diff --git a/core/src/main/java/ch/dissem/bitmessage/entity/valueobject/extended/Message.java b/core/src/main/java/ch/dissem/bitmessage/entity/valueobject/extended/Message.java
index 33e7b81..98c84bd 100644
--- a/core/src/main/java/ch/dissem/bitmessage/entity/valueobject/extended/Message.java
+++ b/core/src/main/java/ch/dissem/bitmessage/entity/valueobject/extended/Message.java
@@ -84,7 +84,7 @@ public class Message implements ExtendedEncoding.ExtendedType {
         }
         packer.packMapHeader(size);
         packer.packString("");
-        packer.packString("message");
+        packer.packString(TYPE);
         packer.packString("subject");
         packer.packString(subject);
         packer.packString("body");
diff --git a/core/src/main/java/ch/dissem/bitmessage/entity/valueobject/extended/Vote.java b/core/src/main/java/ch/dissem/bitmessage/entity/valueobject/extended/Vote.java
index 75cea67..d0beddd 100644
--- a/core/src/main/java/ch/dissem/bitmessage/entity/valueobject/extended/Vote.java
+++ b/core/src/main/java/ch/dissem/bitmessage/entity/valueobject/extended/Vote.java
@@ -58,7 +58,7 @@ public class Vote implements ExtendedEncoding.ExtendedType {
     public void pack(MessagePacker packer) throws IOException {
         packer.packMapHeader(3);
         packer.packString("");
-        packer.packString("vote");
+        packer.packString(TYPE);
         packer.packString("msgId");
         packer.packBinaryHeader(msgId.getHash().length);
         packer.writePayload(msgId.getHash());
diff --git a/core/src/main/java/ch/dissem/bitmessage/factory/ExtendedEncodingFactory.java b/core/src/main/java/ch/dissem/bitmessage/factory/ExtendedEncodingFactory.java
index 0dc419c..29595da 100644
--- a/core/src/main/java/ch/dissem/bitmessage/factory/ExtendedEncodingFactory.java
+++ b/core/src/main/java/ch/dissem/bitmessage/factory/ExtendedEncodingFactory.java
@@ -22,6 +22,7 @@ import java.util.zip.InflaterInputStream;
 public class ExtendedEncodingFactory {
     private static final Logger LOG = LoggerFactory.getLogger(ExtendedEncodingFactory.class);
     private static final ExtendedEncodingFactory INSTANCE = new ExtendedEncodingFactory();
+    private static final String KEY_MESSAGE_TYPE = "";
     private Map<String, ExtendedEncoding.Unpacker<?>> factories = new HashMap<>();
 
     private ExtendedEncodingFactory() {
@@ -39,7 +40,7 @@ public class ExtendedEncodingFactory {
             MessageUnpacker unpacker = MessagePack.newDefaultUnpacker(unzipper);
             int mapSize = unpacker.unpackMapHeader();
             String key = unpacker.unpackString();
-            if (!"".equals(key)) {
+            if (!KEY_MESSAGE_TYPE.equals(key)) {
                 LOG.error("Unexpected content: " + key);
                 return null;
             }
diff --git a/core/src/main/java/ch/dissem/bitmessage/utils/Bytes.java b/core/src/main/java/ch/dissem/bitmessage/utils/Bytes.java
index c0bf554..986c288 100644
--- a/core/src/main/java/ch/dissem/bitmessage/utils/Bytes.java
+++ b/core/src/main/java/ch/dissem/bitmessage/utils/Bytes.java
@@ -16,11 +16,6 @@
 
 package ch.dissem.bitmessage.utils;
 
-import java.io.File;
-import java.io.FileInputStream;
-import java.io.IOException;
-import java.nio.file.Files;
-
 /**
  * A helper class for working with byte arrays interpreted as unsigned big endian integers.
  * This is one part due to the fact that Java doesn't support unsigned numbers, and another