Merge branch 'release/1.0.0'

.travis.yml

@@ -1,2 +1,3 @@
 language: java
-
+jdk:
+  - oraclejdk8

CONTRIBUTING.md

@@ -0,0 +1,24 @@
+# Contributing
+
+We love pull requests from everyone. Please be nice and forgive us
+if we can't process your request right away.
+
+Fork, then clone the repo:
+
+    git clone git@github.com:your-username/Jabit.git
+
+Make sure the tests pass:
+
+    ./gradlew test
+
+Make your change. Add tests for your change. Make the tests pass:
+
+    ./gradlew test
+
+Push to your fork and [submit a pull request][pr].
+
+[pr]: https://github.com/Dissem/Jabit/compare/
+
+Unfortunately we can't always answer right away, so we ask you to have
+some patience. Then we may suggest some changes or improvements or
+alternatives.

README.md

@@ -29,18 +29,21 @@ Setup
 
 Add Jabit as Gradle dependency:
 ```Gradle
-compile 'ch.dissem.jabit:jabit-domain:0.2.0'
+compile 'ch.dissem.jabit:jabit-core:0.2.0'
 ```
 Unless you want to implement your own, also add the following:
 ```Gradle
 compile 'ch.dissem.jabit:jabit-networking:0.2.0'
 compile 'ch.dissem.jabit:jabit-repositories:0.2.0'
+compile 'ch.dissem.jabit:jabit-cryptography-bc:0.2.0'
 ```
 And if you want to import from or export to the Wallet Import Format (used by PyBitmessage) you might also want to add:
 ```Gradle
 compile 'ch.dissem.jabit:jabit-wif:0.2.0'
 ```
 
+For Android clients use `jabit-cryptography-sc` instead of `jabit-cryptography-bc`.
+
 Usage
 -----
 
@@ -53,6 +56,7 @@ BitmessageContext ctx = new BitmessageContext.Builder()
         .messageRepo(new JdbcMessageRepository(jdbcConfig))
         .nodeRegistry(new MemoryNodeRegistry())
         .networkHandler(new NetworkNode())
+        .cryptography(new BouncyCryptography())
         .build();
 ```
 This creates a simple context using a H2 database that will be created in the user's home directory. Next you'll need to

build.gradle

@@ -5,7 +5,7 @@ subprojects {
 
     sourceCompatibility = 1.7
     group = 'ch.dissem.jabit'
-    version = '0.2.0'
+    version = '1.0.0'
 
     ext.isReleaseVersion = !version.endsWith("SNAPSHOT")
 
@@ -13,6 +13,12 @@ subprojects {
         mavenCentral()
     }
 
+    test {
+        testLogging {
+            exceptionFormat = 'full'
+        }
+    }
+
     task javadocJar(type: Jar) {
         classifier = 'javadoc'
         from javadoc
@@ -37,11 +43,6 @@ subprojects {
             mavenDeployer {
                 beforeDeployment { MavenDeployment deployment -> signing.signPom(deployment) }
 
-                if (!hasProperty('ossrhUsername')) {
-                    ext.ossrhUsername = 'dummy'
-                    ext.ossrhPassword = 'dummy'
-                }
-
                 repository(url: "https://oss.sonatype.org/service/local/staging/deploy/maven2/") {
                     authentication(userName: ossrhUsername, password: ossrhPassword)
                 }

core/build.gradle

@@ -0,0 +1,31 @@
+uploadArchives {
+    repositories {
+        mavenDeployer {
+            pom.project {
+                name 'Jabit Core'
+                artifactId = 'jabit-core'
+                description 'A Java implementation of the Bitmessage protocol. This is the core part. You\'ll either need the networking and repositories modules, too, or implement your own.'
+            }
+        }
+    }
+}
+
+configurations {
+    testArtifacts.extendsFrom testRuntime
+}
+
+task testJar(type: Jar) {
+    classifier = 'test'
+    from sourceSets.test.output
+}
+
+artifacts {
+    testArtifacts testJar
+}
+
+dependencies {
+    compile 'org.slf4j:slf4j-api:1.7.12'
+    testCompile 'junit:junit:4.11'
+    testCompile 'org.mockito:mockito-core:1.10.19'
+    testCompile project(':cryptography-bc')
+}

core/src/main/java/ch/dissem/bitmessage/BitmessageContext.java

@@ -0,0 +1,515 @@
+/*
+ * Copyright 2015 Christian Basler
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package ch.dissem.bitmessage;
+
+import ch.dissem.bitmessage.entity.*;
+import ch.dissem.bitmessage.entity.payload.*;
+import ch.dissem.bitmessage.entity.payload.Pubkey.Feature;
+import ch.dissem.bitmessage.entity.valueobject.InventoryVector;
+import ch.dissem.bitmessage.entity.valueobject.Label;
+import ch.dissem.bitmessage.entity.valueobject.PrivateKey;
+import ch.dissem.bitmessage.exception.DecryptionFailedException;
+import ch.dissem.bitmessage.factory.Factory;
+import ch.dissem.bitmessage.ports.*;
+import ch.dissem.bitmessage.utils.Property;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.net.InetAddress;
+import java.util.Arrays;
+import java.util.Timer;
+import java.util.TimerTask;
+import java.util.concurrent.*;
+
+import static ch.dissem.bitmessage.entity.Plaintext.Status.*;
+import static ch.dissem.bitmessage.entity.Plaintext.Type.BROADCAST;
+import static ch.dissem.bitmessage.entity.Plaintext.Type.MSG;
+import static ch.dissem.bitmessage.utils.UnixTime.DAY;
+import static ch.dissem.bitmessage.utils.UnixTime.HOUR;
+import static ch.dissem.bitmessage.utils.UnixTime.MINUTE;
+
+/**
+ * <p>Use this class if you want to create a Bitmessage client.</p>
+ * You'll need the Builder to create a BitmessageContext, and set the following properties:
+ * <ul>
+ * <li>addressRepo</li>
+ * <li>inventory</li>
+ * <li>nodeRegistry</li>
+ * <li>networkHandler</li>
+ * <li>messageRepo</li>
+ * <li>streams</li>
+ * </ul>
+ * <p>The default implementations in the different module builds can be used.</p>
+ * <p>The port defaults to 8444 (the default Bitmessage port)</p>
+ */
+public class BitmessageContext {
+    public static final int CURRENT_VERSION = 3;
+    private final static Logger LOG = LoggerFactory.getLogger(BitmessageContext.class);
+
+    private final ExecutorService pool;
+
+    private final InternalContext ctx;
+
+    private final Listener listener;
+    private final NetworkHandler.MessageListener networkListener;
+
+    private final boolean sendPubkeyOnIdentityCreation;
+
+    private BitmessageContext(Builder builder) {
+        ctx = new InternalContext(builder);
+        listener = builder.listener;
+        networkListener = new DefaultMessageListener(ctx, listener);
+
+        // As this thread is used for parts that do POW, which itself uses parallel threads, only
+        // one should be executed at any time.
+        pool = Executors.newFixedThreadPool(1);
+
+        sendPubkeyOnIdentityCreation = builder.sendPubkeyOnIdentityCreation;
+
+        new Timer().schedule(new TimerTask() {
+            @Override
+            public void run() {
+                ctx.getProofOfWorkService().doMissingProofOfWork();
+            }
+        }, 30_000); // After 30 seconds
+    }
+
+    public AddressRepository addresses() {
+        return ctx.getAddressRepository();
+    }
+
+    public MessageRepository messages() {
+        return ctx.getMessageRepository();
+    }
+
+    public BitmessageAddress createIdentity(boolean shorter, Feature... features) {
+        final BitmessageAddress identity = new BitmessageAddress(new PrivateKey(
+                shorter,
+                ctx.getStreams()[0],
+                ctx.getNetworkNonceTrialsPerByte(),
+                ctx.getNetworkExtraBytes(),
+                features
+        ));
+        ctx.getAddressRepository().save(identity);
+        if (sendPubkeyOnIdentityCreation) {
+            pool.submit(new Runnable() {
+                @Override
+                public void run() {
+                    ctx.sendPubkey(identity, identity.getStream());
+                }
+            });
+        }
+        return identity;
+    }
+
+    public void addDistributedMailingList(String address, String alias) {
+        // TODO
+        throw new RuntimeException("not implemented");
+    }
+
+    public void broadcast(final BitmessageAddress from, final String subject, final String message) {
+        pool.submit(new Runnable() {
+            @Override
+            public void run() {
+                Plaintext msg = new Plaintext.Builder(BROADCAST)
+                        .from(from)
+                        .message(subject, message)
+                        .build();
+
+                LOG.info("Sending message.");
+                msg.setStatus(DOING_PROOF_OF_WORK);
+                ctx.getMessageRepository().save(msg);
+                ctx.send(
+                        from,
+                        from,
+                        Factory.getBroadcast(from, msg),
+                        +2 * DAY
+                );
+                msg.setStatus(SENT);
+                msg.addLabels(ctx.getMessageRepository().getLabels(Label.Type.BROADCAST, Label.Type.SENT));
+                ctx.getMessageRepository().save(msg);
+            }
+        });
+    }
+
+    public void send(final BitmessageAddress from, final BitmessageAddress to, final String subject, final String message) {
+        if (from.getPrivateKey() == null) {
+            throw new IllegalArgumentException("'From' must be an identity, i.e. have a private key.");
+        }
+        pool.submit(new Runnable() {
+            @Override
+            public void run() {
+                Plaintext msg = new Plaintext.Builder(MSG)
+                        .from(from)
+                        .to(to)
+                        .message(subject, message)
+                        .labels(messages().getLabels(Label.Type.SENT))
+                        .build();
+                if (to.getPubkey() == null) {
+                    tryToFindMatchingPubkey(to);
+                }
+                if (to.getPubkey() == null) {
+                    LOG.info("Public key is missing from recipient. Requesting.");
+                    requestPubkey(from, to);
+                    msg.setStatus(PUBKEY_REQUESTED);
+                    ctx.getMessageRepository().save(msg);
+                } else {
+                    LOG.info("Sending message.");
+                    msg.setStatus(DOING_PROOF_OF_WORK);
+                    ctx.getMessageRepository().save(msg);
+                    ctx.send(
+                            from,
+                            to,
+                            new Msg(msg),
+                            +2 * DAY
+                    );
+                    msg.setStatus(SENT);
+                    msg.addLabels(ctx.getMessageRepository().getLabels(Label.Type.SENT));
+                    ctx.getMessageRepository().save(msg);
+                }
+            }
+        });
+    }
+
+    public void send(final Plaintext msg) {
+        if (msg.getFrom() == null || msg.getFrom().getPrivateKey() == null) {
+            throw new IllegalArgumentException("'From' must be an identity, i.e. have a private key.");
+        }
+        pool.submit(new Runnable() {
+            @Override
+            public void run() {
+                BitmessageAddress to = msg.getTo();
+                if (to.getPubkey() == null) {
+                    tryToFindMatchingPubkey(to);
+                }
+                if (to.getPubkey() == null) {
+                    LOG.info("Public key is missing from recipient. Requesting.");
+                    requestPubkey(msg.getFrom(), to);
+                    msg.setStatus(PUBKEY_REQUESTED);
+                    ctx.getMessageRepository().save(msg);
+                } else {
+                    LOG.info("Sending message.");
+                    msg.setStatus(DOING_PROOF_OF_WORK);
+                    ctx.getMessageRepository().save(msg);
+                    ctx.send(
+                            msg.getFrom(),
+                            to,
+                            new Msg(msg),
+                            +2 * DAY
+                    );
+                    msg.setStatus(SENT);
+                    msg.addLabels(ctx.getMessageRepository().getLabels(Label.Type.SENT));
+                    ctx.getMessageRepository().save(msg);
+                }
+            }
+        });
+    }
+
+    private void requestPubkey(BitmessageAddress requestingIdentity, BitmessageAddress address) {
+        ctx.send(
+                requestingIdentity,
+                address,
+                new GetPubkey(address),
+                +28 * DAY
+        );
+    }
+
+    public void startup() {
+        ctx.getNetworkHandler().start(networkListener);
+    }
+
+    public void shutdown() {
+        ctx.getNetworkHandler().stop();
+    }
+
+    /**
+     * @param host             a trusted node that must be reliable (it's used for every synchronization)
+     * @param port             of the trusted host, default is 8444
+     * @param timeoutInSeconds synchronization should end no later than about 5 seconds after the timeout elapsed, even
+     *                         if not all objects were fetched
+     * @param wait             waits for the synchronization thread to finish
+     */
+    public void synchronize(InetAddress host, int port, long timeoutInSeconds, boolean wait) {
+        Future<?> future = ctx.getNetworkHandler().synchronize(host, port, networkListener, timeoutInSeconds);
+        if (wait) {
+            try {
+                future.get();
+            } catch (InterruptedException e) {
+                LOG.info("Thread was interrupted. Trying to shut down synchronization and returning.");
+                future.cancel(true);
+            } catch (CancellationException | ExecutionException e) {
+                LOG.debug(e.getMessage(), e);
+            }
+        }
+    }
+
+    /**
+     * Send a custom message to a specific node (that should implement handling for this message type) and returns
+     * the response, which in turn is expected to be a {@link CustomMessage}.
+     *
+     * @param server  the node's address
+     * @param port    the node's port
+     * @param request the request
+     * @return the response
+     */
+    public CustomMessage send(InetAddress server, int port, CustomMessage request) {
+        return ctx.getNetworkHandler().send(server, port, request);
+    }
+
+    public void cleanup() {
+        ctx.getInventory().cleanup();
+    }
+
+    public boolean isRunning() {
+        return ctx.getNetworkHandler().isRunning();
+    }
+
+    public void addContact(BitmessageAddress contact) {
+        ctx.getAddressRepository().save(contact);
+        tryToFindMatchingPubkey(contact);
+        if (contact.getPubkey() == null) {
+            ctx.requestPubkey(contact);
+        }
+    }
+
+    private void tryToFindMatchingPubkey(BitmessageAddress address) {
+        for (ObjectMessage object : ctx.getInventory().getObjects(address.getStream(), address.getVersion(), ObjectType.PUBKEY)) {
+            try {
+                Pubkey pubkey = (Pubkey) object.getPayload();
+                if (address.getVersion() == 4) {
+                    V4Pubkey v4Pubkey = (V4Pubkey) pubkey;
+                    if (Arrays.equals(address.getTag(), v4Pubkey.getTag())) {
+                        v4Pubkey.decrypt(address.getPublicDecryptionKey());
+                        if (object.isSignatureValid(v4Pubkey)) {
+                            address.setPubkey(v4Pubkey);
+                            ctx.getAddressRepository().save(address);
+                            break;
+                        } else {
+                            LOG.info("Found pubkey for " + address + " but signature is invalid");
+                        }
+                    }
+                } else {
+                    if (Arrays.equals(pubkey.getRipe(), address.getRipe())) {
+                        address.setPubkey(pubkey);
+                        ctx.getAddressRepository().save(address);
+                        break;
+                    }
+                }
+            } catch (Exception e) {
+                LOG.debug(e.getMessage(), e);
+            }
+        }
+    }
+
+    public void addSubscribtion(BitmessageAddress address) {
+        address.setSubscribed(true);
+        ctx.getAddressRepository().save(address);
+        tryToFindBroadcastsForAddress(address);
+    }
+
+    private void tryToFindBroadcastsForAddress(BitmessageAddress address) {
+        for (ObjectMessage object : ctx.getInventory().getObjects(address.getStream(), Broadcast.getVersion(address), ObjectType.BROADCAST)) {
+            try {
+                Broadcast broadcast = (Broadcast) object.getPayload();
+                broadcast.decrypt(address);
+                listener.receive(broadcast.getPlaintext());
+            } catch (DecryptionFailedException ignore) {
+            } catch (Exception e) {
+                LOG.debug(e.getMessage(), e);
+            }
+        }
+    }
+
+    public Property status() {
+        return new Property("status", null,
+                ctx.getNetworkHandler().getNetworkStatus()
+        );
+    }
+
+    /**
+     * Returns the {@link InternalContext} - normally you wouldn't need it,
+     * unless you are doing something crazy with the protocol.
+     */
+    public InternalContext internals() {
+        return ctx;
+    }
+
+    public interface Listener {
+        void receive(Plaintext plaintext);
+    }
+
+    public static final class Builder {
+        int port = 8444;
+        Inventory inventory;
+        NodeRegistry nodeRegistry;
+        NetworkHandler networkHandler;
+        AddressRepository addressRepo;
+        MessageRepository messageRepo;
+        ProofOfWorkRepository proofOfWorkRepository;
+        ProofOfWorkEngine proofOfWorkEngine;
+        Cryptography cryptography;
+        MessageCallback messageCallback;
+        CustomCommandHandler customCommandHandler;
+        Listener listener;
+        int connectionLimit = 150;
+        long connectionTTL = 30 * MINUTE;
+        boolean sendPubkeyOnIdentityCreation = true;
+        long pubkeyTTL = 28;
+
+        public Builder() {
+        }
+
+        public Builder port(int port) {
+            this.port = port;
+            return this;
+        }
+
+        public Builder inventory(Inventory inventory) {
+            this.inventory = inventory;
+            return this;
+        }
+
+        public Builder nodeRegistry(NodeRegistry nodeRegistry) {
+            this.nodeRegistry = nodeRegistry;
+            return this;
+        }
+
+        public Builder networkHandler(NetworkHandler networkHandler) {
+            this.networkHandler = networkHandler;
+            return this;
+        }
+
+        public Builder addressRepo(AddressRepository addressRepo) {
+            this.addressRepo = addressRepo;
+            return this;
+        }
+
+        public Builder messageRepo(MessageRepository messageRepo) {
+            this.messageRepo = messageRepo;
+            return this;
+        }
+
+        public Builder powRepo(ProofOfWorkRepository proofOfWorkRepository) {
+            this.proofOfWorkRepository = proofOfWorkRepository;
+            return this;
+        }
+
+        public Builder cryptography(Cryptography cryptography) {
+            this.cryptography = cryptography;
+            return this;
+        }
+
+        public Builder messageCallback(MessageCallback callback) {
+            this.messageCallback = callback;
+            return this;
+        }
+
+        public Builder customCommandHandler(CustomCommandHandler handler) {
+            this.customCommandHandler = handler;
+            return this;
+        }
+
+        public Builder proofOfWorkEngine(ProofOfWorkEngine proofOfWorkEngine) {
+            this.proofOfWorkEngine = proofOfWorkEngine;
+            return this;
+        }
+
+        public Builder listener(Listener listener) {
+            this.listener = listener;
+            return this;
+        }
+
+        public Builder connectionLimit(int connectionLimit) {
+            this.connectionLimit = connectionLimit;
+            return this;
+        }
+
+        public Builder connectionTTL(int hours) {
+            this.connectionTTL = hours * HOUR;
+            return this;
+        }
+
+        /**
+         * By default a client will send the public key when an identity is being created. On weaker devices
+         * this behaviour might not be desirable.
+         */
+        public Builder doNotSendPubkeyOnIdentityCreation() {
+            this.sendPubkeyOnIdentityCreation = false;
+            return this;
+        }
+
+        /**
+         * Time to live in seconds for public keys the client sends. Defaults to the maximum of 28 days,
+         * but on weak devices smaller values might be desirable.
+         * <p>
+         * Please be aware that this might cause some problems where you can't receive a message (the
+         * sender can't receive your public key) in some special situations. Also note that it's probably
+         * not a good idea to set it too low.
+         * </p>
+         */
+        public Builder pubkeyTTL(long days) {
+            if (days < 0 || days > 28 * DAY) throw new IllegalArgumentException("TTL must be between 1 and 28 days");
+            this.pubkeyTTL = days;
+            return this;
+        }
+
+        public BitmessageContext build() {
+            nonNull("inventory", inventory);
+            nonNull("nodeRegistry", nodeRegistry);
+            nonNull("networkHandler", networkHandler);
+            nonNull("addressRepo", addressRepo);
+            nonNull("messageRepo", messageRepo);
+            nonNull("proofOfWorkRepo", proofOfWorkRepository);
+            if (proofOfWorkEngine == null) {
+                proofOfWorkEngine = new MultiThreadedPOWEngine();
+            }
+            if (messageCallback == null) {
+                messageCallback = new MessageCallback() {
+                    @Override
+                    public void proofOfWorkStarted(ObjectPayload message) {
+                    }
+
+                    @Override
+                    public void proofOfWorkCompleted(ObjectPayload message) {
+                    }
+
+                    @Override
+                    public void messageOffered(ObjectPayload message, InventoryVector iv) {
+                    }
+
+                    @Override
+                    public void messageAcknowledged(InventoryVector iv) {
+                    }
+                };
+            }
+            if (customCommandHandler == null) {
+                customCommandHandler = new CustomCommandHandler() {
+                    @Override
+                    public MessagePayload handle(CustomMessage request) {
+                        throw new RuntimeException("Received custom request, but no custom command handler configured.");
+                    }
+                };
+            }
+            return new BitmessageContext(this);
+        }
+
+        private void nonNull(String name, Object o) {
+            if (o == null) throw new IllegalStateException(name + " must not be null");
+        }
+    }
+
+}

core/src/main/java/ch/dissem/bitmessage/DefaultMessageListener.java

@@ -69,9 +69,10 @@ class DefaultMessageListener implements NetworkHandler.MessageListener {
     }
 
     protected void receive(ObjectMessage object, GetPubkey getPubkey) {
-        BitmessageAddress identity = ctx.getAddressRepo().findIdentity(getPubkey.getRipeTag());
+        BitmessageAddress identity = ctx.getAddressRepository().findIdentity(getPubkey.getRipeTag());
         if (identity != null && identity.getPrivateKey() != null) {
-            LOG.debug("Got pubkey request for identity " + identity);
+            LOG.info("Got pubkey request for identity " + identity);
+            // FIXME: only send pubkey if it wasn't sent in the last 28 days
             ctx.sendPubkey(identity, object.getStream());
         }
     }
@@ -81,40 +82,42 @@ class DefaultMessageListener implements NetworkHandler.MessageListener {
         try {
             if (pubkey instanceof V4Pubkey) {
                 V4Pubkey v4Pubkey = (V4Pubkey) pubkey;
-                address = ctx.getAddressRepo().findContact(v4Pubkey.getTag());
+                address = ctx.getAddressRepository().findContact(v4Pubkey.getTag());
                 if (address != null) {
                     v4Pubkey.decrypt(address.getPublicDecryptionKey());
                 }
             } else {
-                address = ctx.getAddressRepo().findContact(pubkey.getRipe());
+                address = ctx.getAddressRepository().findContact(pubkey.getRipe());
             }
             if (address != null) {
-                address.setPubkey(pubkey);
+                updatePubkey(address, pubkey);
-                LOG.debug("Got pubkey for contact " + address);
-                ctx.getAddressRepo().save(address);
-                List<Plaintext> messages = ctx.getMessageRepository().findMessages(Plaintext.Status.PUBKEY_REQUESTED, address);
-                LOG.debug("Sending " + messages.size() + " messages for contact " + address);
-                for (Plaintext msg : messages) {
-                    msg.setStatus(DOING_PROOF_OF_WORK);
-                    ctx.getMessageRepository().save(msg);
-                    ctx.send(
-                            msg.getFrom(),
-                            msg.getTo(),
-                            new Msg(msg),
-                            +2 * DAY,
-                            ctx.getNonceTrialsPerByte(msg.getTo()),
-                            ctx.getExtraBytes(msg.getTo())
-                    );
-                    msg.setStatus(SENT);
-                    ctx.getMessageRepository().save(msg);
-                }
             }
         } catch (DecryptionFailedException ignore) {
         }
     }
 
+    private void updatePubkey(BitmessageAddress address, Pubkey pubkey){
+        address.setPubkey(pubkey);
+        LOG.info("Got pubkey for contact " + address);
+        ctx.getAddressRepository().save(address);
+        List<Plaintext> messages = ctx.getMessageRepository().findMessages(Plaintext.Status.PUBKEY_REQUESTED, address);
+        LOG.info("Sending " + messages.size() + " messages for contact " + address);
+        for (Plaintext msg : messages) {
+            msg.setStatus(DOING_PROOF_OF_WORK);
+            ctx.getMessageRepository().save(msg);
+            ctx.send(
+                    msg.getFrom(),
+                    msg.getTo(),
+                    new Msg(msg),
+                    +2 * DAY
+            );
+            msg.setStatus(SENT);
+            ctx.getMessageRepository().save(msg);
+        }
+    }
+
     protected void receive(ObjectMessage object, Msg msg) throws IOException {
-        for (BitmessageAddress identity : ctx.getAddressRepo().getIdentities()) {
+        for (BitmessageAddress identity : ctx.getAddressRepository().getIdentities()) {
             try {
                 msg.decrypt(identity.getPrivateKey().getPrivateEncryptionKey());
                 msg.getPlaintext().setTo(identity);
@@ -126,6 +129,7 @@ class DefaultMessageListener implements NetworkHandler.MessageListener {
                     msg.getPlaintext().setInventoryVector(object.getInventoryVector());
                     ctx.getMessageRepository().save(msg.getPlaintext());
                     listener.receive(msg.getPlaintext());
+                    updatePubkey(msg.getPlaintext().getFrom(), msg.getPlaintext().getFrom().getPubkey());
                 }
                 break;
             } catch (DecryptionFailedException ignore) {
@@ -135,7 +139,7 @@ class DefaultMessageListener implements NetworkHandler.MessageListener {
 
     protected void receive(ObjectMessage object, Broadcast broadcast) throws IOException {
         byte[] tag = broadcast instanceof V5Broadcast ? ((V5Broadcast) broadcast).getTag() : null;
-        for (BitmessageAddress subscription : ctx.getAddressRepo().getSubscriptions(broadcast.getVersion())) {
+        for (BitmessageAddress subscription : ctx.getAddressRepository().getSubscriptions(broadcast.getVersion())) {
             if (tag != null && !Arrays.equals(tag, subscription.getTag())) {
                 continue;
             }
@@ -149,6 +153,7 @@ class DefaultMessageListener implements NetworkHandler.MessageListener {
                     broadcast.getPlaintext().setInventoryVector(object.getInventoryVector());
                     ctx.getMessageRepository().save(broadcast.getPlaintext());
                     listener.receive(broadcast.getPlaintext());
+                    updatePubkey(broadcast.getPlaintext().getFrom(), broadcast.getPlaintext().getFrom().getPubkey());
                 }
             } catch (DecryptionFailedException ignore) {
             }

core/src/main/java/ch/dissem/bitmessage/InternalContext.java

@@ -16,12 +16,14 @@
 
 package ch.dissem.bitmessage;
 
-import ch.dissem.bitmessage.entity.*;
+import ch.dissem.bitmessage.entity.BitmessageAddress;
+import ch.dissem.bitmessage.entity.Encrypted;
+import ch.dissem.bitmessage.entity.ObjectMessage;
 import ch.dissem.bitmessage.entity.payload.Broadcast;
 import ch.dissem.bitmessage.entity.payload.GetPubkey;
 import ch.dissem.bitmessage.entity.payload.ObjectPayload;
 import ch.dissem.bitmessage.ports.*;
-import ch.dissem.bitmessage.utils.Security;
+import ch.dissem.bitmessage.utils.Singleton;
 import ch.dissem.bitmessage.utils.UnixTime;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -29,8 +31,6 @@ import org.slf4j.LoggerFactory;
 import java.io.IOException;
 import java.util.TreeSet;
 
-import static ch.dissem.bitmessage.utils.UnixTime.DAY;
-
 /**
  * The internal context should normally only be used for port implementations. If you need it in your client
  * implementation, you're either doing something wrong, something very weird, or the BitmessageContext should
@@ -42,32 +42,64 @@ import static ch.dissem.bitmessage.utils.UnixTime.DAY;
 public class InternalContext {
     private final static Logger LOG = LoggerFactory.getLogger(InternalContext.class);
 
+    private final Cryptography cryptography;
     private final Inventory inventory;
     private final NodeRegistry nodeRegistry;
     private final NetworkHandler networkHandler;
     private final AddressRepository addressRepository;
     private final MessageRepository messageRepository;
+    private final ProofOfWorkRepository proofOfWorkRepository;
     private final ProofOfWorkEngine proofOfWorkEngine;
+    private final MessageCallback messageCallback;
+    private final CustomCommandHandler customCommandHandler;
+    private final ProofOfWorkService proofOfWorkService;
 
     private final TreeSet<Long> streams = new TreeSet<>();
     private final int port;
-    private long networkNonceTrialsPerByte = 1000;
+    private final long clientNonce;
-    private long networkExtraBytes = 1000;
+    private final long networkNonceTrialsPerByte = 1000;
-    private long clientNonce;
+    private final long networkExtraBytes = 1000;
+    private final long pubkeyTTL;
+    private long connectionTTL;
+    private int connectionLimit;
 
     public InternalContext(BitmessageContext.Builder builder) {
+        this.cryptography = builder.cryptography;
         this.inventory = builder.inventory;
         this.nodeRegistry = builder.nodeRegistry;
         this.networkHandler = builder.networkHandler;
         this.addressRepository = builder.addressRepo;
         this.messageRepository = builder.messageRepo;
+        this.proofOfWorkRepository = builder.proofOfWorkRepository;
+        this.proofOfWorkService = new ProofOfWorkService();
         this.proofOfWorkEngine = builder.proofOfWorkEngine;
-        this.clientNonce = Security.randomNonce();
+        this.clientNonce = cryptography.randomNonce();
+        this.messageCallback = builder.messageCallback;
+        this.customCommandHandler = builder.customCommandHandler;
+        this.port = builder.port;
+        this.connectionLimit = builder.connectionLimit;
+        this.connectionTTL = builder.connectionTTL;
+        this.pubkeyTTL = builder.pubkeyTTL;
 
-        port = builder.port;
+        Singleton.initialize(cryptography);
-        streams.add(1L); // FIXME
 
-        init(inventory, nodeRegistry, networkHandler, addressRepository, messageRepository, proofOfWorkEngine);
+        // TODO: streams of new identities and subscriptions should also be added. This works only after a restart.
+        for (BitmessageAddress address : addressRepository.getIdentities()) {
+            streams.add(address.getStream());
+        }
+        for (BitmessageAddress address : addressRepository.getSubscriptions()) {
+            streams.add(address.getStream());
+        }
+        if (streams.isEmpty()) {
+            streams.add(1L);
+        }
+
+        init(cryptography, inventory, nodeRegistry, networkHandler, addressRepository, messageRepository,
+                proofOfWorkRepository, proofOfWorkService, proofOfWorkEngine,
+                messageCallback, customCommandHandler);
+        for (BitmessageAddress identity : addressRepository.getIdentities()) {
+            streams.add(identity.getStream());
+        }
     }
 
     private void init(Object... objects) {
@@ -78,6 +110,10 @@ public class InternalContext {
         }
     }
 
+    public Cryptography getCryptography() {
+        return cryptography;
+    }
+
     public Inventory getInventory() {
         return inventory;
     }
@@ -90,7 +126,7 @@ public class InternalContext {
         return networkHandler;
     }
 
-    public AddressRepository getAddressRepo() {
+    public AddressRepository getAddressRepository() {
         return addressRepository;
     }
 
@@ -98,10 +134,18 @@ public class InternalContext {
         return messageRepository;
     }
 
+    public ProofOfWorkRepository getProofOfWorkRepository() {
+        return proofOfWorkRepository;
+    }
+
     public ProofOfWorkEngine getProofOfWorkEngine() {
         return proofOfWorkEngine;
     }
 
+    public ProofOfWorkService getProofOfWorkService() {
+        return proofOfWorkService;
+    }
+
     public long[] getStreams() {
         long[] result = new long[streams.size()];
         int i = 0;
@@ -111,14 +155,6 @@ public class InternalContext {
         return result;
     }
 
-    public void addStream(long stream) {
-        streams.add(stream);
-    }
-
-    public void removeStream(long stream) {
-        streams.remove(stream);
-    }
-
     public int getPort() {
         return port;
     }
@@ -127,26 +163,17 @@ public class InternalContext {
         return networkNonceTrialsPerByte;
     }
 
-    public long getNonceTrialsPerByte(BitmessageAddress address) {
-        long nonceTrialsPerByte = address.getPubkey().getNonceTrialsPerByte();
-        return networkNonceTrialsPerByte > nonceTrialsPerByte ? networkNonceTrialsPerByte : nonceTrialsPerByte;
-    }
-
     public long getNetworkExtraBytes() {
         return networkExtraBytes;
     }
 
-    public long getExtraBytes(BitmessageAddress address) {
+    public void send(final BitmessageAddress from, BitmessageAddress to, final ObjectPayload payload,
-        long extraBytes = address.getPubkey().getExtraBytes();
+                     final long timeToLive) {
-        return networkExtraBytes > extraBytes ? networkExtraBytes : extraBytes;
-    }
-
-    public void send(BitmessageAddress from, BitmessageAddress to, ObjectPayload payload, long timeToLive, long nonceTrialsPerByte, long extraBytes) {
         try {
             if (to == null) to = from;
             long expires = UnixTime.now(+timeToLive);
             LOG.info("Expires at " + expires);
-            ObjectMessage object = new ObjectMessage.Builder()
+            final ObjectMessage object = new ObjectMessage.Builder()
                     .stream(to.getStream())
                     .expiresTime(expires)
                     .payload(payload)
@@ -159,64 +186,58 @@ public class InternalContext {
             } else if (payload instanceof Encrypted) {
                 object.encrypt(to.getPubkey());
             }
-            Security.doProofOfWork(object, proofOfWorkEngine, nonceTrialsPerByte, extraBytes);
+            messageCallback.proofOfWorkStarted(payload);
-            if (payload instanceof PlaintextHolder) {
+            proofOfWorkService.doProofOfWork(to, object);
-                Plaintext plaintext = ((PlaintextHolder) payload).getPlaintext();
-                plaintext.setInventoryVector(object.getInventoryVector());
-                messageRepository.save(plaintext);
-            }
-            inventory.storeObject(object);
-            networkHandler.offer(object.getInventoryVector());
         } catch (IOException e) {
             throw new RuntimeException(e);
         }
     }
 
-    public void sendPubkey(BitmessageAddress identity, long targetStream) {
+    public void sendPubkey(final BitmessageAddress identity, final long targetStream) {
         try {
-            long expires = UnixTime.now(+28 * DAY);
+            long expires = UnixTime.now(pubkeyTTL);
             LOG.info("Expires at " + expires);
-            ObjectMessage response = new ObjectMessage.Builder()
+            final ObjectMessage response = new ObjectMessage.Builder()
                     .stream(targetStream)
                     .expiresTime(expires)
                     .payload(identity.getPubkey())
                     .build();
             response.sign(identity.getPrivateKey());
-            response.encrypt(Security.createPublicKey(identity.getPublicDecryptionKey()).getEncoded(false));
+            response.encrypt(cryptography.createPublicKey(identity.getPublicDecryptionKey()));
-            Security.doProofOfWork(response, proofOfWorkEngine, networkNonceTrialsPerByte, networkExtraBytes);
+            messageCallback.proofOfWorkStarted(identity.getPubkey());
-            if (response.isSigned()) {
+            // TODO: remember that the pubkey is just about to be sent, and on which stream!
-                response.sign(identity.getPrivateKey());
+            proofOfWorkService.doProofOfWork(response);
-            }
-            if (response instanceof Encrypted) {
-                response.encrypt(Security.createPublicKey(identity.getPublicDecryptionKey()).getEncoded(false));
-            }
-            inventory.storeObject(response);
-            networkHandler.offer(response.getInventoryVector());
-            // TODO: save that the pubkey was just sent, and on which stream!
         } catch (IOException e) {
             throw new RuntimeException(e);
         }
     }
 
-    public void requestPubkey(BitmessageAddress contact) {
+    public void requestPubkey(final BitmessageAddress contact) {
-        long expires = UnixTime.now(+2 * DAY);
+        long expires = UnixTime.now(+pubkeyTTL);
         LOG.info("Expires at " + expires);
-        ObjectMessage response = new ObjectMessage.Builder()
+        final ObjectMessage response = new ObjectMessage.Builder()
                 .stream(contact.getStream())
                 .expiresTime(expires)
                 .payload(new GetPubkey(contact))
                 .build();
-        Security.doProofOfWork(response, proofOfWorkEngine, networkNonceTrialsPerByte, networkExtraBytes);
+        messageCallback.proofOfWorkStarted(response.getPayload());
-        inventory.storeObject(response);
+        proofOfWorkService.doProofOfWork(response);
-        networkHandler.offer(response.getInventoryVector());
     }
 
     public long getClientNonce() {
         return clientNonce;
     }
 
-    public void setClientNonce(long clientNonce) {
+    public long getConnectionTTL() {
-        this.clientNonce = clientNonce;
+        return connectionTTL;
+    }
+
+    public int getConnectionLimit() {
+        return connectionLimit;
+    }
+
+    public CustomCommandHandler getCustomCommandHandler() {
+        return customCommandHandler;
     }
 
     public interface ContextHolder {

core/src/main/java/ch/dissem/bitmessage/MessageCallback.java

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2015 Christian Basler
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package ch.dissem.bitmessage;
+
+import ch.dissem.bitmessage.entity.payload.ObjectPayload;
+import ch.dissem.bitmessage.entity.valueobject.InventoryVector;
+
+/**
+ * Callback for message sending events, mostly so the user can be notified when POW is done.
+ */
+public interface MessageCallback {
+    /**
+     * Called before calculation of proof of work begins.
+     */
+    void proofOfWorkStarted(ObjectPayload message);
+
+    /**
+     * Called after calculation of proof of work finished.
+     */
+    void proofOfWorkCompleted(ObjectPayload message);
+
+    /**
+     * Called once the message is offered to the network. Please note that this doesn't mean the message was sent,
+     * if the client is not connected to the network it's just stored in the inventory.
+     * <p>
+     * Also, please note that this is where the original payload as well as the {@link InventoryVector} of the sent
+     * message is available. If the callback needs the IV for some reason, it should be retrieved here. (Plaintext
+     * and Broadcast messages will have their IV property set automatically though.)
+     * </p>
+     */
+    void messageOffered(ObjectPayload message, InventoryVector iv);
+
+    /**
+     * This isn't called yet, as ACK messages aren't being processed yet. Also, this is only relevant for Plaintext
+     * messages.
+     */
+    void messageAcknowledged(InventoryVector iv);
+}

core/src/main/java/ch/dissem/bitmessage/ProofOfWorkService.java

@@ -0,0 +1,82 @@
+package ch.dissem.bitmessage;
+
+import ch.dissem.bitmessage.entity.BitmessageAddress;
+import ch.dissem.bitmessage.entity.ObjectMessage;
+import ch.dissem.bitmessage.entity.Plaintext;
+import ch.dissem.bitmessage.entity.PlaintextHolder;
+import ch.dissem.bitmessage.ports.MessageRepository;
+import ch.dissem.bitmessage.ports.ProofOfWorkEngine;
+import ch.dissem.bitmessage.ports.ProofOfWorkRepository;
+import ch.dissem.bitmessage.ports.Cryptography;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.List;
+
+import static ch.dissem.bitmessage.utils.Singleton.security;
+
+/**
+ * @author Christian Basler
+ */
+public class ProofOfWorkService implements ProofOfWorkEngine.Callback, InternalContext.ContextHolder {
+    private final static Logger LOG = LoggerFactory.getLogger(ProofOfWorkService.class);
+
+    private Cryptography cryptography;
+    private InternalContext ctx;
+    private ProofOfWorkRepository powRepo;
+    private MessageRepository messageRepo;
+
+    public void doMissingProofOfWork() {
+        List<byte[]> items = powRepo.getItems();
+        if (items.isEmpty()) return;
+
+        LOG.info("Doing POW for " + items.size() + " tasks.");
+        for (byte[] initialHash : items) {
+            ProofOfWorkRepository.Item item = powRepo.getItem(initialHash);
+            cryptography.doProofOfWork(item.object, item.nonceTrialsPerByte, item.extraBytes, this);
+        }
+    }
+
+    public void doProofOfWork(ObjectMessage object) {
+        doProofOfWork(null, object);
+    }
+
+    public void doProofOfWork(BitmessageAddress recipient, ObjectMessage object) {
+        long nonceTrialsPerByte = recipient == null ?
+                ctx.getNetworkNonceTrialsPerByte() : recipient.getPubkey().getNonceTrialsPerByte();
+        long extraBytes = recipient == null ?
+                ctx.getNetworkExtraBytes() : recipient.getPubkey().getExtraBytes();
+
+        powRepo.putObject(object, nonceTrialsPerByte, extraBytes);
+        if (object.getPayload() instanceof PlaintextHolder) {
+            Plaintext plaintext = ((PlaintextHolder) object.getPayload()).getPlaintext();
+            plaintext.setInitialHash(cryptography.getInitialHash(object));
+            messageRepo.save(plaintext);
+        }
+        cryptography.doProofOfWork(object, nonceTrialsPerByte, extraBytes, this);
+    }
+
+    @Override
+    public void onNonceCalculated(byte[] initialHash, byte[] nonce) {
+        ObjectMessage object = powRepo.getItem(initialHash).object;
+        object.setNonce(nonce);
+//        messageCallback.proofOfWorkCompleted(payload);
+        Plaintext plaintext = messageRepo.getMessage(initialHash);
+        if (plaintext != null) {
+            plaintext.setInventoryVector(object.getInventoryVector());
+            messageRepo.save(plaintext);
+        }
+        ctx.getInventory().storeObject(object);
+        ctx.getProofOfWorkRepository().removeObject(initialHash);
+        ctx.getNetworkHandler().offer(object.getInventoryVector());
+//        messageCallback.messageOffered(payload, object.getInventoryVector());
+    }
+
+    @Override
+    public void setContext(InternalContext ctx) {
+        this.ctx = ctx;
+        this.cryptography = security();
+        this.powRepo = ctx.getProofOfWorkRepository();
+        this.messageRepo = ctx.getMessageRepository();
+    }
+}

core/src/main/java/ch/dissem/bitmessage/entity/BitmessageAddress.java

@@ -19,22 +19,27 @@ package ch.dissem.bitmessage.entity;
 import ch.dissem.bitmessage.entity.payload.Pubkey;
 import ch.dissem.bitmessage.entity.payload.V4Pubkey;
 import ch.dissem.bitmessage.entity.valueobject.PrivateKey;
-import ch.dissem.bitmessage.utils.*;
+import ch.dissem.bitmessage.utils.AccessCounter;
+import ch.dissem.bitmessage.utils.Base58;
+import ch.dissem.bitmessage.utils.Bytes;
+import ch.dissem.bitmessage.utils.Encode;
 
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
+import java.io.Serializable;
 import java.util.Arrays;
 import java.util.Objects;
 
 import static ch.dissem.bitmessage.utils.Decode.bytes;
 import static ch.dissem.bitmessage.utils.Decode.varInt;
+import static ch.dissem.bitmessage.utils.Singleton.security;
 
 /**
  * A Bitmessage address. Can be a user's private address, an address string without public keys or a recipient's address
  * holding private keys.
  */
-public class BitmessageAddress {
+public class BitmessageAddress implements Serializable {
     private final long version;
     private final long stream;
     private final byte[] ripe;
@@ -62,19 +67,19 @@ public class BitmessageAddress {
             Encode.varInt(version, os);
             Encode.varInt(stream, os);
             if (version < 4) {
-                byte[] checksum = Security.sha512(os.toByteArray(), ripe);
+                byte[] checksum = security().sha512(os.toByteArray(), ripe);
                 this.tag = null;
                 this.publicDecryptionKey = Arrays.copyOfRange(checksum, 0, 32);
             } else {
                 // for tag and decryption key, the checksum has to be created with 0x00 padding
-                byte[] checksum = Security.doubleSha512(os.toByteArray(), ripe);
+                byte[] checksum = security().doubleSha512(os.toByteArray(), ripe);
                 this.tag = Arrays.copyOfRange(checksum, 32, 64);
                 this.publicDecryptionKey = Arrays.copyOfRange(checksum, 0, 32);
             }
             // but for the address and its checksum they need to be stripped
             int offset = Bytes.numberOfLeadingZeros(ripe);
             os.write(ripe, offset, ripe.length - offset);
-            byte[] checksum = Security.doubleSha512(os.toByteArray());
+            byte[] checksum = security().doubleSha512(os.toByteArray());
             os.write(checksum, 0, 4);
             this.address = "BM-" + Base58.encode(os.toByteArray());
         } catch (IOException e) {
@@ -82,7 +87,7 @@ public class BitmessageAddress {
         }
     }
 
-    BitmessageAddress(Pubkey publicKey) {
+    public BitmessageAddress(Pubkey publicKey) {
         this(publicKey.getVersion(), publicKey.getStream(), publicKey.getRipe());
         this.pubkey = publicKey;
     }
@@ -103,18 +108,18 @@ public class BitmessageAddress {
             this.ripe = Bytes.expand(bytes(in, bytes.length - counter.length() - 4), 20);
 
             // test checksum
-            byte[] checksum = Security.doubleSha512(bytes, bytes.length - 4);
+            byte[] checksum = security().doubleSha512(bytes, bytes.length - 4);
             byte[] expectedChecksum = bytes(in, 4);
             for (int i = 0; i < 4; i++) {
                 if (expectedChecksum[i] != checksum[i])
                     throw new IllegalArgumentException("Checksum of address failed");
             }
             if (version < 4) {
-                checksum = Security.sha512(Arrays.copyOfRange(bytes, 0, counter.length()), ripe);
+                checksum = security().sha512(Arrays.copyOfRange(bytes, 0, counter.length()), ripe);
                 this.tag = null;
                 this.publicDecryptionKey = Arrays.copyOfRange(checksum, 0, 32);
             } else {
-                checksum = Security.doubleSha512(Arrays.copyOfRange(bytes, 0, counter.length()), ripe);
+                checksum = security().doubleSha512(Arrays.copyOfRange(bytes, 0, counter.length()), ripe);
                 this.tag = Arrays.copyOfRange(checksum, 32, 64);
                 this.publicDecryptionKey = Arrays.copyOfRange(checksum, 0, 32);
             }
@@ -129,7 +134,7 @@ public class BitmessageAddress {
             Encode.varInt(version, out);
             Encode.varInt(stream, out);
             out.write(ripe);
-            return Arrays.copyOfRange(Security.doubleSha512(out.toByteArray()), 32, 64);
+            return Arrays.copyOfRange(security().doubleSha512(out.toByteArray()), 32, 64);
         } catch (IOException e) {
             throw new RuntimeException(e);
         }

core/src/main/java/ch/dissem/bitmessage/entity/CustomMessage.java

@@ -0,0 +1,96 @@
+/*
+ * Copyright 2015 Christian Basler
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package ch.dissem.bitmessage.entity;
+
+import ch.dissem.bitmessage.utils.AccessCounter;
+import ch.dissem.bitmessage.utils.Encode;
+
+import java.io.*;
+
+import static ch.dissem.bitmessage.utils.Decode.bytes;
+import static ch.dissem.bitmessage.utils.Decode.varString;
+
+/**
+ * @author Christian Basler
+ */
+public class CustomMessage implements MessagePayload {
+    public static final String COMMAND_ERROR = "ERROR";
+
+    private final String command;
+    private final byte[] data;
+
+    public CustomMessage(String command) {
+        this.command = command;
+        this.data = null;
+    }
+
+    public CustomMessage(String command, byte[] data) {
+        this.command = command;
+        this.data = data;
+    }
+
+    public static CustomMessage read(InputStream in, int length) throws IOException {
+        AccessCounter counter = new AccessCounter();
+        return new CustomMessage(varString(in, counter), bytes(in, length - counter.length()));
+    }
+
+    @Override
+    public Command getCommand() {
+        return Command.CUSTOM;
+    }
+
+    public String getCustomCommand() {
+        return command;
+    }
+
+    public byte[] getData() {
+        if (data != null) {
+            return data;
+        } else {
+            try {
+                ByteArrayOutputStream out = new ByteArrayOutputStream();
+                write(out);
+                return out.toByteArray();
+            } catch (IOException e) {
+                throw new RuntimeException(e);
+            }
+        }
+    }
+
+    @Override
+    public void write(OutputStream out) throws IOException {
+        if (data != null) {
+            Encode.varString(command, out);
+            out.write(data);
+        } else {
+            throw new RuntimeException("Tried to write custom message without data. " +
+                    "Programmer: did you forget to override #write()?");
+        }
+    }
+
+    public boolean isError() {
+        return COMMAND_ERROR.equals(command);
+    }
+
+    public static CustomMessage error(String message) {
+        try {
+            return new CustomMessage(COMMAND_ERROR, message.getBytes("UTF-8"));
+        } catch (UnsupportedEncodingException e) {
+            throw new RuntimeException(e);
+        }
+    }
+}

core/src/main/java/ch/dissem/bitmessage/entity/GetData.java

@@ -44,10 +44,10 @@ public class GetData implements MessagePayload {
     }
 
     @Override
-    public void write(OutputStream stream) throws IOException {
+    public void write(OutputStream out) throws IOException {
-        Encode.varInt(inventory.size(), stream);
+        Encode.varInt(inventory.size(), out);
         for (InventoryVector iv : inventory) {
-            iv.write(stream);
+            iv.write(out);
         }
     }
 

core/src/main/java/ch/dissem/bitmessage/entity/Inv.java

@@ -44,10 +44,10 @@ public class Inv implements MessagePayload {
     }
 
     @Override
-    public void write(OutputStream stream) throws IOException {
+    public void write(OutputStream out) throws IOException {
-        Encode.varInt(inventory.size(), stream);
+        Encode.varInt(inventory.size(), out);
         for (InventoryVector iv : inventory) {
-            iv.write(stream);
+            iv.write(out);
         }
     }
 

core/src/main/java/ch/dissem/bitmessage/entity/MessagePayload.java

@@ -23,6 +23,6 @@ public interface MessagePayload extends Streamable {
     Command getCommand();
 
     enum Command {
-        VERSION, VERACK, ADDR, INV, GETDATA, OBJECT
+        VERSION, VERACK, ADDR, INV, GETDATA, OBJECT, CUSTOM
     }
 }

core/src/main/java/ch/dissem/bitmessage/entity/NetworkMessage.java

@@ -26,7 +26,7 @@ import java.security.GeneralSecurityException;
 import java.security.NoSuchAlgorithmException;
 import java.security.NoSuchProviderException;
 
-import static ch.dissem.bitmessage.utils.Security.sha512;
+import static ch.dissem.bitmessage.utils.Singleton.security;
 
 /**
  * A network message is exchanged between two nodes.
@@ -48,7 +48,7 @@ public class NetworkMessage implements Streamable {
      * First 4 bytes of sha512(payload)
      */
     private byte[] getChecksum(byte[] bytes) throws NoSuchProviderException, NoSuchAlgorithmException {
-        byte[] d = sha512(bytes);
+        byte[] d = security().sha512(bytes);
         return new byte[]{d[0], d[1], d[2], d[3]};
     }
 

core/src/main/java/ch/dissem/bitmessage/entity/ObjectMessage.java

@@ -24,12 +24,13 @@ import ch.dissem.bitmessage.entity.valueobject.PrivateKey;
 import ch.dissem.bitmessage.exception.DecryptionFailedException;
 import ch.dissem.bitmessage.utils.Bytes;
 import ch.dissem.bitmessage.utils.Encode;
-import ch.dissem.bitmessage.utils.Security;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.OutputStream;
 
+import static ch.dissem.bitmessage.utils.Singleton.security;
+
 /**
  * The 'object' command sends an object that is shared throughout the network.
  */
@@ -89,7 +90,9 @@ public class ObjectMessage implements MessagePayload {
     }
 
     public InventoryVector getInventoryVector() {
-        return new InventoryVector(Bytes.truncate(Security.doubleSha512(nonce, getPayloadBytesWithoutNonce()), 32));
+        return new InventoryVector(
+                Bytes.truncate(security().doubleSha512(nonce, getPayloadBytesWithoutNonce()), 32)
+        );
     }
 
     private boolean isEncrypted() {
@@ -113,7 +116,7 @@ public class ObjectMessage implements MessagePayload {
 
     public void sign(PrivateKey key) {
         if (payload.isSigned()) {
-            payload.setSignature(Security.getSignature(getBytesToSign(), key));
+            payload.setSignature(security().getSignature(getBytesToSign(), key));
         }
     }
 
@@ -147,12 +150,16 @@ public class ObjectMessage implements MessagePayload {
 
     public boolean isSignatureValid(Pubkey pubkey) throws IOException {
         if (isEncrypted()) throw new IllegalStateException("Payload must be decrypted first");
-        return Security.isSignatureValid(getBytesToSign(), payload.getSignature(), pubkey);
+        return security().isSignatureValid(getBytesToSign(), payload.getSignature(), pubkey);
     }
 
     @Override
     public void write(OutputStream out) throws IOException {
-        out.write(nonce);
+        if (nonce != null) {
+            out.write(nonce);
+        } else {
+            out.write(new byte[8]);
+        }
         out.write(getPayloadBytesWithoutNonce());
     }
 

core/src/main/java/ch/dissem/bitmessage/entity/Plaintext.java

@@ -21,6 +21,7 @@ import ch.dissem.bitmessage.entity.valueobject.Label;
 import ch.dissem.bitmessage.factory.Factory;
 import ch.dissem.bitmessage.utils.Decode;
 import ch.dissem.bitmessage.utils.Encode;
+import ch.dissem.bitmessage.utils.UnixTime;
 
 import java.io.*;
 import java.util.*;
@@ -43,6 +44,7 @@ public class Plaintext implements Streamable {
     private Long received;
 
     private Set<Label> labels;
+    private byte[] initialHash;
 
     private Plaintext(Builder builder) {
         id = builder.id;
@@ -63,6 +65,7 @@ public class Plaintext implements Streamable {
     public static Plaintext read(Type type, InputStream in) throws IOException {
         return readWithoutSignature(type, in)
                 .signature(Decode.varBytes(in))
+                .received(UnixTime.now())
                 .build();
     }
 
@@ -131,6 +134,15 @@ public class Plaintext implements Streamable {
         this.signature = signature;
     }
 
+    public boolean isUnread() {
+        for (Label label : labels) {
+            if (label.getType() == Label.Type.UNREAD) {
+                return true;
+            }
+        }
+        return false;
+    }
+
     public void write(OutputStream out, boolean includeSignature) throws IOException {
         Encode.varInt(from.getVersion(), out);
         Encode.varInt(from.getStream(), out);
@@ -249,6 +261,14 @@ public class Plaintext implements Streamable {
         }
     }
 
+    public void setInitialHash(byte[] initialHash) {
+        this.initialHash = initialHash;
+    }
+
+    public byte[] getInitialHash() {
+        return initialHash;
+    }
+
     public enum Encoding {
         IGNORE(0), TRIVIAL(1), SIMPLE(2);
 

core/src/main/java/ch/dissem/bitmessage/entity/Streamable.java

@@ -18,10 +18,11 @@ package ch.dissem.bitmessage.entity;
 
 import java.io.IOException;
 import java.io.OutputStream;
+import java.io.Serializable;
 
 /**
  * An object that can be written to an {@link OutputStream}
  */
-public interface Streamable {
+public interface Streamable extends Serializable {
     void write(OutputStream stream) throws IOException;
 }

core/src/main/java/ch/dissem/bitmessage/entity/payload/Broadcast.java

@@ -21,11 +21,11 @@ import ch.dissem.bitmessage.entity.Encrypted;
 import ch.dissem.bitmessage.entity.Plaintext;
 import ch.dissem.bitmessage.entity.PlaintextHolder;
 import ch.dissem.bitmessage.exception.DecryptionFailedException;
-import ch.dissem.bitmessage.utils.Security;
 
 import java.io.IOException;
 
 import static ch.dissem.bitmessage.entity.Plaintext.Type.BROADCAST;
+import static ch.dissem.bitmessage.utils.Singleton.security;
 
 /**
  * Users who are subscribed to the sending address will see the message appear in their inbox.
@@ -78,7 +78,7 @@ public abstract class Broadcast extends ObjectPayload implements Encrypted, Plai
     }
 
     public void encrypt() throws IOException {
-        encrypt(Security.createPublicKey(plaintext.getFrom().getPublicDecryptionKey()).getEncoded(false));
+        encrypt(security().createPublicKey(plaintext.getFrom().getPublicDecryptionKey()));
     }
 
     @Override

core/src/main/java/ch/dissem/bitmessage/entity/payload/CryptoBox.java

@@ -17,28 +17,16 @@
 package ch.dissem.bitmessage.entity.payload;
 
 import ch.dissem.bitmessage.entity.Streamable;
-import ch.dissem.bitmessage.entity.valueobject.PrivateKey;
 import ch.dissem.bitmessage.exception.DecryptionFailedException;
 import ch.dissem.bitmessage.utils.*;
-import org.bouncycastle.crypto.BufferedBlockCipher;
-import org.bouncycastle.crypto.CipherParameters;
-import org.bouncycastle.crypto.InvalidCipherTextException;
-import org.bouncycastle.crypto.engines.AESEngine;
-import org.bouncycastle.crypto.modes.CBCBlockCipher;
-import org.bouncycastle.crypto.paddings.PKCS7Padding;
-import org.bouncycastle.crypto.paddings.PaddedBufferedBlockCipher;
-import org.bouncycastle.crypto.params.KeyParameter;
-import org.bouncycastle.crypto.params.ParametersWithIV;
-import org.bouncycastle.math.ec.ECFieldElement;
-import org.bouncycastle.math.ec.ECPoint;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.io.*;
-import java.math.BigInteger;
 import java.util.Arrays;
 
 import static ch.dissem.bitmessage.entity.valueobject.PrivateKey.PRIVATE_KEY_SIZE;
+import static ch.dissem.bitmessage.utils.Singleton.security;
 
 
 public class CryptoBox implements Streamable {
@@ -46,35 +34,38 @@ public class CryptoBox implements Streamable {
 
     private final byte[] initializationVector;
     private final int curveType;
-    private final ECPoint R;
+    private final byte[] R;
     private final byte[] mac;
     private byte[] encrypted;
 
-    public CryptoBox(Streamable data, byte[] encryptionKey) throws IOException {
+    private long addressVersion;
-        this(data, Security.keyToPoint(encryptionKey));
+
+
+    public CryptoBox(Streamable data, byte[] K) throws IOException {
+        this(Encode.bytes(data), K);
     }
 
-    public CryptoBox(Streamable data, ECPoint K) throws IOException {
+    public CryptoBox(byte[] data, byte[] K) throws IOException {
         curveType = 0x02CA;
 
         // 1. The destination public key is called K.
         // 2. Generate 16 random bytes using a secure random number generator. Call them IV.
-        initializationVector = Security.randomBytes(16);
+        initializationVector = security().randomBytes(16);
 
         // 3. Generate a new random EC key pair with private key called r and public key called R.
-        byte[] r = Security.randomBytes(PRIVATE_KEY_SIZE);
+        byte[] r = security().randomBytes(PRIVATE_KEY_SIZE);
-        R = Security.createPublicKey(r);
+        R = security().createPublicKey(r);
         // 4. Do an EC point multiply with public key K and private key r. This gives you public key P.
-        ECPoint P = K.multiply(Security.keyToBigInt(r)).normalize();
+        byte[] P = security().multiply(K, r);
-        byte[] X = P.getXCoord().getEncoded();
+        byte[] X = Points.getX(P);
         // 5. Use the X component of public key P and calculate the SHA512 hash H.
-        byte[] H = Security.sha512(X);
+        byte[] H = security().sha512(X);
         // 6. The first 32 bytes of H are called key_e and the last 32 bytes are called key_m.
         byte[] key_e = Arrays.copyOfRange(H, 0, 32);
         byte[] key_m = Arrays.copyOfRange(H, 32, 64);
         // 7. Pad the input text to a multiple of 16 bytes, in accordance to PKCS7.
         // 8. Encrypt the data with AES-256-CBC, using IV as initialization vector, key_e as encryption key and the padded input text as payload. Call the output cipher text.
-        encrypted = crypt(true, Encode.bytes(data), key_e);
+        encrypted = security().crypt(true, data, key_e, initializationVector);
         // 9. Calculate a 32 byte MAC with HMACSHA256, using key_m as salt and IV + R + cipher text as data. Call the output MAC.
         mac = calculateMac(key_m);
 
@@ -84,7 +75,7 @@ public class CryptoBox implements Streamable {
     private CryptoBox(Builder builder) {
         initializationVector = builder.initializationVector;
         curveType = builder.curveType;
-        R = Security.createPoint(builder.xComponent, builder.yComponent);
+        R = security().createPoint(builder.xComponent, builder.yComponent);
         encrypted = builder.encrypted;
         mac = builder.mac;
     }
@@ -102,18 +93,17 @@ public class CryptoBox implements Streamable {
     }
 
     /**
-     * @param privateKey a private key, typically should be 32 bytes long
+     * @param k a private key, typically should be 32 bytes long
      * @return an InputStream yielding the decrypted data
      * @throws DecryptionFailedException if the payload can't be decrypted using this private key
      * @see <a href='https://bitmessage.org/wiki/Encryption#Decryption'>https://bitmessage.org/wiki/Encryption#Decryption</a>
      */
-    public InputStream decrypt(byte[] privateKey) throws DecryptionFailedException {
+    public InputStream decrypt(byte[] k) throws DecryptionFailedException {
         // 1. The private key used to decrypt is called k.
-        BigInteger k = Security.keyToBigInt(privateKey);
         // 2. Do an EC point multiply with private key k and public key R. This gives you public key P.
-        ECPoint P = R.multiply(k).normalize();
+        byte[] P = security().multiply(R, k);
         // 3. Use the X component of public key P and calculate the SHA512 hash H.
-        byte[] H = Security.sha512(P.getXCoord().getEncoded());
+        byte[] H = security().sha512(Arrays.copyOfRange(P, 1, 33));
         // 4. The first 32 bytes of H are called key_e and the last 32 bytes are called key_m.
         byte[] key_e = Arrays.copyOfRange(H, 0, 32);
         byte[] key_m = Arrays.copyOfRange(H, 32, 64);
@@ -126,49 +116,28 @@ public class CryptoBox implements Streamable {
 
         // 7. Decrypt the cipher text with AES-256-CBC, using IV as initialization vector, key_e as decryption key
         //    and the cipher text as payload. The output is the padded input text.
-        return new ByteArrayInputStream(crypt(false, encrypted, key_e));
+        return new ByteArrayInputStream(security().crypt(false, encrypted, key_e, initializationVector));
     }
 
     private byte[] calculateMac(byte[] key_m) {
         try {
             ByteArrayOutputStream macData = new ByteArrayOutputStream();
             writeWithoutMAC(macData);
-            return Security.mac(key_m, macData.toByteArray());
+            return security().mac(key_m, macData.toByteArray());
         } catch (IOException e) {
             throw new RuntimeException(e);
         }
     }
 
-    private byte[] crypt(boolean encrypt, byte[] data, byte[] key_e) {
-        BufferedBlockCipher cipher = new PaddedBufferedBlockCipher(new CBCBlockCipher(new AESEngine()), new PKCS7Padding());
-
-        CipherParameters params = new ParametersWithIV(new KeyParameter(key_e), initializationVector);
-
-        cipher.init(encrypt, params);
-
-        byte[] buffer = new byte[cipher.getOutputSize(data.length)];
-        int length = cipher.processBytes(data, 0, data.length, buffer, 0);
-        try {
-            length += cipher.doFinal(buffer, length);
-        } catch (InvalidCipherTextException e) {
-            throw new IllegalArgumentException(e);
-        }
-        if (length < buffer.length) {
-            return Arrays.copyOfRange(buffer, 0, length);
-        }
-        return buffer;
-    }
-
     private void writeWithoutMAC(OutputStream out) throws IOException {
         out.write(initializationVector);
         Encode.int16(curveType, out);
-        writeCoordinateComponent(out, R.getXCoord());
+        writeCoordinateComponent(out, Points.getX(R));
-        writeCoordinateComponent(out, R.getYCoord());
+        writeCoordinateComponent(out, Points.getY(R));
         out.write(encrypted);
     }
 
-    private void writeCoordinateComponent(OutputStream out, ECFieldElement coord) throws IOException {
+    private void writeCoordinateComponent(OutputStream out, byte[] x) throws IOException {
-        byte[] x = coord.getEncoded();
         int offset = Bytes.numberOfLeadingZeros(x);
         int length = x.length - offset;
         Encode.int16(length, out);
@@ -195,7 +164,7 @@ public class CryptoBox implements Streamable {
         }
 
         public Builder curveType(int curveType) {
-            if (curveType != 0x2CA) LOG.debug("Unexpected curve type " + curveType);
+            if (curveType != 0x2CA) LOG.trace("Unexpected curve type " + curveType);
             this.curveType = curveType;
             return this;
         }

core/src/main/java/ch/dissem/bitmessage/entity/payload/ObjectPayload.java

@@ -21,6 +21,7 @@ import ch.dissem.bitmessage.entity.Streamable;
 
 import java.io.IOException;
 import java.io.OutputStream;
+import java.io.Serializable;
 
 /**
  * The payload of an 'object' command. This is shared by the network.

core/src/main/java/ch/dissem/bitmessage/entity/payload/Pubkey.java

@@ -20,8 +20,7 @@ import java.io.IOException;
 import java.io.OutputStream;
 import java.util.ArrayList;
 
-import static ch.dissem.bitmessage.utils.Security.ripemd160;
+import static ch.dissem.bitmessage.utils.Singleton.security;
-import static ch.dissem.bitmessage.utils.Security.sha512;
 
 /**
  * Public keys for signing and encryption, the answer to a 'getpubkey' request.
@@ -34,7 +33,7 @@ public abstract class Pubkey extends ObjectPayload {
     }
 
     public static byte[] getRipe(byte[] publicSigningKey, byte[] publicEncryptionKey) {
-        return ripemd160(sha512(publicSigningKey, publicEncryptionKey));
+        return security().ripemd160(security().sha512(publicSigningKey, publicEncryptionKey));
     }
 
     public abstract byte[] getSigningKey();
@@ -44,7 +43,7 @@ public abstract class Pubkey extends ObjectPayload {
     public abstract int getBehaviorBitfield();
 
     public byte[] getRipe() {
-        return ripemd160(sha512(getSigningKey(), getEncryptionKey()));
+        return security().ripemd160(security().sha512(getSigningKey(), getEncryptionKey()));
     }
 
     public long getNonceTrialsPerByte() {

core/src/main/java/ch/dissem/bitmessage/entity/valueobject/InventoryVector.java

@@ -21,9 +21,10 @@ import ch.dissem.bitmessage.utils.Strings;
 
 import java.io.IOException;
 import java.io.OutputStream;
+import java.io.Serializable;
 import java.util.Arrays;
 
-public class InventoryVector implements Streamable {
+public class InventoryVector implements Streamable, Serializable {
     /**
      * Hash of the object
      */
@@ -37,7 +38,6 @@ public class InventoryVector implements Streamable {
         InventoryVector that = (InventoryVector) o;
 
         return Arrays.equals(hash, that.hash);
-
     }
 
     @Override

core/src/main/java/ch/dissem/bitmessage/entity/valueobject/Label.java

@@ -16,9 +16,10 @@
 
 package ch.dissem.bitmessage.entity.valueobject;
 
+import java.io.Serializable;
 import java.util.Objects;
 
-public class Label {
+public class Label implements Serializable {
     private Object id;
     private String label;
     private Type type;

core/src/main/java/ch/dissem/bitmessage/entity/valueobject/PrivateKey.java

@@ -18,18 +18,18 @@ package ch.dissem.bitmessage.entity.valueobject;
 
 import ch.dissem.bitmessage.entity.Streamable;
 import ch.dissem.bitmessage.entity.payload.Pubkey;
-import ch.dissem.bitmessage.entity.payload.V3Pubkey;
-import ch.dissem.bitmessage.entity.payload.V4Pubkey;
 import ch.dissem.bitmessage.factory.Factory;
 import ch.dissem.bitmessage.utils.Bytes;
 import ch.dissem.bitmessage.utils.Decode;
 import ch.dissem.bitmessage.utils.Encode;
-import ch.dissem.bitmessage.utils.Security;
 
 import java.io.*;
 
+import static ch.dissem.bitmessage.utils.Singleton.security;
+
 /**
- * Created by chris on 18.04.15.
+ * Represents a private key. Additional information (stream, version, features, ...) is stored in the accompanying
+ * {@link Pubkey} object.
  */
 public class PrivateKey implements Streamable {
     public static final int PRIVATE_KEY_SIZE = 32;
@@ -45,15 +45,15 @@ public class PrivateKey implements Streamable {
         byte[] pubEK;
         byte[] ripe;
         do {
-            privSK = Security.randomBytes(PRIVATE_KEY_SIZE);
+            privSK = security().randomBytes(PRIVATE_KEY_SIZE);
-            privEK = Security.randomBytes(PRIVATE_KEY_SIZE);
+            privEK = security().randomBytes(PRIVATE_KEY_SIZE);
-            pubSK = Security.createPublicKey(privSK).getEncoded(false);
+            pubSK = security().createPublicKey(privSK);
-            pubEK = Security.createPublicKey(privEK).getEncoded(false);
+            pubEK = security().createPublicKey(privEK);
             ripe = Pubkey.getRipe(pubSK, pubEK);
         } while (ripe[0] != 0 || (shorter && ripe[1] != 0));
         this.privateSigningKey = privSK;
         this.privateEncryptionKey = privEK;
-        this.pubkey = Security.createPubkey(Pubkey.LATEST_VERSION, stream, privateSigningKey, privateEncryptionKey,
+        this.pubkey = security().createPubkey(Pubkey.LATEST_VERSION, stream, privateSigningKey, privateEncryptionKey,
                 nonceTrialsPerByte, extraBytes, features);
     }
 
@@ -66,9 +66,9 @@ public class PrivateKey implements Streamable {
     public PrivateKey(long version, long stream, String passphrase, long nonceTrialsPerByte, long extraBytes, Pubkey.Feature... features) {
         try {
             // FIXME: this is most definitely wrong
-            this.privateSigningKey = Bytes.truncate(Security.sha512(passphrase.getBytes("UTF-8"), new byte[]{0}), 32);
+            this.privateSigningKey = Bytes.truncate(security().sha512(passphrase.getBytes("UTF-8"), new byte[]{0}), 32);
-            this.privateEncryptionKey = Bytes.truncate(Security.sha512(passphrase.getBytes("UTF-8"), new byte[]{1}), 32);
+            this.privateEncryptionKey = Bytes.truncate(security().sha512(passphrase.getBytes("UTF-8"), new byte[]{1}), 32);
-            this.pubkey = Security.createPubkey(version, stream, privateSigningKey, privateEncryptionKey,
+            this.pubkey = security().createPubkey(version, stream, privateSigningKey, privateEncryptionKey,
                     nonceTrialsPerByte, extraBytes, features);
         } catch (UnsupportedEncodingException e) {
             throw new RuntimeException(e);

core/src/main/java/ch/dissem/bitmessage/factory/Factory.java

@@ -23,7 +23,6 @@ import ch.dissem.bitmessage.entity.Plaintext;
 import ch.dissem.bitmessage.entity.payload.*;
 import ch.dissem.bitmessage.entity.valueobject.PrivateKey;
 import ch.dissem.bitmessage.exception.NodeException;
-import ch.dissem.bitmessage.utils.Security;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -32,6 +31,8 @@ import java.io.InputStream;
 import java.net.SocketException;
 import java.net.SocketTimeoutException;
 
+import static ch.dissem.bitmessage.utils.Singleton.security;
+
 /**
  * Creates {@link NetworkMessage} objects from {@link InputStream InputStreams}
  */
@@ -115,8 +116,8 @@ public class Factory {
         BitmessageAddress temp = new BitmessageAddress(address);
         PrivateKey privateKey = new PrivateKey(privateSigningKey, privateEncryptionKey,
                 createPubkey(temp.getVersion(), temp.getStream(),
-                        Security.createPublicKey(privateSigningKey).getEncoded(false),
+                        security().createPublicKey(privateSigningKey),
-                        Security.createPublicKey(privateEncryptionKey).getEncoded(false),
+                        security().createPublicKey(privateEncryptionKey),
                         nonceTrialsPerByte, extraBytes, behaviourBitfield));
         BitmessageAddress result = new BitmessageAddress(privateKey);
         if (!result.getAddress().equals(address)) {
@@ -126,11 +127,17 @@ public class Factory {
         return result;
     }
 
-    public static BitmessageAddress generatePrivateAddress(boolean shorter, long stream, Pubkey.Feature... features) {
+    public static BitmessageAddress generatePrivateAddress(boolean shorter,
+                                                           long stream,
+                                                           Pubkey.Feature... features) {
         return new BitmessageAddress(new PrivateKey(shorter, stream, 1000, 1000, features));
     }
 
-    static ObjectPayload getObjectPayload(long objectType, long version, long streamNumber, InputStream stream, int length) throws IOException {
+    static ObjectPayload getObjectPayload(long objectType,
+                                          long version,
+                                          long streamNumber,
+                                          InputStream stream,
+                                          int length) throws IOException {
         ObjectType type = ObjectType.fromNumber(objectType);
         if (type != null) {
             switch (type) {
@@ -147,7 +154,7 @@ public class Factory {
             }
         }
         // fallback: just store the message - we don't really care what it is
-//        LOG.info("Unexpected object type: " + objectType);
+        LOG.trace("Unexpected object type: " + objectType);
         return GenericPayload.read(version, stream, streamNumber, length);
     }
 

core/src/main/java/ch/dissem/bitmessage/factory/V3MessageFactory.java

@@ -24,7 +24,6 @@ import ch.dissem.bitmessage.entity.valueobject.NetworkAddress;
 import ch.dissem.bitmessage.exception.NodeException;
 import ch.dissem.bitmessage.utils.AccessCounter;
 import ch.dissem.bitmessage.utils.Decode;
-import ch.dissem.bitmessage.utils.Security;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -33,6 +32,7 @@ import java.io.IOException;
 import java.io.InputStream;
 
 import static ch.dissem.bitmessage.entity.NetworkMessage.MAGIC_BYTES;
+import static ch.dissem.bitmessage.utils.Singleton.security;
 
 /**
  * Creates protocol v3 network messages from {@link InputStream InputStreams}
@@ -44,6 +44,9 @@ class V3MessageFactory {
         findMagic(in);
         String command = getCommand(in);
         int length = (int) Decode.uint32(in);
+        if (length > 1600003) {
+            throw new NodeException("Payload of " + length + " bytes received, no more than 1600003 was expected.");
+        }
         byte[] checksum = Decode.bytes(in, 4);
 
         byte[] payloadBytes = Decode.bytes(in, length);
@@ -73,12 +76,18 @@ class V3MessageFactory {
                 return parseGetData(stream);
             case "object":
                 return readObject(stream, length);
+            case "custom":
+                return readCustom(stream, length);
             default:
                 LOG.debug("Unknown command: " + command);
                 return null;
         }
     }
 
+    private static MessagePayload readCustom(InputStream in, int length) throws IOException {
+        return CustomMessage.read(in, length);
+    }
+
     public static ObjectMessage readObject(InputStream in, int length) throws IOException {
         AccessCounter counter = new AccessCounter();
         byte nonce[] = Decode.bytes(in, 8, counter);
@@ -92,7 +101,7 @@ class V3MessageFactory {
         try {
             ByteArrayInputStream dataStream = new ByteArrayInputStream(data);
             payload = Factory.getObjectPayload(objectType, version, stream, dataStream, data.length);
-        } catch (IOException e) {
+        } catch (Exception e) {
             LOG.trace("Could not parse object payload - using generic payload instead", e);
             payload = new GenericPayload(version, stream, data);
         }
@@ -174,7 +183,7 @@ class V3MessageFactory {
     }
 
     private static boolean testChecksum(byte[] checksum, byte[] payload) {
-        byte[] payloadChecksum = Security.sha512(payload);
+        byte[] payloadChecksum = security().sha512(payload);
         for (int i = 0; i < checksum.length; i++) {
             if (checksum[i] != payloadChecksum[i]) {
                 return false;
@@ -185,10 +194,10 @@ class V3MessageFactory {
 
     private static String getCommand(InputStream stream) throws IOException {
         byte[] bytes = new byte[12];
-        int end = -1;
+        int end = bytes.length;
         for (int i = 0; i < bytes.length; i++) {
             bytes[i] = (byte) stream.read();
-            if (end == -1) {
+            if (end == bytes.length) {
                 if (bytes[i] == 0) end = i;
             } else {
                 if (bytes[i] != 0) throw new IOException("'\\0' padding expected for command");

core/src/main/java/ch/dissem/bitmessage/ports/AbstractCryptography.java

@@ -0,0 +1,183 @@
+/*
+ * Copyright 2015 Christian Basler
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package ch.dissem.bitmessage.ports;
+
+import ch.dissem.bitmessage.InternalContext;
+import ch.dissem.bitmessage.entity.ObjectMessage;
+import ch.dissem.bitmessage.entity.payload.Pubkey;
+import ch.dissem.bitmessage.exception.InsufficientProofOfWorkException;
+import ch.dissem.bitmessage.factory.Factory;
+import ch.dissem.bitmessage.utils.Bytes;
+import ch.dissem.bitmessage.utils.UnixTime;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.crypto.Mac;
+import javax.crypto.spec.SecretKeySpec;
+import java.io.IOException;
+import java.math.BigInteger;
+import java.security.GeneralSecurityException;
+import java.security.MessageDigest;
+import java.security.SecureRandom;
+
+import static ch.dissem.bitmessage.utils.Numbers.max;
+
+/**
+ * Implements everything that isn't directly dependent on either Spongy- or Bouncycastle.
+ */
+public abstract class AbstractCryptography implements Cryptography, InternalContext.ContextHolder {
+    public static final Logger LOG = LoggerFactory.getLogger(Cryptography.class);
+    private static final SecureRandom RANDOM = new SecureRandom();
+    private static final BigInteger TWO = BigInteger.valueOf(2);
+    private static final BigInteger TWO_POW_64 = TWO.pow(64);
+    private static final BigInteger TWO_POW_16 = TWO.pow(16);
+
+    private final String provider;
+    private InternalContext context;
+
+    protected AbstractCryptography(String provider) {
+        this.provider = provider;
+    }
+
+    @Override
+    public void setContext(InternalContext context) {
+        this.context = context;
+    }
+
+    public byte[] sha512(byte[]... data) {
+        return hash("SHA-512", data);
+    }
+
+    public byte[] doubleSha512(byte[]... data) {
+        MessageDigest mda = md("SHA-512");
+        for (byte[] d : data) {
+            mda.update(d);
+        }
+        return mda.digest(mda.digest());
+    }
+
+    public byte[] doubleSha512(byte[] data, int length) {
+        MessageDigest mda = md("SHA-512");
+        mda.update(data, 0, length);
+        return mda.digest(mda.digest());
+    }
+
+    public byte[] ripemd160(byte[]... data) {
+        return hash("RIPEMD160", data);
+    }
+
+    public byte[] doubleSha256(byte[] data, int length) {
+        MessageDigest mda = md("SHA-256");
+        mda.update(data, 0, length);
+        return mda.digest(mda.digest());
+    }
+
+    public byte[] sha1(byte[]... data) {
+        return hash("SHA-1", data);
+    }
+
+    public byte[] randomBytes(int length) {
+        byte[] result = new byte[length];
+        RANDOM.nextBytes(result);
+        return result;
+    }
+
+    public void doProofOfWork(ObjectMessage object, long nonceTrialsPerByte,
+                              long extraBytes, ProofOfWorkEngine.Callback callback) {
+        nonceTrialsPerByte = max(nonceTrialsPerByte, context.getNetworkNonceTrialsPerByte());
+        extraBytes = max(extraBytes, context.getNetworkExtraBytes());
+
+        byte[] initialHash = getInitialHash(object);
+
+        byte[] target = getProofOfWorkTarget(object, nonceTrialsPerByte, extraBytes);
+
+        context.getProofOfWorkEngine().calculateNonce(initialHash, target, callback);
+    }
+
+    public void checkProofOfWork(ObjectMessage object, long nonceTrialsPerByte, long extraBytes)
+            throws IOException {
+        byte[] target = getProofOfWorkTarget(object, nonceTrialsPerByte, extraBytes);
+        byte[] value = doubleSha512(object.getNonce(), getInitialHash(object));
+        if (Bytes.lt(target, value, 8)) {
+            throw new InsufficientProofOfWorkException(target, value);
+        }
+    }
+
+    @Override
+    public byte[] getInitialHash(ObjectMessage object) {
+        return sha512(object.getPayloadBytesWithoutNonce());
+    }
+
+    @Override
+    public byte[] getProofOfWorkTarget(ObjectMessage object, long nonceTrialsPerByte, long extraBytes) {
+        if (nonceTrialsPerByte == 0) nonceTrialsPerByte = context.getNetworkNonceTrialsPerByte();
+        if (extraBytes == 0) extraBytes = context.getNetworkExtraBytes();
+
+        BigInteger TTL = BigInteger.valueOf(object.getExpiresTime() - UnixTime.now());
+        BigInteger numerator = TWO_POW_64;
+        BigInteger powLength = BigInteger.valueOf(object.getPayloadBytesWithoutNonce().length + extraBytes);
+        BigInteger denominator = BigInteger.valueOf(nonceTrialsPerByte)
+                .multiply(
+                        powLength.add(
+                                powLength.multiply(TTL).divide(TWO_POW_16)
+                        )
+                );
+        return Bytes.expand(numerator.divide(denominator).toByteArray(), 8);
+    }
+
+    private byte[] hash(String algorithm, byte[]... data) {
+        MessageDigest mda = md(algorithm);
+        for (byte[] d : data) {
+            mda.update(d);
+        }
+        return mda.digest();
+    }
+
+    private MessageDigest md(String algorithm) {
+        try {
+            return MessageDigest.getInstance(algorithm, provider);
+        } catch (GeneralSecurityException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    public byte[] mac(byte[] key_m, byte[] data) {
+        try {
+            Mac mac = Mac.getInstance("HmacSHA256", provider);
+            mac.init(new SecretKeySpec(key_m, "HmacSHA256"));
+            return mac.doFinal(data);
+        } catch (GeneralSecurityException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    public Pubkey createPubkey(long version, long stream, byte[] privateSigningKey, byte[] privateEncryptionKey,
+                               long nonceTrialsPerByte, long extraBytes, Pubkey.Feature... features) {
+        return Factory.createPubkey(version, stream,
+                createPublicKey(privateSigningKey),
+                createPublicKey(privateEncryptionKey),
+                nonceTrialsPerByte, extraBytes, features);
+    }
+
+    public BigInteger keyToBigInt(byte[] privateKey) {
+        return new BigInteger(1, privateKey);
+    }
+
+    public long randomNonce() {
+        return RANDOM.nextLong();
+    }
+}

core/src/main/java/ch/dissem/bitmessage/ports/Cryptography.java

@@ -0,0 +1,210 @@
+/*
+ * Copyright 2015 Christian Basler
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License. 
+ */
+
+package ch.dissem.bitmessage.ports;
+
+import ch.dissem.bitmessage.entity.ObjectMessage;
+import ch.dissem.bitmessage.entity.payload.Pubkey;
+import ch.dissem.bitmessage.exception.InsufficientProofOfWorkException;
+
+import java.io.IOException;
+import java.math.BigInteger;
+import java.security.MessageDigest;
+import java.security.SecureRandom;
+
+/**
+ * Provides some methods to help with hashing and encryption. All randoms are created using {@link SecureRandom},
+ * which should be secure enough.
+ */
+public interface Cryptography {
+    /**
+     * A helper method to calculate SHA-512 hashes. Please note that a new {@link MessageDigest} object is created at
+     * each call (to ensure thread safety), so you shouldn't use this if you need to do many hash calculations in
+     * success on the same thread.
+     *
+     * @param data to get hashed
+     * @return SHA-512 hash of data
+     */
+    byte[] sha512(byte[]... data);
+
+    /**
+     * A helper method to calculate doubleSHA-512 hashes. Please note that a new {@link MessageDigest} object is created
+     * at each call (to ensure thread safety), so you shouldn't use this if you need to do many hash calculations in
+     * success on the same thread.
+     *
+     * @param data to get hashed
+     * @return SHA-512 hash of data
+     */
+    byte[] doubleSha512(byte[]... data);
+
+    /**
+     * A helper method to calculate double SHA-512 hashes. This method allows to only use a part of the available bytes
+     * to use for the hash calculation.
+     * <p>
+     * Please note that a new {@link MessageDigest} object is created at each call (to ensure thread safety), so you
+     * shouldn't use this if you need to do many hash calculations in short order on the same thread.
+     * </p>
+     *
+     * @param data   to get hashed
+     * @param length number of bytes to be taken into account
+     * @return SHA-512 hash of data
+     */
+    byte[] doubleSha512(byte[] data, int length);
+
+    /**
+     * A helper method to calculate RIPEMD-160 hashes. Supplying multiple byte arrays has the same result as a
+     * concatenation of all arrays, but might perform better.
+     * <p>
+     * Please note that a new {@link MessageDigest} object is created at
+     * each call (to ensure thread safety), so you shouldn't use this if you need to do many hash calculations in short
+     * order on the same thread.
+     * </p>
+     *
+     * @param data to get hashed
+     * @return RIPEMD-160 hash of data
+     */
+    byte[] ripemd160(byte[]... data);
+
+    /**
+     * A helper method to calculate double SHA-256 hashes. This method allows to only use a part of the available bytes
+     * to use for the hash calculation.
+     * <p>
+     * Please note that a new {@link MessageDigest} object is created at
+     * each call (to ensure thread safety), so you shouldn't use this if you need to do many hash calculations in short
+     * order on the same thread.
+     * </p>
+     *
+     * @param data   to get hashed
+     * @param length number of bytes to be taken into account
+     * @return SHA-256 hash of data
+     */
+    byte[] doubleSha256(byte[] data, int length);
+
+    /**
+     * A helper method to calculate SHA-1 hashes. Supplying multiple byte arrays has the same result as a
+     * concatenation of all arrays, but might perform better.
+     * <p>
+     * Please note that a new {@link MessageDigest} object is created at
+     * each call (to ensure thread safety), so you shouldn't use this if you need to do many hash calculations in short
+     * order on the same thread.
+     * </p>
+     *
+     * @param data to get hashed
+     * @return SHA hash of data
+     */
+    byte[] sha1(byte[]... data);
+
+    /**
+     * @param length number of bytes to return
+     * @return an array of the given size containing random bytes
+     */
+    byte[] randomBytes(int length);
+
+    /**
+     * Calculates the proof of work. This might take a long time, depending on the hardware, message size and time to
+     * live.
+     *
+     * @param object             to do the proof of work for
+     * @param nonceTrialsPerByte difficulty
+     * @param extraBytes         bytes to add to the object size (makes it more difficult to send small messages)
+     * @param callback           to handle nonce once it's calculated
+     */
+    void doProofOfWork(ObjectMessage object, long nonceTrialsPerByte,
+                       long extraBytes, ProofOfWorkEngine.Callback callback);
+
+    /**
+     * @param object             to be checked
+     * @param nonceTrialsPerByte difficulty
+     * @param extraBytes         bytes to add to the object size
+     * @throws InsufficientProofOfWorkException if proof of work doesn't check out (makes it more difficult to send small messages)
+     */
+    void checkProofOfWork(ObjectMessage object, long nonceTrialsPerByte, long extraBytes)
+            throws IOException;
+
+    byte[] getInitialHash(ObjectMessage object);
+
+    byte[] getProofOfWorkTarget(ObjectMessage object, long nonceTrialsPerByte, long extraBytes);
+
+    /**
+     * Calculates the MAC for a message (data)
+     *
+     * @param key_m the symmetric key used
+     * @param data  the message data to calculate the MAC for
+     * @return the MAC
+     */
+    byte[] mac(byte[] key_m, byte[] data);
+
+    /**
+     * @param encrypt if true, encrypts data, otherwise tries to decrypt it.
+     * @param data
+     * @param key_e
+     * @return
+     */
+    byte[] crypt(boolean encrypt, byte[] data, byte[] key_e, byte[] initializationVector);
+
+    /**
+     * Create a new public key fom given private keys.
+     *
+     * @param version              of the public key / address
+     * @param stream               of the address
+     * @param privateSigningKey    private key used for signing
+     * @param privateEncryptionKey private key used for encryption
+     * @param nonceTrialsPerByte   proof of work difficulty
+     * @param extraBytes           bytes to add for the proof of work (make it harder for small messages)
+     * @param features             of the address
+     * @return a public key object
+     */
+    Pubkey createPubkey(long version, long stream, byte[] privateSigningKey, byte[] privateEncryptionKey,
+                        long nonceTrialsPerByte, long extraBytes, Pubkey.Feature... features);
+
+    /**
+     * @param privateKey private key as byte array
+     * @return a public key corresponding to the given private key
+     */
+    byte[] createPublicKey(byte[] privateKey);
+
+    /**
+     * @param privateKey private key as byte array
+     * @return a big integer representation (unsigned) of the given bytes
+     */
+    BigInteger keyToBigInt(byte[] privateKey);
+
+    /**
+     * @param data      to check
+     * @param signature the signature of the message
+     * @param pubkey    the sender's public key
+     * @return true if the signature is valid, false otherwise
+     */
+    boolean isSignatureValid(byte[] data, byte[] signature, Pubkey pubkey);
+
+    /**
+     * Calculate the signature of data, using the given private key.
+     *
+     * @param data       to be signed
+     * @param privateKey to be used for signing
+     * @return the signature
+     */
+    byte[] getSignature(byte[] data, ch.dissem.bitmessage.entity.valueobject.PrivateKey privateKey);
+
+    /**
+     * @return a random number of type long
+     */
+    long randomNonce();
+
+    byte[] multiply(byte[] k, byte[] r);
+
+    byte[] createPoint(byte[] x, byte[] y);
+}

core/src/main/java/ch/dissem/bitmessage/ports/CustomCommandHandler.java

@@ -16,25 +16,12 @@
 
 package ch.dissem.bitmessage.ports;
 
-import ch.dissem.bitmessage.entity.ObjectMessage;
+import ch.dissem.bitmessage.entity.CustomMessage;
-import ch.dissem.bitmessage.entity.valueobject.InventoryVector;
+import ch.dissem.bitmessage.entity.MessagePayload;
-import ch.dissem.bitmessage.utils.Property;
-
-import java.io.IOException;
 
 /**
- * Handles incoming messages
+ * @author Christian Basler
  */
-public interface NetworkHandler {
+public interface CustomCommandHandler {
-    void start(MessageListener listener);
+    MessagePayload handle(CustomMessage request);
-
-    void stop();
-
-    void offer(InventoryVector iv);
-
-    Property getNetworkStatus();
-
-    interface MessageListener {
-        void receive(ObjectMessage object) throws IOException;
-    }
 }

core/src/main/java/ch/dissem/bitmessage/ports/Inventory.java

@@ -26,15 +26,32 @@ import java.util.List;
  * The Inventory stores and retrieves objects, cleans up outdated objects and can tell which objects are still missing.
  */
 public interface Inventory {
+    /**
+     * Returns the IVs of all valid objects we have for the given streams
+     */
     List<InventoryVector> getInventory(long... streams);
 
+    /**
+     * Returns the IVs of all objects in the offer that we don't have already. Implementations are allowed to
+     * ignore the streams parameter, but it must be set when calling this method.
+     */
     List<InventoryVector> getMissing(List<InventoryVector> offer, long... streams);
 
     ObjectMessage getObject(InventoryVector vector);
 
+    /**
+     * This method is mainly used to search for public keys to newly added addresses or broadcasts from new
+     * subscriptions.
+     */
     List<ObjectMessage> getObjects(long stream, long version, ObjectType... types);
 
     void storeObject(ObjectMessage object);
 
+    boolean contains(ObjectMessage object);
+
+    /**
+     * Deletes all objects that expired 5 minutes ago or earlier
+     * (so we don't accidentally request objects we just deleted)
+     */
     void cleanup();
 }

core/src/main/java/ch/dissem/bitmessage/ports/MemoryNodeRegistry.java

@@ -14,10 +14,9 @@
  * limitations under the License.
  */
 
-package ch.dissem.bitmessage.repository;
+package ch.dissem.bitmessage.ports;
 
 import ch.dissem.bitmessage.entity.valueobject.NetworkAddress;
-import ch.dissem.bitmessage.ports.NodeRegistry;
 import ch.dissem.bitmessage.utils.UnixTime;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -35,10 +34,10 @@ import static java.util.Collections.newSetFromMap;
 public class MemoryNodeRegistry implements NodeRegistry {
     private static final Logger LOG = LoggerFactory.getLogger(MemoryNodeRegistry.class);
 
-    private final Map<Long, Set<NetworkAddress>> stableNodes = new HashMap<>();
+    private final Map<Long, Set<NetworkAddress>> stableNodes = new ConcurrentHashMap<>();
     private final Map<Long, Set<NetworkAddress>> knownNodes = new ConcurrentHashMap<>();
 
-    public MemoryNodeRegistry() {
+    private void loadStableNodes() {
         try (InputStream in = getClass().getClassLoader().getResourceAsStream("nodes.txt")) {
             Scanner scanner = new Scanner(in);
             long stream = 0;
@@ -56,14 +55,21 @@ public class MemoryNodeRegistry implements NodeRegistry {
                         stableNodes.put(stream, streamSet);
                     } else if (streamSet != null) {
                         int portIndex = line.lastIndexOf(':');
-                        InetAddress inetAddress = InetAddress.getByName(line.substring(0, portIndex));
+                        InetAddress[] inetAddresses = InetAddress.getAllByName(line.substring(0, portIndex));
                         int port = Integer.valueOf(line.substring(portIndex + 1));
-                        streamSet.add(new NetworkAddress.Builder().ip(inetAddress).port(port).stream(stream).build());
+                        for (InetAddress inetAddress : inetAddresses) {
+                            streamSet.add(new NetworkAddress.Builder().ip(inetAddress).port(port).stream(stream).build());
+                        }
                     }
                 } catch (IOException e) {
                     LOG.warn(e.getMessage(), e);
                 }
             }
+            if (LOG.isDebugEnabled()) {
+                for (Map.Entry<Long, Set<NetworkAddress>> e : stableNodes.entrySet()) {
+                    LOG.debug("Stream " + e.getKey() + ": loaded " + e.getValue().size() + " bootstrap nodes.");
+                }
+            }
         } catch (IOException e) {
             throw new RuntimeException(e);
         }
@@ -82,9 +88,16 @@ public class MemoryNodeRegistry implements NodeRegistry {
                         known.remove(node);
                     }
                 }
-            } else if (stableNodes.containsKey(stream)) {
+            } else {
-                // To reduce load on stable nodes, only return one
+                Set<NetworkAddress> nodes = stableNodes.get(stream);
-                result.add(selectRandom(stableNodes.get(stream)));
+                if (nodes == null || nodes.isEmpty()) {
+                    loadStableNodes();
+                    nodes = stableNodes.get(stream);
+                }
+                if (nodes != null && !nodes.isEmpty()) {
+                    // To reduce load on stable nodes, only return one
+                    result.add(selectRandom(nodes));
+                }
             }
         }
         return selectRandom(limit, result);

core/src/main/java/ch/dissem/bitmessage/ports/MessageRepository.java

@@ -28,12 +28,18 @@ public interface MessageRepository {
 
     List<Label> getLabels(Label.Type... types);
 
+    int countUnread(Label label);
+
+    Plaintext getMessage(byte[] initialHash);
+
     List<Plaintext> findMessages(Label label);
 
     List<Plaintext> findMessages(Status status);
 
     List<Plaintext> findMessages(Status status, BitmessageAddress recipient);
 
+    List<Plaintext> findMessages(BitmessageAddress sender);
+
     void save(Plaintext message);
 
     void remove(Plaintext message);

core/src/main/java/ch/dissem/bitmessage/ports/MultiThreadedPOWEngine.java

@@ -24,6 +24,7 @@ import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.concurrent.Semaphore;
 
 import static ch.dissem.bitmessage.utils.Bytes.inc;
 
@@ -31,46 +32,53 @@ import static ch.dissem.bitmessage.utils.Bytes.inc;
  * A POW engine using all available CPU cores.
  */
 public class MultiThreadedPOWEngine implements ProofOfWorkEngine {
-    private static Logger LOG = LoggerFactory.getLogger(MultiThreadedPOWEngine.class);
+    private static final Logger LOG = LoggerFactory.getLogger(MultiThreadedPOWEngine.class);
+    private static final Semaphore semaphore = new Semaphore(1, true);
 
+    /**
+     * This method will block until all pending nonce calculations are done, but not wait for its own calculation
+     * to finish.
+     * (This implementation becomes very inefficient if multiple nonce are calculated at the same time.)
+     *
+     * @param initialHash the SHA-512 hash of the object to send, sans nonce
+     * @param target      the target, representing an unsigned long
+     * @param callback    called with the calculated nonce as argument. The ProofOfWorkEngine implementation must make
+     */
     @Override
-    public byte[] calculateNonce(byte[] initialHash, byte[] target) {
+    public void calculateNonce(byte[] initialHash, byte[] target, Callback callback) {
+        try {
+            semaphore.acquire();
+        } catch (InterruptedException e) {
+            throw new RuntimeException(e);
+        }
+        callback = new CallbackWrapper(callback);
         int cores = Runtime.getRuntime().availableProcessors();
         if (cores > 255) cores = 255;
         LOG.info("Doing POW using " + cores + " cores");
-        long time = System.currentTimeMillis();
         List<Worker> workers = new ArrayList<>(cores);
         for (int i = 0; i < cores; i++) {
-            Worker w = new Worker(workers, (byte) cores, i, initialHash, target);
+            Worker w = new Worker(workers, (byte) cores, i, initialHash, target, callback);
             workers.add(w);
         }
         for (Worker w : workers) {
+            // Doing this in the previous loop might cause a ConcurrentModificationException in the worker
+            // if a worker finds a nonce while new ones are still being added.
             w.start();
         }
-        for (Worker w : workers) {
-            try {
-                w.join();
-            } catch (InterruptedException e) {
-                throw new RuntimeException(e);
-            }
-            if (w.isSuccessful()) {
-                LOG.info("Nonce calculated in " + ((System.currentTimeMillis() - time) / 1000) + " seconds");
-                return w.getNonce();
-            }
-        }
-        throw new RuntimeException("All workers ended without yielding a nonce - something is seriously broken!");
     }
 
     private static class Worker extends Thread {
+        private final Callback callback;
         private final byte numberOfCores;
         private final List<Worker> workers;
         private final byte[] initialHash;
         private final byte[] target;
         private final MessageDigest mda;
         private final byte[] nonce = new byte[8];
-        private boolean successful = false;
 
-        public Worker(List<Worker> workers, byte numberOfCores, int core, byte[] initialHash, byte[] target) {
+        public Worker(List<Worker> workers, byte numberOfCores, int core, byte[] initialHash, byte[] target,
+                      Callback callback) {
+            this.callback = callback;
             this.numberOfCores = numberOfCores;
             this.workers = workers;
             this.initialHash = initialHash;
@@ -84,14 +92,6 @@ public class MultiThreadedPOWEngine implements ProofOfWorkEngine {
             }
         }
 
-        public boolean isSuccessful() {
-            return successful;
-        }
-
-        public byte[] getNonce() {
-            return nonce;
-        }
-
         @Override
         public void run() {
             do {
@@ -99,13 +99,43 @@ public class MultiThreadedPOWEngine implements ProofOfWorkEngine {
                 mda.update(nonce);
                 mda.update(initialHash);
                 if (!Bytes.lt(target, mda.digest(mda.digest()), 8)) {
-                    successful = true;
+                    synchronized (callback) {
-                    for (Worker w : workers) {
+                        if (!Thread.interrupted()) {
-                        w.interrupt();
+                            for (Worker w : workers) {
+                                w.interrupt();
+                            }
+                            // Clear interrupted flag for callback
+                            Thread.interrupted();
+                            callback.onNonceCalculated(initialHash, nonce);
+                        }
                     }
                     return;
                 }
             } while (!Thread.interrupted());
         }
     }
+
+    public static class CallbackWrapper implements Callback {
+        private final Callback callback;
+        private final long startTime;
+        private boolean waiting = true;
+
+        public CallbackWrapper(Callback callback) {
+            this.startTime = System.currentTimeMillis();
+            this.callback = callback;
+        }
+
+        @Override
+        public void onNonceCalculated(byte[] initialHash, byte[] nonce) {
+            // Prevents the callback from being called twice if two nonces are found simultaneously
+            synchronized (this) {
+                if (waiting) {
+                    semaphore.release();
+                    LOG.info("Nonce calculated in " + ((System.currentTimeMillis() - startTime) / 1000) + " seconds");
+                    waiting = false;
+                    callback.onNonceCalculated(initialHash, nonce);
+                }
+            }
+        }
+    }
 }

core/src/main/java/ch/dissem/bitmessage/ports/NetworkHandler.java

@@ -0,0 +1,73 @@
+/*
+ * Copyright 2015 Christian Basler
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package ch.dissem.bitmessage.ports;
+
+import ch.dissem.bitmessage.entity.CustomMessage;
+import ch.dissem.bitmessage.entity.ObjectMessage;
+import ch.dissem.bitmessage.entity.valueobject.InventoryVector;
+import ch.dissem.bitmessage.utils.Property;
+
+import java.io.IOException;
+import java.net.InetAddress;
+import java.util.concurrent.Future;
+
+/**
+ * Handles incoming messages
+ */
+public interface NetworkHandler {
+    /**
+     * Connects to the trusted host, fetches and offers new messages and disconnects afterwards.
+     * <p>
+     * An implementation should disconnect if either the timeout is reached or the returned thread is interrupted.
+     * </p>
+     */
+    Future<?> synchronize(InetAddress server, int port, MessageListener listener, long timeoutInSeconds);
+
+    /**
+     * Send a custom message to a specific node (that should implement handling for this message type) and returns
+     * the response, which in turn is expected to be a {@link CustomMessage}.
+     *
+     * @param server  the node's address
+     * @param port    the node's port
+     * @param request the request
+     * @return the response
+     */
+    CustomMessage send(InetAddress server, int port, CustomMessage request);
+
+    /**
+     * Start a full network node, accepting incoming connections and relaying objects.
+     */
+    void start(MessageListener listener);
+
+    /**
+     * Stop the full network node.
+     */
+    void stop();
+
+    /**
+     * Offer new objects to up to 8 random nodes.
+     */
+    void offer(InventoryVector iv);
+
+    Property getNetworkStatus();
+
+    boolean isRunning();
+
+    interface MessageListener {
+        void receive(ObjectMessage object) throws IOException;
+    }
+}

core/src/main/java/ch/dissem/bitmessage/ports/ProofOfWorkEngine.java

@@ -24,9 +24,17 @@ public interface ProofOfWorkEngine {
      * Returns a nonce, such that the first 8 bytes from sha512(sha512(nonce||initialHash)) represent a unsigned long
      * smaller than target.
      *
-     * @param initialHash        the SHA-512 hash of the object to send, sans nonce
+     * @param initialHash the SHA-512 hash of the object to send, sans nonce
-     * @param target             the target, representing an unsigned long
+     * @param target      the target, representing an unsigned long
-     * @return 8 bytes nonce
+     * @param callback    called with the calculated nonce as argument. The ProofOfWorkEngine implementation must make
+     *                    sure this is only called once.
      */
-    byte[] calculateNonce(byte[] initialHash, byte[] target);
+    void calculateNonce(byte[] initialHash, byte[] target, Callback callback);
+
+    interface Callback {
+        /**
+         * @param nonce 8 bytes nonce
+         */
+        void onNonceCalculated(byte[] initialHash, byte[] nonce);
+    }
 }

core/src/main/java/ch/dissem/bitmessage/ports/ProofOfWorkRepository.java

@@ -0,0 +1,32 @@
+package ch.dissem.bitmessage.ports;
+
+import ch.dissem.bitmessage.entity.ObjectMessage;
+
+import java.util.List;
+
+/**
+ * Objects that proof of work is currently being done for.
+ *
+ * @author Christian Basler
+ */
+public interface ProofOfWorkRepository {
+    Item getItem(byte[] initialHash);
+
+    List<byte[]> getItems();
+
+    void putObject(ObjectMessage object, long nonceTrialsPerByte, long extraBytes);
+
+    void removeObject(byte[] initialHash);
+
+    class Item {
+        public final ObjectMessage object;
+        public final long nonceTrialsPerByte;
+        public final long extraBytes;
+
+        public Item(ObjectMessage object, long nonceTrialsPerByte, long extraBytes) {
+            this.object = object;
+            this.nonceTrialsPerByte = nonceTrialsPerByte;
+            this.extraBytes = extraBytes;
+        }
+    }
+}

core/src/main/java/ch/dissem/bitmessage/ports/SimplePOWEngine.java

@@ -23,11 +23,15 @@ import java.security.MessageDigest;
 import static ch.dissem.bitmessage.utils.Bytes.inc;
 
 /**
- * Created by chris on 14.04.15.
+ * You should really use the MultiThreadedPOWEngine, but this one might help you grok the other one.
+ * <p>
+ * <strong>Warning:</strong> implementations probably depend on POW being asynchronous, that's
+ * another reason not to use this one.
+ * </p>
  */
 public class SimplePOWEngine implements ProofOfWorkEngine {
     @Override
-    public byte[] calculateNonce(byte[] initialHash, byte[] target) {
+    public void calculateNonce(byte[] initialHash, byte[] target, Callback callback) {
         byte[] nonce = new byte[8];
         MessageDigest mda;
         try {
@@ -40,6 +44,6 @@ public class SimplePOWEngine implements ProofOfWorkEngine {
             mda.update(nonce);
             mda.update(initialHash);
         } while (Bytes.lt(target, mda.digest(mda.digest()), 8));
-        return nonce;
+        callback.onNonceCalculated(initialHash, nonce);
     }
 }

core/src/main/java/ch/dissem/bitmessage/utils/Bytes.java

@@ -16,12 +16,6 @@
 
 package ch.dissem.bitmessage.utils;
 
-import ch.dissem.bitmessage.entity.Streamable;
-
-import java.io.ByteArrayOutputStream;
-import java.io.IOException;
-import java.util.Arrays;
-
 /**
  * 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
@@ -91,6 +85,8 @@ public class Bytes {
         if (a < 0) return b < 0 && a < b;
         if (b < 0) return a >= 0 || a < b;
         return a < b;
+        // This would be easier to understand, but is (slightly) slower:
+        // return (a & 0xff) < (b & 0xff);
     }
 
     /**

core/src/main/java/ch/dissem/bitmessage/utils/CallbackWaiter.java

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2015 Christian Basler
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package ch.dissem.bitmessage.utils;
+
+/**
+ * Waits for a value within a callback method to be set.
+ */
+public class CallbackWaiter<T> {
+    private final long startTime = System.currentTimeMillis();
+    private volatile boolean isSet;
+    private T value;
+    private long time;
+
+    public void setValue(T value) {
+        synchronized (this) {
+            this.time = System.currentTimeMillis() - startTime;
+            this.value = value;
+            this.isSet = true;
+        }
+    }
+
+    public T waitForValue() throws InterruptedException {
+        while (!isSet) {
+            Thread.sleep(100);
+        }
+        synchronized (this) {
+            return value;
+        }
+    }
+
+    public long getTime() {
+        return time;
+    }
+}

core/src/main/java/ch/dissem/bitmessage/utils/Decode.java

@@ -130,9 +130,13 @@ public class Decode {
     }
 
     public static String varString(InputStream stream) throws IOException {
-        int length = (int) varInt(stream);
+        return varString(stream, null);
+    }
+
+    public static String varString(InputStream stream, AccessCounter counter) throws IOException {
+        int length = (int) varInt(stream, counter);
         // FIXME: technically, it says the length in characters, but I think this one might be correct
         // otherwise it will get complicated, as we'll need to read UTF-8 char by char...
-        return new String(bytes(stream, length), "utf-8");
+        return new String(bytes(stream, length, counter), "utf-8");
     }
 }

core/src/main/java/ch/dissem/bitmessage/utils/Encode.java

@@ -103,20 +103,30 @@ public class Encode {
         inc(counter, 8);
     }
 
-    public static void varString(String value, OutputStream stream) throws IOException {
+    public static void varString(String value, OutputStream out) throws IOException {
         byte[] bytes = value.getBytes("utf-8");
-        // FIXME: technically, it says the length in characters, but I think this one might be correct
+        // Technically, it says the length in characters, but I think this one might be correct.
+        // It doesn't really matter, as only ASCII characters are being used.
         // see also Decode#varString()
-        varInt(bytes.length, stream);
+        varInt(bytes.length, out);
-        stream.write(bytes);
+        out.write(bytes);
+    }
+
+    public static void varBytes(byte[] data, OutputStream out) throws IOException {
+        varInt(data.length, out);
+        out.write(data);
     }
 
     /**
+     * Serializes a {@link Streamable} object and returns the byte array.
+     *
      * @param streamable the object to be serialized
      * @return an array of bytes representing the given streamable object.
      * @throws IOException if an I/O error occurs.
      */
     public static byte[] bytes(Streamable streamable) throws IOException {
+        if (streamable == null) return null;
+
         ByteArrayOutputStream stream = new ByteArrayOutputStream();
         streamable.write(stream);
         return stream.toByteArray();

core/src/main/java/ch/dissem/bitmessage/utils/Numbers.java

@@ -0,0 +1,10 @@
+package ch.dissem.bitmessage.utils;
+
+/**
+ * Created by chrig on 07.12.2015.
+ */
+public class Numbers {
+    public static long max(long a, long b) {
+        return a > b ? a : b;
+    }
+}

core/src/main/java/ch/dissem/bitmessage/utils/Points.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2015 Christian Basler
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package ch.dissem.bitmessage.utils;
+
+import java.util.Arrays;
+
+/**
+ * Created by chris on 20.07.15.
+ */
+public class Points {
+    public static byte[] getX(byte[] P) {
+        return Arrays.copyOfRange(P, 1, ((P.length - 1) / 2) + 1);
+    }
+
+    public static byte[] getY(byte[] P) {
+        return Arrays.copyOfRange(P, ((P.length - 1) / 2) + 1, P.length);
+    }
+}

core/src/main/java/ch/dissem/bitmessage/utils/Property.java

@@ -16,8 +16,16 @@
 
 package ch.dissem.bitmessage.utils;
 
+import java.util.Arrays;
+import java.util.Objects;
+
 /**
- * Created by chris on 14.06.15.
+ * Some property that has a name, a value and/or other properties. This can be used for any purpose, but is for now
+ * used to contain different status information. It is by default displayed in some JSON inspired human readable
+ * notation, but you might only want to rely on the 'human readable' part.
+ * <p>
+ * If you need a real JSON representation, please add a method <code>toJson()</code>.
+ * </p>
  */
 public class Property {
     private String name;
@@ -30,6 +38,36 @@ public class Property {
         this.properties = properties;
     }
 
+    public String getName() {
+        return name;
+    }
+
+    public Object getValue() {
+        return value;
+    }
+
+    /**
+     * Returns the property if available or <code>null</code> otherwise.
+     * Subproperties can be requested by submitting the sequence of properties.
+     */
+    public Property getProperty(String... name) {
+        if (name == null || name.length == 0) return null;
+
+        for (Property p : properties) {
+            if (Objects.equals(name[0], p.name)) {
+                if (name.length == 1)
+                    return p;
+                else
+                    return p.getProperty(Arrays.copyOfRange(name, 1, name.length));
+            }
+        }
+        return null;
+    }
+
+    public Property[] getProperties() {
+        return properties;
+    }
+
     @Override
     public String toString() {
         return toString("");

core/src/main/java/ch/dissem/bitmessage/utils/Singleton.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2015 Christian Basler
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package ch.dissem.bitmessage.utils;
+
+import ch.dissem.bitmessage.ports.Cryptography;
+
+/**
+ * Created by chris on 20.07.15.
+ */
+public class Singleton {
+    private static Cryptography cryptography;
+
+    public static void initialize(Cryptography cryptography) {
+        synchronized (Singleton.class) {
+            if (Singleton.cryptography == null) {
+                Singleton.cryptography = cryptography;
+            }
+        }
+    }
+
+    public static Cryptography security() {
+        return cryptography;
+    }
+}

core/src/main/resources/nodes.txt

@@ -0,0 +1,8 @@
+[stream 1]
+
+dissem.ch:8444
+bootstrap8080.bitmessage.org:8080
+bootstrap8444.bitmessage.org:8444
+
+[stream 2]
+# none yet

core/src/test/java/ch/dissem/bitmessage/DecryptionTest.java

@@ -21,6 +21,7 @@ import ch.dissem.bitmessage.entity.ObjectMessage;
 import ch.dissem.bitmessage.entity.payload.V4Broadcast;
 import ch.dissem.bitmessage.entity.payload.V5Broadcast;
 import ch.dissem.bitmessage.exception.DecryptionFailedException;
+import ch.dissem.bitmessage.utils.TestBase;
 import ch.dissem.bitmessage.utils.TestUtils;
 import org.junit.Test;
 
@@ -29,7 +30,7 @@ import java.io.IOException;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
 
-public class DecryptionTest {
+public class DecryptionTest extends TestBase {
     @Test
     public void ensureV4BroadcastIsDecryptedCorrectly() throws IOException, DecryptionFailedException {
         BitmessageAddress address = new BitmessageAddress("BM-2D9Vc5rFxxR5vTi53T9gkLfemViHRMVLQZ");

core/src/test/java/ch/dissem/bitmessage/EncryptionTest.java

@@ -24,20 +24,20 @@ import ch.dissem.bitmessage.entity.payload.GenericPayload;
 import ch.dissem.bitmessage.entity.payload.Msg;
 import ch.dissem.bitmessage.entity.valueobject.PrivateKey;
 import ch.dissem.bitmessage.exception.DecryptionFailedException;
-import ch.dissem.bitmessage.utils.Security;
+import ch.dissem.bitmessage.utils.TestBase;
 import ch.dissem.bitmessage.utils.TestUtils;
 import org.junit.Test;
 
 import java.io.IOException;
 
+import static ch.dissem.bitmessage.utils.Singleton.security;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
-import static org.junit.Assert.assertTrue;
 
-public class EncryptionTest {
+public class EncryptionTest extends TestBase {
     @Test
     public void ensureDecryptedDataIsSameAsBeforeEncryption() throws IOException, DecryptionFailedException {
-        GenericPayload before = new GenericPayload(0, 1, Security.randomBytes(100));
+        GenericPayload before = new GenericPayload(0, 1, security().randomBytes(100));
 
         PrivateKey privateKey = new PrivateKey(false, 1, 1000, 1000);
         CryptoBox cryptoBox = new CryptoBox(before, privateKey.getPubkey().getEncryptionKey());

core/src/test/java/ch/dissem/bitmessage/SignatureTest.java

@@ -25,6 +25,7 @@ import ch.dissem.bitmessage.entity.payload.Pubkey;
 import ch.dissem.bitmessage.entity.payload.V4Pubkey;
 import ch.dissem.bitmessage.entity.valueobject.PrivateKey;
 import ch.dissem.bitmessage.exception.DecryptionFailedException;
+import ch.dissem.bitmessage.utils.TestBase;
 import ch.dissem.bitmessage.utils.TestUtils;
 import org.junit.Test;
 
@@ -33,7 +34,7 @@ import java.util.Date;
 
 import static org.junit.Assert.*;
 
-public class SignatureTest {
+public class SignatureTest extends TestBase {
     @Test
     public void ensureValidationWorks() throws IOException {
         ObjectMessage object = TestUtils.loadObjectMessage(3, "V3Pubkey.payload");

core/src/test/java/ch/dissem/bitmessage/entity/BitmessageAddressTest.java

@@ -27,6 +27,7 @@ import java.io.IOException;
 import java.util.Arrays;
 
 import static ch.dissem.bitmessage.entity.payload.Pubkey.Feature.DOES_ACK;
+import static ch.dissem.bitmessage.utils.Singleton.security;
 import static org.junit.Assert.*;
 
 public class BitmessageAddressTest {
@@ -102,7 +103,7 @@ public class BitmessageAddressTest {
         System.out.println("\n\n" + Strings.hex(privsigningkey) + "\n\n");
 
         BitmessageAddress address = new BitmessageAddress(new PrivateKey(privsigningkey, privencryptionkey,
-                Security.createPubkey(3, 1, privsigningkey, privencryptionkey, 320, 14000)));
+                security().createPubkey(3, 1, privsigningkey, privencryptionkey, 320, 14000)));
         assertEquals(address_string, address.getAddress());
     }
 
@@ -119,7 +120,7 @@ public class BitmessageAddressTest {
         if (bytes.length != 37)
             throw new IOException("Unknown format: 37 bytes expected, but secret " + walletImportFormat + " was " + bytes.length + " long");
 
-        byte[] hash = Security.doubleSha256(bytes, 33);
+        byte[] hash = security().doubleSha256(bytes, 33);
         for (int i = 0; i < 4; i++) {
             if (hash[i] != bytes[33 + i]) throw new IOException("Hash check failed for secret " + walletImportFormat);
         }
@@ -132,7 +133,7 @@ public class BitmessageAddressTest {
         byte[] privsigningkey = getSecret("5KMWqfCyJZGFgW6QrnPJ6L9Gatz25B51y7ErgqNr1nXUVbtZbdU");
         byte[] privencryptionkey = getSecret("5JXXWEuhHQEPk414SzEZk1PHDRi8kCuZd895J7EnKeQSahJPxGz");
         BitmessageAddress address = new BitmessageAddress(new PrivateKey(privsigningkey, privencryptionkey,
-                Security.createPubkey(4, 1, privsigningkey, privencryptionkey, 320, 14000)));
+                security().createPubkey(4, 1, privsigningkey, privencryptionkey, 320, 14000)));
         assertEquals("BM-2cV5f9EpzaYARxtoruSpa6pDoucSf9ZNke", address.getAddress());
     }
 

core/src/test/java/ch/dissem/bitmessage/entity/SerializationTest.java

@@ -17,21 +17,23 @@
 package ch.dissem.bitmessage.entity;
 
 import ch.dissem.bitmessage.entity.payload.*;
-import ch.dissem.bitmessage.exception.DecryptionFailedException;
+import ch.dissem.bitmessage.entity.valueobject.InventoryVector;
+import ch.dissem.bitmessage.entity.valueobject.Label;
 import ch.dissem.bitmessage.factory.Factory;
+import ch.dissem.bitmessage.utils.TestBase;
 import ch.dissem.bitmessage.utils.TestUtils;
 import org.junit.Test;
 
-import java.io.ByteArrayInputStream;
+import java.io.*;
-import java.io.ByteArrayOutputStream;
+import java.lang.reflect.Field;
-import java.io.IOException;
+import java.util.ArrayList;
-import java.io.InputStream;
+import java.util.Collections;
 
 import static ch.dissem.bitmessage.entity.Plaintext.Type.MSG;
-import static org.junit.Assert.assertArrayEquals;
+import static ch.dissem.bitmessage.utils.Singleton.security;
-import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.*;
 
-public class SerializationTest {
+public class SerializationTest extends TestBase {
     @Test
     public void ensureGetPubkeyIsDeserializedAndSerializedCorrectly() throws IOException {
         doTest("V2GetPubkey.payload", 2, GetPubkey.class);
@@ -75,7 +77,7 @@ public class SerializationTest {
     }
 
     @Test
-    public void ensurePlaintextIsSerializedAndDeserializedCorrectly() throws IOException, DecryptionFailedException {
+    public void ensurePlaintextIsSerializedAndDeserializedCorrectly() throws Exception {
         Plaintext p1 = new Plaintext.Builder(MSG)
                 .from(TestUtils.loadIdentity("BM-2cSqjfJ8xK6UUn5Rw3RpdGQ9RsDkBhWnS8"))
                 .to(TestUtils.loadContact())
@@ -87,16 +89,57 @@ public class SerializationTest {
         p1.write(out);
         ByteArrayInputStream in = new ByteArrayInputStream(out.toByteArray());
         Plaintext p2 = Plaintext.read(MSG, in);
+
+        // Received is automatically set on deserialization, so we'll need to set it to 0
+        Field received = Plaintext.class.getDeclaredField("received");
+        received.setAccessible(true);
+        received.set(p2, 0L);
+
         assertEquals(p1, p2);
     }
 
+    @Test
+    public void ensureNetworkMessageIsSerializedAndDeserializedCorrectly() throws Exception {
+        ArrayList<InventoryVector> ivs = new ArrayList<>(50000);
+        for (int i = 0; i < 50000; i++) {
+            ivs.add(new InventoryVector(security().randomBytes(32)));
+        }
+
+        Inv inv = new Inv.Builder().inventory(ivs).build();
+        NetworkMessage before = new NetworkMessage(inv);
+        ByteArrayOutputStream out = new ByteArrayOutputStream();
+        before.write(out);
+
+        NetworkMessage after = Factory.getNetworkMessage(3, new ByteArrayInputStream(out.toByteArray()));
+        Inv invAfter = (Inv) after.getPayload();
+        assertEquals(ivs, invAfter.getInventory());
+    }
+
     private void doTest(String resourceName, int version, Class<?> expectedPayloadType) throws IOException {
         byte[] data = TestUtils.getBytes(resourceName);
         InputStream in = new ByteArrayInputStream(data);
         ObjectMessage object = Factory.getObjectMessage(version, in, data.length);
         ByteArrayOutputStream out = new ByteArrayOutputStream();
+        assertNotNull(object);
         object.write(out);
         assertArrayEquals(data, out.toByteArray());
         assertEquals(expectedPayloadType.getCanonicalName(), object.getPayload().getClass().getCanonicalName());
     }
+
+    @Test
+    public void ensureSystemSerializationWorks() throws Exception {
+        Plaintext plaintext = new Plaintext.Builder(MSG)
+                .from(TestUtils.loadContact())
+                .to(TestUtils.loadIdentity("BM-2cSqjfJ8xK6UUn5Rw3RpdGQ9RsDkBhWnS8"))
+                .labels(Collections.singletonList(new Label("Test", Label.Type.INBOX, 0)))
+                .message("Test", "Test Test.\nTest")
+                .build();
+        ByteArrayOutputStream out = new ByteArrayOutputStream();
+        ObjectOutputStream oos = new ObjectOutputStream(out);
+        oos.writeObject(plaintext);
+
+        ByteArrayInputStream in = new ByteArrayInputStream(out.toByteArray());
+        ObjectInputStream ois = new ObjectInputStream(in);
+        assertEquals(plaintext, ois.readObject());
+    }
 }

core/src/test/java/ch/dissem/bitmessage/ports/ProofOfWorkEngineTest.java

@@ -0,0 +1,72 @@
+/*
+ * Copyright 2015 Christian Basler
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package ch.dissem.bitmessage.ports;
+
+import ch.dissem.bitmessage.utils.Bytes;
+import ch.dissem.bitmessage.utils.CallbackWaiter;
+import ch.dissem.bitmessage.utils.TestBase;
+import org.junit.Test;
+
+import static ch.dissem.bitmessage.utils.Singleton.security;
+import static org.junit.Assert.assertTrue;
+
+public class ProofOfWorkEngineTest extends TestBase {
+    @Test(timeout = 90_000)
+    public void testSimplePOWEngine() throws InterruptedException {
+        testPOW(new SimplePOWEngine());
+    }
+
+    @Test(timeout = 90_000)
+    public void testThreadedPOWEngine() throws InterruptedException {
+        testPOW(new MultiThreadedPOWEngine());
+    }
+
+    private void testPOW(ProofOfWorkEngine engine) throws InterruptedException {
+        byte[] initialHash = security().sha512(new byte[]{1, 3, 6, 4});
+        byte[] target = {0, 0, 0, -1, -1, -1, -1, -1};
+
+        final CallbackWaiter<byte[]> waiter1 = new CallbackWaiter<>();
+        engine.calculateNonce(initialHash, target,
+                new ProofOfWorkEngine.Callback() {
+                    @Override
+                    public void onNonceCalculated(byte[] initialHash, byte[] nonce) {
+                        waiter1.setValue(nonce);
+                    }
+                });
+        byte[] nonce = waiter1.waitForValue();
+        System.out.println("Calculating nonce took " + waiter1.getTime() + "ms");
+        assertTrue(Bytes.lt(security().doubleSha512(nonce, initialHash), target, 8));
+
+        // Let's add a second (shorter) run to find possible multi threading issues
+        byte[] initialHash2 = security().sha512(new byte[]{1, 3, 6, 5});
+        byte[] target2 = {0, 0, -1, -1, -1, -1, -1, -1};
+
+        final CallbackWaiter<byte[]> waiter2 = new CallbackWaiter<>();
+        engine.calculateNonce(initialHash2, target2,
+                new ProofOfWorkEngine.Callback() {
+                    @Override
+                    public void onNonceCalculated(byte[] initialHash, byte[] nonce) {
+                        waiter2.setValue(nonce);
+                    }
+                });
+        byte[] nonce2 = waiter2.waitForValue();
+        System.out.println("Calculating nonce took " + waiter2.getTime() + "ms");
+        assertTrue(Bytes.lt(security().doubleSha512(nonce2, initialHash2), target2, 8));
+        assertTrue("Second nonce must be quicker to find", waiter1.getTime() > waiter2.getTime());
+    }
+
+}

core/src/test/java/ch/dissem/bitmessage/utils/BytesTest.java

@@ -16,6 +16,7 @@
 
 package ch.dissem.bitmessage.utils;
 
+import org.junit.Ignore;
 import org.junit.Test;
 
 import java.io.IOException;
@@ -25,16 +26,13 @@ import java.util.Random;
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 
-/**
- * Created by chris on 10.04.15.
- */
 public class BytesTest {
     public static final Random rnd = new Random();
 
     @Test
     public void ensureExpandsCorrectly() {
         byte[] source = {1};
-        byte[] expected = {0,1};
+        byte[] expected = {0, 1};
         assertArrayEquals(expected, Bytes.expand(source, 2));
     }
 
@@ -56,6 +54,24 @@ public class BytesTest {
         }
     }
 
+    /**
+     * This test is used to compare different implementations of the single byte lt comparison. It an safely be ignored.
+     */
+    @Test
+    @Ignore
+    public void testLowerThanSingleByte() {
+        byte[] a = new byte[1];
+        byte[] b = new byte[1];
+        for (int i = 0; i < 255; i++) {
+            for (int j = 0; j < 255; j++) {
+                System.out.println("a = " + i + "\tb = " + j);
+                a[0] = (byte) i;
+                b[0] = (byte) j;
+                assertEquals(i < j, Bytes.lt(a, b));
+            }
+        }
+    }
+
     @Test
     public void testLowerThan() {
         for (int i = 0; i < 1000; i++) {

core/src/test/java/ch/dissem/bitmessage/utils/DecodeTest.java

@@ -22,9 +22,6 @@ import java.io.*;
 
 import static org.junit.Assert.assertEquals;
 
-/**
- * Created by chris on 20.03.15.
- */
 public class DecodeTest {
     @Test
     public void ensureDecodingWorks() throws Exception {

core/src/test/java/ch/dissem/bitmessage/utils/EncodeTest.java

@@ -23,9 +23,6 @@ import java.io.IOException;
 
 import static org.junit.Assert.assertEquals;
 
-/**
- * Created by chris on 13.03.15.
- */
 public class EncodeTest {
     @Test
     public void testUint8() throws IOException {

core/src/test/java/ch/dissem/bitmessage/utils/TestBase.java

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2015 Christian Basler
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package ch.dissem.bitmessage.utils;
+
+import ch.dissem.bitmessage.cryptography.bc.BouncyCryptography;
+
+/**
+ * Created by chris on 20.07.15.
+ */
+public class TestBase {
+    static {
+        Singleton.initialize(new BouncyCryptography());
+    }
+}