Merge branch 'feature/server-pow' into develop

.gitignore

@@ -1,4 +1,6 @@
 # Project specific files
+admins.conf
+clients.conf
 *list.conf
 config.properties
 /*.db

build.gradle

@@ -44,6 +44,7 @@ dependencies {
     compile 'ch.dissem.jabit:jabit-networking:0.2.1-SNAPSHOT'
     compile 'ch.dissem.jabit:jabit-repositories:0.2.1-SNAPSHOT'
     compile 'ch.dissem.jabit:jabit-security-bouncy:0.2.1-SNAPSHOT'
+    compile 'ch.dissem.jabit:jabit-extensions:0.2.1-SNAPSHOT'
 
     compile 'com.h2database:h2:1.4.187'
 

gradle/wrapper/gradle-wrapper.properties

@@ -3,4 +3,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-2.5-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-2.8-all.zip

src/main/java/ch/dissem/bitmessage/server/CleanupJob.java

@@ -1,3 +1,19 @@
+/*
+ * 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.server;
 
 import ch.dissem.bitmessage.BitmessageContext;
@@ -7,7 +23,7 @@ import org.slf4j.LoggerFactory;
 import java.util.TimerTask;
 
 /**
- * Created by chrigu on 04.10.15.
+ * @author Christian Basler
  */
 public class CleanupJob extends TimerTask {
     private static final Logger LOG = LoggerFactory.getLogger(CleanupJob.class);

src/main/java/ch/dissem/bitmessage/server/Constants.java

@@ -0,0 +1,13 @@
+package ch.dissem.bitmessage.server;
+
+/**
+ * Created by chrigu on 22.11.15.
+ */
+public interface Constants {
+    String ADMIN_LIST = "admins.conf";
+    String CLIENT_LIST = "clients.conf";
+
+    String WHITELIST = "whitelist.conf";
+    String SHORTLIST = "shortlist.conf";
+    String BLACKLIST = "blacklist.conf";
+}

src/main/java/ch/dissem/bitmessage/server/Converter.java

@@ -1,3 +1,19 @@
+/*
+ * 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.server;
 
 import ch.dissem.bitmessage.entity.BitmessageAddress;

src/main/java/ch/dissem/bitmessage/server/JabitServerConfig.java

@@ -1,13 +1,29 @@
+/*
+ * 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.server;
 
 import ch.dissem.bitmessage.BitmessageContext;
+import ch.dissem.bitmessage.entity.BitmessageAddress;
 import ch.dissem.bitmessage.networking.DefaultNetworkHandler;
-import ch.dissem.bitmessage.ports.MemoryNodeRegistry;
-import ch.dissem.bitmessage.repository.JdbcAddressRepository;
-import ch.dissem.bitmessage.repository.JdbcConfig;
-import ch.dissem.bitmessage.repository.JdbcInventory;
-import ch.dissem.bitmessage.repository.JdbcMessageRepository;
+import ch.dissem.bitmessage.ports.*;
+import ch.dissem.bitmessage.repository.*;
 import ch.dissem.bitmessage.security.bc.BouncySecurity;
+import ch.dissem.bitmessage.server.repository.ServerProofOfWorkRepository;
+import ch.dissem.bitmessage.utils.Singleton;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
@@ -16,6 +32,9 @@ import springfox.documentation.spring.web.plugins.Docket;
 
 import java.util.Set;
 
+import static ch.dissem.bitmessage.server.Constants.*;
+import static java.util.stream.Collectors.toSet;
+
 @Configuration
 public class JabitServerConfig {
     public static final int SHORTLIST_SIZE = 5;
@@ -27,28 +46,102 @@ public class JabitServerConfig {
     @Value("${bitmessage.connection.limit}")
     private int connectionLimit;
 
+    @Bean
+    public JdbcConfig jdbcConfig() {
+        return new JdbcConfig("jdbc:h2:file:./jabit;AUTO_SERVER=TRUE;DB_CLOSE_DELAY=10", "sa", null);
+    }
+
+    @Bean
+    public AddressRepository addressRepo() {
+        return new JdbcAddressRepository(jdbcConfig());
+    }
+
+    @Bean
+    public Inventory inventory() {
+        return new JdbcInventory(jdbcConfig());
+    }
+
+    @Bean
+    public MessageRepository messageRepo() {
+        return new JdbcMessageRepository(jdbcConfig());
+    }
+
+    @Bean
+    public ProofOfWorkRepository proofOfWorkRepo() {
+        return new JdbcProofOfWorkRepository(jdbcConfig());
+    }
+
+    @Bean
+    public NodeRegistry nodeRegistry() {
+        return new MemoryNodeRegistry();
+    }
+
+    @Bean
+    public NetworkHandler networkHandler() {
+        return new DefaultNetworkHandler();
+    }
+
+    @Bean
+    public Security security() {
+        BouncySecurity security = new BouncySecurity();
+        Singleton.initialize(security); // needed for admins and clients
+        return security;
+    }
+
+    @Bean
+    public BitmessageContext.Listener serverListener() {
+        return new ServerListener(admins(), clients(), whitelist(), shortlist(), blacklist());
+    }
+
+    @Bean
+    public ServerProofOfWorkRepository serverProofOfWorkRepository() {
+        return new ServerProofOfWorkRepository(jdbcConfig());
+    }
+    @Bean
+    public CustomCommandHandler commandHandler() {
+        return new ProofOfWorkRequestHandler(serverProofOfWorkRepository(), clients());
+    }
+
     @Bean
     public BitmessageContext bitmessageContext() {
-        JdbcConfig config = new JdbcConfig("jdbc:h2:file:./jabit;AUTO_SERVER=TRUE", "sa", null);
         return new BitmessageContext.Builder()
-                .addressRepo(new JdbcAddressRepository(config))
-                .inventory(new JdbcInventory(config))
-                .messageRepo(new JdbcMessageRepository(config))
-                .nodeRegistry(new MemoryNodeRegistry())
-                .networkHandler(new DefaultNetworkHandler())
-                .security(new BouncySecurity())
+                .addressRepo(addressRepo())
+                .inventory(inventory())
+                .messageRepo(messageRepo())
+                .nodeRegistry(nodeRegistry())
+                .powRepo(proofOfWorkRepo())
+                .networkHandler(networkHandler())
+                .listener(serverListener())
+                .customCommandHandler(commandHandler())
+                .security(security())
                 .port(port)
                 .connectionLimit(connectionLimit)
                 .connectionTTL(connectionTTL)
-                .listener(plaintext -> {
-                })
                 .build();
     }
 
+    @Bean
+    public Set<BitmessageAddress> admins() {
+        security();
+        return Utils.readOrCreateList(
+                ADMIN_LIST,
+                "# Admins can send commands to the server.\n"
+        ).stream().map(BitmessageAddress::new).collect(toSet());
+    }
+
+    @Bean
+    public Set<BitmessageAddress> clients() {
+        security();
+        return Utils.readOrCreateList(
+                CLIENT_LIST,
+                "# Clients may send incomplete objects for proof of work.\n"
+        ).stream().map(BitmessageAddress::new).collect(toSet());
+    }
+
     @Bean
     public Set<String> whitelist() {
         return Utils.readOrCreateList(
-                "whitelist.conf",
+                WHITELIST,
                 "# If there are any Bitmessage addresses in the whitelist, only those will be shown.\n" +
                         "# blacklist.conf will be ignored, but shortlist.conf will be applied to whitelisted addresses.\n"
         );
@@ -57,7 +150,7 @@ public class JabitServerConfig {
     @Bean
     public Set<String> shortlist() {
         return Utils.readOrCreateList(
-                "shortlist.conf",
+                SHORTLIST,
                 "# Broadcasts of these addresses will be restricted to the last " + SHORTLIST_SIZE + " entries.\n\n" +
                         "# Time Service:\n" +
                         "BM-BcbRqcFFSQUUmXFKsPJgVQPSiFA3Xash\n\n" +
@@ -69,7 +162,7 @@ public class JabitServerConfig {
     @Bean
     public Set<String> blacklist() {
         return Utils.readOrCreateList(
-                "blacklist.conf",
+                BLACKLIST,
                 "# Bitmessage addresses in this file are being ignored and their broadcasts won't be returned.\n"
         );
     }

src/main/java/ch/dissem/bitmessage/server/JabitServerController.java

@@ -1,3 +1,19 @@
+/*
+ * 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.server;
 
 import ch.dissem.bitmessage.BitmessageContext;

src/main/java/ch/dissem/bitmessage/server/ProofOfWorkRequestHandler.java

@@ -0,0 +1,163 @@
+/*
+ * 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.server;
+
+import ch.dissem.bitmessage.InternalContext;
+import ch.dissem.bitmessage.entity.BitmessageAddress;
+import ch.dissem.bitmessage.entity.CustomMessage;
+import ch.dissem.bitmessage.entity.MessagePayload;
+import ch.dissem.bitmessage.entity.valueobject.PrivateKey;
+import ch.dissem.bitmessage.exception.DecryptionFailedException;
+import ch.dissem.bitmessage.extensions.CryptoCustomMessage;
+import ch.dissem.bitmessage.extensions.pow.ProofOfWorkRequest;
+import ch.dissem.bitmessage.ports.CustomCommandHandler;
+import ch.dissem.bitmessage.ports.ProofOfWorkEngine;
+import ch.dissem.bitmessage.server.repository.ServerProofOfWorkRepository;
+import ch.dissem.bitmessage.utils.UnixTime;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.Collection;
+import java.util.List;
+import java.util.Timer;
+import java.util.TimerTask;
+import java.util.stream.Collectors;
+
+import static ch.dissem.bitmessage.extensions.pow.ProofOfWorkRequest.Request.CALCULATING;
+import static ch.dissem.bitmessage.extensions.pow.ProofOfWorkRequest.Request.COMPLETE;
+import static ch.dissem.bitmessage.utils.UnixTime.DAY;
+
+/**
+ * @author Christian Basler
+ */
+public class ProofOfWorkRequestHandler implements CustomCommandHandler, InternalContext.ContextHolder {
+    private final static Logger LOG = LoggerFactory.getLogger(ProofOfWorkRequestHandler.class);
+
+    private final List<byte[]> decryptionKeys;
+    private final ServerProofOfWorkRepository repo;
+    private BitmessageAddress serverIdentity;
+    private ProofOfWorkEngine engine;
+    private InternalContext context;
+
+    public ProofOfWorkRequestHandler(ServerProofOfWorkRepository repo, Collection<BitmessageAddress> clients) {
+        this.repo = repo;
+        decryptionKeys = clients.stream().map(BitmessageAddress::getPublicDecryptionKey).collect(Collectors.toList());
+        new Timer().schedule(new TimerTask() {
+            @Override
+            public void run() {
+                doMissingProofOfWork();
+            }
+        }, 15_000); // After 15 seconds
+        new Timer().schedule(new TimerTask() {
+            @Override
+            public void run() {
+                repo.cleanupTasks(7 * DAY);
+            }
+        }, 60_000, DAY * 1000); // First time after 1 minute, then daily
+    }
+
+    public void doMissingProofOfWork() {
+        List<ServerProofOfWorkRepository.Task> incompleteTasks = repo.getIncompleteTasks();
+        LOG.info("Doing POW for " + incompleteTasks.size() + " tasks.");
+        for (ServerProofOfWorkRepository.Task task : incompleteTasks) {
+            engine.calculateNonce(task.initialHash, task.target, repo::updateTask);
+        }
+    }
+
+    @Override
+    public MessagePayload handle(CustomMessage message) {
+        try {
+            CryptoCustomMessage<ProofOfWorkRequest> cryptoMessage = CryptoCustomMessage.read(message,
+                    ProofOfWorkRequest::read);
+            ProofOfWorkRequest request = decrypt(cryptoMessage);
+            if (request == null) {
+                return CustomMessage.error(
+                        "Unknown sender. Please ask the server's administrator to add you as a client. " +
+                                "For this he'll need your identity."
+                );
+            }
+            switch (request.getRequest()) {
+                case CALCULATE:
+                    if (!repo.hasTask(request.getInitialHash())) {
+                        repo.storeTask(request);
+                        // TODO: This is probably the place to do some book-keeping
+                        // if we want to bill our customers.
+                        engine.calculateNonce(request.getInitialHash(), request.getData(), repo::updateTask);
+                        return new CryptoCustomMessage<>(
+                                new ProofOfWorkRequest(getIdentity(), request.getInitialHash(), CALCULATING, new byte[0])
+                        );
+                    } else {
+                        byte[] nonce = repo.getNonce(request);
+                        CryptoCustomMessage<ProofOfWorkRequest> response;
+                        if (nonce != null) {
+                            response = new CryptoCustomMessage<>(
+                                    new ProofOfWorkRequest(getIdentity(), request.getInitialHash(), COMPLETE, nonce)
+                            );
+                        } else {
+                            response = new CryptoCustomMessage<>(
+                                    new ProofOfWorkRequest(getIdentity(), request.getInitialHash(), CALCULATING, new byte[0])
+                            );
+                        }
+                        response.signAndEncrypt(serverIdentity, request.getSender().getPubkey().getEncryptionKey());
+                        return response;
+                    }
+            }
+            return null;
+        } catch (IOException e) {
+            return CustomMessage.error(e.getMessage());
+        }
+    }
+
+    private BitmessageAddress getIdentity() {
+        if (serverIdentity == null) {
+            synchronized (this) {
+                if (serverIdentity == null) {
+                    serverIdentity = context.getAddressRepository().getIdentities().stream().findFirst().orElseGet(() -> {
+                        final BitmessageAddress identity = new BitmessageAddress(new PrivateKey(
+                                false,
+                                context.getStreams()[0],
+                                context.getNetworkNonceTrialsPerByte(),
+                                context.getNetworkExtraBytes()
+                        ));
+                        context.getAddressRepository().save(identity);
+                        return identity;
+                    });
+                }
+            }
+        }
+        return serverIdentity;
+    }
+
+    private ProofOfWorkRequest decrypt(CryptoCustomMessage<ProofOfWorkRequest> cryptoMessage) {
+        for (byte[] key : decryptionKeys) {
+            try {
+                return cryptoMessage.decrypt(key);
+            } catch (DecryptionFailedException ignore) {
+            } catch (IOException e) {
+                throw new RuntimeException(e);
+            }
+        }
+        return null;
+    }
+
+    @Override
+    public void setContext(InternalContext context) {
+        this.context = context;
+        this.engine = context.getProofOfWorkEngine();
+    }
+}

src/main/java/ch/dissem/bitmessage/server/ServerListener.java

@@ -0,0 +1,137 @@
+/*
+ * 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.server;
+
+import ch.dissem.bitmessage.BitmessageContext;
+import ch.dissem.bitmessage.entity.BitmessageAddress;
+import ch.dissem.bitmessage.entity.Plaintext;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.Collection;
+import java.util.Scanner;
+
+import static ch.dissem.bitmessage.server.Constants.*;
+
+/**
+ * @author Christian Basler
+ */
+public class ServerListener implements BitmessageContext.Listener {
+    private final static Logger LOG = LoggerFactory.getLogger(ServerListener.class);
+
+    private final Collection<BitmessageAddress> admins;
+    private final Collection<BitmessageAddress> clients;
+
+    private final Collection<String> whitelist;
+    private final Collection<String> shortlist;
+    private final Collection<String> blacklist;
+
+    public ServerListener(Collection<BitmessageAddress> admins,
+                          Collection<BitmessageAddress> clients,
+                          Collection<String> whitelist,
+                          Collection<String> shortlist,
+                          Collection<String> blacklist) {
+        this.admins = admins;
+        this.clients = clients;
+        this.whitelist = whitelist;
+        this.shortlist = shortlist;
+        this.blacklist = blacklist;
+    }
+
+    @Override
+    public void receive(Plaintext message) {
+        if (admins.contains(message.getFrom())) {
+            String[] command = message.getSubject().trim().toLowerCase().split("\\s+");
+            String data = message.getText();
+            if (command.length == 2) {
+                switch (command[1]) {
+                    case "client":
+                    case "clients":
+                        updateUserList(CLIENT_LIST, clients, command[0], data);
+                        break;
+                    case "admin":
+                    case "admins":
+                    case "administrator":
+                    case "administrators":
+                        updateUserList(ADMIN_LIST, admins, command[0], data);
+                        break;
+                    case "whitelist":
+                        updateList(WHITELIST, whitelist, command[0], data);
+                        break;
+                    case "shortlist":
+                        updateList(SHORTLIST, shortlist, command[0], data);
+                        break;
+                    case "blacklist":
+                        updateList(BLACKLIST, blacklist, command[0], data);
+                        break;
+                    default:
+                        LOG.trace("ignoring  unknown command " + message.getSubject());
+                }
+            }
+        }
+    }
+
+    private void updateUserList(String file, Collection<BitmessageAddress> list, String command, String data) {
+        switch (command) {
+            case "set":
+                list.clear();
+            case "add":
+                Scanner scanner = new Scanner(data);
+                while (scanner.hasNextLine()) {
+                    String line = scanner.nextLine();
+                    try {
+                        list.add(new BitmessageAddress(line));
+                    } catch (Exception e) {
+                        LOG.info(command + " " + file + ": ignoring line: " + line);
+                    }
+                }
+                Utils.saveList(file, list.stream().map(BitmessageAddress::getAddress));
+                break;
+            case "remove":
+                list.removeIf(address -> data.contains(address.getAddress()));
+                Utils.saveList(file, list.stream().map(BitmessageAddress::getAddress));
+                break;
+            default:
+                LOG.info("unknown command " + command + " on list " + file);
+        }
+    }
+
+    private void updateList(String file, Collection<String> list, String command, String data) {
+        switch (command) {
+            case "set":
+                list.clear();
+            case "add":
+                Scanner scanner = new Scanner(data);
+                while (scanner.hasNextLine()) {
+                    String line = scanner.nextLine();
+                    try {
+                        list.add(new BitmessageAddress(line).getAddress());
+                    } catch (Exception e) {
+                        LOG.info(command + " " + file + ": ignoring line: " + line);
+                    }
+                }
+                Utils.saveList(file, list.stream());
+                break;
+            case "remove":
+                list.removeIf(data::contains);
+                Utils.saveList(file, list.stream());
+                break;
+            default:
+                LOG.info("unknown command " + command + " on list " + file);
+        }
+    }
+}

src/main/java/ch/dissem/bitmessage/server/Utils.java

@@ -1,10 +1,29 @@
+/*
+ * 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.server;
 
 import java.io.File;
 import java.io.FileNotFoundException;
 import java.io.FileWriter;
 import java.io.IOException;
-import java.util.*;
+import java.util.HashSet;
+import java.util.Scanner;
+import java.util.Set;
+import java.util.stream.Stream;
 
 public class Utils {
     public static Set<String> readOrCreateList(String filename, String content) {
@@ -23,6 +42,24 @@ public class Utils {
         }
     }
 
+    public static void saveList(String filename, Stream<String> content) {
+        try {
+            File file = new File(filename);
+            try (FileWriter fw = new FileWriter(file)) {
+                content.forEach(l -> {
+                    try {
+                        fw.write(l);
+                        fw.write(System.lineSeparator());
+                    } catch (IOException e) {
+                        throw new RuntimeException(e);
+                    }
+                });
+            }
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
     public static Set<String> readList(File file) {
         Set<String> result = new HashSet<>();
         try {
@@ -38,4 +75,11 @@ public class Utils {
         }
         return result;
     }
+
+    public static boolean zero(byte[] nonce) {
+        for (byte b : nonce) {
+            if (b != 0) return false;
+        }
+        return true;
+    }
 }

src/main/java/ch/dissem/bitmessage/server/entities/Update.java

@@ -0,0 +1,30 @@
+/*
+ * 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.server.entities;
+
+/**
+ * @author Christian Basler
+ */
+public class Update<T> {
+    public final T oldValue;
+    public final T newValue;
+
+    public Update(T oldValue, T newValue) {
+        this.oldValue = oldValue;
+        this.newValue = newValue;
+    }
+}

src/main/java/ch/dissem/bitmessage/server/repository/ServerProofOfWorkRepository.java

@@ -0,0 +1,137 @@
+/*
+ * 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.server.repository;
+
+import ch.dissem.bitmessage.extensions.pow.ProofOfWorkRequest;
+import ch.dissem.bitmessage.repository.JdbcConfig;
+import ch.dissem.bitmessage.repository.JdbcHelper;
+import ch.dissem.bitmessage.utils.UnixTime;
+
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.util.LinkedList;
+import java.util.List;
+
+/**
+ * @author Christian Basler
+ */
+public class ServerProofOfWorkRepository extends JdbcHelper {
+
+    public ServerProofOfWorkRepository(JdbcConfig config) {
+        super(config);
+    }
+
+    /**
+     * client (can be removed once the new IV is returned)
+     * IV (without nonce)
+     * IV (with nonce, can be removed once the new IV is returned)
+     * status: calculating, finished, confirmed
+     * data (can be removed once POW calculation is done)
+     */
+    public void storeTask(ProofOfWorkRequest request) {
+        try (Connection connection = config.getConnection()) {
+            PreparedStatement ps = connection.prepareStatement(
+                    "INSERT INTO ProofOfWorkTask (initial_hash, client, target, timestamp) VALUES (?, ?, ?, ?)");
+            ps.setBytes(1, request.getInitialHash());
+            ps.setString(2, request.getSender().getAddress());
+            ps.setBytes(3, request.getData());
+            ps.setLong(4, UnixTime.now());
+            ps.executeUpdate();
+        } catch (SQLException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    public void updateTask(byte[] initalHash, byte[] nonce) {
+        try (Connection connection = config.getConnection()) {
+            PreparedStatement ps = connection.prepareStatement(
+                    "UPDATE ProofOfWorkTask SET nonce = ? WHERE initial_hash = ?");
+            ps.setBytes(1, nonce);
+            ps.setBytes(2, initalHash);
+            ps.executeUpdate();
+        } catch (SQLException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    public byte[] getNonce(ProofOfWorkRequest request) {
+        try (Connection connection = config.getConnection()) {
+            PreparedStatement ps = connection.prepareStatement("SELECT nonce FROM ProofOfWorkTask WHERE initial_hash = ?");
+            ps.setBytes(1, request.getInitialHash());
+            ResultSet rs = ps.executeQuery();
+            if (rs.next()) {
+                return rs.getBytes(1);
+            } else {
+                return null;
+            }
+        } catch (SQLException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    public boolean hasTask(byte[] initialHash) {
+        try (Connection connection = config.getConnection()) {
+            PreparedStatement ps = connection.prepareStatement("SELECT count(1) FROM ProofOfWorkTask WHERE initial_hash = ?");
+            ps.setBytes(1, initialHash);
+            ResultSet rs = ps.executeQuery();
+            rs.next();
+            return rs.getInt(1) > 0;
+        } catch (SQLException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    public List<Task> getIncompleteTasks() {
+        try (Connection connection = config.getConnection()) {
+            List<Task> result = new LinkedList<>();
+            ResultSet rs = connection.createStatement().executeQuery(
+                    "SELECT initial_hash, target FROM ProofOfWorkTask WHERE nonce IS NULL");
+            while (rs.next()) {
+                result.add(new Task(
+                        rs.getBytes(1),
+                        rs.getBytes(2)
+                ));
+            }
+            return result;
+        } catch (SQLException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    public void cleanupTasks(long ageInSeconds) {
+        try (Connection connection = config.getConnection()) {
+            PreparedStatement ps = connection.prepareStatement(
+                    "DELETE FROM ProofOfWorkTask WHERE timestamp < ?");
+            ps.setLong(1, UnixTime.now(-ageInSeconds));
+            ps.executeUpdate();
+        } catch (SQLException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    public static class Task {
+        public final byte[] initialHash;
+        public final byte[] target;
+
+        private Task(byte[] initialHash, byte[] target) {
+            this.initialHash = initialHash;
+            this.target = target;
+        }
+    }
+}

src/main/resources/db/migration/V1.2.1__ProofOfWorkTask.sql

@@ -0,0 +1,7 @@
+CREATE TABLE ProofOfWorkTask (
+  initial_hash BINARY(64)  NOT NULL PRIMARY KEY,
+  client       VARCHAR(40) NOT NULL,
+  target       BINARY(32),
+  nonce        BINARY(8),
+  timestamp    BIGINT      NOT NULL,
+);