class DSA(DigitalSignatureScheme):
# Based on Wikipedia pseudocode.
def __init__(self, hash_function=SHA256, parameters=None):
DigitalSignatureScheme.__init__(self)
self.hash_function = hash_function()
self._init_params_from(parameters)
self.modexp_p = ModularExp(self.p)
self._init_keys()
def _init_params_from(self, parameters):
if parameters is None:
self.p, self.q, self.g = DSAParameterGenerator().generate()
else:
self.p, self.q, self.g = parameters
def _init_keys(self):
self.x = random.randint(1, self.q-1)
self.y = self.modexp_p.value(self.g, self.x)
self.public_key = (self.p, self.q, self.g, self.y)
def sign(self, message):
h = self.hash_function.int_hash(message)
while True:
k = random.randint(1, self.q-1)
r = self.modexp_p.value(self.g, k) % self.q
if r == 0:
continue
k_inv = ModularInverse(self.q).value(k)
s = k_inv*(h + self.x*r) % self.q
if s != 0:
break
return r, s
def verify(self, message, signature):
r, s = signature
if (r <= 0 or r >= self.q) or (s <= 0 or s >= self.q):
return False
h = self.hash_function.int_hash(message)
w = ModularInverse(self.q).value(s)
u1 = (h*w) % self.q
u2 = (r*w) % self.q
g_u1 = self.modexp_p.value(self.g, u1)
y_u2 = self.modexp_p.value(self.y, u2)
v_mod_p = (g_u1*y_u2) % self.p
v = v_mod_p % self.q
return r == v
class DiffieHellman(object):
MAX_INT = 2**64 - 1
def __init__(self, p, g):
self.p = p
self.g = g
self.modexp = ModularExp(self.p)
self.exp = self._choose_secret_exponent()
self.public_key = self._compute_public_key()
def _choose_secret_exponent(self):
return random.randint(1, self.MAX_INT)
def _compute_public_key(self):
return self.modexp.value(self.g, self.exp)
def get_public_key(self):
return self.public_key
def get_secret_from(self, key):
return self.modexp.value(key, self.exp)
class DiffieHellman(object):
MAX_INT = 2**64 - 1
def __init__(self, p, g):
self.p = p
self.g = g
self.modexp = ModularExp(self.p)
self.exp = self._choose_secret_exponent()
self.public_key = self._compute_public_key()
def _choose_secret_exponent(self):
return random.randint(1, self.MAX_INT)
def _compute_public_key(self):
return self.modexp.value(self.g, self.exp)
def get_public_key(self):
return self.public_key
def get_secret_from(self, key):
return self.modexp.value(key, self.exp)
class RSA(PublicKeyCipher):
DEFAULT_E = 65537
DEFAULT_BITS = 2048
def __init__(self, bits=None):
PublicKeyCipher.__init__(self)
bits = bits if bits is not None else self.DEFAULT_BITS
self._init_parameters(bits)
def _init_primes(self, bits):
prime_generator = RandPrime()
bitsize = 1 + bits / 2 if bits % 2 else bits / 2
p = prime_generator.value(n=bitsize)
q = prime_generator.value(n=bitsize)
return p, q
def _init_parameters(self, bits):
p, q = self._init_primes(bits)
totient = (p - 1) * (q - 1)
self.n = p * q
self.modexp = ModularExp(self.n)
self.e = self._choose_e_from(totient)
self.d = ModularInverse(totient).value(self.e)
self.public_key = (self.e, self.n)
def _choose_e_from(self, totient):
# Choose 1 < e < totient s.t. e and totient are coprime.
e = self.DEFAULT_E
gcd = GCD()
while gcd.value(e, totient) != 1:
e += 2
return e
def _encrypt(self, int_plaintext):
return self._exp_with(int_plaintext, self.e)
def _decrypt(self, int_ciphertext):
return self._exp_with(int_ciphertext, self.d)
def _exp_with(self, integer, exponent):
return self.modexp.value(integer, exponent)
class RSA(PublicKeyCipher):
DEFAULT_E = 65537
DEFAULT_BITS = 2048
def __init__(self, bits=None):
PublicKeyCipher.__init__(self)
bits = bits if bits is not None else self.DEFAULT_BITS
self._init_parameters(bits)
def _init_primes(self, bits):
prime_generator = RandPrime()
bitsize = 1+bits/2 if bits%2 else bits/2
p = prime_generator.value(n=bitsize)
q = prime_generator.value(n=bitsize)
return p, q
def _init_parameters(self, bits):
p, q = self._init_primes(bits)
totient = (p-1)*(q-1)
self.n = p*q
self.modexp = ModularExp(self.n)
self.e = self._choose_e_from(totient)
self.d = ModularInverse(totient).value(self.e)
self.public_key = (self.e, self.n)
def _choose_e_from(self, totient):
# Choose 1 < e < totient s.t. e and totient are coprime.
e = self.DEFAULT_E
gcd = GCD()
while gcd.value(e, totient) != 1:
e += 2
return e
def _encrypt(self, int_plaintext):
return self._exp_with(int_plaintext, self.e)
def _decrypt(self, int_ciphertext):
return self._exp_with(int_ciphertext, self.d)
def _exp_with(self, integer, exponent):
return self.modexp.value(integer, exponent)