what if
# m/0'
c1 = m.subkey_for_path("m/0'")
Yeah, here's my proof of work.
Library:
https://pypi.org/project/bitcoinlib/
Test vectors from: https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki
Python code to repro the error:
from bitcoinlib.keys import HDKey
m = HDKey.from_seed('000102030405060708090a0b0c0d0e0f')
assert m.wif_public() == 'xpub661MyMwAqRbcFtXgS5sYJABqqG9YLmC4Q1Rdap9gSE8NqtwybGhePY2gZ29ESFjqJoCu1Rupje8YtGqsefD265TMg7usUDFdp6W1EGMcet8'
assert m.wif_private() == 'xprv9s21ZrQH143K3QTDL4LXw2F7HEK3wJUD2nW2nRk4stbPy6cq3jPPqjiChkVvvNKmPGJxWUtg6LnF5kejMRNNU3TGtRBeJgk33yuGBxrMPHi'
c1 = m.subkey_for_path("m/0")
assert c1.wif_public() == 'xpub68Gmy5EdvgibQVfPdqkBBCHxA5htiqg55crXYuXoQRKfDBFA1WEjWgP6LHhwBZeNK1VTsfTFUHCdrfp1bgwQ9xv5ski8PX9rL2dZXvgGDnw'
# fails here ^
assert c1.wif_private() == 'xprv9uHRZZhk6KAJC1avXpDAp4MDc3sQKNxDiPvvkX8Br5ngLNv1TxvUxt4cV1rGL5hj6KCesnDYUhd7oWgT11eZG7XnxHrnYeSvkzY7d2bhkJ7'
Discussion
I think I tried it with and without the single ticks and they seemed to be ignored. I believe the index is an integer type in the code, which is why I decided to experiment with the prime marker.
I saw the public_bytes has the prefix on it, making it a 33 byte string instead of 32 bytes. However, changing that didn't fix it. So if that is a problem, it's not the only problem.
I'll make sure my code matches however it is written in BIP32 before I post my code again though, just to reduce confusion.
OK, accroding gto BIP32 the ser(P) function *does* include the prefix byte, so that part of the code appears correct after all.