def encryption_oracle(plaintext, key, randomdata):
buff = "Um9sbGluJyBpbiBteSA1LjAKV2l0aCBteSByYWctdG9wIGRvd24gc28gbXkg\
aGFpciBjYW4gYmxvdwpUaGUgZ2lybGllcyBvbiBzdGFuZGJ5IHdhdmluZyBq\
dXN0IHRvIHNheSBoaQpEaWQgeW91IHN0b3A/IE5vLCBJIGp1c3QgZHJvdmUg\
YnkK"
return aes_ecb_encrypt(
paddpkcs7(randomdata + plaintext + base64.b64decode(buff), 16), key)
def aes_ctr(text, key):
resulttext = b''
for i in range(0, len(text), 16):
count = (constants.nonce.to_bytes(8, 'little') +
(i // 16).to_bytes(8, 'little'))
keystream = set2.aes_ecb_encrypt(count, key)
block = text[i:i + 16]
resulttext += set1.xor(block, keystream[:len(block)])
return resulttext
def aes_ctr(binary_blob, aes_key, nonce=0):
'''
Implements stream cipher mode AES
'''
nonce = nonce.to_bytes(8, byteorder='little')
keystream = b''
counter = 0
while len(keystream) < len(binary_blob):
keystream += aes_ecb_encrypt(nonce + counter.to_bytes(8, byteorder='little'), aes_key)
counter += 1
return bytes([a ^ b for a, b in zip(binary_blob, keystream)])
def read_ctr_cipher(ciphertext, key, offset, length, nonce=0):
'''
seeks into the cipherteext using the offset and
returns the decrypted info with length specified
'''
nonce = nonce.to_bytes(8, byteorder='little')
keystream = b''
counter = 0
while len(keystream) < offset + length:
keystream += aes_ecb_encrypt(
nonce + counter.to_bytes(8, byteorder='little'), key)
counter += 1
return bytes([
a ^ b
for a, b in zip(cipher[offset:offset + length], keystream[offset:])
])
def edit_ctr_cipher(ciphertext, key, offset, newtext, nonce=0):
'''
seeks into the ciphertext using the offset and replaces
part of the ciphertext with the encrypted newtext
'''
nonce = nonce.to_bytes(8, byteorder='little')
keystream = b''
counter = 0
while len(keystream) < offset + len(newtext):
keystream += aes_ecb_encrypt(
nonce + counter.to_bytes(8, byteorder='little'), key)
counter += 1
keystream = keystream[offset:]
newcipher = bytes([a ^ b for a, b in zip(newtext, keystream)])
ciphertext = ciphertext[:offset] + newcipher + ciphertext[offset +
len(newcipher):]
return ciphertext
def aes_ctr_encrypt_block(block, key):
return aes_ecb_encrypt(block, key)
def encryption_oracle(cleartext, key):
return aes_ecb_encrypt(paddpkcs7(profile_for(cleartext), 16), key)