def sign(
self,
private_key: bytearray,
digest: bytearray,
rand_k: bytearray = bytearray(b'')) -> bytearray:
"""
Create a signature.
Args:
private_key: Private signature key (as a byte object).
digest: Digest for which the signature is calculated. This value
must be obtained using the 'streebog' algorithm in accordance with
GOST 34.11-2012.
rand_k: Random (pseudo-random) number (as a byte object). By
default, it is generated by the function itself.
Returns:
Signature for provided digest (as a byte object).
Raises:
GOSTSignatureError('GOSTSignatureError: invalid private key value'):
If the private key value is incorrect.
GOSTSignatureError('GOSTSignatureError: invalid digest value'): If
the digest value is incorrect.
GOSTSignatureError('GOSTSignatureError: invalid random value'): If
the random value is incorrect.
"""
if not check_value(private_key, self._size):
raise GOSTSignatureError(
'GOSTSignatureError: invalid private key value')
if not check_value(digest, self._size):
raise GOSTSignatureError(
'GOSTSignatureError: invalid digest value')
sign_e = self._set_e(digest)
sign_r = 0
sign_s = 0
sign_k = 0
if rand_k == bytearray(b''):
rand_k = self._get_rand_k()
if not isinstance(rand_k, (bytes, bytearray)):
private_key = zero_fill(private_key)
raise GOSTSignatureError(
'GOSTSignatureError: invalid random value')
if bytearray_to_int(rand_k) >= self._q:
private_key = zero_fill(private_key)
raise GOSTSignatureError(
'GOSTSignatureError: invalid random value')
while compare_to_zero(int_to_bytearray(sign_s, self._size)):
while compare_to_zero(int_to_bytearray(sign_r, self._size)):
sign_k = bytearray_to_int(rand_k)
sign_c = self._mul_point(sign_k)
sign_r = sign_c[0] % self._q
sign_s = (sign_r * bytearray_to_int(private_key) +
sign_k * sign_e) % self._q
result = int_to_bytearray(sign_r, self._size) + int_to_bytearray(
sign_s, self._size)
private_key = zero_fill(private_key)
return result
def _add(self, x_1: int, x_2: int, y_1: int, y_2: int) -> Tuple[int, int]:
compare_x = compare(int_to_bytearray(x_1, self._size),
int_to_bytearray(x_2, self._size))
compare_y = compare(int_to_bytearray(y_1, self._size),
int_to_bytearray(y_2, self._size))
if compare_x and compare_y:
grad = (3 * x_1 * x_1 + self._a) * self._invert(2 * y_1,
self._p) % self._p
else:
d_x = (x_2 - x_1) % self._p
d_y = (y_2 - y_1) % self._p
grad = (d_y * self._invert(d_x, self._p)) % self._p
x_3 = (grad * grad - x_1 - x_2) % self._p
y_3 = (grad * (x_1 - x_3) - y_1) % self._p
return x_3, y_3
def verify(self, public_key: Any, digest: bytearray,
signature: bytearray) -> bool:
"""
Verify a signature.
Args:
public_key: Public signature key (as a byte object).
digest: Digest for which to be checked signature (as a byte object).
signature: Signature of the digest being checked (as a byte object).
Returns:
The result of the signature verification ('True' or 'False').
Raises:
GOSTSignatureError('GOSTSignatureError: invalid public key value'):
If the public key value is incorrect.
GOSTSignatureError('GOSTSignatureError: invalid signature value'):
If the signature value is incorrect.
GOSTSignatureError('GOSTSignatureError: invalid digest value'): If
the digest value is incorrect.
"""
if not check_value(public_key, self._size * 2):
raise GOSTSignatureError(
'GOSTSignatureError: invalid public key value')
if not check_value(signature, self._size * 2):
raise GOSTSignatureError(
'GOSTSignatureError: invalid signature value')
if not check_value(digest, self._size):
raise GOSTSignatureError(
'GOSTSignatureError: invalid digest value')
public_key = (bytearray_to_int(public_key[:self._size]),
bytearray_to_int(public_key[self._size:]))
sign_r, sign_s = self._get_r_s(signature)
if not self._verify_step_1(sign_r, sign_s):
return False
sign_e = self._set_e(digest)
sign_v = self._invert(sign_e, self._q)
sign_z_1 = sign_s * sign_v % self._q
sign_z_2 = self._q - sign_r * sign_v % self._q
sign_p = self._mul_point(sign_z_1)
sign_q = self._mul_point(sign_z_2, public_key[0], public_key[1])
sign_c = self._add(sign_p[0], sign_q[0], sign_p[1], sign_q[1])
sign_r_check = sign_c[0] % self._q
return compare(int_to_bytearray(sign_r_check, self._size),
int_to_bytearray(sign_r, self._size))
def _get_mac_key(self, value_r):
value_b = b''
if self.block_size == 16:
value_b = _B_128
elif self.block_size == 8:
value_b = _B_64
if msb(value_r) == 0:
int_value = bytearray_to_int(value_r) << 1
key_1 = int_to_bytearray(int_value, self.block_size)
else:
int_value = bytearray_to_int(value_r) << 1
key_1 = add_xor(int_to_bytearray(int_value, self.block_size),
value_b)
if msb(key_1) == 0:
int_value = bytearray_to_int(key_1) << 1
key_2 = int_to_bytearray(int_value, self.block_size)
else:
int_value = bytearray_to_int(key_1) << 1
key_2 = add_xor(int_to_bytearray(int_value, self.block_size),
value_b)
return [key_1, key_2]
def public_key_generate(self, private_key: Any) -> bytearray:
"""
Generate a public key.
Parameters
- private_key: private signature key (as a byte object).
Return: public key (as a byte object).
Exception
- GOSTSignatureError('invalid private key') - if the private key value
is incorrect.
"""
if not check_value(private_key, self._size):
raise GOSTSignatureError('invalid private key')
private_key = bytearray_to_int(private_key)
public_key = self._mul_point(private_key)
public_key_x = int_to_bytearray(public_key[0], self._size)
public_key_y = int_to_bytearray(public_key[1], self._size)
private_key = 0
return public_key_x + public_key_y
def public_key_generate(self, private_key: Any) -> bytearray:
"""
Generate a public key.
Args:
private_key: Private signature key (as a byte object).
Returns:
Public key (as a byte object).
Raises:
GOSTSignatureError('GOSTSignatureError: invalid private key'): If
the private key value is incorrect.
"""
if not check_value(private_key, self._size):
raise GOSTSignatureError('GOSTSignatureError: invalid private key')
private_key = bytearray_to_int(private_key)
public_key = self._mul_point(private_key)
public_key_x = int_to_bytearray(public_key[0], self._size)
public_key_y = int_to_bytearray(public_key[1], self._size)
private_key = 0
return public_key_x + public_key_y
def _set_e(self, digest: bytearray) -> int:
result = bytearray_to_int(digest) % self._q
if compare_to_zero(int_to_bytearray(result, self._size)):
result = 1
return result
def _u_first(self) -> bytearray:
self._hmac_obj.reset()
self._hmac_obj.update(self._salt + int_to_bytearray(self._counter, 4))
return self._hmac_obj.digest()
def _inc_rand_u(self) -> None:
int_rand_u = bytearray_to_int(self._rand_u) + 1 % (2**(_SIZE_M - 1))
self._rand_u = int_to_bytearray(int_rand_u, _SIZE_M - 1)
