Set the number of SHA512 rounds based on the speed of the computer.

src/wallet.cpp

@@ -75,6 +75,19 @@ bool CWallet::ChangeWalletPassphrase(const string& strOldWalletPassphrase, const
                 return false;
             if (CCryptoKeyStore::Unlock(vMasterKey))
             {
+                int64 nStartTime = GetTimeMillis();
+                crypter.SetKeyFromPassphrase(strNewWalletPassphrase, pMasterKey.second.vchSalt, pMasterKey.second.nDeriveIterations, pMasterKey.second.nDerivationMethod);
+                pMasterKey.second.nDeriveIterations = pMasterKey.second.nDeriveIterations * (100 / ((double)(GetTimeMillis() - nStartTime)));
+
+                nStartTime = GetTimeMillis();
+                crypter.SetKeyFromPassphrase(strNewWalletPassphrase, pMasterKey.second.vchSalt, pMasterKey.second.nDeriveIterations, pMasterKey.second.nDerivationMethod);
+                pMasterKey.second.nDeriveIterations = (pMasterKey.second.nDeriveIterations + pMasterKey.second.nDeriveIterations * 100 / ((double)(GetTimeMillis() - nStartTime))) / 2;
+
+                if (pMasterKey.second.nDeriveIterations < 25000)
+                    pMasterKey.second.nDeriveIterations = 25000;
+
+                printf("Wallet passphrase changed to an nDeriveIterations of %i\n", pMasterKey.second.nDeriveIterations);
+
                 if (!crypter.SetKeyFromPassphrase(strNewWalletPassphrase, pMasterKey.second.vchSalt, pMasterKey.second.nDeriveIterations, pMasterKey.second.nDerivationMethod))
                     return false;
                 if (!crypter.Encrypt(vMasterKey, pMasterKey.second.vchCryptedKey))
@@ -112,6 +125,19 @@ bool CWallet::EncryptWallet(const string& strWalletPassphrase)
         RAND_bytes(&kMasterKey.vchSalt[0], WALLET_CRYPTO_SALT_SIZE);
 
         CCrypter crypter;
+        int64 nStartTime = GetTimeMillis();
+        crypter.SetKeyFromPassphrase(strWalletPassphrase, kMasterKey.vchSalt, 25000, kMasterKey.nDerivationMethod);
+        kMasterKey.nDeriveIterations = 2500000 / ((double)(GetTimeMillis() - nStartTime));
+
+        nStartTime = GetTimeMillis();
+        crypter.SetKeyFromPassphrase(strWalletPassphrase, kMasterKey.vchSalt, kMasterKey.nDeriveIterations, kMasterKey.nDerivationMethod);
+        kMasterKey.nDeriveIterations = (kMasterKey.nDeriveIterations + kMasterKey.nDeriveIterations * 100 / ((double)(GetTimeMillis() - nStartTime))) / 2;
+
+        if (kMasterKey.nDeriveIterations < 25000)
+            kMasterKey.nDeriveIterations = 25000;
+
+        printf("Encrypting Wallet with an nDeriveIterations of %i\n", kMasterKey.nDeriveIterations);
+
         if (!crypter.SetKeyFromPassphrase(strWalletPassphrase, kMasterKey.vchSalt, kMasterKey.nDeriveIterations, kMasterKey.nDerivationMethod))
             return false;
         if (!crypter.Encrypt(vMasterKey, kMasterKey.vchCryptedKey))