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Add nonce and initial_value parameters to CTR mode

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Legrandin 2015-12-20 21:27:21 +01:00
parent 6fc0c734a2
commit c74b718aa6
13 changed files with 210 additions and 71 deletions
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74
lib/Crypto/SelfTest/Cipher/test_CTR.py
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@ -43,8 +43,10 @@ class CtrTests(unittest.TestCase):
key_128 = get_tag_random("key_128", 16)
key_192 = get_tag_random("key_192", 24)
ctr_64 = Counter.new(32, prefix=get_tag_random("iv_64", 4))
ctr_128 = Counter.new(64, prefix=get_tag_random("iv_128", 8))
nonce_32 = get_tag_random("nonce_32", 4)
nonce_64 = get_tag_random("nonce_64", 8)
ctr_64 = Counter.new(32, prefix=nonce_32)
ctr_128 = Counter.new(64, prefix=nonce_64)
def test_loopback_128(self):
cipher = AES.new(self.key_128, AES.MODE_CTR, counter=self.ctr_128)
@ -64,10 +66,74 @@ class CtrTests(unittest.TestCase):
pt2 = cipher.decrypt(ct)
self.assertEqual(pt, pt2)
def test_counter_is_required(self):
self.assertRaises(TypeError, AES.new, self.key_128, AES.MODE_CTR)
def test_invalid_counter_parameter(self):
# Counter object is required for ciphers with short block size
self.assertRaises(TypeError, DES3.new, self.key_192, AES.MODE_CTR)
# Positional arguments are not allowed (Counter must be passed as
# keyword)
self.assertRaises(TypeError, AES.new, self.key_128, AES.MODE_CTR, self.ctr_128)
def test_nonce_attribute(self):
# Nonce attribute is the prefix passed to Counter (DES3)
cipher = DES3.new(self.key_192, DES3.MODE_CTR, counter=self.ctr_64)
self.assertEqual(cipher.nonce, self.nonce_32)
# Nonce attribute is the prefix passed to Counter (AES)
cipher = AES.new(self.key_128, AES.MODE_CTR, counter=self.ctr_128)
self.assertEqual(cipher.nonce, self.nonce_64)
# Nonce attribute is not defined if suffix is used in Counter
counter = Counter.new(64, prefix=self.nonce_32, suffix=self.nonce_32)
cipher = AES.new(self.key_128, AES.MODE_CTR, counter=counter)
self.failIf(hasattr(cipher, "nonce"))
def test_nonce_parameter(self):
# Nonce parameter becomes nonce attribute
cipher1 = AES.new(self.key_128, AES.MODE_CTR, nonce=self.nonce_64)
self.assertEqual(cipher1.nonce, self.nonce_64)
counter = Counter.new(64, prefix=self.nonce_64, initial_value=0)
cipher2 = AES.new(self.key_128, AES.MODE_CTR, counter=counter)
self.assertEqual(cipher1.nonce, cipher2.nonce)
pt = get_tag_random("plaintext", 65536)
self.assertEqual(cipher1.encrypt(pt), cipher2.encrypt(pt))
# Nonce is implicitly created (for AES) when no parameters are passed
nonce1 = AES.new(self.key_128, AES.MODE_CTR).nonce
nonce2 = AES.new(self.key_128, AES.MODE_CTR).nonce
self.assertNotEqual(nonce1, nonce2)
self.assertEqual(len(nonce1), 8)
# Nonce can be zero-length
cipher = AES.new(self.key_128, AES.MODE_CTR, nonce=b(""))
self.assertEqual(b(""), cipher.nonce)
# Nonce and Counter are mutually exclusive
self.assertRaises(TypeError, AES.new, self.key_128, AES.MODE_CTR,
counter=self.ctr_128, nonce=self.nonce_64)
def test_initial_value_parameter(self):
# Test with nonce parameter
cipher1 = AES.new(self.key_128, AES.MODE_CTR,
nonce=self.nonce_64, initial_value=0xFFFF)
counter = Counter.new(64, prefix=self.nonce_64, initial_value=0xFFFF)
cipher2 = AES.new(self.key_128, AES.MODE_CTR, counter=counter)
pt = get_tag_random("plaintext", 65536)
self.assertEqual(cipher1.encrypt(pt), cipher2.encrypt(pt))
# Test without nonce parameter
cipher1 = AES.new(self.key_128, AES.MODE_CTR,
initial_value=0xFFFF)
counter = Counter.new(64, prefix=cipher1.nonce, initial_value=0xFFFF)
cipher2 = AES.new(self.key_128, AES.MODE_CTR, counter=counter)
pt = get_tag_random("plaintext", 65536)
self.assertEqual(cipher1.encrypt(pt), cipher2.encrypt(pt))
# Initial_value and Counter are mutually exclusive
self.assertRaises(TypeError, AES.new, self.key_128, AES.MODE_CTR,
counter=self.ctr_128, initial_value=0)
def test_iv_with_matching_length(self):
self.assertRaises(ValueError, AES.new, self.key_128, AES.MODE_CTR,
counter=Counter.new(120))