@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();
   }
 }
 /**
  * Returns all the key chains found in the given list of keys. Typically there will only be one,
  * but in the case of key rotation it can happen that there are multiple chains found.
  */
 public static List<DeterministicKeyChain> fromProtobuf(
     List<Protos.Key> keys, @Nullable KeyCrypter crypter) throws UnreadableWalletException {
   List<DeterministicKeyChain> chains = newLinkedList();
   DeterministicSeed seed = null;
   DeterministicKeyChain chain = null;
   int lookaheadSize = -1;
   for (Protos.Key key : keys) {
     final Protos.Key.Type t = key.getType();
     if (t == Protos.Key.Type.DETERMINISTIC_MNEMONIC) {
       if (chain != null) {
         checkState(lookaheadSize >= 0);
         chain.setLookaheadSize(lookaheadSize);
         chain.maybeLookAhead();
         chains.add(chain);
         chain = null;
       }
       long timestamp = key.getCreationTimestamp() / 1000;
       String passphrase = DEFAULT_PASSPHRASE_FOR_MNEMONIC; // FIXME allow non-empty passphrase
       if (key.hasSecretBytes()) {
         seed = new DeterministicSeed(key.getSecretBytes().toStringUtf8(), passphrase, timestamp);
       } else if (key.hasEncryptedData()) {
         EncryptedData data =
             new EncryptedData(
                 key.getEncryptedData().getInitialisationVector().toByteArray(),
                 key.getEncryptedData().getEncryptedPrivateKey().toByteArray());
         seed = new DeterministicSeed(data, timestamp);
       } else {
         throw new UnreadableWalletException("Malformed key proto: " + key.toString());
       }
       if (log.isDebugEnabled()) log.debug("Deserializing: DETERMINISTIC_MNEMONIC: {}", seed);
     } else if (t == Protos.Key.Type.DETERMINISTIC_KEY) {
       if (!key.hasDeterministicKey())
         throw new UnreadableWalletException(
             "Deterministic key missing extra data: " + key.toString());
       byte[] chainCode = key.getDeterministicKey().getChainCode().toByteArray();
       // Deserialize the path through the tree.
       LinkedList<ChildNumber> path = newLinkedList();
       for (int i : key.getDeterministicKey().getPathList()) path.add(new ChildNumber(i));
       // Deserialize the public key and path.
       ECPoint pubkey = ECKey.CURVE.getCurve().decodePoint(key.getPublicKey().toByteArray());
       final ImmutableList<ChildNumber> immutablePath = ImmutableList.copyOf(path);
       // Possibly create the chain, if we didn't already do so yet.
       boolean isWatchingAccountKey = false;
       boolean isFollowingKey = false;
       // save previous chain if any if the key is marked as following. Current key and the next
       // ones are to be
       // placed in new following key chain
       if (key.getDeterministicKey().getIsFollowing()) {
         if (chain != null) {
           checkState(lookaheadSize >= 0);
           chain.setLookaheadSize(lookaheadSize);
           chain.maybeLookAhead();
           chains.add(chain);
           chain = null;
           seed = null;
         }
         isFollowingKey = true;
       }
       if (chain == null) {
         if (seed == null) {
           DeterministicKey accountKey =
               new DeterministicKey(immutablePath, chainCode, pubkey, null, null);
           if (!accountKey.getPath().equals(ACCOUNT_ZERO_PATH))
             throw new UnreadableWalletException(
                 "Expecting account key but found key with path: "
                     + HDUtils.formatPath(accountKey.getPath()));
           chain = new DeterministicKeyChain(accountKey, isFollowingKey);
           isWatchingAccountKey = true;
         } else {
           chain = new DeterministicKeyChain(seed, crypter);
           chain.lookaheadSize = LAZY_CALCULATE_LOOKAHEAD;
           // If the seed is encrypted, then the chain is incomplete at this point. However, we
           // will load
           // it up below as we parse in the keys. We just need to check at the end that we've
           // loaded
           // everything afterwards.
         }
       }
       // Find the parent key assuming this is not the root key, and not an account key for a
       // watching chain.
       DeterministicKey parent = null;
       if (!path.isEmpty() && !isWatchingAccountKey) {
         ChildNumber index = path.removeLast();
         parent = chain.hierarchy.get(path, false, false);
         path.add(index);
       }
       DeterministicKey detkey;
       if (key.hasSecretBytes()) {
         // Not encrypted: private key is available.
         final BigInteger priv = new BigInteger(1, key.getSecretBytes().toByteArray());
         detkey = new DeterministicKey(immutablePath, chainCode, pubkey, priv, parent);
       } else {
         if (key.hasEncryptedData()) {
           Protos.EncryptedData proto = key.getEncryptedData();
           EncryptedData data =
               new EncryptedData(
                   proto.getInitialisationVector().toByteArray(),
                   proto.getEncryptedPrivateKey().toByteArray());
           checkNotNull(crypter, "Encountered an encrypted key but no key crypter provided");
           detkey = new DeterministicKey(immutablePath, chainCode, crypter, pubkey, data, parent);
         } else {
           // No secret key bytes and key is not encrypted: either a watching key or private key
           // bytes
           // will be rederived on the fly from the parent.
           detkey = new DeterministicKey(immutablePath, chainCode, pubkey, null, parent);
         }
       }
       if (key.hasCreationTimestamp())
         detkey.setCreationTimeSeconds(key.getCreationTimestamp() / 1000);
       if (log.isDebugEnabled()) log.debug("Deserializing: DETERMINISTIC_KEY: {}", detkey);
       if (!isWatchingAccountKey) {
         // If the non-encrypted case, the non-leaf keys (account, internal, external) have already
         // been
         // rederived and inserted at this point and the two lines below are just a no-op. In the
         // encrypted
         // case though, we can't rederive and we must reinsert, potentially building the heirarchy
         // object
         // if need be.
         if (path.size() == 0) {
           // Master key.
           chain.rootKey = detkey;
           chain.hierarchy = new DeterministicHierarchy(detkey);
         } else if (path.size() == 2) {
           if (detkey.getChildNumber().num() == 0) {
             chain.externalKey = detkey;
             chain.issuedExternalKeys = key.getDeterministicKey().getIssuedSubkeys();
             lookaheadSize = Math.max(lookaheadSize, key.getDeterministicKey().getLookaheadSize());
           } else if (detkey.getChildNumber().num() == 1) {
             chain.internalKey = detkey;
             chain.issuedInternalKeys = key.getDeterministicKey().getIssuedSubkeys();
           }
         }
       }
       chain.hierarchy.putKey(detkey);
       chain.basicKeyChain.importKey(detkey);
     }
   }
   if (chain != null) {
     checkState(lookaheadSize >= 0);
     chain.setLookaheadSize(lookaheadSize);
     chain.maybeLookAhead();
     chains.add(chain);
   }
   return chains;
 }