def decrypt(dk: DecryptionKey,
ciphertext: Ciphertext,
dtype: tf.DType = tf.int32) -> tf.Tensor:
c = ciphertext.raw
gxd = tf_big.pow(c, dk.d1, dk.nn)
xd = (gxd - 1) // dk.n
x = (xd * dk.d2) % dk.n
if dtype == tf.variant:
return x
return tf_big.export_tensor(x, dtype=dtype)
def mul(
ek: EncryptionKey,
lhs: Ciphertext,
rhs: tf.Tensor,
do_refresh: bool = True,
) -> Ciphertext:
c = lhs.raw
k = tf_big.import_tensor(rhs)
d = tf_big.pow(c, k) % ek.nn
res = Ciphertext(ek, d)
if not do_refresh:
return res
return refresh(ek, res)
def encrypt(
ek: EncryptionKey,
plaintext: tf.Tensor,
randomness: Optional[Randomness] = None,
) -> Ciphertext:
x = tf_big.import_tensor(plaintext)
randomness = randomness or gen_randomness(ek=ek, shape=x.shape)
r = randomness.raw
assert r.shape == x.shape
gx = 1 + (ek.n * x) % ek.nn
rn = tf_big.pow(r, ek.n, ek.nn)
c = gx * rn % ek.nn
return Ciphertext(ek, c)
def refresh(ek: EncryptionKey, ciphertext: Ciphertext) -> Ciphertext:
c = ciphertext.raw
s = gen_randomness(ek=ek, shape=c.shape).raw
sn = tf_big.pow(s, ek.n, ek.nn)
d = (c * sn) % ek.nn
return Ciphertext(ek, d)