@Override
 public List<Protos.Key> serializeToProtobuf() {
   lock.lock();
   try {
     // Most of the serialization work is delegated to the basic key chain, which will serialize
     // the bulk of the
     // data (handling encryption along the way), and letting us patch it up with the extra data we
     // care about.
     LinkedList<Protos.Key> entries = newLinkedList();
     if (seed != null) {
       Protos.Key.Builder mnemonicEntry = BasicKeyChain.serializeEncryptableItem(seed);
       mnemonicEntry.setType(Protos.Key.Type.DETERMINISTIC_MNEMONIC);
       entries.add(mnemonicEntry.build());
     }
     Map<ECKey, Protos.Key.Builder> keys = basicKeyChain.serializeToEditableProtobufs();
     for (Map.Entry<ECKey, Protos.Key.Builder> entry : keys.entrySet()) {
       DeterministicKey key = (DeterministicKey) entry.getKey();
       Protos.Key.Builder proto = entry.getValue();
       proto.setType(Protos.Key.Type.DETERMINISTIC_KEY);
       final Protos.DeterministicKey.Builder detKey = proto.getDeterministicKeyBuilder();
       detKey.setChainCode(ByteString.copyFrom(key.getChainCode()));
       for (ChildNumber num : key.getPath()) detKey.addPath(num.i());
       if (key.equals(externalKey)) {
         detKey.setIssuedSubkeys(issuedExternalKeys);
         detKey.setLookaheadSize(lookaheadSize);
       } else if (key.equals(internalKey)) {
         detKey.setIssuedSubkeys(issuedInternalKeys);
         detKey.setLookaheadSize(lookaheadSize);
       }
       // Flag the very first key of following keychain.
       if (entries.isEmpty() && isFollowing()) {
         detKey.setIsFollowing(true);
       }
       if (key.getParent() != null) {
         // HD keys inherit the timestamp of their parent if they have one, so no need to serialize
         // it.
         proto.clearCreationTimestamp();
       }
       entries.add(proto.build());
     }
     return entries;
   } finally {
     lock.unlock();
   }
 }
  /**
   * Converts the given wallet to the object representation of the protocol buffers. This can be
   * modified, or additional data fields set, before serialization takes place.
   */
  public Protos.Wallet walletToProto(Wallet wallet) {
    Protos.Wallet.Builder walletBuilder = Protos.Wallet.newBuilder();
    walletBuilder.setNetworkIdentifier(wallet.getNetworkParameters().getId());
    if (wallet.getDescription() != null) {
      walletBuilder.setDescription(wallet.getDescription());
    }

    for (WalletTransaction wtx : wallet.getWalletTransactions()) {
      Protos.Transaction txProto = makeTxProto(wtx);
      walletBuilder.addTransaction(txProto);
    }

    for (ECKey key : wallet.getKeys()) {
      Protos.Key.Builder keyBuilder =
          Protos.Key.newBuilder()
              .setCreationTimestamp(key.getCreationTimeSeconds() * 1000)
              // .setLabel() TODO
              .setType(Protos.Key.Type.ORIGINAL);
      if (key.getPrivKeyBytes() != null)
        keyBuilder.setPrivateKey(ByteString.copyFrom(key.getPrivKeyBytes()));

      EncryptedPrivateKey encryptedPrivateKey = key.getEncryptedPrivateKey();
      if (encryptedPrivateKey != null) {
        // Key is encrypted.
        Protos.EncryptedPrivateKey.Builder encryptedKeyBuilder =
            Protos.EncryptedPrivateKey.newBuilder()
                .setEncryptedPrivateKey(
                    ByteString.copyFrom(encryptedPrivateKey.getEncryptedBytes()))
                .setInitialisationVector(
                    ByteString.copyFrom(encryptedPrivateKey.getInitialisationVector()));

        if (key.getKeyCrypter() == null) {
          throw new IllegalStateException(
              "The encrypted key " + key.toString() + " has no KeyCrypter.");
        } else {
          // If it is a Scrypt + AES encrypted key, set the persisted key type.
          if (key.getKeyCrypter().getUnderstoodEncryptionType()
              == Protos.Wallet.EncryptionType.ENCRYPTED_SCRYPT_AES) {
            keyBuilder.setType(Protos.Key.Type.ENCRYPTED_SCRYPT_AES);
          } else {
            throw new IllegalArgumentException(
                "The key "
                    + key.toString()
                    + " is encrypted with a KeyCrypter of type "
                    + key.getKeyCrypter().getUnderstoodEncryptionType()
                    + ". This WalletProtobufSerialiser does not understand that type of encryption.");
          }
        }
        keyBuilder.setEncryptedPrivateKey(encryptedKeyBuilder);
      }

      // We serialize the public key even if the private key is present for speed reasons: we don't
      // want to do
      // lots of slow EC math to load the wallet, we prefer to store the redundant data instead. It
      // matters more
      // on mobile platforms.
      keyBuilder.setPublicKey(ByteString.copyFrom(key.getPubKey()));
      walletBuilder.addKey(keyBuilder);
    }

    // Populate the lastSeenBlockHash field.
    Sha256Hash lastSeenBlockHash = wallet.getLastBlockSeenHash();
    if (lastSeenBlockHash != null) {
      walletBuilder.setLastSeenBlockHash(hashToByteString(lastSeenBlockHash));
      walletBuilder.setLastSeenBlockHeight(wallet.getLastBlockSeenHeight());
    }

    // Populate the scrypt parameters.
    KeyCrypter keyCrypter = wallet.getKeyCrypter();
    if (keyCrypter == null) {
      // The wallet is unencrypted.
      walletBuilder.setEncryptionType(EncryptionType.UNENCRYPTED);
    } else {
      // The wallet is encrypted.
      walletBuilder.setEncryptionType(keyCrypter.getUnderstoodEncryptionType());
      if (keyCrypter instanceof KeyCrypterScrypt) {
        KeyCrypterScrypt keyCrypterScrypt = (KeyCrypterScrypt) keyCrypter;
        walletBuilder.setEncryptionParameters(keyCrypterScrypt.getScryptParameters());
      } else {
        // Some other form of encryption has been specified that we do not know how to persist.
        throw new RuntimeException(
            "The wallet has encryption of type '"
                + keyCrypter.getUnderstoodEncryptionType()
                + "' but this WalletProtobufSerializer does not know how to persist this.");
      }
    }

    populateExtensions(wallet, walletBuilder);

    // Populate the wallet version.
    walletBuilder.setVersion(wallet.getVersion());

    return walletBuilder.build();
  }