improve sietch generation

lib/src/lightwallet.rs

@@ -170,6 +170,24 @@ impl LightWallet {
         (extsk, extfvk, address)
     }
 
+    fn get_sietch_from_bip39seed(config: &LightClientConfig, bip39_seed: &[u8], pos: u32) ->
+    PaymentAddress<Bls12> {
+    assert_eq!(bip39_seed.len(), 64);
+
+    let extsk: ExtendedSpendingKey = ExtendedSpendingKey::from_path(
+    &ExtendedSpendingKey::master(bip39_seed),
+    &[
+        ChildIndex::Hardened(32),
+        ChildIndex::Hardened(config.get_coin_type()),
+        ChildIndex::Hardened(pos)
+    ],
+    );
+    let extfvk  = ExtendedFullViewingKey::from(&extsk);
+    let address = extfvk.default_address().unwrap().1;
+
+    (address)
+}
+
     pub fn is_shielded_address(addr: &String, config: &LightClientConfig) -> bool {
         match address::RecipientAddress::from_str(addr,
                 config.hrp_sapling_address(), 
@@ -469,10 +487,12 @@ impl LightWallet {
 
         zaddr
     }
+
+ 
    // Add a new Sietch Addr. This will derive a new zdust address from manipluated seed
     pub fn add_zaddrdust(&self) -> String {
    
-
+        let mut seed_bytes = [0u8; 32];
         let pos = self.extsks.read().unwrap().len() as u32;
       
          // Use random generator to create a new Sietch seed every time when call.
@@ -485,16 +505,18 @@ impl LightWallet {
          let dust: &str = &my_string; 
 
 
+         let mut system_rng = OsRng;
+         system_rng.fill(&mut seed_bytes);
+          
+        let bip39_seed = bip39::Seed::new(&Mnemonic::from_entropy(&seed_bytes, Language::English).unwrap(), dust);
 
-        let bip39_seed = bip39::Seed::new(&Mnemonic::from_entropy(&self.seed, Language::English).unwrap(), dust);
+        let address =
+        LightWallet::get_sietch_from_bip39seed(&self.config, &bip39_seed.as_bytes(), pos);
 
-        let (_extsk, _extfvk, address) =
-        LightWallet::get_zaddr_from_bip39seed(&self.config, &bip39_seed.as_bytes(), pos);
-
-        let zaddr = encode_payment_address(self.config.hrp_sapling_address(), &address);
+        let zdust = encode_payment_address(self.config.hrp_sapling_address(), &address);
     
 
-        zaddr
+        zdust
     }
 
     /// Add a new t address to the wallet. This will derive a new address from the seed