do not expose mnemonic_to_seed

lib/bitcoin.py

@@ -706,10 +706,10 @@ def xpub_from_xprv(xprv, testnet=False):
     return EncodeBase58Check(xpub)
 
 
-def bip32_root(seed, testnet=False):
+def bip32_root(mnemonic_seed, testnet=False):
     import hmac
     header_pub, header_priv = _get_headers(testnet)
-    seed = seed.decode('hex')
+    seed = mnemonic_to_seed(mnemonic_seed,'')
     I = hmac.new("Bitcoin seed", seed, hashlib.sha512).digest()
     master_k = I[0:32]
     master_c = I[32:]

lib/wallet.py

@@ -1313,7 +1313,8 @@ class NewWallet(Deterministic_Wallet):
         return xpub
 
     def create_master_keys(self, password):
-        xpriv, xpub = bip32_root(mnemonic_to_seed(self.get_seed(password),'').encode('hex'))
+        seed = self.get_seed(password)
+        xpriv, xpub = bip32_root(seed)
         self.add_master_public_key("m/", xpub)
         self.add_master_private_key("m/", xpriv, password)