def CBCDecryptor(key, ciphertext):
byte_key = key.decode('hex')
cipher = AES.new(key=byte_key)
byte_ct = ciphertext.decode('hex')
split_ct = split_by_length(byte_ct, 16)
iv = split_ct[0]
result = []
for index, block_ct in enumerate(split_ct[1:]):
if index == 0:
block_pt = strxor(cipher.decrypt(block_ct), iv)
else:
block_pt = strxor(cipher.decrypt(block_ct), split_ct[index])
result.append(block_pt)
return ''.join(result)
def CTRDecryptor(key, ciphertext):
byte_key = key.decode('hex')
cipher = AES.new(key=byte_key)
byte_ct = ciphertext.decode('hex')
split_ct = split_by_length(byte_ct, 16)
iv = split_ct[0]
result = []
for index, block_ct in enumerate(split_ct[1:]):
block_iv = copy.deepcopy(iv)
split_block_iv = split_by_length(block_iv, 1)
split_block_iv[-1] = chr(ord(split_block_iv[-1]) + index)
block_iv = ''.join(split_block_iv)
block_pt = strxor(cipher.encrypt(block_iv), block_ct)
result.append(block_pt)
return ''.join(result)
return True # good padding
return False # bad padding
decoded_CT = CT.decode('hex')
split_CT = split_by_length(decoded_CT, 16)
byte_num = len(split_CT)
split_MSG = [[]] * byte_num
po = PaddingOracle()
for i in range(1, byte_num):
IV = split_CT[i - 1]
part_MSG = [''] * 16
for j in range(1, 17):
print j
for k in range(256):
if i == 3 and k == 1:
continue
print k
trial = strxor(chr(k) + ''.join(part_MSG[-j:]), chr(j) * j)
trial_CT = IV[:-j] + strxor(IV[-j:], trial) + split_CT[i]
trial_CT = trial_CT.encode('hex')
# print trial_CT
if po.query(trial_CT): # Issue HTTP query with the given argument
part_MSG[-j] = chr(k)
print j, k, chr(k)
break
else:
continue
split_MSG[i] = part_MSG
print ''.join([''.join(s) for s in split_MSG])
def xor_ith_ct_with_other_cts(i, cts):
result = []
for index, ct in enumerate(cts):
if index != i:
result.append((index, strxor(cts[i], ct)))
return result
def encrypt(key, msg):
c = strxor(key, msg)
print
print c.encode('hex')
return c
ct_analysis = xor_ith_ct_with_other_cts(ct_index, decoded_cts)
ct_analysis.append(('key', ct))
min_length = min([len(x[1]) for x in ct_analysis])
for i in range(min_length):
ith_char = [(x[0], x[1][i]) for x in ct_analysis]
letter_count = \
[m[1] in string.ascii_letters for m in ith_char].count(True)
if letter_count >= 5:
print 'Good Start!'
if len(set([m[1] for m in ith_char])) <= 1:
print 'Ooops!!'
else:
MSGS[ct_index][i] = ' '
for j, char in ith_char:
if j == 'key':
s_key[i] = strxor(char, ' ')
else:
MSGS[j][i] = strxor(char, ' ')
# Part 2: auto trial and tribulation
max_ct_length = max([len(x) for x in decoded_cts])
for i in range(max_ct_length):
for msg_index, msg in enumerate(MSGS):
print "FULL MSG {}: {}".format(msg_index, ''.join(msg))
max_key = ''
max_key_count = 0
result = []
# Running trial