[Wallet] split the keypool in an internal and external part

8 files changed, 180 insertions, 76 deletions

diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 84e7eb60d7..7ab01040f0 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -221,7 +221,7 @@ UniValue getrawchangeaddress(const JSONRPCRequest& request)
 
     CReserveKey reservekey(pwallet);
     CPubKey vchPubKey;
-    if (!reservekey.GetReservedKey(vchPubKey))
+    if (!reservekey.GetReservedKey(vchPubKey, true))
         throw JSONRPCError(RPC_WALLET_KEYPOOL_RAN_OUT, "Error: Keypool ran out, please call keypoolrefill first");
 
     reservekey.KeepKey();
@@ -2418,16 +2418,17 @@ UniValue getwalletinfo(const JSONRPCRequest& request)
             "Returns an object containing various wallet state info.\n"
             "\nResult:\n"
             "{\n"
-            "  \"walletversion\": xxxxx,       (numeric) the wallet version\n"
-            "  \"balance\": xxxxxxx,           (numeric) the total confirmed balance of the wallet in " + CURRENCY_UNIT + "\n"
-            "  \"unconfirmed_balance\": xxx,   (numeric) the total unconfirmed balance of the wallet in " + CURRENCY_UNIT + "\n"
-            "  \"immature_balance\": xxxxxx,   (numeric) the total immature balance of the wallet in " + CURRENCY_UNIT + "\n"
-            "  \"txcount\": xxxxxxx,           (numeric) the total number of transactions in the wallet\n"
-            "  \"keypoololdest\": xxxxxx,      (numeric) the timestamp (seconds since Unix epoch) of the oldest pre-generated key in the key pool\n"
-            "  \"keypoolsize\": xxxx,          (numeric) how many new keys are pre-generated\n"
-            "  \"unlocked_until\": ttt,        (numeric) the timestamp in seconds since epoch (midnight Jan 1 1970 GMT) that the wallet is unlocked for transfers, or 0 if the wallet is locked\n"
-            "  \"paytxfee\": x.xxxx,           (numeric) the transaction fee configuration, set in " + CURRENCY_UNIT + "/kB\n"
-            "  \"hdmasterkeyid\": \"<hash160>\" (string) the Hash160 of the HD master pubkey\n"
+            "  \"walletversion\": xxxxx,          (numeric) the wallet version\n"
+            "  \"balance\": xxxxxxx,              (numeric) the total confirmed balance of the wallet in " + CURRENCY_UNIT + "\n"
+            "  \"unconfirmed_balance\": xxx,      (numeric) the total unconfirmed balance of the wallet in " + CURRENCY_UNIT + "\n"
+            "  \"immature_balance\": xxxxxx,      (numeric) the total immature balance of the wallet in " + CURRENCY_UNIT + "\n"
+            "  \"txcount\": xxxxxxx,              (numeric) the total number of transactions in the wallet\n"
+            "  \"keypoololdest\": xxxxxx,         (numeric) the timestamp (seconds since Unix epoch) of the oldest pre-generated key in the key pool\n"
+            "  \"keypoolsize\": xxxx,             (numeric) how many new keys are pre-generated\n"
+            "  \"keypoolsize_hd_internal\": xxxx, (numeric) how many new keys are pre-generated for internal use (change outputs, 10% of the -keypoolsize target, only appears if HD is enabled)\n"
+            "  \"unlocked_until\": ttt,           (numeric) the timestamp in seconds since epoch (midnight Jan 1 1970 GMT) that the wallet is unlocked for transfers, or 0 if the wallet is locked\n"
+            "  \"paytxfee\": x.xxxx,              (numeric) the transaction fee configuration, set in " + CURRENCY_UNIT + "/kB\n"
+            "  \"hdmasterkeyid\": \"<hash160>\"     (string) the Hash160 of the HD master pubkey\n"
             "}\n"
             "\nExamples:\n"
             + HelpExampleCli("getwalletinfo", "")
@@ -2437,18 +2438,22 @@ UniValue getwalletinfo(const JSONRPCRequest& request)
     LOCK2(cs_main, pwallet->cs_wallet);
 
     UniValue obj(UniValue::VOBJ);
+    size_t kpExternalSize = (int)pwallet->KeypoolCountExternalKeys();
     obj.push_back(Pair("walletversion", pwallet->GetVersion()));
     obj.push_back(Pair("balance",       ValueFromAmount(pwallet->GetBalance())));
     obj.push_back(Pair("unconfirmed_balance", ValueFromAmount(pwallet->GetUnconfirmedBalance())));
     obj.push_back(Pair("immature_balance",    ValueFromAmount(pwallet->GetImmatureBalance())));
     obj.push_back(Pair("txcount",       (int)pwallet->mapWallet.size()));
     obj.push_back(Pair("keypoololdest", pwallet->GetOldestKeyPoolTime()));
-    obj.push_back(Pair("keypoolsize",   (int)pwallet->GetKeyPoolSize()));
+    obj.push_back(Pair("keypoolsize", (int64_t)kpExternalSize));
+    CKeyID masterKeyID = pwallet->GetHDChain().masterKeyID;
+    if (!masterKeyID.IsNull()) {
+        obj.push_back(Pair("keypoolsize_hd_internal",   (int64_t)(pwallet->GetKeyPoolSize() - kpExternalSize)));
+    }
     if (pwallet->IsCrypted()) {
         obj.push_back(Pair("unlocked_until", pwallet->nRelockTime));
     }
     obj.push_back(Pair("paytxfee",      ValueFromAmount(payTxFee.GetFeePerK())));
-    CKeyID masterKeyID = pwallet->GetHDChain().masterKeyID;
     if (!masterKeyID.IsNull())
          obj.push_back(Pair("hdmasterkeyid", masterKeyID.GetHex()));
     return obj;
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 445e40b043..71c97a4e87 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -85,7 +85,7 @@ const CWalletTx* CWallet::GetWalletTx(const uint256& hash) const
     return &(it->second);
 }
 
-CPubKey CWallet::GenerateNewKey()
+CPubKey CWallet::GenerateNewKey(bool internal)
 {
     AssertLockHeld(cs_wallet); // mapKeyMetadata
     bool fCompressed = CanSupportFeature(FEATURE_COMPRPUBKEY); // default to compressed public keys if we want 0.6.0 wallets
@@ -98,7 +98,7 @@ CPubKey CWallet::GenerateNewKey()
 
     // use HD key derivation if HD was enabled during wallet creation
     if (IsHDEnabled()) {
-        DeriveNewChildKey(metadata, secret);
+        DeriveNewChildKey(metadata, secret, (CanSupportFeature(FEATURE_HD_SPLIT) ? internal : false));
     } else {
         secret.MakeNewKey(fCompressed);
     }
@@ -118,13 +118,13 @@ CPubKey CWallet::GenerateNewKey()
     return pubkey;
 }
 
-void CWallet::DeriveNewChildKey(CKeyMetadata& metadata, CKey& secret)
+void CWallet::DeriveNewChildKey(CKeyMetadata& metadata, CKey& secret, bool internal)
 {
     // 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 chainChildKey;         //key at m/0'/0' (external) or m/0'/1' (internal)
     CExtKey childKey;              //key at m/0'/0'/<n>'
 
     // try to get the master key
@@ -137,19 +137,22 @@ void CWallet::DeriveNewChildKey(CKeyMetadata& metadata, CKey& secret)
     // 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 m/0'/0' (external chain) OR m/0'/1' (internal chain)
+    accountKey.Derive(chainChildKey, BIP32_HARDENED_KEY_LIMIT+(internal ? 1 : 0));
 
     // 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) + "'";
+        chainChildKey.Derive(childKey, (internal ? hdChain.nInternalChainCounter : hdChain.nExternalChainCounter) | BIP32_HARDENED_KEY_LIMIT);
+        metadata.hdKeypath = "m/0'/" + std::string(internal ? "1'/"+ std::to_string(hdChain.nInternalChainCounter) : "0'/" + std::to_string(hdChain.nExternalChainCounter)) + "'";
         metadata.hdMasterKeyID = hdChain.masterKeyID;
         // increment childkey index
-        hdChain.nExternalChainCounter++;
+        if (internal)
+            hdChain.nInternalChainCounter++;
+        else
+            hdChain.nExternalChainCounter++;
     } while (HaveKey(childKey.key.GetPubKey().GetID()));
     secret = childKey.key;
 
@@ -799,7 +802,7 @@ bool CWallet::GetAccountPubkey(CPubKey &pubKey, std::string strAccount, bool bFo
 
     // Generate a new key
     if (bForceNew) {
-        if (!GetKeyFromPool(account.vchPubKey))
+        if (!GetKeyFromPool(account.vchPubKey, false))
             return false;
 
         SetAddressBook(account.vchPubKey.GetID(), strAccount, "receive");
@@ -1304,8 +1307,8 @@ bool CWallet::SetHDMasterKey(const CPubKey& pubkey)
 {
     LOCK(cs_wallet);
 
-    // ensure this wallet.dat can only be opened by clients supporting HD
-    SetMinVersion(FEATURE_HD);
+    // ensure this wallet.dat can only be opened by clients supporting HD with chain split
+    SetMinVersion(FEATURE_HD_SPLIT);
 
     // store the keyid (hash160) together with
     // the child index counter in the database
@@ -2445,7 +2448,7 @@ bool CWallet::CreateTransaction(const std::vector<CRecipient>& vecSend, CWalletT
                         // Reserve a new key pair from key pool
                         CPubKey vchPubKey;
                         bool ret;
-                        ret = reservekey.GetReservedKey(vchPubKey);
+                        ret = reservekey.GetReservedKey(vchPubKey, true);
                         if (!ret)
                         {
                             strFailReason = _("Keypool ran out, please call keypoolrefill first");
@@ -2899,18 +2902,31 @@ bool CWallet::NewKeyPool()
         if (IsLocked())
             return false;
 
-        int64_t nKeys = std::max(GetArg("-keypool", DEFAULT_KEYPOOL_SIZE), (int64_t)0);
-        for (int i = 0; i < nKeys; i++)
-        {
-            int64_t nIndex = i+1;
-            walletdb.WritePool(nIndex, CKeyPool(GenerateNewKey()));
-            setKeyPool.insert(nIndex);
-        }
-        LogPrintf("CWallet::NewKeyPool wrote %d new keys\n", nKeys);
+        TopUpKeyPool();
+        LogPrintf("CWallet::NewKeyPool rewrote keypool\n");
     }
     return true;
 }
 
+size_t CWallet::KeypoolCountExternalKeys()
+{
+    AssertLockHeld(cs_wallet); // setKeyPool
+
+    CWalletDB walletdb(strWalletFile);
+
+    // count amount of external keys
+    size_t amountE = 0;
+    for(const int64_t& id : setKeyPool)
+    {
+        CKeyPool tmpKeypool;
+        if (!walletdb.ReadPool(id, tmpKeypool))
+            throw std::runtime_error(std::string(__func__) + ": read failed");
+        amountE += !tmpKeypool.fInternal;
+    }
+
+    return amountE;
+}
+
 bool CWallet::TopUpKeyPool(unsigned int kpSize)
 {
     {
@@ -2919,8 +2935,6 @@ bool CWallet::TopUpKeyPool(unsigned int kpSize)
         if (IsLocked())
             return false;
 
-        CWalletDB walletdb(strWalletFile);
-
         // Top up key pool
         unsigned int nTargetSize;
         if (kpSize > 0)
@@ -2928,21 +2942,39 @@ bool CWallet::TopUpKeyPool(unsigned int kpSize)
         else
             nTargetSize = std::max(GetArg("-keypool", DEFAULT_KEYPOOL_SIZE), (int64_t) 0);
 
-        while (setKeyPool.size() < (nTargetSize + 1))
+        // count amount of available keys (internal, external)
+        // make sure the keypool of external keys fits the user selected target (-keypool)
+        // generate +20% internal keys (minimum 2 keys)
+        int64_t amountExternal = KeypoolCountExternalKeys();
+        int64_t amountInternal = setKeyPool.size() - amountExternal;
+        int64_t targetInternal = max((int64_t)ceil(nTargetSize * 0.2), (int64_t) 2);
+        int64_t missingExternal = max( (int64_t)(nTargetSize - amountExternal), (int64_t) 0);
+        int64_t missingInternal = max(targetInternal - amountInternal, (int64_t) 0);
+
+        if (!IsHDEnabled() || !CanSupportFeature(FEATURE_HD_SPLIT))
+        {
+            // don't create extra internal keys
+            missingInternal = 0;
+        }
+        bool internal = false;
+        CWalletDB walletdb(strWalletFile);
+        for (int64_t i = missingInternal + missingExternal; i--;)
         {
             int64_t nEnd = 1;
+            if (i < missingInternal)
+                internal = true;
             if (!setKeyPool.empty())
                 nEnd = *(--setKeyPool.end()) + 1;
-            if (!walletdb.WritePool(nEnd, CKeyPool(GenerateNewKey())))
+            if (!walletdb.WritePool(nEnd, CKeyPool(GenerateNewKey(internal), internal)))
                 throw std::runtime_error(std::string(__func__) + ": writing generated key failed");
             setKeyPool.insert(nEnd);
-            LogPrintf("keypool added key %d, size=%u\n", nEnd, setKeyPool.size());
+            LogPrintf("keypool added key %d, size=%u, internal=%d\n", nEnd, setKeyPool.size(), internal);
         }
     }
     return true;
 }
 
-void CWallet::ReserveKeyFromKeyPool(int64_t& nIndex, CKeyPool& keypool)
+void CWallet::ReserveKeyFromKeyPool(int64_t& nIndex, CKeyPool& keypool, bool internal)
 {
     nIndex = -1;
     keypool.vchPubKey = CPubKey();
@@ -2958,14 +2990,24 @@ void CWallet::ReserveKeyFromKeyPool(int64_t& nIndex, CKeyPool& keypool)
 
         CWalletDB walletdb(strWalletFile);
 
-        nIndex = *(setKeyPool.begin());
-        setKeyPool.erase(setKeyPool.begin());
-        if (!walletdb.ReadPool(nIndex, keypool))
-            throw std::runtime_error(std::string(__func__) + ": read failed");
-        if (!HaveKey(keypool.vchPubKey.GetID()))
-            throw std::runtime_error(std::string(__func__) + ": unknown key in key pool");
-        assert(keypool.vchPubKey.IsValid());
-        LogPrintf("keypool reserve %d\n", nIndex);
+        // try to find a key that matches the internal/external filter
+        for(const int64_t& id : setKeyPool)
+        {
+            CKeyPool tmpKeypool;
+            if (!walletdb.ReadPool(id, tmpKeypool))
+                throw std::runtime_error(std::string(__func__) + ": read failed");
+            if (!HaveKey(tmpKeypool.vchPubKey.GetID()))
+                throw std::runtime_error(std::string(__func__) + ": unknown key in key pool");
+            if (!IsHDEnabled() || tmpKeypool.fInternal == internal)
+            {
+                nIndex = id;
+                keypool = tmpKeypool;
+                setKeyPool.erase(id);
+                assert(keypool.vchPubKey.IsValid());
+                LogPrintf("keypool reserve %d\n", nIndex);
+                return;
+            }
+        }
     }
 }
 
@@ -2990,17 +3032,17 @@ void CWallet::ReturnKey(int64_t nIndex)
     LogPrintf("keypool return %d\n", nIndex);
 }
 
-bool CWallet::GetKeyFromPool(CPubKey& result)
+bool CWallet::GetKeyFromPool(CPubKey& result, bool internal)
 {
     int64_t nIndex = 0;
     CKeyPool keypool;
     {
         LOCK(cs_wallet);
-        ReserveKeyFromKeyPool(nIndex, keypool);
+        ReserveKeyFromKeyPool(nIndex, keypool, internal);
         if (nIndex == -1)
         {
             if (IsLocked()) return false;
-            result = GenerateNewKey();
+            result = GenerateNewKey(internal);
             return true;
         }
         KeepKey(nIndex);
@@ -3205,12 +3247,12 @@ std::set<CTxDestination> CWallet::GetAccountAddresses(const std::string& strAcco
     return result;
 }
 
-bool CReserveKey::GetReservedKey(CPubKey& pubkey)
+bool CReserveKey::GetReservedKey(CPubKey& pubkey, bool internal)
 {
     if (nIndex == -1)
     {
         CKeyPool keypool;
-        pwallet->ReserveKeyFromKeyPool(nIndex, keypool);
+        pwallet->ReserveKeyFromKeyPool(nIndex, keypool, internal);
         if (nIndex != -1)
             vchPubKey = keypool.vchPubKey;
         else {
@@ -3629,7 +3671,7 @@ CWallet* CWallet::CreateWalletFromFile(const std::string walletFile)
                 throw std::runtime_error(std::string(__func__) + ": Storing master key failed");
         }
         CPubKey newDefaultKey;
-        if (walletInstance->GetKeyFromPool(newDefaultKey)) {
+        if (walletInstance->GetKeyFromPool(newDefaultKey, false)) {
             walletInstance->SetDefaultKey(newDefaultKey);
             if (!walletInstance->SetAddressBook(walletInstance->vchDefaultKey.GetID(), "", "receive")) {
                 InitError(_("Cannot write default address") += "\n");
@@ -3890,10 +3932,11 @@ CKeyPool::CKeyPool()
     nTime = GetTime();
 }
 
-CKeyPool::CKeyPool(const CPubKey& vchPubKeyIn)
+CKeyPool::CKeyPool(const CPubKey& vchPubKeyIn, bool internalIn)
 {
     nTime = GetTime();
     vchPubKey = vchPubKeyIn;
+    fInternal = internalIn;
 }
 
 CWalletKey::CWalletKey(int64_t nExpires)
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index ae4321eef8..bf6c5a2a87 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -86,6 +86,10 @@ enum WalletFeature
     FEATURE_COMPRPUBKEY = 60000, // compressed public keys
 
     FEATURE_HD = 130000, // Hierarchical key derivation after BIP32 (HD Wallet)
+
+    //TODO: FEATURE_HD_SPLIT needs to be bumped to 140000 once we branch of 0.14 //
+    FEATURE_HD_SPLIT = 139900, // Wallet with HD chain split (change outputs will use m/0'/1'/k)
+
     FEATURE_LATEST = FEATURE_COMPRPUBKEY // HD is optional, use FEATURE_COMPRPUBKEY as latest version
 };
 
@@ -96,9 +100,10 @@ class CKeyPool
 public:
     int64_t nTime;
     CPubKey vchPubKey;
+    bool fInternal; // for change outputs
 
     CKeyPool();
-    CKeyPool(const CPubKey& vchPubKeyIn);
+    CKeyPool(const CPubKey& vchPubKeyIn, bool internalIn);
 
     ADD_SERIALIZE_METHODS;
 
@@ -109,6 +114,13 @@ public:
             READWRITE(nVersion);
         READWRITE(nTime);
         READWRITE(vchPubKey);
+        if (nVersion >= FEATURE_HD_SPLIT)
+            READWRITE(fInternal);
+        else
+        {
+            if (ser_action.ForRead())
+                fInternal = false;
+        }
     }
 };
 
@@ -774,8 +786,8 @@ public:
      * keystore implementation
      * Generate a new key
      */
-    CPubKey GenerateNewKey();
-    void DeriveNewChildKey(CKeyMetadata& metadata, CKey& secret);
+    CPubKey GenerateNewKey(bool internal = false);
+    void DeriveNewChildKey(CKeyMetadata& metadata, CKey& secret, bool internal = false);
     //! Adds a key to the store, and saves it to disk.
     bool AddKeyPubKey(const CKey& key, const CPubKey &pubkey) override;
     //! Adds a key to the store, without saving it to disk (used by LoadWallet)
@@ -883,11 +895,12 @@ public:
     static CAmount GetRequiredFee(unsigned int nTxBytes);
 
     bool NewKeyPool();
+    size_t KeypoolCountExternalKeys();
     bool TopUpKeyPool(unsigned int kpSize = 0);
-    void ReserveKeyFromKeyPool(int64_t& nIndex, CKeyPool& keypool);
+    void ReserveKeyFromKeyPool(int64_t& nIndex, CKeyPool& keypool, bool internal);
     void KeepKey(int64_t nIndex);
     void ReturnKey(int64_t nIndex);
-    bool GetKeyFromPool(CPubKey &key);
+    bool GetKeyFromPool(CPubKey &key, bool internal = false);
     int64_t GetOldestKeyPoolTime();
     void GetAllReserveKeys(std::set<CKeyID>& setAddress) const;
 
@@ -1063,7 +1076,7 @@ public:
     }
 
     void ReturnKey();
-    bool GetReservedKey(CPubKey &pubkey);
+    bool GetReservedKey(CPubKey &pubkey, bool internal = false);
     void KeepKey();
     void KeepScript() { KeepKey(); }
 };
diff --git a/src/wallet/walletdb.h b/src/wallet/walletdb.h
index 4d7dfb727e..016296f259 100644
--- a/src/wallet/walletdb.h
+++ b/src/wallet/walletdb.h
@@ -46,9 +46,12 @@ class CHDChain
 {
 public:
     uint32_t nExternalChainCounter;
+    uint32_t nInternalChainCounter;
     CKeyID masterKeyID; //!< master key hash160
 
-    static const int CURRENT_VERSION = 1;
+    static const int VERSION_HD_BASE        = 1;
+    static const int VERSION_HD_CHAIN_SPLIT = 2;
+    static const int CURRENT_VERSION        = VERSION_HD_CHAIN_SPLIT;
     int nVersion;
 
     CHDChain() { SetNull(); }
@@ -58,6 +61,8 @@ public:
     {
         READWRITE(this->nVersion);
         READWRITE(nExternalChainCounter);
+        if (this->nVersion >= VERSION_HD_CHAIN_SPLIT)
+            READWRITE(nInternalChainCounter);
         READWRITE(masterKeyID);
     }
 
@@ -65,6 +70,7 @@ public:
     {
         nVersion = CHDChain::CURRENT_VERSION;
         nExternalChainCounter = 0;
+        nInternalChainCounter = 0;
         masterKeyID.SetNull();
     }
 };
diff --git a/test/functional/fundrawtransaction.py b/test/functional/fundrawtransaction.py
index 1dc00f2ba1..a28ff94655 100755
--- a/test/functional/fundrawtransaction.py
+++ b/test/functional/fundrawtransaction.py
@@ -467,6 +467,8 @@ class RawTransactionsTest(BitcoinTestFramework):
 
         # drain the keypool
         self.nodes[1].getnewaddress()
+        self.nodes[1].getrawchangeaddress()
+        self.nodes[1].getrawchangeaddress()
         inputs = []
         outputs = {self.nodes[0].getnewaddress():1.1}
         rawTx = self.nodes[1].createrawtransaction(inputs, outputs)
@@ -476,6 +478,7 @@ class RawTransactionsTest(BitcoinTestFramework):
 
         #refill the keypool
         self.nodes[1].walletpassphrase("test", 100)
+        self.nodes[1].keypoolrefill(8) #need to refill the keypool to get an internal change address
         self.nodes[1].walletlock()
 
         assert_raises_jsonrpc(-13, "walletpassphrase", self.nodes[1].sendtoaddress, self.nodes[0].getnewaddress(), 1.2)
diff --git a/test/functional/keypool.py b/test/functional/keypool.py
index cee58563f0..26585fc4ad 100755
--- a/test/functional/keypool.py
+++ b/test/functional/keypool.py
@@ -27,28 +27,38 @@ class KeyPoolTest(BitcoinTestFramework):
         wallet_info = nodes[0].getwalletinfo()
         assert(addr_before_encrypting_data['hdmasterkeyid'] != wallet_info['hdmasterkeyid'])
         assert(addr_data['hdmasterkeyid'] == wallet_info['hdmasterkeyid'])
-        
         assert_raises_jsonrpc(-12, "Error: Keypool ran out, please call keypoolrefill first", nodes[0].getnewaddress)
 
-        # put three new keys in the keypool
+        # put six (plus 2) new keys in the keypool (100% external-, +20% internal-keys, 2 in min)
         nodes[0].walletpassphrase('test', 12000)
-        nodes[0].keypoolrefill(3)
+        nodes[0].keypoolrefill(6)
         nodes[0].walletlock()
+        wi = nodes[0].getwalletinfo()
+        assert_equal(wi['keypoolsize_hd_internal'], 2)
+        assert_equal(wi['keypoolsize'], 6)
 
-        # drain the keys
+        # drain the internal keys
+        nodes[0].getrawchangeaddress()
+        nodes[0].getrawchangeaddress()
         addr = set()
-        addr.add(nodes[0].getrawchangeaddress())
-        addr.add(nodes[0].getrawchangeaddress())
-        addr.add(nodes[0].getrawchangeaddress())
-        addr.add(nodes[0].getrawchangeaddress())
-        # assert that four unique addresses were returned
-        assert(len(addr) == 4)
         # the next one should fail
         assert_raises_jsonrpc(-12, "Keypool ran out", nodes[0].getrawchangeaddress)
 
+        # drain the external keys
+        addr.add(nodes[0].getnewaddress())
+        addr.add(nodes[0].getnewaddress())
+        addr.add(nodes[0].getnewaddress())
+        addr.add(nodes[0].getnewaddress())
+        addr.add(nodes[0].getnewaddress())
+        addr.add(nodes[0].getnewaddress())
+        assert(len(addr) == 6)
+        # the next one should fail
+        assert_raises_jsonrpc(-12, "Error: Keypool ran out, please call keypoolrefill first", nodes[0].getnewaddress)
+
         # refill keypool with three new addresses
         nodes[0].walletpassphrase('test', 1)
         nodes[0].keypoolrefill(3)
+
         # test walletpassphrase timeout
         time.sleep(1.1)
         assert_equal(nodes[0].getwalletinfo()["unlocked_until"], 0)
@@ -57,9 +67,14 @@ class KeyPoolTest(BitcoinTestFramework):
         nodes[0].generate(1)
         nodes[0].generate(1)
         nodes[0].generate(1)
-        nodes[0].generate(1)
         assert_raises_jsonrpc(-12, "Keypool ran out", nodes[0].generate, 1)
 
+        nodes[0].walletpassphrase('test', 100)
+        nodes[0].keypoolrefill(100)
+        wi = nodes[0].getwalletinfo()
+        assert_equal(wi['keypoolsize_hd_internal'], 20)
+        assert_equal(wi['keypoolsize'], 100)
+
     def __init__(self):
         super().__init__()
         self.setup_clean_chain = False
diff --git a/test/functional/wallet-dump.py b/test/functional/wallet-dump.py
index b819b72b75..7eaa8090b5 100755
--- a/test/functional/wallet-dump.py
+++ b/test/functional/wallet-dump.py
@@ -88,7 +88,7 @@ class WalletDumpTest(BitcoinTestFramework):
             read_dump(tmpdir + "/node0/wallet.unencrypted.dump", addrs, None)
         assert_equal(found_addr, test_addr_count)  # all keys must be in the dump
         assert_equal(found_addr_chg, 50)  # 50 blocks where mined
-        assert_equal(found_addr_rsv, 90 + 1)  # keypool size (TODO: fix off-by-one)
+        assert_equal(found_addr_rsv, 90*1.2) # 90 keys plus 20% internal keys
 
         #encrypt wallet, restart, unlock and dump
         self.nodes[0].encryptwallet('test')
@@ -102,8 +102,8 @@ class WalletDumpTest(BitcoinTestFramework):
         found_addr, found_addr_chg, found_addr_rsv, hd_master_addr_enc = \
             read_dump(tmpdir + "/node0/wallet.encrypted.dump", addrs, hd_master_addr_unenc)
         assert_equal(found_addr, test_addr_count)
-        assert_equal(found_addr_chg, 90 + 1 + 50)  # old reserve keys are marked as change now
-        assert_equal(found_addr_rsv, 90 + 1)  # keypool size (TODO: fix off-by-one)
+        assert_equal(found_addr_chg, 90*1.2 + 50)  # old reserve keys are marked as change now
+        assert_equal(found_addr_rsv, 90*1.2) 
 
 if __name__ == '__main__':
     WalletDumpTest().main ()
diff --git a/test/functional/wallet-hd.py b/test/functional/wallet-hd.py
index c40662dc3d..b17f788433 100755
--- a/test/functional/wallet-hd.py
+++ b/test/functional/wallet-hd.py
@@ -42,6 +42,11 @@ class WalletHDTest(BitcoinTestFramework):
         masterkeyid = self.nodes[1].getwalletinfo()['hdmasterkeyid']
         assert_equal(len(masterkeyid), 40)
 
+        #create an internal key
+        change_addr = self.nodes[1].getrawchangeaddress()
+        change_addrV= self.nodes[1].validateaddress(change_addr);
+        assert_equal(change_addrV["hdkeypath"], "m/0'/1'/0'") #first internal child key
+
         # Import a non-HD private key in the HD wallet
         non_hd_add = self.nodes[0].getnewaddress()
         self.nodes[1].importprivkey(self.nodes[0].dumpprivkey(non_hd_add))
@@ -65,6 +70,11 @@ class WalletHDTest(BitcoinTestFramework):
         self.nodes[0].sendtoaddress(non_hd_add, 1)
         self.nodes[0].generate(1)
 
+        #create an internal key (again)
+        change_addr = self.nodes[1].getrawchangeaddress()
+        change_addrV= self.nodes[1].validateaddress(change_addr);
+        assert_equal(change_addrV["hdkeypath"], "m/0'/1'/1'") #second internal child key
+
         self.sync_all()
         assert_equal(self.nodes[1].getbalance(), num_hd_adds + 1)
 
@@ -90,6 +100,15 @@ class WalletHDTest(BitcoinTestFramework):
         #connect_nodes_bi(self.nodes, 0, 1)
         assert_equal(self.nodes[1].getbalance(), num_hd_adds + 1)
 
+        #send a tx and make sure its using the internal chain for the changeoutput
+        txid = self.nodes[1].sendtoaddress(self.nodes[0].getnewaddress(), 1)
+        outs = self.nodes[1].decoderawtransaction(self.nodes[1].gettransaction(txid)['hex'])['vout'];
+        keypath = ""
+        for out in outs:
+            if out['value'] != 1:
+                keypath = self.nodes[1].validateaddress(out['scriptPubKey']['addresses'][0])['hdkeypath']
+        
+        assert(keypath[0:7] == "m/0'/1'")
 
 if __name__ == '__main__':
     WalletHDTest().main ()