def reenc_with_r(self, r):
"""
We would do this homomorphically, except
that's no good when we do plaintext encoding of 1.
"""
new_c = Ciphertext()
new_c.alpha = (self.alpha * pow(self.pk.g, r, self.pk.p)) % self.pk.p
new_c.beta = (self.beta * pow(self.pk.y, r, self.pk.p)) % self.pk.p
new_c.pk = self.pk
return new_c
def reenc_with_r(self, r):
"""
We would do this homomorphically, except
that's no good when we do plaintext encoding of 1.
"""
new_c = Ciphertext()
new_c.alpha = (self.alpha * pow(self.pk.g, r, self.pk.p)) % self.pk.p
new_c.beta = (self.beta * pow(self.pk.y, r, self.pk.p)) % self.pk.p
new_c.pk = self.pk
return new_c
def __mul__(self, other):
"""
Homomorphic Multiplication of ciphertexts.
"""
if type(other) == int and (other == 0 or other == 1):
return self
if self.pk != other.pk:
logging.info(self.pk)
logging.info(other.pk)
raise Exception('different PKs!')
new = Ciphertext()
new.pk = self.pk
new.alpha = (self.alpha * other.alpha) % self.pk.p
new.beta = (self.beta * other.beta) % self.pk.p
return new
def __mul__(self,other):
"""
Homomorphic Multiplication of ciphertexts.
"""
if type(other) == int and (other == 0 or other == 1):
return self
if self.pk != other.pk:
logging.info(self.pk)
logging.info(other.pk)
raise Exception('different PKs!')
new = Ciphertext()
new.pk = self.pk
new.alpha = (self.alpha * other.alpha) % self.pk.p
new.beta = (self.beta * other.beta) % self.pk.p
return new
def encrypt_with_r(self, plaintext, r, encode_message=False):
"""
expecting plaintext.m to be a big integer
"""
ciphertext = Ciphertext()
ciphertext.pk = self
# make sure m is in the right subgroup
if encode_message:
y = plaintext.m + 1
if pow(y, self.q, self.p) == 1:
m = y
else:
m = -y % self.p
else:
m = plaintext.m
ciphertext.alpha = pow(self.g, r, self.p)
ciphertext.beta = (m * pow(self.y, r, self.p)) % self.p
return ciphertext
def encrypt_with_r(self, plaintext, r, encode_message= False):
"""
expecting plaintext.m to be a big integer
"""
ciphertext = Ciphertext()
ciphertext.pk = self
# make sure m is in the right subgroup
if encode_message:
y = plaintext.m + 1
if pow(y, self.q, self.p) == 1:
m = y
else:
m = -y % self.p
else:
m = plaintext.m
ciphertext.alpha = pow(self.g, r, self.p)
ciphertext.beta = (m * pow(self.y, r, self.p)) % self.p
return ciphertext
