def compute_server_values(self,
username,
verifier,
byte_size=DEFAULT_SECRETSIZE):
'''Calculates server values'''
l = self.N.bit_length()
self.b = obj_to_int(get_randombytes(byte_size))
k = obj_to_int(compute_hash(self.N, compute_padding(self.g, l)))
self.B = (k * verifier + pow(self.g, self.b, self.N)) % self.N
return self.B
def compute_client_values(self, byte_size=DEFAULT_SECRETSIZE):
'''
Computes client's private and public values:
a = random()
A = g^a % N
'''
self.a = obj_to_int(get_randombytes(byte_size))
self.A = pow(self.g, self.a, self.N)
return self.A
def compute_premaster_secret(self, salt, server_B):
'''Calculates client premaster secret'''
server_B = obj_to_int(server_B)
l = self.N.bit_length()
padded_client_A = compute_padding(self.A, l)
padded_server_B = compute_padding(server_B, l)
u = obj_to_int(compute_hash(padded_client_A, padded_server_B))
x = self._compute_x(salt, self.username, self.password)
padded_g = compute_padding(self.g, l)
k = obj_to_int(compute_hash(self.N, padded_g))
t1 = server_B - k * pow(self.g, x, self.N)
t2 = self.a + u * x
self.premaster_secret = pow(t1, t2, self.N)
return self.premaster_secret
def compute_premaster_secret(self, salt, server_B):
'''
Calculates client premaster secret
u = SHA1(PAD(A) | PAD(B))
k = SHA1(N | PAD(g))
x = SHA1(s | SHA1(I | ":" | P))
<premaster secret> = (B - (k * g^x)) ^ (a + (u * x)) % N
'''
server_B = obj_to_int(server_B)
l = self.N.bit_length()
padded_client_A = compute_padding(self.A, l)
padded_server_B = compute_padding(server_B, l)
u = obj_to_int(compute_hash(padded_client_A, padded_server_B))
x = self._compute_x(salt, self.username, self.password)
padded_g = compute_padding(self.g, l)
k = obj_to_int(compute_hash(self.N, padded_g))
t1 = server_B - k * pow(self.g, x, self.N)
t2 = self.a + u * x
self.premaster_secret = pow(t1, t2, self.N)
return self.premaster_secret
def compute_premaster_secret(self,
username,
salt,
verifier,
client_A,
scs=DEFAULT_SECRETSIZE):
'''Calculates server premaster secret'''
l = self.N.bit_length()
padded_client_A = compute_padding(client_A, l)
padded_server_B = compute_padding(self.B, l)
u = obj_to_int(compute_hash(padded_client_A, padded_server_B))
self.premaster_secret = pow(client_A * pow(verifier, u, self.N),
self.b, self.N)
return self.premaster_secret