feat: Add BIP32 master extended private key to test vectors.

CHANGELOG.rst

@@ -11,7 +11,7 @@ The format is based on `Keep a Changelog`_, and this project adheres to
 `Unreleased`_
 -------------
 
-No changes yet
+- Added BIP32 master extended private key to test vectors.
 
 .. _Unreleased: https://github.com/trezor/python-shamir-mnemonic/compare/v0.2.2...HEAD
 

README.rst

@@ -96,9 +96,12 @@ command:
 Test vectors
 ------------
 
-The test vectors in vectors.json are given as a list of triples. The first member of the
-triple is a description of the test vector, the second member is a list of mnemonics and
-the third member is the master secret which results from combining the mnemonics. The
-master secret is encoded as a string containing two hexadecimal digits for each byte. If
+The test vectors in vectors.json are given as a list of quadruples:
+* The first member is a description of the test vector.
+* The second member is a list of mnemonics.
+* The third member is the master secret which results from combining the mnemonics.
+* The fourth member is the BIP32 master extended private key derived from the master secret.
+
+The master secret is encoded as a string containing two hexadecimal digits for each byte. If
 the string is empty, then attempting to combine the given set of mnemonics should result
 in error. The passphrase "TREZOR" is used for all valid sets of mnemonics.

generate_vectors.py

@@ -3,6 +3,7 @@
 import random
 
 import attr
+from bip32utils import BIP32Key
 
 from shamir_mnemonic import constants, rs1024, shamir, wordlist
 from shamir_mnemonic.share import Share
@@ -14,7 +15,8 @@ def random_bytes(n):
 
 def output(description, mnemonics, secret):
     output.i += 1
-    output.data.append((f"{output.i}. {description}", mnemonics, secret.hex()))
+    xprv = BIP32Key.fromEntropy(secret).ExtendedKey() if secret else ""
+    output.data.append((f"{output.i}. {description}", mnemonics, secret.hex(), xprv))
 
 
 def encode_mnemonic(*args):

test_shamir.py

@@ -4,6 +4,7 @@
 from random import shuffle
 
 import pytest
+from bip32utils import BIP32Key
 
 import shamir_mnemonic as shamir
 from shamir_mnemonic import MnemonicError
@@ -134,11 +135,15 @@ def test_invalid_sharing():
 def test_vectors():
     with open("vectors.json", "r") as f:
         vectors = json.load(f)
-    for description, mnemonics, secret in vectors:
-        if secret:
-            assert bytes.fromhex(secret) == shamir.combine_mnemonics(
+    for description, mnemonics, secret_hex, xprv in vectors:
+        if secret_hex:
+            secret = bytes.fromhex(secret_hex)
+            assert secret == shamir.combine_mnemonics(
                 mnemonics, b"TREZOR"
             ), 'Incorrect secret for test vector "{}".'.format(description)
+            assert (
+                BIP32Key.fromEntropy(secret).ExtendedKey() == xprv
+            ), 'Incorrect xprv for test vector "{}".'.format(description)
         else:
             with pytest.raises(MnemonicError):
                 shamir.combine_mnemonics(mnemonics)