def decode_byte(b1, server, b_size):
decoded_byte = 0
for k in range(0, 256):
b1[b_size - 1] = k
c_text = server.aes_128_ecb(str(bytes(b1), 'latin1'))
if detect_ecb(binascii.hexlify(c_text)):
decoded_byte = k
break
return decoded_byte
# if padding_found:
# for k in range(0, last_byte):
# b_array.pop()
#
# return bytes(b_array).decode('ascii')
if __name__ == '__main__':
s = Server()
# find the block size used by the server
block_size = find_block_size(s)
# try to detect ecb mode
two_blocks = [ord('x')] * block_size * 2
ecb_detected = detect_ecb(
binascii.hexlify(s.aes_128_ecb(str(bytes(two_blocks), 'latin1'))))
# decrypt the unknown string
if ecb_detected:
match_block = [ord('x')
] * block_size # block used to match unknown bytes
plain_blocks = []
i = 0
while True:
# controls offset so the next unknown byte is always the last in a block
offset_block = make_offset_block(i % block_size, block_size)
b = match_block + offset_block
b_array = bytearray(my_encode(plaintext))
# randomly prepend 5-10 bytes
random_prepend = os.urandom(1)
num_prepend_bytes = 5 + random_prepend[0] % 6 # noOfPrependBytes
for i in range(0, num_prepend_bytes):
b_array.append(os.urandom(1)[0])
# randomly append 5-10 bytes
random_append = os.urandom(1)
num_append_bytes = 5 + random_append[0] % 6 # noOfAppendBytes
for j in range(0, num_append_bytes):
b_array.insert(0, os.urandom(1)[0])
# create modified plaintext
plaintext = bytes(b_array)
# encrypt
if mode == 0:
ciphertext = encrypt_ecb(plaintext, random_key, True)
else:
random_iv = os.urandom(16)
ciphertext = bytes(my_encode(encrypt_cbc(plaintext, random_key, random_iv)))
# ciphertext = bytes(test_encrypt(plaintext, random_key, random_iv))
# print detected mode
if detect_ecb(binascii.hexlify(ciphertext)):
print("ECB mode detected")
else:
print("CBC mode detected")