Do not break backward compatibility during wallet encryption

src/wallet/wallet.cpp

@@ -639,7 +639,9 @@ bool CWallet::EncryptWallet(const SecureString& strWalletPassphrase)
         if (IsHDEnabled()) {
             CKey key;
             CPubKey masterPubKey = GenerateNewHDMasterKey();
-            if (!SetHDMasterKey(masterPubKey))
+            // preserve the old chains version to not break backward compatibility
+            CHDChain oldChain = GetHDChain();
+            if (!SetHDMasterKey(masterPubKey, &oldChain))
                 return false;
         }
 
@@ -1306,13 +1308,17 @@ CPubKey CWallet::GenerateNewHDMasterKey()
     return pubkey;
 }
 
-bool CWallet::SetHDMasterKey(const CPubKey& pubkey)
+bool CWallet::SetHDMasterKey(const CPubKey& pubkey, CHDChain *possibleOldChain)
 {
     LOCK(cs_wallet);
     // store the keyid (hash160) together with
     // the child index counter in the database
     // as a hdchain object
     CHDChain newHdChain;
+    if (possibleOldChain) {
+        // preserve the old chains version
+        newHdChain.nVersion = possibleOldChain->nVersion;
+    }
     newHdChain.masterKeyID = pubkey.GetID();
     SetHDChain(newHdChain, false);
 

src/wallet/wallet.h

@@ -1055,8 +1055,10 @@ public:
     /* Generates a new HD master key (will not be activated) */
     CPubKey GenerateNewHDMasterKey();
     
-    /* Set the current HD master key (will reset the chain child index counters) */
-    bool SetHDMasterKey(const CPubKey& key);
+    /* Set the current HD master key (will reset the chain child index counters)
+       If possibleOldChain is provided, the parameters from the old chain (version)
+       will be preserved. */
+    bool SetHDMasterKey(const CPubKey& key, CHDChain *possibleOldChain = nullptr);
 };
 
 /** A key allocated from the key pool. */