bip32: refactor whole module. clean-up.

electrum/bip32.py

@@ -3,7 +3,7 @@
 # file LICENCE or http://www.opensource.org/licenses/mit-license.php
 
 import hashlib
-from typing import List
+from typing import List, Tuple, NamedTuple, Union, Iterable
 
 from .util import bfh, bh2u, BitcoinException, print_error
 from . import constants
@@ -13,110 +13,112 @@ from .bitcoin import rev_hex, int_to_hex, EncodeBase58Check, DecodeBase58Check
 
 
 BIP32_PRIME = 0x80000000
+UINT32_MAX = (1 << 32) - 1
 
 
 def protect_against_invalid_ecpoint(func):
     def func_wrapper(*args):
-        n = args[-1]
+        child_index = args[-1]
         while True:
-            is_prime = n & BIP32_PRIME
+            is_prime = child_index & BIP32_PRIME
             try:
-                return func(*args[:-1], n=n)
+                return func(*args[:-1], child_index=child_index)
             except ecc.InvalidECPointException:
                 print_error('bip32 protect_against_invalid_ecpoint: skipping index')
-                n += 1
-                is_prime2 = n & BIP32_PRIME
+                child_index += 1
+                is_prime2 = child_index & BIP32_PRIME
                 if is_prime != is_prime2: raise OverflowError()
     return func_wrapper
 
 
-# Child private key derivation function (from master private key)
-# k = master private key (32 bytes)
-# c = master chain code (extra entropy for key derivation) (32 bytes)
-# n = the index of the key we want to derive. (only 32 bits will be used)
-# If n is hardened (i.e. the 32nd bit is set), the resulting private key's
-#  corresponding public key can NOT be determined without the master private key.
-# However, if n is not hardened, the resulting private key's corresponding
-#  public key can be determined without the master private key.
 @protect_against_invalid_ecpoint
-def CKD_priv(k, c, n):
-    if n < 0: raise ValueError('the bip32 index needs to be non-negative')
-    is_prime = n & BIP32_PRIME
-    return _CKD_priv(k, c, bfh(rev_hex(int_to_hex(n,4))), is_prime)
+def CKD_priv(parent_privkey: bytes, parent_chaincode: bytes, child_index: int) -> Tuple[bytes, bytes]:
+    """Child private key derivation function (from master private key)
+    If n is hardened (i.e. the 32nd bit is set), the resulting private key's
+    corresponding public key can NOT be determined without the master private key.
+    However, if n is not hardened, the resulting private key's corresponding
+    public key can be determined without the master private key.
+    """
+    if child_index < 0: raise ValueError('the bip32 index needs to be non-negative')
+    is_hardened_child = bool(child_index & BIP32_PRIME)
+    return _CKD_priv(parent_privkey=parent_privkey,
+                     parent_chaincode=parent_chaincode,
+                     child_index=bfh(rev_hex(int_to_hex(child_index, 4))),
+                     is_hardened_child=is_hardened_child)
 
 
-def _CKD_priv(k, c, s, is_prime):
+def _CKD_priv(parent_privkey: bytes, parent_chaincode: bytes,
+              child_index: bytes, is_hardened_child: bool) -> Tuple[bytes, bytes]:
     try:
-        keypair = ecc.ECPrivkey(k)
+        keypair = ecc.ECPrivkey(parent_privkey)
     except ecc.InvalidECPointException as e:
         raise BitcoinException('Impossible xprv (not within curve order)') from e
-    cK = keypair.get_public_key_bytes(compressed=True)
-    data = bytes([0]) + k + s if is_prime else cK + s
-    I = hmac_oneshot(c, data, hashlib.sha512)
+    parent_pubkey = keypair.get_public_key_bytes(compressed=True)
+    if is_hardened_child:
+        data = bytes([0]) + parent_privkey + child_index
+    else:
+        data = parent_pubkey + child_index
+    I = hmac_oneshot(parent_chaincode, data, hashlib.sha512)
     I_left = ecc.string_to_number(I[0:32])
-    k_n = (I_left + ecc.string_to_number(k)) % ecc.CURVE_ORDER
-    if I_left >= ecc.CURVE_ORDER or k_n == 0:
+    child_privkey = (I_left + ecc.string_to_number(parent_privkey)) % ecc.CURVE_ORDER
+    if I_left >= ecc.CURVE_ORDER or child_privkey == 0:
         raise ecc.InvalidECPointException()
-    k_n = ecc.number_to_string(k_n, ecc.CURVE_ORDER)
-    c_n = I[32:]
-    return k_n, c_n
-
-# Child public key derivation function (from public key only)
-# K = master public key
-# c = master chain code
-# n = index of key we want to derive
-# This function allows us to find the nth public key, as long as n is
-#  not hardened. If n is hardened, we need the master private key to find it.
+    child_privkey = ecc.number_to_string(child_privkey, ecc.CURVE_ORDER)
+    child_chaincode = I[32:]
+    return child_privkey, child_chaincode
+
+
+
 @protect_against_invalid_ecpoint
-def CKD_pub(cK, c, n):
-    if n < 0: raise ValueError('the bip32 index needs to be non-negative')
-    if n & BIP32_PRIME: raise Exception()
-    return _CKD_pub(cK, c, bfh(rev_hex(int_to_hex(n,4))))
-
-# helper function, callable with arbitrary string.
-# note: 's' does not need to fit into 32 bits here! (c.f. trustedcoin billing)
-def _CKD_pub(cK, c, s):
-    I = hmac_oneshot(c, cK + s, hashlib.sha512)
-    pubkey = ecc.ECPrivkey(I[0:32]) + ecc.ECPubkey(cK)
+def CKD_pub(parent_pubkey: bytes, parent_chaincode: bytes, child_index: int) -> Tuple[bytes, bytes]:
+    """Child public key derivation function (from public key only)
+    This function allows us to find the nth public key, as long as n is
+    not hardened. If n is hardened, we need the master private key to find it.
+    """
+    if child_index < 0: raise ValueError('the bip32 index needs to be non-negative')
+    if child_index & BIP32_PRIME: raise Exception('not possible to derive hardened child from parent pubkey')
+    return _CKD_pub(parent_pubkey=parent_pubkey,
+                    parent_chaincode=parent_chaincode,
+                    child_index=bfh(rev_hex(int_to_hex(child_index, 4))))
+
+
+# helper function, callable with arbitrary 'child_index' byte-string.
+# i.e.: 'child_index' does not need to fit into 32 bits here! (c.f. trustedcoin billing)
+def _CKD_pub(parent_pubkey: bytes, parent_chaincode: bytes, child_index: bytes) -> Tuple[bytes, bytes]:
+    I = hmac_oneshot(parent_chaincode, parent_pubkey + child_index, hashlib.sha512)
+    pubkey = ecc.ECPrivkey(I[0:32]) + ecc.ECPubkey(parent_pubkey)
     if pubkey.is_at_infinity():
         raise ecc.InvalidECPointException()
-    cK_n = pubkey.get_public_key_bytes(compressed=True)
-    c_n = I[32:]
-    return cK_n, c_n
+    child_pubkey = pubkey.get_public_key_bytes(compressed=True)
+    child_chaincode = I[32:]
+    return child_pubkey, child_chaincode
 
 
-def xprv_header(xtype, *, net=None):
+def xprv_header(xtype: str, *, net=None) -> bytes:
     if net is None:
         net = constants.net
-    return bfh("%08x" % net.XPRV_HEADERS[xtype])
+    return net.XPRV_HEADERS[xtype].to_bytes(length=4, byteorder="big")
 
 
-def xpub_header(xtype, *, net=None):
+def xpub_header(xtype: str, *, net=None) -> bytes:
     if net is None:
         net = constants.net
-    return bfh("%08x" % net.XPUB_HEADERS[xtype])
-
-
-def serialize_xprv(xtype, c, k, depth=0, fingerprint=b'\x00'*4,
-                   child_number=b'\x00'*4, *, net=None):
-    if not ecc.is_secret_within_curve_range(k):
-        raise BitcoinException('Impossible xprv (not within curve order)')
-    xprv = xprv_header(xtype, net=net) \
-           + bytes([depth]) + fingerprint + child_number + c + bytes([0]) + k
-    return EncodeBase58Check(xprv)
-
-
-def serialize_xpub(xtype, c, cK, depth=0, fingerprint=b'\x00'*4,
-                   child_number=b'\x00'*4, *, net=None):
-    xpub = xpub_header(xtype, net=net) \
-           + bytes([depth]) + fingerprint + child_number + c + cK
-    return EncodeBase58Check(xpub)
+    return net.XPUB_HEADERS[xtype].to_bytes(length=4, byteorder="big")
 
 
 class InvalidMasterKeyVersionBytes(BitcoinException): pass
 
 
-def deserialize_xkey(xkey, prv, *, net=None):
+class BIP32Node(NamedTuple):
+    xtype: str
+    eckey: Union[ecc.ECPubkey, ecc.ECPrivkey]
+    chaincode: bytes
+    depth: int = 0
+    fingerprint: bytes = b'\x00'*4
+    child_number: bytes = b'\x00'*4
+
+    @classmethod
+    def from_xkey(cls, xkey: str, *, net=None) -> 'BIP32Node':
         if net is None:
             net = constants.net
         xkey = DecodeBase58Check(xkey)
@@ -126,144 +128,184 @@ def deserialize_xkey(xkey, prv, *, net=None):
         depth = xkey[4]
         fingerprint = xkey[5:9]
         child_number = xkey[9:13]
-    c = xkey[13:13+32]
+        chaincode = xkey[13:13 + 32]
         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: {}'
-                                           .format(hex(header)))
-    xtype = list(headers.keys())[list(headers.values()).index(header)]
-    n = 33 if prv else 32
-    K_or_k = xkey[13+n:]
-    if prv and not ecc.is_secret_within_curve_range(K_or_k):
-        raise BitcoinException('Impossible xprv (not within curve order)')
-    return xtype, depth, fingerprint, child_number, c, K_or_k
-
-
-def deserialize_xpub(xkey, *, net=None):
-    return deserialize_xkey(xkey, False, net=net)
+        if header in net.XPRV_HEADERS_INV:
+            headers_inv = net.XPRV_HEADERS_INV
+            is_private = True
+        elif header in net.XPUB_HEADERS_INV:
+            headers_inv = net.XPUB_HEADERS_INV
+            is_private = False
+        else:
+            raise InvalidMasterKeyVersionBytes(f'Invalid extended key format: {hex(header)}')
+        xtype = headers_inv[header]
+        if is_private:
+            eckey = ecc.ECPrivkey(xkey[13 + 33:])
+        else:
+            eckey = ecc.ECPubkey(xkey[13 + 32:])
+        return BIP32Node(xtype=xtype,
+                         eckey=eckey,
+                         chaincode=chaincode,
+                         depth=depth,
+                         fingerprint=fingerprint,
+                         child_number=child_number)
+
+    @classmethod
+    def from_rootseed(cls, seed: bytes, *, xtype: str) -> 'BIP32Node':
+        I = hmac_oneshot(b"Bitcoin seed", seed, hashlib.sha512)
+        master_k = I[0:32]
+        master_c = I[32:]
+        return BIP32Node(xtype=xtype,
+                         eckey=ecc.ECPrivkey(master_k),
+                         chaincode=master_c)
+
+    def to_xprv(self, *, net=None) -> str:
+        if not self.is_private():
+            raise Exception("cannot serialize as xprv; private key missing")
+        payload = (xprv_header(self.xtype, net=net) +
+                   bytes([self.depth]) +
+                   self.fingerprint +
+                   self.child_number +
+                   self.chaincode +
+                   bytes([0]) +
+                   self.eckey.get_secret_bytes())
+        assert len(payload) == 78, f"unexpected xprv payload len {len(payload)}"
+        return EncodeBase58Check(payload)
+
+    def to_xpub(self, *, net=None) -> str:
+        payload = (xpub_header(self.xtype, net=net) +
+                   bytes([self.depth]) +
+                   self.fingerprint +
+                   self.child_number +
+                   self.chaincode +
+                   self.eckey.get_public_key_bytes(compressed=True))
+        assert len(payload) == 78, f"unexpected xpub payload len {len(payload)}"
+        return EncodeBase58Check(payload)
+
+    def to_xkey(self, *, net=None) -> str:
+        if self.is_private():
+            return self.to_xprv(net=net)
+        else:
+            return self.to_xpub(net=net)
+
+    def convert_to_public(self) -> 'BIP32Node':
+        if not self.is_private():
+            return self
+        pubkey = ecc.ECPubkey(self.eckey.get_public_key_bytes())
+        return self._replace(eckey=pubkey)
+
+    def is_private(self) -> bool:
+        return isinstance(self.eckey, ecc.ECPrivkey)
+
+    def subkey_at_private_derivation(self, path: Union[str, Iterable[int]]) -> 'BIP32Node':
+        if isinstance(path, str):
+            path = convert_bip32_path_to_list_of_uint32(path)
+        if not self.is_private():
+            raise Exception("cannot do bip32 private derivation; private key missing")
+        if not path:
+            return self
+        depth = self.depth
+        chaincode = self.chaincode
+        privkey = self.eckey.get_secret_bytes()
+        for child_index in path:
+            parent_privkey = privkey
+            privkey, chaincode = CKD_priv(privkey, chaincode, child_index)
+            depth += 1
+        parent_pubkey = ecc.ECPrivkey(parent_privkey).get_public_key_bytes(compressed=True)
+        fingerprint = hash_160(parent_pubkey)[0:4]
+        child_number = child_index.to_bytes(length=4, byteorder="big")
+        return BIP32Node(xtype=self.xtype,
+                         eckey=ecc.ECPrivkey(privkey),
+                         chaincode=chaincode,
+                         depth=depth,
+                         fingerprint=fingerprint,
+                         child_number=child_number)
+
+    def subkey_at_public_derivation(self, path: Union[str, Iterable[int]]) -> 'BIP32Node':
+        if isinstance(path, str):
+            path = convert_bip32_path_to_list_of_uint32(path)
+        if not path:
+            return self.convert_to_public()
+        depth = self.depth
+        chaincode = self.chaincode
+        pubkey = self.eckey.get_public_key_bytes(compressed=True)
+        for child_index in path:
+            parent_pubkey = pubkey
+            pubkey, chaincode = CKD_pub(pubkey, chaincode, child_index)
+            depth += 1
+        fingerprint = hash_160(parent_pubkey)[0:4]
+        child_number = child_index.to_bytes(length=4, byteorder="big")
+        return BIP32Node(xtype=self.xtype,
+                         eckey=ecc.ECPubkey(pubkey),
+                         chaincode=chaincode,
+                         depth=depth,
+                         fingerprint=fingerprint,
+                         child_number=child_number)
 
-def deserialize_xprv(xkey, *, net=None):
-    return deserialize_xkey(xkey, True, net=net)
 
 def xpub_type(x):
-    return deserialize_xpub(x)[0]
+    return BIP32Node.from_xkey(x).xtype
 
 
 def is_xpub(text):
     try:
-        deserialize_xpub(text)
-        return True
+        node = BIP32Node.from_xkey(text)
+        return not node.is_private()
     except:
         return False
 
 
 def is_xprv(text):
     try:
-        deserialize_xprv(text)
-        return True
+        node = BIP32Node.from_xkey(text)
+        return node.is_private()
     except:
         return False
 
 
 def xpub_from_xprv(xprv):
-    xtype, depth, fingerprint, child_number, c, k = deserialize_xprv(xprv)
-    cK = ecc.ECPrivkey(k).get_public_key_bytes(compressed=True)
-    return serialize_xpub(xtype, c, cK, depth, fingerprint, child_number)
+    return BIP32Node.from_xkey(xprv).to_xpub()
 
 
-def bip32_root(seed, xtype):
-    I = hmac_oneshot(b"Bitcoin seed", seed, hashlib.sha512)
-    master_k = I[0:32]
-    master_c = I[32:]
-    # create xprv first, as that will check if master_k is within curve order
-    xprv = serialize_xprv(xtype, master_c, master_k)
-    cK = ecc.ECPrivkey(master_k).get_public_key_bytes(compressed=True)
-    xpub = serialize_xpub(xtype, master_c, cK)
-    return xprv, xpub
-
-
-def xpub_from_pubkey(xtype, cK):
-    if cK[0] not in (0x02, 0x03):
-        raise ValueError('Unexpected first byte: {}'.format(cK[0]))
-    return serialize_xpub(xtype, b'\x00'*32, cK)
-
-
-def bip32_derivation(s: str) -> int:
-    if not s.startswith('m/'):
-        raise ValueError('invalid bip32 derivation path: {}'.format(s))
-    s = s[2:]
-    for n in s.split('/'):
-        if n == '': continue
-        i = int(n[:-1]) + BIP32_PRIME if n[-1] == "'" else int(n)
-        yield i
-
 def convert_bip32_path_to_list_of_uint32(n: str) -> List[int]:
     """Convert bip32 path to list of uint32 integers with prime flags
     m/0/-1/1' -> [0, 0x80000001, 0x80000001]
 
     based on code in trezorlib
     """
+    if not n:
+        return []
+    if n.endswith("/"):
+        n = n[:-1]
+    n = n.split('/')
+    # cut leading "m" if present, but do not require it
+    if n[0] == "m":
+        n = n[1:]
     path = []
-    for x in n.split('/')[1:]:
-        if x == '': continue
+    for x in n:
+        if x == '':
+            # gracefully allow repeating "/" chars in path.
+            # makes concatenating paths easier
+            continue
         prime = 0
-        if x.endswith("'"):
-            x = x.replace('\'', '')
+        if x.endswith("'") or x.endswith("h"):
+            x = x[:-1]
             prime = BIP32_PRIME
         if x.startswith('-'):
             prime = BIP32_PRIME
-        path.append(abs(int(x)) | prime)
+        child_index = abs(int(x)) | prime
+        if child_index > UINT32_MAX:
+            raise ValueError(f"bip32 path child index too large: {child_index} > {UINT32_MAX}")
+        path.append(child_index)
     return path
 
-def is_bip32_derivation(x: str) -> bool:
+
+def is_bip32_derivation(s: str) -> bool:
     try:
-        [ i for i in bip32_derivation(x)]
-        return True
-    except :
+        if not s.startswith('m/'):
             return False
-
-def bip32_private_derivation(xprv, branch, sequence):
-    if not sequence.startswith(branch):
-        raise ValueError('incompatible branch ({}) and sequence ({})'
-                         .format(branch, sequence))
-    if branch == sequence:
-        return xprv, xpub_from_xprv(xprv)
-    xtype, depth, fingerprint, child_number, c, k = deserialize_xprv(xprv)
-    sequence = sequence[len(branch):]
-    for n in sequence.split('/'):
-        if n == '': continue
-        i = int(n[:-1]) + BIP32_PRIME if n[-1] == "'" else int(n)
-        parent_k = k
-        k, c = CKD_priv(k, c, i)
-        depth += 1
-    parent_cK = ecc.ECPrivkey(parent_k).get_public_key_bytes(compressed=True)
-    fingerprint = hash_160(parent_cK)[0:4]
-    child_number = bfh("%08X"%i)
-    cK = ecc.ECPrivkey(k).get_public_key_bytes(compressed=True)
-    xpub = serialize_xpub(xtype, c, cK, depth, fingerprint, child_number)
-    xprv = serialize_xprv(xtype, c, k, depth, fingerprint, child_number)
-    return xprv, xpub
-
-
-def bip32_public_derivation(xpub, branch, sequence):
-    xtype, depth, fingerprint, child_number, c, cK = deserialize_xpub(xpub)
-    if not sequence.startswith(branch):
-        raise ValueError('incompatible branch ({}) and sequence ({})'
-                         .format(branch, sequence))
-    sequence = sequence[len(branch):]
-    for n in sequence.split('/'):
-        if n == '': continue
-        i = int(n)
-        parent_cK = cK
-        cK, c = CKD_pub(cK, c, i)
-        depth += 1
-    fingerprint = hash_160(parent_cK)[0:4]
-    child_number = bfh("%08X"%i)
-    return serialize_xpub(xtype, c, cK, depth, fingerprint, child_number)
-
-
-def bip32_private_key(sequence, k, chain):
-    for i in sequence:
-        k, chain = CKD_priv(k, chain, i)
-    return k
+        convert_bip32_path_to_list_of_uint32(s)
+    except:
+        return False
+    else:
+        return True

electrum/commands.py

@@ -39,6 +39,7 @@ from .util import bfh, bh2u, format_satoshis, json_decode, print_error, json_enc
 from . import bitcoin
 from .bitcoin import is_address,  hash_160, COIN, TYPE_ADDRESS
 from . import bip32
+from .bip32 import BIP32Node
 from .i18n import _
 from .transaction import Transaction, multisig_script, TxOutput
 from .paymentrequest import PR_PAID, PR_UNPAID, PR_UNKNOWN, PR_EXPIRED
@@ -439,12 +440,11 @@ class Commands:
     @command('')
     def convert_xkey(self, xkey, xtype):
         """Convert xtype of a master key. e.g. xpub -> ypub"""
-        is_xprv = bip32.is_xprv(xkey)
-        if not bip32.is_xpub(xkey) and not is_xprv:
+        try:
+            node = BIP32Node.from_xkey(xkey)
+        except:
             raise Exception('xkey should be a master public/private key')
-        _, depth, fingerprint, child_number, c, cK = bip32.deserialize_xkey(xkey, is_xprv)
-        serialize = bip32.serialize_xprv if is_xprv else bip32.serialize_xpub
-        return serialize(xtype, c, cK, depth, fingerprint, child_number)
+        return node._replace(xtype=xtype).to_xkey()
 
     @command('wp')
     def getseed(self, password=None):

electrum/constants.py

@@ -26,6 +26,8 @@
 import os
 import json
 
+from .util import inv_dict
+
 
 def read_json(filename, default):
     path = os.path.join(os.path.dirname(__file__), filename)
@@ -63,6 +65,7 @@ class BitcoinMainnet(AbstractNet):
         'p2wpkh':      0x04b2430c,  # zprv
         'p2wsh':       0x02aa7a99,  # Zprv
     }
+    XPRV_HEADERS_INV = inv_dict(XPRV_HEADERS)
     XPUB_HEADERS = {
         'standard':    0x0488b21e,  # xpub
         'p2wpkh-p2sh': 0x049d7cb2,  # ypub
@@ -70,6 +73,7 @@ class BitcoinMainnet(AbstractNet):
         'p2wpkh':      0x04b24746,  # zpub
         'p2wsh':       0x02aa7ed3,  # Zpub
     }
+    XPUB_HEADERS_INV = inv_dict(XPUB_HEADERS)
     BIP44_COIN_TYPE = 0
 
 
@@ -92,6 +96,7 @@ class BitcoinTestnet(AbstractNet):
         'p2wpkh':      0x045f18bc,  # vprv
         'p2wsh':       0x02575048,  # Vprv
     }
+    XPRV_HEADERS_INV = inv_dict(XPRV_HEADERS)
     XPUB_HEADERS = {
         'standard':    0x043587cf,  # tpub
         'p2wpkh-p2sh': 0x044a5262,  # upub
@@ -99,6 +104,7 @@ class BitcoinTestnet(AbstractNet):
         'p2wpkh':      0x045f1cf6,  # vpub
         'p2wsh':       0x02575483,  # Vpub
     }
+    XPUB_HEADERS_INV = inv_dict(XPUB_HEADERS)
     BIP44_COIN_TYPE = 1
 
 

electrum/ecc.py

@@ -229,6 +229,9 @@ class ECPubkey(object):
     def point(self) -> Tuple[int, int]:
         return self._pubkey.point.x(), self._pubkey.point.y()
 
+    def __repr__(self):
+        return f"<ECPubkey {self.get_public_key_hex()}>"
+
     def __mul__(self, other: int):
         if not isinstance(other, int):
             raise TypeError('multiplication not defined for ECPubkey and {}'.format(type(other)))
@@ -375,6 +378,12 @@ class ECPrivkey(ECPubkey):
         privkey_32bytes = number_to_string(scalar, CURVE_ORDER)
         return privkey_32bytes
 
+    def __repr__(self):
+        return f"<ECPrivkey {self.get_public_key_hex()}>"
+
+    def get_secret_bytes(self) -> bytes:
+        return number_to_string(self.secret_scalar, CURVE_ORDER)
+
     def sign(self, data: bytes, sigencode=None, sigdecode=None) -> bytes:
         if sigencode is None:
             sigencode = sig_string_from_r_and_s

electrum/keystore.py

@@ -31,10 +31,8 @@ from typing import Tuple
 from . import bitcoin, ecc, constants, bip32
 from .bitcoin import (deserialize_privkey, serialize_privkey,
                       public_key_to_p2pkh)
-from .bip32 import (bip32_public_derivation, deserialize_xpub, CKD_pub,
-                    bip32_root, deserialize_xprv, bip32_private_derivation,
-                    bip32_private_key, bip32_derivation, BIP32_PRIME,
-                    is_xpub, is_xprv)
+from .bip32 import (convert_bip32_path_to_list_of_uint32, BIP32_PRIME,
+                    is_xpub, is_xprv, BIP32Node)
 from .ecc import string_to_number, number_to_string
 from .crypto import (pw_decode, pw_encode, sha256, sha256d, PW_HASH_VERSION_LATEST,
                      SUPPORTED_PW_HASH_VERSIONS, UnsupportedPasswordHashVersion)
@@ -133,6 +131,9 @@ class Software_KeyStore(KeyStore):
     def check_password(self, password):
         raise NotImplementedError()  # implemented by subclasses
 
+    def get_private_key(self, *args, **kwargs) -> Tuple[bytes, bool]:
+        raise NotImplementedError()  # implemented by subclasses
+
 
 class Imported_KeyStore(Software_KeyStore):
     # keystore for imported private keys
@@ -263,7 +264,8 @@ class Xpub:
     def derive_pubkey(self, for_change, n):
         xpub = self.xpub_change if for_change else self.xpub_receive
         if xpub is None:
-            xpub = bip32_public_derivation(self.xpub, "", "/%d"%for_change)
+            rootnode = BIP32Node.from_xkey(self.xpub)
+            xpub = rootnode.subkey_at_public_derivation((for_change,)).to_xpub()
             if for_change:
                 self.xpub_change = xpub
             else:
@@ -272,10 +274,8 @@ class Xpub:
 
     @classmethod
     def get_pubkey_from_xpub(self, xpub, sequence):
-        _, _, _, _, c, cK = deserialize_xpub(xpub)
-        for i in sequence:
-            cK, c = CKD_pub(cK, c, i)
-        return bh2u(cK)
+        node = BIP32Node.from_xkey(xpub).subkey_at_public_derivation(sequence)
+        return node.eckey.get_public_key_hex(compressed=True)
 
     def get_xpubkey(self, c, i):
         s = ''.join(map(lambda x: bitcoin.int_to_hex(x,2), (c, i)))
@@ -334,7 +334,7 @@ class BIP32_KeyStore(Deterministic_KeyStore, Xpub):
 
     def check_password(self, password):
         xprv = pw_decode(self.xprv, password, version=self.pw_hash_version)
-        if deserialize_xprv(xprv)[4] != deserialize_xpub(self.xpub)[4]:
+        if BIP32Node.from_xkey(xprv).chaincode != BIP32Node.from_xkey(self.xpub).chaincode:
             raise InvalidPassword()
 
     def update_password(self, old_password, new_password):
@@ -360,14 +360,14 @@ class BIP32_KeyStore(Deterministic_KeyStore, Xpub):
         self.xpub = bip32.xpub_from_xprv(xprv)
 
     def add_xprv_from_seed(self, bip32_seed, xtype, derivation):
-        xprv, xpub = bip32_root(bip32_seed, xtype)
-        xprv, xpub = bip32_private_derivation(xprv, "m/", derivation)
-        self.add_xprv(xprv)
+        rootnode = BIP32Node.from_rootseed(bip32_seed, xtype=xtype)
+        node = rootnode.subkey_at_private_derivation(derivation)
+        self.add_xprv(node.to_xprv())
 
     def get_private_key(self, sequence, password):
         xprv = self.get_master_private_key(password)
-        _, _, _, _, c, k = deserialize_xprv(xprv)
-        pk = bip32_private_key(sequence, k, c)
+        node = BIP32Node.from_xkey(xprv).subkey_at_private_derivation(sequence)
+        pk = node.eckey.get_secret_bytes()
         return pk, True
 
 
@@ -658,7 +658,7 @@ def xtype_from_derivation(derivation: str) -> str:
     elif derivation.startswith("m/45'"):
         return 'standard'
 
-    bip32_indices = list(bip32_derivation(derivation))
+    bip32_indices = convert_bip32_path_to_list_of_uint32(derivation)
     if len(bip32_indices) >= 4:
         if bip32_indices[0] == 48 + BIP32_PRIME:
             # m / purpose' / coin_type' / account' / script_type' / change / address_index

electrum/mnemonic.py

@@ -126,7 +126,7 @@ class Mnemonic(object):
         print_error("wordlist has %d words"%len(self.wordlist))
 
     @classmethod
-    def mnemonic_to_seed(self, mnemonic, passphrase):
+    def mnemonic_to_seed(self, mnemonic, passphrase) -> bytes:
         PBKDF2_ROUNDS = 2048
         mnemonic = normalize_text(mnemonic)
         passphrase = passphrase or ''

electrum/plugins/coldcard/coldcard.py

@@ -6,7 +6,7 @@ from struct import pack, unpack
 import os, sys, time, io
 import traceback
 
-from electrum.bip32 import serialize_xpub, deserialize_xpub, InvalidMasterKeyVersionBytes
+from electrum.bip32 import BIP32Node, InvalidMasterKeyVersionBytes
 from electrum.i18n import _
 from electrum.plugin import Device
 from electrum.keystore import Hardware_KeyStore, xpubkey_to_pubkey, Xpub
@@ -40,12 +40,7 @@ try:
         def mitm_verify(self, sig, expect_xpub):
             # verify a signature (65 bytes) over the session key, using the master bip32 node
             # - customized to use specific EC library of Electrum.
-            from electrum.ecc import ECPubkey
-
-            xtype, depth, parent_fingerprint, child_number, chain_code, K_or_k \
-                = deserialize_xpub(expect_xpub)
-
-            pubkey = ECPubkey(K_or_k)
+            pubkey = BIP32Node.from_xkey(expect_xpub).eckey
             try:
                 pubkey.verify_message_hash(sig[1:65], self.session_key)
                 return True
@@ -191,12 +186,12 @@ class CKCCClient:
         # TODO handle timeout?
         # change type of xpub to the requested type
         try:
-            __, depth, fingerprint, child_number, c, cK = deserialize_xpub(xpub)
+            node = BIP32Node.from_xkey(xpub)
         except InvalidMasterKeyVersionBytes:
             raise UserFacingException(_('Invalid xpub magic. Make sure your {} device is set to the correct chain.')
                                       .format(self.device)) from None
         if xtype != 'standard':
-            xpub = serialize_xpub(xtype, c, cK, depth, fingerprint, child_number)
+            xpub = node._replace(xtype=xtype).to_xpub()
         return xpub
 
     def ping_check(self):

electrum/plugins/cosigner_pool/qt.py

@@ -29,8 +29,9 @@ from xmlrpc.client import ServerProxy
 from PyQt5.QtCore import QObject, pyqtSignal
 from PyQt5.QtWidgets import QPushButton
 
-from electrum import util, keystore, ecc, bip32, crypto
+from electrum import util, keystore, ecc, crypto
 from electrum import transaction
+from electrum.bip32 import BIP32Node
 from electrum.plugin import BasePlugin, hook
 from electrum.i18n import _
 from electrum.wallet import Multisig_Wallet
@@ -131,12 +132,12 @@ class Plugin(BasePlugin):
         self.cosigner_list = []
         for key, keystore in wallet.keystores.items():
             xpub = keystore.get_master_public_key()
-            K = bip32.deserialize_xpub(xpub)[-1]
-            _hash = bh2u(crypto.sha256d(K))
+            pubkey = BIP32Node.from_xkey(xpub).eckey.get_public_key_bytes(compressed=True)
+            _hash = bh2u(crypto.sha256d(pubkey))
             if not keystore.is_watching_only():
                 self.keys.append((key, _hash, window))
             else:
-                self.cosigner_list.append((window, xpub, K, _hash))
+                self.cosigner_list.append((window, xpub, pubkey, _hash))
         if self.listener:
             self.listener.set_keyhashes([t[1] for t in self.keys])
 
@@ -221,9 +222,8 @@ class Plugin(BasePlugin):
         if not xprv:
             return
         try:
-            k = bip32.deserialize_xprv(xprv)[-1]
-            EC = ecc.ECPrivkey(k)
-            message = bh2u(EC.decrypt_message(message))
+            privkey = BIP32Node.from_xkey(xprv).eckey
+            message = bh2u(privkey.decrypt_message(message))
         except Exception as e:
             traceback.print_exc(file=sys.stdout)
             window.show_error(_('Error decrypting message') + ':\n' + str(e))

electrum/plugins/digitalbitbox/digitalbitbox.py

@@ -18,7 +18,7 @@ import time
 from electrum.crypto import sha256d, EncodeAES_base64, EncodeAES_bytes, DecodeAES_bytes, hmac_oneshot
 from electrum.bitcoin import (TYPE_ADDRESS, push_script, var_int, public_key_to_p2pkh,
                               is_address)
-from electrum.bip32 import serialize_xpub, deserialize_xpub
+from electrum.bip32 import BIP32Node
 from electrum import ecc
 from electrum.ecc import msg_magic
 from electrum.wallet import Standard_Wallet
@@ -118,8 +118,8 @@ class DigitalBitbox_Client():
             # only ever returns the mainnet standard type, but it is agnostic
             # to the type when signing.
             if xtype != 'standard' or constants.net.TESTNET:
-                _, depth, fingerprint, child_number, c, cK = deserialize_xpub(xpub, net=constants.BitcoinMainnet)
-                xpub = serialize_xpub(xtype, c, cK, depth, fingerprint, child_number)
+                node = BIP32Node.from_xkey(xpub, net=constants.BitcoinMainnet)
+                xpub = node._replace(xtype=xtype).to_xpub()
             return xpub
         else:
             raise Exception('no reply')

electrum/plugins/keepkey/clientbase.py

@@ -1,10 +1,11 @@
 import time
 from struct import pack
 
+from electrum import ecc
 from electrum.i18n import _
 from electrum.util import PrintError, UserCancelled
 from electrum.keystore import bip39_normalize_passphrase
-from electrum.bip32 import serialize_xpub, convert_bip32_path_to_list_of_uint32
+from electrum.bip32 import BIP32Node, convert_bip32_path_to_list_of_uint32
 
 
 class GuiMixin(object):
@@ -154,7 +155,12 @@ class KeepKeyClientBase(GuiMixin, PrintError):
         address_n = self.expand_path(bip32_path)
         creating = False
         node = self.get_public_node(address_n, creating).node
-        return serialize_xpub(xtype, node.chain_code, node.public_key, node.depth, self.i4b(node.fingerprint), self.i4b(node.child_num))
+        return BIP32Node(xtype=xtype,
+                         eckey=ecc.ECPubkey(node.public_key),
+                         chaincode=node.chain_code,
+                         depth=node.depth,
+                         fingerprint=self.i4b(node.fingerprint),
+                         child_number=self.i4b(node.child_num)).to_xpub()
 
     def toggle_passphrase(self):
         if self.features.passphrase_protection:

electrum/plugins/keepkey/keepkey.py

@@ -4,7 +4,7 @@ import sys
 
 from electrum.util import bfh, bh2u, UserCancelled, UserFacingException
 from electrum.bitcoin import TYPE_ADDRESS, TYPE_SCRIPT
-from electrum.bip32 import deserialize_xpub
+from electrum.bip32 import BIP32Node
 from electrum import constants
 from electrum.i18n import _
 from electrum.transaction import deserialize, Transaction
@@ -227,13 +227,13 @@ class KeepKeyPlugin(HW_PluginBase):
                                        label, language)
 
     def _make_node_path(self, xpub, address_n):
-        _, depth, fingerprint, child_num, chain_code, key = deserialize_xpub(xpub)
+        bip32node = BIP32Node.from_xkey(xpub)
         node = self.types.HDNodeType(
-            depth=depth,
-            fingerprint=int.from_bytes(fingerprint, 'big'),
-            child_num=int.from_bytes(child_num, 'big'),
-            chain_code=chain_code,
-            public_key=key,
+            depth=bip32node.depth,
+            fingerprint=int.from_bytes(bip32node.fingerprint, 'big'),
+            child_num=int.from_bytes(bip32node.child_number, 'big'),
+            chain_code=bip32node.chaincode,
+            public_key=bip32node.eckey.get_public_key_bytes(compressed=True),
         )
         return self.types.HDNodePathType(node=node, address_n=address_n)
 

electrum/plugins/ledger/ledger.py

@@ -3,8 +3,9 @@ import hashlib
 import sys
 import traceback
 
+from electrum import ecc
 from electrum.bitcoin import TYPE_ADDRESS, int_to_hex, var_int
-from electrum.bip32 import serialize_xpub
+from electrum.bip32 import BIP32Node
 from electrum.i18n import _
 from electrum.keystore import Hardware_KeyStore
 from electrum.transaction import Transaction
@@ -112,8 +113,12 @@ class Ledger_Client():
         depth = len(splitPath)
         lastChild = splitPath[len(splitPath) - 1].split('\'')
         childnum = int(lastChild[0]) if len(lastChild) == 1 else 0x80000000 | int(lastChild[0])
-        xpub = serialize_xpub(xtype, nodeData['chainCode'], publicKey, depth, self.i4b(fingerprint), self.i4b(childnum))
-        return xpub
+        return BIP32Node(xtype=xtype,
+                         eckey=ecc.ECPubkey(publicKey),
+                         chaincode=nodeData['chainCode'],
+                         depth=depth,
+                         fingerprint=self.i4b(fingerprint),
+                         child_number=self.i4b(childnum)).to_xpub()
 
     def has_detached_pin_support(self, client):
         try:

electrum/plugins/safe_t/clientbase.py

@@ -1,10 +1,11 @@
 import time
 from struct import pack
 
+from electrum import ecc
 from electrum.i18n import _
 from electrum.util import PrintError, UserCancelled
 from electrum.keystore import bip39_normalize_passphrase
-from electrum.bip32 import serialize_xpub, convert_bip32_path_to_list_of_uint32
+from electrum.bip32 import BIP32Node, convert_bip32_path_to_list_of_uint32
 
 
 class GuiMixin(object):
@@ -156,7 +157,12 @@ class SafeTClientBase(GuiMixin, PrintError):
         address_n = self.expand_path(bip32_path)
         creating = False
         node = self.get_public_node(address_n, creating).node
-        return serialize_xpub(xtype, node.chain_code, node.public_key, node.depth, self.i4b(node.fingerprint), self.i4b(node.child_num))
+        return BIP32Node(xtype=xtype,
+                         eckey=ecc.ECPubkey(node.public_key),
+                         chaincode=node.chain_code,
+                         depth=node.depth,
+                         fingerprint=self.i4b(node.fingerprint),
+                         child_number=self.i4b(node.child_num)).to_xpub()
 
     def toggle_passphrase(self):
         if self.features.passphrase_protection:

electrum/plugins/safe_t/safe_t.py

@@ -4,7 +4,7 @@ import sys
 
 from electrum.util import bfh, bh2u, versiontuple, UserCancelled, UserFacingException
 from electrum.bitcoin import TYPE_ADDRESS, TYPE_SCRIPT
-from electrum.bip32 import deserialize_xpub
+from electrum.bip32 import BIP32Node
 from electrum import constants
 from electrum.i18n import _
 from electrum.plugin import Device
@@ -244,13 +244,13 @@ class SafeTPlugin(HW_PluginBase):
                                        label, language)
 
     def _make_node_path(self, xpub, address_n):
-        _, depth, fingerprint, child_num, chain_code, key = deserialize_xpub(xpub)
+        bip32node = BIP32Node.from_xkey(xpub)
         node = self.types.HDNodeType(
-            depth=depth,
-            fingerprint=int.from_bytes(fingerprint, 'big'),
-            child_num=int.from_bytes(child_num, 'big'),
-            chain_code=chain_code,
-            public_key=key,
+            depth=bip32node.depth,
+            fingerprint=int.from_bytes(bip32node.fingerprint, 'big'),
+            child_num=int.from_bytes(bip32node.child_number, 'big'),
+            chain_code=bip32node.chaincode,
+            public_key=bip32node.eckey.get_public_key_bytes(compressed=True),
         )
         return self.types.HDNodePathType(node=node, address_n=address_n)
 

electrum/plugins/trezor/clientbase.py

@@ -1,10 +1,11 @@
 import time
 from struct import pack
 
+from electrum import ecc
 from electrum.i18n import _
 from electrum.util import PrintError, UserCancelled, UserFacingException
 from electrum.keystore import bip39_normalize_passphrase
-from electrum.bip32 import serialize_xpub, convert_bip32_path_to_list_of_uint32 as parse_path
+from electrum.bip32 import BIP32Node, convert_bip32_path_to_list_of_uint32 as parse_path
 
 from trezorlib.client import TrezorClient
 from trezorlib.exceptions import TrezorFailure, Cancelled, OutdatedFirmwareError
@@ -120,7 +121,12 @@ class TrezorClientBase(PrintError):
         address_n = parse_path(bip32_path)
         with self.run_flow(creating_wallet=creating):
             node = trezorlib.btc.get_public_node(self.client, address_n).node
-        return serialize_xpub(xtype, node.chain_code, node.public_key, node.depth, self.i4b(node.fingerprint), self.i4b(node.child_num))
+        return BIP32Node(xtype=xtype,
+                         eckey=ecc.ECPubkey(node.public_key),
+                         chaincode=node.chain_code,
+                         depth=node.depth,
+                         fingerprint=self.i4b(node.fingerprint),
+                         child_number=self.i4b(node.child_num)).to_xpub()
 
     def toggle_passphrase(self):
         if self.features.passphrase_protection:

electrum/plugins/trezor/trezor.py

@@ -3,7 +3,7 @@ import sys
 
 from electrum.util import bfh, bh2u, versiontuple, UserCancelled, UserFacingException
 from electrum.bitcoin import TYPE_ADDRESS, TYPE_SCRIPT
-from electrum.bip32 import deserialize_xpub, convert_bip32_path_to_list_of_uint32 as parse_path
+from electrum.bip32 import BIP32Node, convert_bip32_path_to_list_of_uint32 as parse_path
 from electrum import constants
 from electrum.i18n import _
 from electrum.plugin import Device
@@ -241,13 +241,13 @@ class TrezorPlugin(HW_PluginBase):
             raise RuntimeError("Unsupported recovery method")
 
     def _make_node_path(self, xpub, address_n):
-        _, depth, fingerprint, child_num, chain_code, key = deserialize_xpub(xpub)
+        bip32node = BIP32Node.from_xkey(xpub)
         node = HDNodeType(
-            depth=depth,
-            fingerprint=int.from_bytes(fingerprint, 'big'),
-            child_num=int.from_bytes(child_num, 'big'),
-            chain_code=chain_code,
-            public_key=key,
+            depth=bip32node.depth,
+            fingerprint=int.from_bytes(bip32node.fingerprint, 'big'),
+            child_num=int.from_bytes(bip32node.child_number, 'big'),
+            chain_code=bip32node.chaincode,
+            public_key=bip32node.eckey.get_public_key_bytes(compressed=True),
         )
         return HDNodePathType(node=node, address_n=address_n)
 

electrum/plugins/trustedcoin/trustedcoin.py

@@ -37,8 +37,7 @@ from aiohttp import ClientResponse
 
 from electrum import ecc, constants, keystore, version, bip32, bitcoin
 from electrum.bitcoin import TYPE_ADDRESS
-from electrum.bip32 import (deserialize_xpub, deserialize_xprv, bip32_private_key, CKD_pub,
-                            serialize_xpub, bip32_root, bip32_private_derivation, xpub_type)
+from electrum.bip32 import CKD_pub, BIP32Node, xpub_type
 from electrum.crypto import sha256
 from electrum.transaction import TxOutput
 from electrum.mnemonic import Mnemonic, seed_type, is_any_2fa_seed_type
@@ -59,9 +58,8 @@ def get_signing_xpub(xtype):
         raise NotImplementedError('xtype: {}'.format(xtype))
     if xtype == 'standard':
         return xpub
-    _, depth, fingerprint, child_number, c, cK = bip32.deserialize_xpub(xpub)
-    xpub = bip32.serialize_xpub(xtype, c, cK, depth, fingerprint, child_number)
-    return xpub
+    node = BIP32Node.from_xkey(xpub)
+    return node._replace(xtype=xtype).to_xpub()
 
 def get_billing_xpub():
     if constants.net.TESTNET:
@@ -388,20 +386,26 @@ def get_user_id(storage):
     short_id = hashlib.sha256(long_id).hexdigest()
     return long_id, short_id
 
-def make_xpub(xpub, s):
-    version, _, _, _, c, cK = deserialize_xpub(xpub)
-    cK2, c2 = bip32._CKD_pub(cK, c, s)
-    return serialize_xpub(version, c2, cK2)
+def make_xpub(xpub, s) -> str:
+    rootnode = BIP32Node.from_xkey(xpub)
+    child_pubkey, child_chaincode = bip32._CKD_pub(parent_pubkey=rootnode.eckey.get_public_key_bytes(compressed=True),
+                                                   parent_chaincode=rootnode.chaincode,
+                                                   child_index=s)
+    child_node = BIP32Node(xtype=rootnode.xtype,
+                           eckey=ecc.ECPubkey(child_pubkey),
+                           chaincode=child_chaincode)
+    return child_node.to_xpub()
 
 def make_billing_address(wallet, num, addr_type):
     long_id, short_id = wallet.get_user_id()
     xpub = make_xpub(get_billing_xpub(), long_id)
-    version, _, _, _, c, cK = deserialize_xpub(xpub)
-    cK, c = CKD_pub(cK, c, num)
+    usernode = BIP32Node.from_xkey(xpub)
+    child_node = usernode.subkey_at_public_derivation([num])
+    pubkey = child_node.eckey.get_public_key_bytes(compressed=True)
     if addr_type == 'legacy':
-        return bitcoin.public_key_to_p2pkh(cK)
+        return bitcoin.public_key_to_p2pkh(pubkey)
     elif addr_type == 'segwit':
-        return bitcoin.public_key_to_p2wpkh(cK)
+        return bitcoin.public_key_to_p2wpkh(pubkey)
     else:
         raise ValueError(f'unexpected billing type: {addr_type}')
 
@@ -538,9 +542,9 @@ class TrustedCoinPlugin(BasePlugin):
         assert is_any_2fa_seed_type(t)
         xtype = 'standard' if t == '2fa' else 'p2wsh'
         bip32_seed = Mnemonic.mnemonic_to_seed(seed, passphrase)
-        xprv, xpub = bip32_root(bip32_seed, xtype)
-        xprv, xpub = bip32_private_derivation(xprv, "m/", derivation)
-        return xprv, xpub
+        rootnode = BIP32Node.from_rootseed(bip32_seed, xtype=xtype)
+        child_node = rootnode.subkey_at_private_derivation(derivation)
+        return child_node.to_xprv(), child_node.to_xpub()
 
     @classmethod
     def xkeys_from_seed(self, seed, passphrase):
@@ -721,9 +725,8 @@ class TrustedCoinPlugin(BasePlugin):
         challenge = r.get('challenge')
         message = 'TRUSTEDCOIN CHALLENGE: ' + challenge
         def f(xprv):
-            _, _, _, _, c, k = deserialize_xprv(xprv)
-            pk = bip32_private_key([0, 0], k, c)
-            key = ecc.ECPrivkey(pk)
+            rootnode = BIP32Node.from_xkey(xprv)
+            key = rootnode.subkey_at_private_derivation((0, 0)).eckey
             sig = key.sign_message(message, True)
             return base64.b64encode(sig).decode()
 

electrum/tests/test_bitcoin.py

@@ -9,7 +9,7 @@ from electrum.bitcoin import (public_key_to_p2pkh, address_from_private_key,
                               is_compressed_privkey, EncodeBase58Check,
                               script_num_to_hex, push_script, add_number_to_script, int_to_hex,
                               opcodes)
-from electrum.bip32 import (bip32_root, bip32_public_derivation, bip32_private_derivation,
+from electrum.bip32 import (BIP32Node,
                             xpub_from_xprv, xpub_type, is_xprv, is_bip32_derivation,
                             is_xpub, convert_bip32_path_to_list_of_uint32)
 from electrum.crypto import sha256d, SUPPORTED_PW_HASH_VERSIONS
@@ -405,19 +405,18 @@ class Test_xprv_xpub(SequentialTestCase):
          'xtype': 'p2wpkh'},
     )
 
-    def _do_test_bip32(self, seed, sequence):
-        xprv, xpub = bip32_root(bfh(seed), 'standard')
+    def _do_test_bip32(self, seed: str, sequence):
+        node = BIP32Node.from_rootseed(bfh(seed), xtype='standard')
+        xprv, xpub = node.to_xprv(), node.to_xpub()
         self.assertEqual("m/", sequence[0:2])
-        path = 'm'
         sequence = sequence[2:]
         for n in sequence.split('/'):
-            child_path = path + '/' + n
             if n[-1] != "'":
-                xpub2 = bip32_public_derivation(xpub, path, child_path)
-            xprv, xpub = bip32_private_derivation(xprv, path, child_path)
+                xpub2 = BIP32Node.from_xkey(xpub).subkey_at_public_derivation(n).to_xpub()
+            node = BIP32Node.from_xkey(xprv).subkey_at_private_derivation(n)
+            xprv, xpub = node.to_xprv(), node.to_xpub()
             if n[-1] != "'":
                 self.assertEqual(xpub, xpub2)
-            path = child_path
 
         return xpub, xprv
 
@@ -474,7 +473,7 @@ class Test_xprv_xpub(SequentialTestCase):
     def test_convert_bip32_path_to_list_of_uint32(self):
         self.assertEqual([0, 0x80000001, 0x80000001], convert_bip32_path_to_list_of_uint32("m/0/-1/1'"))
         self.assertEqual([], convert_bip32_path_to_list_of_uint32("m/"))
-        self.assertEqual([2147483692, 2147488889, 221], convert_bip32_path_to_list_of_uint32("m/44'/5241'/221"))
+        self.assertEqual([2147483692, 2147488889, 221], convert_bip32_path_to_list_of_uint32("m/44'/5241h/221"))
 
     def test_xtype_from_derivation(self):
         self.assertEqual('standard', xtype_from_derivation("m/44'"))