Move key derivation logic from GenerateNewKey to DeriveNewChildKey

src/wallet/wallet.cpp

@@ -100,43 +100,7 @@ CPubKey CWallet::GenerateNewKey()
 
     // use HD key derivation if HD was enabled during wallet creation
     if (IsHDEnabled()) {
-        // for now we use a fixed keypath scheme of m/0'/0'/k
-        CKey key;                      //master key seed (256bit)
-        CExtKey masterKey;             //hd master key
-        CExtKey accountKey;            //key at m/0'
-        CExtKey externalChainChildKey; //key at m/0'/0'
-        CExtKey childKey;              //key at m/0'/0'/<n>'
-
-        // try to get the master key
-        if (!GetKey(hdChain.masterKeyID, key))
-            throw std::runtime_error(std::string(__func__) + ": Master key not found");
-
-        masterKey.SetMaster(key.begin(), key.size());
-
-        // derive m/0'
-        // use hardened derivation (child keys >= 0x80000000 are hardened after bip32)
-        masterKey.Derive(accountKey, BIP32_HARDENED_KEY_LIMIT);
-
-        // derive m/0'/0'
-        accountKey.Derive(externalChainChildKey, BIP32_HARDENED_KEY_LIMIT);
-
-        // derive child key at next index, skip keys already known to the wallet
-        do
-        {
-            // always derive hardened keys
-            // childIndex | BIP32_HARDENED_KEY_LIMIT = derive childIndex in hardened child-index-range
-            // example: 1 | BIP32_HARDENED_KEY_LIMIT == 0x80000001 == 2147483649
-            externalChainChildKey.Derive(childKey, hdChain.nExternalChainCounter | BIP32_HARDENED_KEY_LIMIT);
-            metadata.hdKeypath     = "m/0'/0'/"+std::to_string(hdChain.nExternalChainCounter)+"'";
-            metadata.hdMasterKeyID = hdChain.masterKeyID;
-            // increment childkey index
-            hdChain.nExternalChainCounter++;
-        } while(HaveKey(childKey.key.GetPubKey().GetID()));
-        secret = childKey.key;
-
-        // update the chain model in the database
-        if (!CWalletDB(strWalletFile).WriteHDChain(hdChain))
-            throw std::runtime_error(std::string(__func__) + ": Writing HD chain model failed");
+        DeriveNewChildKey(metadata, secret);
     } else {
         secret.MakeNewKey(fCompressed);
     }
@@ -157,6 +121,46 @@ CPubKey CWallet::GenerateNewKey()
     return pubkey;
 }
 
+void CWallet::DeriveNewChildKey(CKeyMetadata& metadata, CKey& secret)
+{
+    // for now we use a fixed keypath scheme of m/0'/0'/k
+    CKey key;                      //master key seed (256bit)
+    CExtKey masterKey;             //hd master key
+    CExtKey accountKey;            //key at m/0'
+    CExtKey externalChainChildKey; //key at m/0'/0'
+    CExtKey childKey;              //key at m/0'/0'/<n>'
+
+    // try to get the master key
+    if (!GetKey(hdChain.masterKeyID, key))
+        throw std::runtime_error(std::string(__func__) + ": Master key not found");
+
+    masterKey.SetMaster(key.begin(), key.size());
+
+    // derive m/0'
+    // use hardened derivation (child keys >= 0x80000000 are hardened after bip32)
+    masterKey.Derive(accountKey, BIP32_HARDENED_KEY_LIMIT);
+
+    // derive m/0'/0'
+    accountKey.Derive(externalChainChildKey, BIP32_HARDENED_KEY_LIMIT);
+
+    // derive child key at next index, skip keys already known to the wallet
+    do {
+        // always derive hardened keys
+        // childIndex | BIP32_HARDENED_KEY_LIMIT = derive childIndex in hardened child-index-range
+        // example: 1 | BIP32_HARDENED_KEY_LIMIT == 0x80000001 == 2147483649
+        externalChainChildKey.Derive(childKey, hdChain.nExternalChainCounter | BIP32_HARDENED_KEY_LIMIT);
+        metadata.hdKeypath = "m/0'/0'/" + std::to_string(hdChain.nExternalChainCounter) + "'";
+        metadata.hdMasterKeyID = hdChain.masterKeyID;
+        // increment childkey index
+        hdChain.nExternalChainCounter++;
+    } while (HaveKey(childKey.key.GetPubKey().GetID()));
+    secret = childKey.key;
+
+    // update the chain model in the database
+    if (!CWalletDB(strWalletFile).WriteHDChain(hdChain))
+        throw std::runtime_error(std::string(__func__) + ": Writing HD chain model failed");
+}
+
 bool CWallet::AddKeyPubKey(const CKey& secret, const CPubKey &pubkey)
 {
     AssertLockHeld(cs_wallet); // mapKeyMetadata

src/wallet/wallet.h

@@ -698,6 +698,7 @@ public:
      * Generate a new key
      */
     CPubKey GenerateNewKey();
+    void DeriveNewChildKey(CKeyMetadata& metadata, CKey& secret);
     //! Adds a key to the store, and saves it to disk.
     bool AddKeyPubKey(const CKey& key, const CPubKey &pubkey);
     //! Adds a key to the store, without saving it to disk (used by LoadWallet)