BIP85 - Removed dependency for using bip85 reference library

- Added bip85.py hmac_512 function embit didn't have it
      - Changed default setting to disable the BIP85 GEN function in seed menu, need to enable it in the settings

requirements.txt

@@ -8,4 +8,3 @@ RPi.GPIO==0.7.0
 six==1.16.0
 spidev==3.5
 urtypes @ git+https://github.com/jreesun/urtypes.git@e0d0db277ec2339650343eaf7b220fffb9233241
-bip85==0.2.0

src/seedsigner/gui/screens/seed_screens.py

@@ -1744,7 +1744,7 @@ class BIP85SeedWordsScreen(WarningEdgesMixin, ButtonListScreen):
         #num_words = 12
         # Can only render 4 words per screen
         words_per_page = 4
-        mnemonic = self.seed.get_bip85_child(self.seed.bip85_index, self.seed.bip85_num_words).split()
+        mnemonic = self.seed.get_bip85_child_mnemonic(self.seed.bip85_index, self.seed.bip85_num_words).split()
         # Slice the mnemonic to our current 4-word section
         self.mnemonic = mnemonic[self.page_index*words_per_page:(self.page_index + 1)*words_per_page]
         self.body_x = 0

src/seedsigner/helpers/bip85.py

@@ -0,0 +1,7 @@
+import hashlib
+import hmac
+
+def hmac_sha512(message_k):
+    return hmac.new(key=b'bip-entropy-from-k', msg=message_k, digestmod=hashlib.sha512).digest()
+
+

src/seedsigner/models/seed.py

@@ -5,9 +5,8 @@ from binascii import hexlify
 from embit import bip39, bip32
 from embit.networks import NETWORKS
 from typing import List
-from bip85 import BIP85
-from bip85 import app
 
+from seedsigner.helpers.bip85 import hmac_sha512
 from seedsigner.models.settings import SettingsConstants
 
 class InvalidSeedException(Exception):
@@ -121,20 +120,26 @@ class Seed:
         xprv = root.derive(wallet_path)
         xpub = xprv.to_public()
         return xpub
-    
-    def get_bip85_child(self, bip85_index: int, bip85_num_words: int, wallet_path: str = '/', network: str = SettingsConstants.MAINNET):
-        bip85_seed: str = ""
-        bip85 = BIP85()
-       
-        passphrase = self._passphrase
-        language = 'english' 
 
+    # Derives a BIP85 mnemonic (seed word) from the master seed words using embit functions
+    def get_bip85_child_mnemonic(self, bip85_index: int, bip85_num_words: int, wallet_path: str = '/',
+                                 network: str = SettingsConstants.MAINNET):
+        passphrase = self._passphrase
+        # language = 'english'
+        # lang_code = 0
+        # Need to add language later for path, defaults to English (0)
+        path = "m/83696968'/39'/0'/{bip85_num_words}'/{bip85_index}'".format(bip85_num_words=bip85_num_words,
+                                                                             bip85_index=bip85_index)
         seed = bip39.mnemonic_to_seed(self.mnemonic_str, password=self._passphrase, wordlist=self.wordlist)
         xprv = embit.bip32.HDKey.from_seed(seed)
-        bip85_seed = app.bip39(xprv, language, bip85_num_words, bip85_index)
-        return bip85_seed
 
-    ### override operators    
+        # Derive k
+        xprv = xprv.derive(path)
+        entropy = hmac_sha512(xprv.secret)
+        width = round(bip85_num_words / 12 * 16)
+        return bip39.mnemonic_from_bytes(entropy[:width])
+
+    ### override operators
     def __eq__(self, other):
         if isinstance(other, Seed):
             return self.seed_bytes == other.seed_bytes

src/seedsigner/models/settings_definition.py

@@ -397,7 +397,7 @@ class SettingsDefinition:
                       attr_name=SettingsConstants.SETTING__GEN_BIP85,
                       display_name="Generate BIP85",
                       visibility=SettingsConstants.VISIBILITY__ADVANCED,
-                      default_value=SettingsConstants.OPTION__ENABLED),
+                      default_value=SettingsConstants.OPTION__DISABLED),
 
         SettingsEntry(category=SettingsConstants.CATEGORY__FEATURES,
                       attr_name=SettingsConstants.SETTING__SIG_TYPES,