コード例 #1
0
def padding_is_valid(ciphertext, iv):
    key = open('unknown_key.txt', 'r').read().splitlines()[0]
    cipher = AES.new(key, AES.MODE_CBC, iv)
    plaintext = cipher.decrypt(ciphertext)
    try:
        x = (strip_padding(plaintext))
    except cryptopals.BadPadding as err:
        return False
    else:
        return True
コード例 #2
0
def padding_is_valid(ciphertext, iv):
    key = open('unknown_key.txt', 'r').read().splitlines()[0]
    cipher = AES.new(key, AES.MODE_CBC, iv)
    plaintext = cipher.decrypt(ciphertext)
    try:
        x = (strip_padding(plaintext))
    except cryptopals.BadPadding as err:
        return False
    else:
        return True
コード例 #3
0
def check_ciphertext(ciphertext):
    key = open('unknown_key.txt', 'r').read().splitlines()[0]
    my_iv = key
    cipher = AES.new(key, AES.MODE_CBC, IV=my_iv)
    blocksize = 16
    plaintext = strip_padding(cipher.decrypt(my_iv + ciphertext)[blocksize:])
    for character in plaintext:
        if ord(character) > 127:
            raise BadCharacter(plaintext)
    if 'AUTHORIZED ADMIN' in plaintext:
        print "Server thinks that:" + plaintext
        return True
    else:
        print "Server thinks you are a normal user. Welcome!"
        return False
コード例 #4
0
def check_ciphertext(ciphertext):
    key = open('unknown_key.txt', 'r').read().splitlines()[0]
    my_iv = key
    cipher = AES.new(key, AES.MODE_CBC, IV = my_iv)
    blocksize = 16
    plaintext = strip_padding(cipher.decrypt(my_iv + ciphertext)[blocksize:])
    for character in plaintext:
        if ord(character) > 127:
            raise BadCharacter(plaintext)
    if 'AUTHORIZED ADMIN' in plaintext:
        print "Server thinks that:" + plaintext
        return True
    else:
        print "Server thinks you are a normal user. Welcome!"
        return False
コード例 #5
0
# TODO: Problem 2.5 (13): ECB cut-and-paste
cryptopals.copypasta_attack()

# TODO: Problem 2.6 (14): Byte-at-a-time ECB decryption (Harder)
# Googling ``stimulus'' and ``response'' totally helped here :P
# http://www.blackhat.com/presentations/bh-usa-06/BH-US-06-Eng.pdf
consistent_key = cryptopals.random_aes_key()
random_prepend = cryptopals.random_length_bytes()
assert equals(
    cryptopals.decrypt_magic_text_harder(solutions.problem_12, consistent_key, random_prepend),
    solutions.soln_12
)

# TODO: Problem 2.7 (15): PKCS#7 padding validation
assert equals(
    cryptopals.strip_padding(b'ICE ICE BABY\x04\x04\x04\x04'),
    b'ICE ICE BABY'
)

try:
    cryptopals.strip_padding(b'ICE ICE BABY\x05\x05\x05\x05')
    assert equals(1,2)
except cryptopals.PaddingException:
    pass

try:
    cryptopals.strip_padding(b'ICE ICE BABY\x01\x02\x03\x04')
    assert equals(1,2)
except cryptopals.PaddingException:
    pass
コード例 #6
0
ファイル: chal17.py プロジェクト: zimolzak/crypto-challenges
for blocknum in range(len(ciph) / blocksize):
    if blocknum == 0:
        Ca = iv  # There is smarter way, without the IF.
    else:
        Ca = ciph[blocksize * (blocknum - 1):blocksize * blocknum]
    Cb = ciph[blocksize * blocknum:blocksize * (blocknum + 1)]
    for n_bytes in range(1, blocksize + 1):
        guess = ""
        for charnum in range(2, 256):  # Might be screwed if it is \x01
            guess = chr(charnum)
            b = Ca[-(n_bytes):]
            g = guess + plaintext[blocknum]  # p[b] will be incomplete
            x = chr(n_bytes) * (n_bytes)
            Cac = Ca[:-(n_bytes)] + cryptopals.xor_str(
                cryptopals.xor_str(b, g), x)
            if fakeserver.padding_is_valid(Cac + Cb, iv):
                break
        plaintext[blocknum] = guess + plaintext[blocknum]

output = cryptopals.strip_padding(''.join(plaintext))
print output

#### tests ####
assert (cryptopals.strip_padding(fakeserver.cheat(ciph, iv)) == output)

for i in range(100):
    [ciph, iv] = fakeserver.random_ciphertext_iv()
    assert (fakeserver.padding_is_valid(ciph, iv))

cryptopals.warn("Passed assertions (" + __file__ + ")")