From d7c5949365cf061020e5dfb82ca26171c0692eb6 Mon Sep 17 00:00:00 2001
From: SomberNight <somber.night@protonmail.com>
Date: Mon, 26 Nov 2018 01:16:26 +0100
Subject: [PATCH] prefer int.from_bytes over int('0x'+hex, 16)

---
 electrum/bip32.py      | 2 +-
 electrum/blockchain.py | 9 +++++----
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/electrum/bip32.py b/electrum/bip32.py
index 0f671b286..22b0fbce9 100644
--- a/electrum/bip32.py
+++ b/electrum/bip32.py
@@ -127,7 +127,7 @@ def deserialize_xkey(xkey, prv, *, net=None):
     fingerprint = xkey[5:9]
     child_number = xkey[9:13]
     c = xkey[13:13+32]
-    header = int('0x' + bh2u(xkey[0:4]), 16)
+    header = int.from_bytes(xkey[0:4], byteorder='big')
     headers = net.XPRV_HEADERS if prv else net.XPUB_HEADERS
     if header not in headers.values():
         raise InvalidMasterKeyVersionBytes('Invalid extended key format: {}'
diff --git a/electrum/blockchain.py b/electrum/blockchain.py
index 5609c41e2..9f1e0c018 100644
--- a/electrum/blockchain.py
+++ b/electrum/blockchain.py
@@ -56,7 +56,7 @@ def deserialize_header(s: bytes, height: int) -> dict:
         raise InvalidHeader('Invalid header: {}'.format(s))
     if len(s) != HEADER_SIZE:
         raise InvalidHeader('Invalid header length: {}'.format(len(s)))
-    hex_to_int = lambda s: int('0x' + bh2u(s[::-1]), 16)
+    hex_to_int = lambda s: int.from_bytes(s, byteorder='little')
     h = {}
     h['version'] = hex_to_int(s[0:4])
     h['prev_block_hash'] = hash_encode(s[4:36])
@@ -187,8 +187,9 @@ class Blockchain(util.PrintError):
         bits = self.target_to_bits(target)
         if bits != header.get('bits'):
             raise Exception("bits mismatch: %s vs %s" % (bits, header.get('bits')))
-        if int('0x' + _hash, 16) > target:
-            raise Exception("insufficient proof of work: %s vs target %s" % (int('0x' + _hash, 16), target))
+        block_hash_as_num = int.from_bytes(bfh(_hash), byteorder='big')
+        if block_hash_as_num > target:
+            raise Exception(f"insufficient proof of work: {block_hash_as_num} vs target {target}")
 
     def verify_chunk(self, index: int, data: bytes) -> None:
         num = len(data) // HEADER_SIZE
@@ -384,7 +385,7 @@ class Blockchain(util.PrintError):
         c = ("%064x" % target)[2:]
         while c[:2] == '00' and len(c) > 6:
             c = c[2:]
-        bitsN, bitsBase = len(c) // 2, int('0x' + c[:6], 16)
+        bitsN, bitsBase = len(c) // 2, int.from_bytes(bfh(c[:6]), byteorder='big')
         if bitsBase >= 0x800000:
             bitsN += 1
             bitsBase >>= 8