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add support for non-hardened derivation for hot storage (#521)

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* add support for non-hardened derivation for hot storage

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This commit is contained in:
Stepan Snigirev 2020-10-16 18:37:02 +02:00 • committed by GitHub
parent 180e877a68
commit a2cf195561
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1 changed files with 16 additions and 6 deletions
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22
src/cryptoadvance/specter/devices/bitcoin_core.py
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@ -245,8 +245,8 @@ def derive_xpubs_from_xprv(xprv, paths: list, rpc):
# we need parent for fingerprint
parent = xprv
for idx in derivation[:-1]:
parent = get_child(parent, idx)
child = get_child(parent, derivation[-1])
parent = get_child(parent, idx, rpc)
child = get_child(parent, derivation[-1], rpc)
derived_xprvs.append((parent, child))
xpubs = []
for parent, child in derived_xprvs:
@ -272,12 +272,10 @@ def swap_fingerprint(xpub, fingerprint):
N = 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141
def get_child(xprv, index):
def get_child(xprv, index, rpc=None):
"""Derives a child from xprv but without fingerprint information"""
if index > 0xFFFFFFFF or index < 0:
raise ValueError("Index should be between 0 and 2^32")
if index < 0x80000000:
raise ValueError("Can't do non-hardened")
stream = BytesIO(decode_base58(xprv))
version = stream.read(4)
@ -287,8 +285,20 @@ def get_child(xprv, index):
chain_code = stream.read(32)
stream.read(1)
secret = stream.read(32)
key = b"\x00" + secret
data = b"\x00" + secret + index.to_bytes(4, "big")
if index < 0x80000000:
if rpc is None:
raise ValueError("Can't do non-hardened without rpc")
# non hardened - we need pubkey
else:
# convert to public
res = rpc.getdescriptorinfo(f"wpkh({xprv})")
xpub = res["descriptor"].split("(")[1].split(")")[0]
# decode pubkey
key = decode_base58(xpub)[-33:]
data = key + index.to_bytes(4, "big")
raw = hmac.new(chain_code, data, digestmod="sha512").digest()
tweak = raw[:32]
chain_code = raw[32:]