[feat] #150 Add DUBP Mnemonic SigningKey feature

Add signing_key from DUBP Mnemonic

See the RFC0014 of the Duniter Project

Close #150 (closed).

duniterpy/key/signing_key.py

@@ -22,7 +22,7 @@ from typing import Optional, Union, TypeVar, Type
 import libnacl.sign
 import pyaes
 from libnacl.utils import load_key
-from hashlib import scrypt
+from hashlib import scrypt, sha256
 
 from .scrypt_params import ScryptParams
 from .base58 import Base58Encoder
@@ -509,3 +509,31 @@ Data: {data}""".format(
         seed = bytes(base64.b64decode(secret)[0:32])
 
         return cls(seed)
+
+    @classmethod
+    def from_dubp_mnemonic(
+        cls, mnemonic: str, scrypt_params: ScryptParams = None
+    ) -> SigningKeyType:
+        """
+        Generate key pair instance from a DUBP mnemonic passphrase
+
+        See https://git.duniter.org/documents/rfcs/blob/dubp-mnemonic/rfc/0014_Dubp_Mnemonic.md
+
+        :param mnemonic: Passphrase generated from a mnemonic algorithm
+        :param scrypt_params: ScryptParams instance (default=None)
+        :return:
+        """
+        if scrypt_params is None:
+            scrypt_params = ScryptParams()
+
+        _password = mnemonic.encode("utf-8")  # type: bytes
+        _salt = sha256(b"dubp" + _password).digest()  # type: bytes
+        _seed = scrypt(
+            password=_password,
+            salt=_salt,
+            n=scrypt_params.N,  # 4096
+            r=scrypt_params.r,  # 16
+            p=scrypt_params.p,  # 1
+            dklen=scrypt_params.seed_length,  # 32
+        )  # type: bytes
+        return cls(_seed)