(AESSegmentModeOfOperation):
'''AES Cipher Feedback Mode of Operation.
o A stream-cipher, so input does not need to be padded to blocks,
but does need to be padded to segment_size
Also see:
o
https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Cipher_feedback_.28CFB.29
o See NIST SP800-38A
(http://csrc.nist.gov/publications/nistpubs/800-38a/sp800-38a.pdf); section
6.3'''
name = "Cipher Feedback (CFB)"
def __init__(self, key, iv, segment_size = 1):
if segment_size == 0: segment_size = 1
if iv is None:
self._shift_register = [ 0 ] * 16
elif len(iv) != 16:
raise ValueError('initialization vector must be 16 bytes')
else:
self._shift_register = _string_to_bytes(iv)
self._segment_bytes = segment_size
AESBlockModeOfOperation.__init__(self, key)
segment_bytes = property(lambda s: s._segment_bytes)
def encrypt(self, plaintext):
if len(plaintext) % self._segment_bytes != 0:
raise ValueError('plaintext block must be a multiple of
segment_size')
#plaintext = _string_to_bytes(plaintext)
# Break block into segments
encrypted = [ ]
for i in xrange(0, len(plaintext), self._segment_bytes):
plaintext_segment = plaintext[i: i + self._segment_bytes]
xor_segment =
self._aes.encrypt(self._shift_register)[:len(plaintext_segment)]
cipher_segment = [ (p ^ x) for (p, x) in zip(plaintext_segment,
xor_segment) ]
# Shift the top bits out and the ciphertext in
self._shift_register =
_concat_list(self._shift_register[len(cipher_segment):], cipher_segment)
encrypted.extend(cipher_segment)
return encrypted #_bytes_to_string(encrypted)
def decrypt(self, ciphertext):
if len(ciphertext) % self._segment_bytes != 0:
raise ValueError('ciphertext block must be a multiple of
segment_size')
#ciphertext = _string_to_bytes(ciphertext)
print("starting decryption .. ")
# Break block into segments
decrypted = [ ]
for i in xrange(0, len(ciphertext), self._segment_bytes):
#print("dec 1")
cipher_segment = ciphertext[i: i + self._segment_bytes]
#print("dec 2")
xor_segment =
self._aes.encrypt(self._shift_register)[:len(cipher_segment)]
#print("dec 3")
plaintext_segment = [ (p ^ x) for (p, x) in zip(cipher_segment,
xor_segment) ]
#print("dec 4")
# Shift the top bits out and the ciphertext in
self._shift_register =
_concat_list(self._shift_register[len(cipher_segment):], cipher_segment)
#print("dec 5")
decrypted.extend(plaintext_segment)
#print("dec 6")
print("finished decrypt")
return decrypted#_bytes_to_string(decrypted)
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