def run_p10():
print('Problem 10')
INPUT = b642b(open('set2p10.txt').read())
KEY = b'YELLOW SUBMARINE'
IV = bytes(BLOCKSIZE)
output = AES128_CBC_decrypt(IV + INPUT, KEY)
print('First 3 lines of output:')
for line in output.splitlines()[:3]:
print(line.decode())
print()
yield c
ctr += 1
CTR_TEST = b'hello potato, i am a cheese'
def AES128_CTR_crypt(key, nonce, data):
"""
# Isn't this a hilarious test?
>>> AES128_CTR_crypt(b'YELLOW SUBMARINE', 1, CTR_TEST) != CTR_TEST
True
>>> AES128_CTR_crypt(b'YELLOW SUBMARINE', 1, AES128_CTR_crypt(b'YELLOW SUBMARINE', 1, CTR_TEST)) == CTR_TEST
True
"""
nonce = int2bytes(nonce, BLOCKSIZE//2)
return bytes(x^y for x, y in zip(AES128_CTR_keystream(key, nonce), data))
P18_CIPHERTEXT = b642b(
'L77na/nrFsKvynd6HzOoG7GHTLXsTVu9qvY/2syLXzhPweyyMTJULu/6/kXX0KSvoOLSFQ==')
P18_KEY = b'YELLOW SUBMARINE'
P18_NONCE = 0
def run_p18():
print('Problem 18')
print('Decryption:', AES128_CTR_crypt(P18_KEY, P18_NONCE, P18_CIPHERTEXT))
"""
// ------------------------------------------------------------
19. Break fixed-nonce CTR mode using substitions
Take your CTR encrypt/decrypt function and fix its nonce value to
0. Generate a random AES key.
that last byte position.
d. Make a dictionary of every possible last byte by feeding different
strings to the oracle; for instance, "AAAAAAAA", "AAAAAAAB",
"AAAAAAAC", remembering the first block of each invocation.
e. Match the output of the one-byte-short input to one of the entries
in your dictionary. You've now discovered the first byte of
unknown-string.
f. Repeat for the next byte.
"""
SECRET_SUFFIX_12 = b642b("""
Um9sbGluJyBpbiBteSA1LjAKV2l0aCBteSByYWctdG9wIGRvd24gc28gbXkg
aGFpciBjYW4gYmxvdwpUaGUgZ2lybGllcyBvbiBzdGFuZGJ5IHdhdmluZyBq
dXN0IHRvIHNheSBoaQpEaWQgeW91IHN0b3A/IE5vLCBJIGp1c3QgZHJvdmUg
YnkK
""")
KEY_12 = os.urandom(KEYSIZE)
def secret_suffix_oracle(secret_suffix, data):
return AES128_encrypt(pkcs7pad(data + secret_suffix, BLOCKSIZE),
KEY_12)
def p12_oracle(data):
return secret_suffix_oracle(SECRET_SUFFIX_12, data)
def find_block_size(oracle):
def oracle_len(length):
return len(oracle(bytes(length)))
