ecc: abstract away some usage of python-ecdsa: randrange

electrum/daemon.py

@@ -30,7 +30,7 @@ import traceback
 import sys
 import threading
 from typing import Dict, Optional, Tuple, Iterable
-from base64 import b64decode
+from base64 import b64decode, b64encode
 from collections import defaultdict
 
 import aiohttp
@@ -44,7 +44,7 @@ from aiorpcx import TaskGroup
 from .network import Network
 from .util import (json_decode, to_bytes, to_string, profiler, standardize_path, constant_time_compare)
 from .util import PR_PAID, PR_EXPIRED, get_request_status
-from .util import log_exceptions, ignore_exceptions
+from .util import log_exceptions, ignore_exceptions, randrange
 from .wallet import Wallet, Abstract_Wallet
 from .storage import WalletStorage
 from .wallet_db import WalletDB
@@ -124,11 +124,10 @@ def get_rpc_credentials(config: SimpleConfig) -> Tuple[str, str]:
     rpc_password = config.get('rpcpassword', None)
     if rpc_user is None or rpc_password is None:
         rpc_user = 'user'
-        import ecdsa, base64
         bits = 128
         nbytes = bits // 8 + (bits % 8 > 0)
-        pw_int = ecdsa.util.randrange(pow(2, bits))
-        pw_b64 = base64.b64encode(
+        pw_int = randrange(pow(2, bits))
+        pw_b64 = b64encode(
             pw_int.to_bytes(nbytes, 'big'), b'-_')
         rpc_password = to_string(pw_b64, 'ascii')
         config.set_key('rpcuser', rpc_user)

electrum/ecc.py

@@ -35,7 +35,7 @@ from ecdsa.curves import SECP256k1
 from ecdsa.ellipticcurve import Point
 from ecdsa.util import string_to_number, number_to_string
 
-from .util import bfh, bh2u, assert_bytes, to_bytes, InvalidPassword, profiler
+from .util import bfh, bh2u, assert_bytes, to_bytes, InvalidPassword, profiler, randrange
 from .crypto import (sha256d, aes_encrypt_with_iv, aes_decrypt_with_iv, hmac_oneshot)
 from .ecc_fast import do_monkey_patching_of_python_ecdsa_internals_with_libsecp256k1
 from . import msqr
@@ -145,7 +145,7 @@ class _MyVerifyingKey(ecdsa.VerifyingKey):
         G = curve.generator
         order = G.order()
         # extract r,s from signature
-        r, s = util.sigdecode_string(sig, order)
+        r, s = get_r_and_s_from_sig_string(sig, order)
         # 1.1
         x = r + (recid//2) * order
         # 1.3
@@ -299,7 +299,7 @@ class ECPubkey(object):
             raise Exception('Wrong encoding')
         ecdsa_point = self._pubkey.point
         verifying_key = _MyVerifyingKey.from_public_point(ecdsa_point, curve=SECP256k1)
-        verifying_key.verify_digest(sig_string, msg_hash, sigdecode=ecdsa.util.sigdecode_string)
+        verifying_key.verify_digest(sig_string, msg_hash, sigdecode=get_r_and_s_from_sig_string)
 
     def encrypt_message(self, message: bytes, magic: bytes = b'BIE1') -> bytes:
         """
@@ -416,7 +416,7 @@ class ECPrivkey(ECPubkey):
 
     @classmethod
     def generate_random_key(cls):
-        randint = ecdsa.util.randrange(CURVE_ORDER)
+        randint = randrange(CURVE_ORDER)
         ephemeral_exponent = number_to_string(randint, CURVE_ORDER)
         return ECPrivkey(ephemeral_exponent)
 

electrum/mnemonic.py

@@ -28,9 +28,7 @@ import hashlib
 import unicodedata
 import string
 
-import ecdsa
-
-from .util import resource_path, bfh, bh2u
+from .util import resource_path, bfh, bh2u, randrange
 from .crypto import hmac_oneshot
 from . import version
 from .logging import Logger
@@ -180,7 +178,7 @@ class Mnemonic(Logger):
         entropy = 1
         while entropy < pow(2, n - bpw):
             # try again if seed would not contain enough words
-            entropy = ecdsa.util.randrange(pow(2, n))
+            entropy = randrange(pow(2, n))
         nonce = 0
         while True:
             nonce += 1

electrum/tests/test_bitcoin.py

@@ -16,7 +16,7 @@ from electrum.bip32 import (BIP32Node, convert_bip32_intpath_to_strpath,
 from electrum.crypto import sha256d, SUPPORTED_PW_HASH_VERSIONS
 from electrum import ecc, crypto, constants
 from electrum.ecc import number_to_string, string_to_number
-from electrum.util import bfh, bh2u, InvalidPassword
+from electrum.util import bfh, bh2u, InvalidPassword, randrange
 from electrum.storage import WalletStorage
 from electrum.keystore import xtype_from_derivation
 
@@ -103,7 +103,7 @@ class Test_bitcoin(ElectrumTestCase):
     def _do_test_crypto(self, message):
         G = ecc.generator()
         _r  = G.order()
-        pvk = ecdsa.util.randrange(_r)
+        pvk = randrange(_r)
 
         Pub = pvk*G
         pubkey_c = Pub.get_public_key_bytes(True)

electrum/util.py

@@ -47,6 +47,7 @@ from aiohttp_socks import SocksConnector, SocksVer
 from aiorpcx import TaskGroup
 import certifi
 import dns.resolver
+import ecdsa
 
 from .i18n import _
 from .logging import get_logger, Logger
@@ -1266,3 +1267,9 @@ def resolve_dns_srv(host: str):
             'port': srv.port,
         }
     return [dict_from_srv_record(srv) for srv in srv_records]
+
+
+def randrange(bound: int) -> int:
+    """Return a random integer k such that 1 <= k < bound, uniformly
+    distributed across that range."""
+    return ecdsa.util.randrange(bound)