bip85 child seeds via embit.bip85.derive_mnemonic()

requirements.txt

@@ -1,4 +1,4 @@
-embit==0.6.1
+embit==0.7.0
 numpy==1.21.1
 picamera==1.13
 Pillow==8.2.0

src/seedsigner/models/seed.py

@@ -1,7 +1,7 @@
 import unicodedata
 
 from binascii import hexlify
-from embit import bip39, bip32
+from embit import bip39, bip32, bip85
 from embit.networks import NETWORKS
 from typing import List
 
@@ -121,25 +121,8 @@ class Seed:
         root = bip32.HDKey.from_seed(self.seed_bytes, version=NETWORKS[SettingsConstants.map_network_to_embit(network)]["xprv"])
 
         # TODO: Support other bip-39 wordlist languages!
-        # As per the BIP85 spec, 39 is the application number used for bip39 mnemonic,
-        # we use the selected word count and the index to form the full path.
-        path = "m/83696968'/39'/0'/{bip85_num_words}'/{bip85_index}'".format(
-                            bip85_num_words=bip85_num_words,
-                            bip85_index=bip85_index)
 
-        # Derive the child xprv (HDKey) using the path format defined above
-        xprv = root.derive(path)
-
-        # The xprv.secret plus the BIP85 key is hashed together using hmac sha512.
-        entropy = hmac.new(key=b'bip-entropy-from-k', msg=xprv.secret, digestmod=hashlib.sha512).digest()
-
-        # Calculate number of bytes to retain for the entropy
-        # 24 words the width is 32bytes (256bits)
-        # 12 words the width is 16bytes (128bits)
-        width = round(bip85_num_words / 12 * 16)
-
-        # Return the derived BIP85 child mnemonic using the truncated derived entropy
-        return bip39.mnemonic_from_bytes(entropy[:width])
+        return bip85.derive_mnemonic(root, bip85_num_words, bip85_index)
         
 
     ### override operators