def ModExp(a, b, c):
"""Uses openssl, if available, to do a^b mod c where a,b,c are longs."""
if not _FOUND_SSL:
return pow(a, b, c)
# convert arbitrary long args to bytes
bytes_a = number.LongToBytes(a)
bytes_b = number.LongToBytes(b)
bytes_c = number.LongToBytes(c)
# convert bytes to (pointer to) Bignums.
bn_a = ssl.BN_bin2bn(bytes_a, len(bytes_a), 0)
bn_b = ssl.BN_bin2bn(bytes_b, len(bytes_b), 0)
bn_c = ssl.BN_bin2bn(bytes_c, len(bytes_c), 0)
bn_result = ssl.BN_new()
ctx = ssl.BN_CTX_new()
# exponentiate and convert result to long
ssl.BN_mod_exp(bn_result, bn_a, bn_b, bn_c, ctx)
num_bytes_in_result = _NumBytesBn(bn_result)
bytes_result = ctypes.create_string_buffer(num_bytes_in_result)
ssl.BN_bn2bin(bn_result, bytes_result)
long_result = number.BytesToLong(bytes_result.raw)
# clean up
ssl.BN_CTX_free(ctx)
ssl.BN_free(bn_a)
ssl.BN_free(bn_b)
ssl.BN_free(bn_c)
ssl.BN_free(bn_result)
return long_result
def testLongToBytes(self):
self.assertEqual(struct.pack('>I', 3), number.LongToBytes(3))
self.assertEqual(struct.pack('>2I', 1, 7),
number.LongToBytes(4294967303))
self.assertEqual(struct.pack('>3I', 1, 0, 0),
number.LongToBytes(2**64))
self.assertEqual(
struct.pack('>6I', 1, 1, 1, 1, 1, 7),
number.LongToBytes(2**160 + 2**128 + 2**96 + 2**64 + 2**32 + 7))
def __init__(self, key):
super(HomomorphicFloatCipher, self).__init__()
self._paillier = pcrypto.Paillier(key)
# Store raw binary nsquare as a string using '\x' syntax which can be passed
# in a query.
nsquare_bytes = number.LongToBytes(self._paillier.nsquare)
self.nsquare = '\\x' + '\\x'.join(x.encode('hex') for x in nsquare_bytes)
def Encrypt(self, plaintext):
"""Encrypts float and returns a base64 encoding of ciphertext as bytes.
Args:
plaintext: float
Returns:
encrypted plaintext, converted to bytes, and base64 encoded.
Raises:
ValueError: when plaintext is not a float.
"""
if not isinstance(plaintext, float):
raise ValueError('Expected float type data but got: %s' %
type(plaintext))
return base64.b64encode(
number.LongToBytes(self._paillier.EncryptFloat(plaintext)))
def Encrypt(self, plaintext):
"""Encrypts int64 and returns a base64 encoding of ciphertext as bytes.
Args:
plaintext: either a int or long to be encrypted
Returns:
encrypted plaintext, converted to bytes, and base64 encoded.
Raises:
ValueError: when plaintext is neither an int, nor a long.
"""
if not isinstance(plaintext, int) and not isinstance(plaintext, long):
raise ValueError('Expected int or long type data but got: %s' %
type(plaintext))
return base64.b64encode(
number.LongToBytes(self._paillier.EncryptInt64(plaintext)))
