From f73b6b5d2398f14b353fbdd83145214b157a02ad Mon Sep 17 00:00:00 2001
From: SomberNight <somber.night@protonmail.com>
Date: Mon, 9 Dec 2019 03:35:20 +0100
Subject: [PATCH] keystore: cache derive_pubkey

---
 electrum/base_wizard.py |  2 +-
 electrum/keystore.py    | 16 +++++++++++-----
 run_electrum            |  4 ++--
 3 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/electrum/base_wizard.py b/electrum/base_wizard.py
index 54cee186d..bb757a5f2 100644
--- a/electrum/base_wizard.py
+++ b/electrum/base_wizard.py
@@ -369,7 +369,7 @@ class BaseWizard(Logger):
         elif purpose == HWD_SETUP_DECRYPT_WALLET:
             derivation = get_derivation_used_for_hw_device_encryption()
             xpub = self.plugin.get_xpub(device_info.device.id_, derivation, 'standard', self)
-            password = keystore.Xpub.get_pubkey_from_xpub(xpub, ())
+            password = keystore.Xpub.get_pubkey_from_xpub(xpub, ()).hex()
             try:
                 storage.decrypt(password)
             except InvalidPassword:
diff --git a/electrum/keystore.py b/electrum/keystore.py
index 572771c9c..95c6cb239 100644
--- a/electrum/keystore.py
+++ b/electrum/keystore.py
@@ -28,6 +28,7 @@ from unicodedata import normalize
 import hashlib
 import re
 from typing import Tuple, TYPE_CHECKING, Union, Sequence, Optional, Dict, List, NamedTuple
+from functools import lru_cache
 
 from . import bitcoin, ecc, constants, bip32
 from .bitcoin import deserialize_privkey, serialize_privkey
@@ -402,8 +403,8 @@ class Xpub:
         self._root_fingerprint = root_fingerprint
         self._derivation_prefix = normalize_bip32_derivation(derivation_prefix)
 
-    def derive_pubkey(self, for_change, n) -> str:
-        for_change = int(for_change)
+    @lru_cache(maxsize=None)
+    def _derive_pubkey_bytes(self, for_change: int, n: int) -> bytes:
         assert for_change in (0, 1)
         xpub = self.xpub_change if for_change else self.xpub_receive
         if xpub is None:
@@ -415,10 +416,15 @@ class Xpub:
                 self.xpub_receive = xpub
         return self.get_pubkey_from_xpub(xpub, (n,))
 
+    def derive_pubkey(self, for_change: int, n: int) -> str:
+        for_change = int(for_change)
+        assert for_change in (0, 1)
+        return self._derive_pubkey_bytes(for_change, n).hex()
+
     @classmethod
-    def get_pubkey_from_xpub(self, xpub, sequence):
+    def get_pubkey_from_xpub(self, xpub: str, sequence) -> bytes:
         node = BIP32Node.from_xkey(xpub).subkey_at_public_derivation(sequence)
-        return node.eckey.get_public_key_hex(compressed=True)
+        return node.eckey.get_public_key_bytes(compressed=True)
 
 
 class BIP32_KeyStore(Deterministic_KeyStore, Xpub):
@@ -692,7 +698,7 @@ class Hardware_KeyStore(KeyStore, Xpub):
         client = self.plugin.get_client(self)
         derivation = get_derivation_used_for_hw_device_encryption()
         xpub = client.get_xpub(derivation, "standard")
-        password = self.get_pubkey_from_xpub(xpub, ())
+        password = self.get_pubkey_from_xpub(xpub, ()).hex()
         return password
 
     def has_usable_connection_with_device(self) -> bool:
diff --git a/run_electrum b/run_electrum
index efa742909..d68a368cf 100755
--- a/run_electrum
+++ b/run_electrum
@@ -178,7 +178,7 @@ def get_connected_hw_devices(plugins):
     return devices
 
 
-def get_password_for_hw_device_encrypted_storage(plugins):
+def get_password_for_hw_device_encrypted_storage(plugins) -> str:
     devices = get_connected_hw_devices(plugins)
     if len(devices) == 0:
         print_msg("Error: No connected hw device found. Cannot decrypt this wallet.")
@@ -194,7 +194,7 @@ def get_password_for_hw_device_encrypted_storage(plugins):
         xpub = plugin.get_xpub(device_info.device.id_, derivation, 'standard', plugin.handler)
     except UserCancelled:
         sys.exit(0)
-    password = keystore.Xpub.get_pubkey_from_xpub(xpub, ())
+    password = keystore.Xpub.get_pubkey_from_xpub(xpub, ()).hex()
     return password