CryptoNext persistance layer mockup

Initial sketch of the peripheral storage infrastructure for the new
axolotl-based encryption scheme.

build.gradle

@@ -36,6 +36,7 @@ dependencies {
 	compile 'de.measite.minidns:minidns:0.1.3'
 	compile 'de.timroes.android:EnhancedListView:0.3.4'
 	compile 'me.leolin:ShortcutBadger:1.1.1@aar'
+	compile 'org.whispersystems:axolotl-android:1.3.4'
 }
 
 android {

src/main/java/eu/siacs/conversations/crypto/axolotl/AxolotlService.java

@@ -0,0 +1,440 @@
+package eu.siacs.conversations.crypto.axolotl;
+
+import android.util.Log;
+
+import org.whispersystems.libaxolotl.AxolotlAddress;
+import org.whispersystems.libaxolotl.IdentityKey;
+import org.whispersystems.libaxolotl.IdentityKeyPair;
+import org.whispersystems.libaxolotl.InvalidKeyException;
+import org.whispersystems.libaxolotl.InvalidKeyIdException;
+import org.whispersystems.libaxolotl.ecc.Curve;
+import org.whispersystems.libaxolotl.ecc.ECKeyPair;
+import org.whispersystems.libaxolotl.state.AxolotlStore;
+import org.whispersystems.libaxolotl.state.PreKeyRecord;
+import org.whispersystems.libaxolotl.state.SessionRecord;
+import org.whispersystems.libaxolotl.state.SignedPreKeyRecord;
+import org.whispersystems.libaxolotl.util.KeyHelper;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import eu.siacs.conversations.Config;
+import eu.siacs.conversations.entities.Account;
+import eu.siacs.conversations.entities.Conversation;
+import eu.siacs.conversations.entities.Message;
+import eu.siacs.conversations.services.XmppConnectionService;
+import eu.siacs.conversations.xmpp.jid.InvalidJidException;
+import eu.siacs.conversations.xmpp.jid.Jid;
+
+public class AxolotlService {
+
+    private Account account;
+    private XmppConnectionService mXmppConnectionService;
+    private SQLiteAxolotlStore axolotlStore;
+    private Map<Jid,XmppAxolotlSession> sessions;
+
+    public static class SQLiteAxolotlStore implements AxolotlStore {
+
+        public static final String PREKEY_TABLENAME = "prekeys";
+        public static final String SIGNED_PREKEY_TABLENAME = "signed_prekeys";
+        public static final String SESSION_TABLENAME = "signed_prekeys";
+        public static final String NAME = "name";
+        public static final String DEVICE_ID = "device_id";
+        public static final String ID = "id";
+        public static final String KEY = "key";
+        public static final String ACCOUNT = "account";
+
+        public static final String JSONKEY_IDENTITY_KEY_PAIR = "axolotl_key";
+        public static final String JSONKEY_REGISTRATION_ID = "axolotl_reg_id";
+
+        private final Account account;
+        private final XmppConnectionService mXmppConnectionService;
+
+        private final IdentityKeyPair identityKeyPair;
+        private final int localRegistrationId;
+
+
+        private static IdentityKeyPair generateIdentityKeyPair() {
+            Log.d(Config.LOGTAG, "Generating axolotl IdentityKeyPair...");
+            ECKeyPair identityKeyPairKeys = Curve.generateKeyPair();
+            IdentityKeyPair ownKey = new IdentityKeyPair(new IdentityKey(identityKeyPairKeys.getPublicKey()),
+                    identityKeyPairKeys.getPrivateKey());
+            return ownKey;
+        }
+
+        private static int generateRegistrationId() {
+            Log.d(Config.LOGTAG, "Generating axolotl registration ID...");
+            int reg_id = KeyHelper.generateRegistrationId(false);
+            return reg_id;
+        }
+
+        public SQLiteAxolotlStore(Account account, XmppConnectionService service) {
+            this.account = account;
+            this.mXmppConnectionService = service;
+            this.identityKeyPair = loadIdentityKeyPair();
+            this.localRegistrationId = loadRegistrationId();
+        }
+
+        // --------------------------------------
+        // IdentityKeyStore
+        // --------------------------------------
+
+        private IdentityKeyPair loadIdentityKeyPair() {
+            String serializedKey = this.account.getKey(JSONKEY_IDENTITY_KEY_PAIR);
+            IdentityKeyPair ownKey;
+            if( serializedKey != null ) {
+                try {
+                    ownKey = new IdentityKeyPair(serializedKey.getBytes());
+                } catch (InvalidKeyException e) {
+                    Log.d(Config.LOGTAG, "Invalid key stored for account " + account.getJid() + ": " + e.getMessage());
+                    return null;
+                }
+            } else {
+                Log.d(Config.LOGTAG, "Could not retrieve axolotl key for account " + account.getJid());
+                ownKey = generateIdentityKeyPair();
+                boolean success = this.account.setKey(JSONKEY_IDENTITY_KEY_PAIR, new String(ownKey.serialize()));
+                if(success) {
+                    mXmppConnectionService.databaseBackend.updateAccount(account);
+                } else {
+                    Log.e(Config.LOGTAG, "Failed to write new key to the database!");
+                }
+            }
+            return ownKey;
+        }
+
+        private int loadRegistrationId() {
+            String regIdString = this.account.getKey(JSONKEY_REGISTRATION_ID);
+            int reg_id;
+            if (regIdString != null) {
+                reg_id = Integer.valueOf(regIdString);
+            } else {
+                Log.d(Config.LOGTAG, "Could not retrieve axolotl registration id for account " + account.getJid());
+                reg_id = generateRegistrationId();
+                boolean success = this.account.setKey(JSONKEY_REGISTRATION_ID,""+reg_id);
+                if(success) {
+                    mXmppConnectionService.databaseBackend.updateAccount(account);
+                } else {
+                    Log.e(Config.LOGTAG, "Failed to write new key to the database!");
+                }
+            }
+            return reg_id;
+        }
+
+        /**
+         * Get the local client's identity key pair.
+         *
+         * @return The local client's persistent identity key pair.
+         */
+        @Override
+        public IdentityKeyPair getIdentityKeyPair() {
+            return identityKeyPair;
+        }
+
+        /**
+         * Return the local client's registration ID.
+         * <p/>
+         * Clients should maintain a registration ID, a random number
+         * between 1 and 16380 that's generated once at install time.
+         *
+         * @return the local client's registration ID.
+         */
+        @Override
+        public int getLocalRegistrationId() {
+            return localRegistrationId;
+        }
+
+        /**
+         * Save a remote client's identity key
+         * <p/>
+         * Store a remote client's identity key as trusted.
+         *
+         * @param name        The name of the remote client.
+         * @param identityKey The remote client's identity key.
+         */
+        @Override
+        public void saveIdentity(String name, IdentityKey identityKey) {
+            try {
+                Jid contactJid = Jid.fromString(name);
+                Conversation conversation = this.mXmppConnectionService.find(this.account, contactJid);
+                if (conversation != null) {
+                    conversation.getContact().addAxolotlIdentityKey(identityKey, false);
+                    mXmppConnectionService.updateConversationUi();
+                    mXmppConnectionService.syncRosterToDisk(conversation.getAccount());
+                }
+            } catch (final InvalidJidException e) {
+                Log.e(Config.LOGTAG, "Failed to save identityKey for contact name " + name + ": " + e.toString());
+            }
+        }
+
+        /**
+         * Verify a remote client's identity key.
+         * <p/>
+         * Determine whether a remote client's identity is trusted.  Convention is
+         * that the TextSecure protocol is 'trust on first use.'  This means that
+         * an identity key is considered 'trusted' if there is no entry for the recipient
+         * in the local store, or if it matches the saved key for a recipient in the local
+         * store.  Only if it mismatches an entry in the local store is it considered
+         * 'untrusted.'
+         *
+         * @param name        The name of the remote client.
+         * @param identityKey The identity key to verify.
+         * @return true if trusted, false if untrusted.
+         */
+        @Override
+        public boolean isTrustedIdentity(String name, IdentityKey identityKey) {
+            try {
+                Jid contactJid = Jid.fromString(name);
+                Conversation conversation = this.mXmppConnectionService.find(this.account, contactJid);
+                if (conversation != null) {
+                    List<IdentityKey> trustedKeys = conversation.getContact().getTrustedAxolotlIdentityKeys();
+                    return trustedKeys.contains(identityKey);
+                } else {
+                    return false;
+                }
+            } catch (final InvalidJidException e) {
+                Log.e(Config.LOGTAG, "Failed to save identityKey for contact name" + name + ": " + e.toString());
+                return false;
+            }
+        }
+
+        // --------------------------------------
+        // SessionStore
+        // --------------------------------------
+
+        /**
+         * Returns a copy of the {@link SessionRecord} corresponding to the recipientId + deviceId tuple,
+         * or a new SessionRecord if one does not currently exist.
+         * <p/>
+         * It is important that implementations return a copy of the current durable information.  The
+         * returned SessionRecord may be modified, but those changes should not have an effect on the
+         * durable session state (what is returned by subsequent calls to this method) without the
+         * store method being called here first.
+         *
+         * @param address The name and device ID of the remote client.
+         * @return a copy of the SessionRecord corresponding to the recipientId + deviceId tuple, or
+         * a new SessionRecord if one does not currently exist.
+         */
+        @Override
+        public SessionRecord loadSession(AxolotlAddress address) {
+            SessionRecord session = mXmppConnectionService.databaseBackend.loadSession(this.account, address);
+            return (session!=null)?session:new SessionRecord();
+        }
+
+        /**
+         * Returns all known devices with active sessions for a recipient
+         *
+         * @param name the name of the client.
+         * @return all known sub-devices with active sessions.
+         */
+        @Override
+        public List<Integer> getSubDeviceSessions(String name) {
+            return mXmppConnectionService.databaseBackend.getSubDeviceSessions(account,
+                    new AxolotlAddress(name,0));
+        }
+
+        /**
+         * Commit to storage the {@link SessionRecord} for a given recipientId + deviceId tuple.
+         *
+         * @param address the address of the remote client.
+         * @param record  the current SessionRecord for the remote client.
+         */
+        @Override
+        public void storeSession(AxolotlAddress address, SessionRecord record) {
+            mXmppConnectionService.databaseBackend.storeSession(account, address, record);
+        }
+
+        /**
+         * Determine whether there is a committed {@link SessionRecord} for a recipientId + deviceId tuple.
+         *
+         * @param address the address of the remote client.
+         * @return true if a {@link SessionRecord} exists, false otherwise.
+         */
+        @Override
+        public boolean containsSession(AxolotlAddress address) {
+            return mXmppConnectionService.databaseBackend.containsSession(account, address);
+        }
+
+        /**
+         * Remove a {@link SessionRecord} for a recipientId + deviceId tuple.
+         *
+         * @param address the address of the remote client.
+         */
+        @Override
+        public void deleteSession(AxolotlAddress address) {
+            mXmppConnectionService.databaseBackend.deleteSession(account, address);
+        }
+
+        /**
+         * Remove the {@link SessionRecord}s corresponding to all devices of a recipientId.
+         *
+         * @param name the name of the remote client.
+         */
+        @Override
+        public void deleteAllSessions(String name) {
+            mXmppConnectionService.databaseBackend.deleteAllSessions(account,
+                    new AxolotlAddress(name,0));
+        }
+
+        // --------------------------------------
+        // PreKeyStore
+        // --------------------------------------
+
+        /**
+         * Load a local PreKeyRecord.
+         *
+         * @param preKeyId the ID of the local PreKeyRecord.
+         * @return the corresponding PreKeyRecord.
+         * @throws InvalidKeyIdException when there is no corresponding PreKeyRecord.
+         */
+        @Override
+        public PreKeyRecord loadPreKey(int preKeyId) throws InvalidKeyIdException {
+            PreKeyRecord record = mXmppConnectionService.databaseBackend.loadPreKey(account, preKeyId);
+            if(record == null) {
+                throw new InvalidKeyIdException("No such PreKeyRecord!");
+            }
+            return record;
+        }
+
+        /**
+         * Store a local PreKeyRecord.
+         *
+         * @param preKeyId the ID of the PreKeyRecord to store.
+         * @param record   the PreKeyRecord.
+         */
+        @Override
+        public void storePreKey(int preKeyId, PreKeyRecord record) {
+            mXmppConnectionService.databaseBackend.storePreKey(account, record);
+        }
+
+        /**
+         * @param preKeyId A PreKeyRecord ID.
+         * @return true if the store has a record for the preKeyId, otherwise false.
+         */
+        @Override
+        public boolean containsPreKey(int preKeyId) {
+            return mXmppConnectionService.databaseBackend.containsPreKey(account, preKeyId);
+        }
+
+        /**
+         * Delete a PreKeyRecord from local storage.
+         *
+         * @param preKeyId The ID of the PreKeyRecord to remove.
+         */
+        @Override
+        public void removePreKey(int preKeyId) {
+            mXmppConnectionService.databaseBackend.deletePreKey(account, preKeyId);
+        }
+
+        // --------------------------------------
+        // SignedPreKeyStore
+        // --------------------------------------
+
+        /**
+         * Load a local SignedPreKeyRecord.
+         *
+         * @param signedPreKeyId the ID of the local SignedPreKeyRecord.
+         * @return the corresponding SignedPreKeyRecord.
+         * @throws InvalidKeyIdException when there is no corresponding SignedPreKeyRecord.
+         */
+        @Override
+        public SignedPreKeyRecord loadSignedPreKey(int signedPreKeyId) throws InvalidKeyIdException {
+            SignedPreKeyRecord record = mXmppConnectionService.databaseBackend.loadSignedPreKey(account, signedPreKeyId);
+            if(record == null) {
+                throw new InvalidKeyIdException("No such PreKeyRecord!");
+            }
+            return record;
+        }
+
+        /**
+         * Load all local SignedPreKeyRecords.
+         *
+         * @return All stored SignedPreKeyRecords.
+         */
+        @Override
+        public List<SignedPreKeyRecord> loadSignedPreKeys() {
+            return mXmppConnectionService.databaseBackend.loadSignedPreKeys(account);
+        }
+
+        /**
+         * Store a local SignedPreKeyRecord.
+         *
+         * @param signedPreKeyId the ID of the SignedPreKeyRecord to store.
+         * @param record         the SignedPreKeyRecord.
+         */
+        @Override
+        public void storeSignedPreKey(int signedPreKeyId, SignedPreKeyRecord record) {
+            mXmppConnectionService.databaseBackend.storeSignedPreKey(account, record);
+        }
+
+        /**
+         * @param signedPreKeyId A SignedPreKeyRecord ID.
+         * @return true if the store has a record for the signedPreKeyId, otherwise false.
+         */
+        @Override
+        public boolean containsSignedPreKey(int signedPreKeyId) {
+            return mXmppConnectionService.databaseBackend.containsSignedPreKey(account, signedPreKeyId);
+        }
+
+        /**
+         * Delete a SignedPreKeyRecord from local storage.
+         *
+         * @param signedPreKeyId The ID of the SignedPreKeyRecord to remove.
+         */
+        @Override
+        public void removeSignedPreKey(int signedPreKeyId) {
+            mXmppConnectionService.databaseBackend.deleteSignedPreKey(account, signedPreKeyId);
+        }
+    }
+
+    private static class XmppAxolotlSession {
+        private List<Message> untrustedMessages;
+        private AxolotlStore axolotlStore;
+
+        public XmppAxolotlSession(SQLiteAxolotlStore axolotlStore) {
+            this.untrustedMessages = new ArrayList<>();
+            this.axolotlStore = axolotlStore;
+        }
+
+        public void trust() {
+            for (Message message : this.untrustedMessages) {
+                message.trust();
+            }
+            this.untrustedMessages = null;
+        }
+
+        public boolean isTrusted() {
+            return (this.untrustedMessages == null);
+        }
+
+        public String processReceiving(XmppAxolotlMessage incomingMessage) {
+            return null;
+        }
+
+        public XmppAxolotlMessage processSending(String outgoingMessage) {
+            return null;
+        }
+    }
+
+    public AxolotlService(Account account, XmppConnectionService connectionService) {
+        this.mXmppConnectionService = connectionService;
+        this.account = account;
+        this.axolotlStore = new SQLiteAxolotlStore(this.account, this.mXmppConnectionService);
+        this.sessions = new HashMap<>();
+    }
+
+    public void trustSession(Jid counterpart) {
+        XmppAxolotlSession session = sessions.get(counterpart);
+        if(session != null) {
+            session.trust();
+        }
+    }
+
+    public boolean isTrustedSession(Jid counterpart) {
+        XmppAxolotlSession session = sessions.get(counterpart);
+        return session != null && session.isTrusted();
+    }
+
+
+}

src/main/java/eu/siacs/conversations/crypto/axolotl/XmppAxolotlMessage.java

@@ -0,0 +1,4 @@
+package eu.siacs.conversations.crypto.axolotl;
+
+public class XmppAxolotlMessage {
+}

src/main/java/eu/siacs/conversations/entities/Account.java

@@ -254,6 +254,10 @@ public class Account extends AbstractEntity {
 		return keys;
 	}
 
+	public String getKey(final String name) {
+		return this.keys.optString(name, null);
+	}
+
 	public boolean setKey(final String keyName, final String keyValue) {
 		try {
 			this.keys.put(keyName, keyValue);

src/main/java/eu/siacs/conversations/entities/Contact.java

@@ -2,15 +2,19 @@ package eu.siacs.conversations.entities;
 
 import android.content.ContentValues;
 import android.database.Cursor;
+import android.util.Log;
 
 import org.json.JSONArray;
 import org.json.JSONException;
 import org.json.JSONObject;
+import org.whispersystems.libaxolotl.IdentityKey;
+import org.whispersystems.libaxolotl.InvalidKeyException;
 
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Locale;
 
+import eu.siacs.conversations.Config;
 import eu.siacs.conversations.utils.UIHelper;
 import eu.siacs.conversations.xml.Element;
 import eu.siacs.conversations.xmpp.jid.InvalidJidException;
@@ -183,6 +187,7 @@ public class Contact implements ListItem, Blockable {
 	}
 
 	public ContentValues getContentValues() {
+		synchronized (this.keys) {
 			final ContentValues values = new ContentValues();
 			values.put(ACCOUNT, accountUuid);
 			values.put(SYSTEMNAME, systemName);
@@ -198,6 +203,7 @@ public class Contact implements ListItem, Blockable {
 			values.put(GROUPS, groups.toString());
 			return values;
 		}
+	}
 
 	public int getSubscription() {
 		return this.subscription;
@@ -281,6 +287,7 @@ public class Contact implements ListItem, Blockable {
 	}
 
 	public ArrayList<String> getOtrFingerprints() {
+		synchronized (this.keys) {
 			final ArrayList<String> fingerprints = new ArrayList<String>();
 			try {
 				if (this.keys.has("otr_fingerprints")) {
@@ -297,8 +304,9 @@ public class Contact implements ListItem, Blockable {
 			}
 			return fingerprints;
 		}
-
+	}
 	public boolean addOtrFingerprint(String print) {
+		synchronized (this.keys) {
 			if (getOtrFingerprints().contains(print)) {
 				return false;
             }
@@ -306,7 +314,6 @@ public class Contact implements ListItem, Blockable {
 				JSONArray fingerprints;
 				if (!this.keys.has("otr_fingerprints")) {
 					fingerprints = new JSONArray();
-
 				} else {
 					fingerprints = this.keys.getJSONArray("otr_fingerprints");
 				}
@@ -317,8 +324,10 @@ public class Contact implements ListItem, Blockable {
 				return false;
 			}
 		}
+	}
 
 	public long getPgpKeyId() {
+		synchronized (this.keys) {
 			if (this.keys.has("pgp_keyid")) {
 				try {
 					return this.keys.getLong("pgp_keyid");
@@ -329,14 +338,57 @@ public class Contact implements ListItem, Blockable {
 				return 0;
 			}
 		}
+	}
 
 	public void setPgpKeyId(long keyId) {
+		synchronized (this.keys) {
 			try {
 				this.keys.put("pgp_keyid", keyId);
 			} catch (final JSONException ignored) {
+			}
+		}
+	}
 
+	public List<IdentityKey> getTrustedAxolotlIdentityKeys() {
+		synchronized (this.keys) {
+			JSONArray serializedKeyItems = this.keys.optJSONArray("axolotl_identity_key");
+			List<IdentityKey> identityKeys = new ArrayList<>();
+			if(serializedKeyItems != null) {
+				for(int i = 0; i<serializedKeyItems.length();++i) {
+					try {
+						String serializedKeyItem = serializedKeyItems.getString(i);
+						IdentityKey identityKey = new IdentityKey(serializedKeyItem.getBytes(), 0);
+						identityKeys.add(identityKey);
+					} catch (InvalidKeyException e) {
+						Log.e(Config.LOGTAG, "Invalid axolotl identity key encountered at" + this.getJid() + ": " + e.getMessage());
+					} catch (JSONException e) {
+						Log.e(Config.LOGTAG, "Error retrieving axolotl identity key at" + this.getJid() + ": " + e.getMessage());
 					}
 				}
+			}
+			return identityKeys;
+		}
+	}
+
+	public boolean addAxolotlIdentityKey(IdentityKey identityKey, boolean trusted) {
+		synchronized (this.keys) {
+			JSONArray keysList;
+			try {
+				keysList = this.keys.getJSONArray("axolotl_identity_key");
+			} catch (JSONException e) {
+				keysList = new JSONArray();
+			}
+			keysList.put(new String(identityKey.serialize()));
+			try {
+				this.keys.put("axolotl_identity_key", keysList);
+			} catch (JSONException e) {
+				Log.e(Config.LOGTAG, "Error adding Identity Key to Contact " + this.getJid() + ": " + e.getMessage());
+				return false;
+			}
+		}
+		return true;
+	}
+
 
 	public void setOption(int option) {
 		this.subscription |= 1 << option;
@@ -441,6 +493,7 @@ public class Contact implements ListItem, Blockable {
 	}
 
 	public boolean deleteOtrFingerprint(String fingerprint) {
+		synchronized (this.keys) {
 			boolean success = false;
 			try {
 				if (this.keys.has("otr_fingerprints")) {
@@ -461,6 +514,7 @@ public class Contact implements ListItem, Blockable {
 				return false;
 			}
 		}
+	}
 
 	public boolean trusted() {
 		return getOption(Options.FROM) && getOption(Options.TO);

src/main/java/eu/siacs/conversations/entities/Message.java

@@ -65,6 +65,7 @@ public class Message extends AbstractEntity {
 	protected int encryption;
 	protected int status;
 	protected int type;
+	private boolean isTrusted = true;
 	protected String relativeFilePath;
 	protected boolean read = true;
 	protected String remoteMsgId = null;
@@ -653,4 +654,16 @@ public class Message extends AbstractEntity {
 		public int width = 0;
 		public int height = 0;
 	}
+
+	public void trust() {
+		this.isTrusted = true;
+	}
+
+	public void distrust() {
+		this.isTrusted = false;
+	}
+
+	public boolean isTrusted() {
+		return this.isTrusted;
+	}
 }

src/main/java/eu/siacs/conversations/persistance/DatabaseBackend.java

@@ -1,10 +1,12 @@
 package eu.siacs.conversations.persistance;
 
+import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.CopyOnWriteArrayList;
 
 import eu.siacs.conversations.Config;
+import eu.siacs.conversations.crypto.axolotl.AxolotlService;
 import eu.siacs.conversations.entities.Account;
 import eu.siacs.conversations.entities.Contact;
 import eu.siacs.conversations.entities.Conversation;
@@ -13,6 +15,7 @@ import eu.siacs.conversations.entities.Roster;
 import eu.siacs.conversations.xmpp.jid.InvalidJidException;
 import eu.siacs.conversations.xmpp.jid.Jid;
 
+import android.content.ContentValues;
 import android.content.Context;
 import android.database.Cursor;
 import android.database.sqlite.SQLiteCantOpenDatabaseException;
@@ -20,6 +23,11 @@ import android.database.sqlite.SQLiteDatabase;
 import android.database.sqlite.SQLiteOpenHelper;
 import android.util.Log;
 
+import org.whispersystems.libaxolotl.AxolotlAddress;
+import org.whispersystems.libaxolotl.state.PreKeyRecord;
+import org.whispersystems.libaxolotl.state.SessionRecord;
+import org.whispersystems.libaxolotl.state.SignedPreKeyRecord;
+
 public class DatabaseBackend extends SQLiteOpenHelper {
 
 	private static DatabaseBackend instance = null;
@@ -39,6 +47,40 @@ public class DatabaseBackend extends SQLiteOpenHelper {
 			+ ") ON DELETE CASCADE, UNIQUE(" + Contact.ACCOUNT + ", "
 			+ Contact.JID + ") ON CONFLICT REPLACE);";
 
+	private static String CREATE_PREKEYS_STATEMENT = "CREATE TABLE "
+			+ AxolotlService.SQLiteAxolotlStore.PREKEY_TABLENAME + "("
+				+ AxolotlService.SQLiteAxolotlStore.ID + " INTEGER, "
+				+ AxolotlService.SQLiteAxolotlStore.KEY + "TEXT, FOREIGN KEY("
+					+ AxolotlService.SQLiteAxolotlStore.ACCOUNT
+				+ ") REFERENCES " + Account.TABLENAME + "(" + Account.UUID + ") ON DELETE CASCADE, "
+				+ "UNIQUE( " + AxolotlService.SQLiteAxolotlStore.ACCOUNT + ", "
+					+ AxolotlService.SQLiteAxolotlStore.ID
+				+ ") ON CONFLICT REPLACE"
+			+");";
+
+	private static String CREATE_SIGNED_PREKEYS_STATEMENT = "CREATE TABLE "
+			+ AxolotlService.SQLiteAxolotlStore.SIGNED_PREKEY_TABLENAME + "("
+				+ AxolotlService.SQLiteAxolotlStore.ID + " INTEGER, "
+				+ AxolotlService.SQLiteAxolotlStore.KEY + "TEXT, FOREIGN KEY("
+					+ AxolotlService.SQLiteAxolotlStore.ACCOUNT
+				+ ") REFERENCES " + Account.TABLENAME + "(" + Account.UUID + ") ON DELETE CASCADE, "
+				+ "UNIQUE( " + AxolotlService.SQLiteAxolotlStore.ACCOUNT + ", "
+					+ AxolotlService.SQLiteAxolotlStore.ID
+				+ ") ON CONFLICT REPLACE"+
+			");";
+
+	private static String CREATE_SESSIONS_STATEMENT = "CREATE TABLE "
+			+ AxolotlService.SQLiteAxolotlStore.SESSION_TABLENAME + "("
+                + AxolotlService.SQLiteAxolotlStore.NAME + " TEXT, "
+                + AxolotlService.SQLiteAxolotlStore.DEVICE_ID+ " INTEGER, "
+                + AxolotlService.SQLiteAxolotlStore.KEY + "TEXT, FOREIGN KEY("
+                    + AxolotlService.SQLiteAxolotlStore.ACCOUNT
+				+ ") REFERENCES " + Account.TABLENAME + "(" + Account.UUID + ") ON DELETE CASCADE, "
+                + "UNIQUE( " + AxolotlService.SQLiteAxolotlStore.ACCOUNT + ", "
+                    + AxolotlService.SQLiteAxolotlStore.NAME
+				+ ") ON CONFLICT REPLACE"
+			+");";
+
 	private DatabaseBackend(Context context) {
 		super(context, DATABASE_NAME, null, DATABASE_VERSION);
 	}
@@ -481,4 +523,223 @@ public class DatabaseBackend extends SQLiteOpenHelper {
 		cursor.close();
 		return list;
 	}
+
+	private Cursor getCursorForSession(Account account, AxolotlAddress contact) {
+		final SQLiteDatabase db = this.getReadableDatabase();
+		String[] columns = null;
+		String[] selectionArgs = {account.getUuid(),
+				contact.getName(),
+				Integer.toString(contact.getDeviceId())};
+		Cursor cursor = db.query(AxolotlService.SQLiteAxolotlStore.SESSION_TABLENAME,
+				columns,
+				AxolotlService.SQLiteAxolotlStore.ACCOUNT + " = ? AND "
+						+ AxolotlService.SQLiteAxolotlStore.NAME + " = ? AND "
+						+ AxolotlService.SQLiteAxolotlStore.DEVICE_ID + " = ? ",
+				selectionArgs,
+				null, null, null);
+
+		return cursor;
+	}
+
+	public SessionRecord loadSession(Account account, AxolotlAddress contact) {
+		SessionRecord session = null;
+        Cursor cursor = getCursorForSession(account, contact);
+		if(cursor.getCount() != 0) {
+			cursor.moveToFirst();
+			try {
+				session = new SessionRecord(cursor.getString(cursor.getColumnIndex(AxolotlService.SQLiteAxolotlStore.KEY)).getBytes());
+			} catch (IOException e) {
+				throw new AssertionError(e);
+			}
+        }
+        cursor.close();
+		return session;
+	}
+
+	public List<Integer> getSubDeviceSessions(Account account, AxolotlAddress contact) {
+		List<Integer> devices = new ArrayList<>();
+		final SQLiteDatabase db = this.getReadableDatabase();
+		String[] columns = {AxolotlService.SQLiteAxolotlStore.DEVICE_ID};
+		String[] selectionArgs = {account.getUuid(),
+				contact.getName()};
+		Cursor cursor = db.query(AxolotlService.SQLiteAxolotlStore.SESSION_TABLENAME,
+				columns,
+				AxolotlService.SQLiteAxolotlStore.ACCOUNT + " = ? AND "
+						+ AxolotlService.SQLiteAxolotlStore.NAME + " = ? AND ",
+				selectionArgs,
+				null, null, null);
+
+		while(cursor.moveToNext()) {
+			devices.add(cursor.getInt(
+					cursor.getColumnIndex(AxolotlService.SQLiteAxolotlStore.DEVICE_ID)));
+		}
+
+		cursor.close();
+		return devices;
+	}
+
+	public boolean containsSession(Account account, AxolotlAddress contact) {
+		Cursor cursor = getCursorForSession(account, contact);
+		int count = cursor.getCount();
+		cursor.close();
+		return count != 0;
+	}
+
+	public void storeSession(Account account, AxolotlAddress contact, SessionRecord session) {
+		SQLiteDatabase db = this.getWritableDatabase();
+		ContentValues values = new ContentValues();
+		values.put(AxolotlService.SQLiteAxolotlStore.NAME, contact.getName());
+		values.put(AxolotlService.SQLiteAxolotlStore.DEVICE_ID, contact.getDeviceId());
+		values.put(AxolotlService.SQLiteAxolotlStore.KEY, session.serialize());
+		values.put(AxolotlService.SQLiteAxolotlStore.ACCOUNT, account.getUuid());
+		db.insert(AxolotlService.SQLiteAxolotlStore.SESSION_TABLENAME, null, values);
+	}
+
+	public void deleteSession(Account account, AxolotlAddress contact) {
+		SQLiteDatabase db = this.getWritableDatabase();
+		String[] args = {account.getUuid(),
+				contact.getName(),
+				Integer.toString(contact.getDeviceId())};
+		db.delete(AxolotlService.SQLiteAxolotlStore.SESSION_TABLENAME,
+				AxolotlService.SQLiteAxolotlStore.ACCOUNT + " = ? AND "
+						+ AxolotlService.SQLiteAxolotlStore.NAME + " = ? AND "
+						+ AxolotlService.SQLiteAxolotlStore.DEVICE_ID + " = ? ",
+				args);
+	}
+
+	public void deleteAllSessions(Account account, AxolotlAddress contact) {
+		SQLiteDatabase db = this.getWritableDatabase();
+		String[] args = {account.getUuid(), contact.getName()};
+		db.delete(AxolotlService.SQLiteAxolotlStore.SESSION_TABLENAME,
+				AxolotlService.SQLiteAxolotlStore.ACCOUNT + "=? AND "
+						+ AxolotlService.SQLiteAxolotlStore.NAME + " = ?",
+				args);
+	}
+
+	private Cursor getCursorForPreKey(Account account, int preKeyId) {
+		SQLiteDatabase db = this.getReadableDatabase();
+		String[] columns = {AxolotlService.SQLiteAxolotlStore.KEY};
+		String[] selectionArgs = {account.getUuid(), Integer.toString(preKeyId)};
+		Cursor cursor = db.query(AxolotlService.SQLiteAxolotlStore.PREKEY_TABLENAME,
+				columns,
+				AxolotlService.SQLiteAxolotlStore.ACCOUNT + "=? AND "
+						+ AxolotlService.SQLiteAxolotlStore.ID + "=?",
+				selectionArgs,
+				null, null, null);
+
+		return cursor;
+	}
+
+	public PreKeyRecord loadPreKey(Account account, int preKeyId) {
+		PreKeyRecord record = null;
+		Cursor cursor = getCursorForPreKey(account, preKeyId);
+		if(cursor.getCount() != 0) {
+			cursor.moveToFirst();
+			try {
+				record = new PreKeyRecord(cursor.getString(cursor.getColumnIndex(AxolotlService.SQLiteAxolotlStore.KEY)).getBytes());
+			} catch (IOException e ) {
+				throw new AssertionError(e);
+			}
+		}
+		cursor.close();
+		return record;
+	}
+
+	public boolean containsPreKey(Account account, int preKeyId) {
+		Cursor cursor = getCursorForPreKey(account, preKeyId);
+		int count = cursor.getCount();
+		cursor.close();
+		return count != 0;
+	}
+
+	public void storePreKey(Account account, PreKeyRecord record) {
+		SQLiteDatabase db = this.getWritableDatabase();
+		ContentValues values = new ContentValues();
+		values.put(AxolotlService.SQLiteAxolotlStore.ID, record.getId());
+		values.put(AxolotlService.SQLiteAxolotlStore.KEY, record.serialize());
+		values.put(AxolotlService.SQLiteAxolotlStore.ACCOUNT, account.getUuid());
+		db.insert(AxolotlService.SQLiteAxolotlStore.PREKEY_TABLENAME, null, values);
+	}
+
+	public void deletePreKey(Account account, int preKeyId) {
+		SQLiteDatabase db = this.getWritableDatabase();
+		String[] args = {account.getUuid(), Integer.toString(preKeyId)};
+		db.delete(AxolotlService.SQLiteAxolotlStore.PREKEY_TABLENAME,
+				AxolotlService.SQLiteAxolotlStore.ACCOUNT + "=? AND "
+						+ AxolotlService.SQLiteAxolotlStore.ID + "=?",
+				args);
+	}
+
+	private Cursor getCursorForSignedPreKey(Account account, int signedPreKeyId) {
+		SQLiteDatabase db = this.getReadableDatabase();
+		String[] columns = {AxolotlService.SQLiteAxolotlStore.KEY};
+		String[] selectionArgs = {account.getUuid(), Integer.toString(signedPreKeyId)};
+		Cursor cursor = db.query(AxolotlService.SQLiteAxolotlStore.SIGNED_PREKEY_TABLENAME,
+				columns,
+				AxolotlService.SQLiteAxolotlStore.ACCOUNT + "=? AND " + AxolotlService.SQLiteAxolotlStore.ID + "=?",
+				selectionArgs,
+				null, null, null);
+
+		return cursor;
+	}
+
+	public SignedPreKeyRecord loadSignedPreKey(Account account, int signedPreKeyId) {
+		SignedPreKeyRecord record = null;
+		Cursor cursor = getCursorForPreKey(account, signedPreKeyId);
+		if(cursor.getCount() != 0) {
+			cursor.moveToFirst();
+			try {
+				record = new SignedPreKeyRecord(cursor.getString(cursor.getColumnIndex(AxolotlService.SQLiteAxolotlStore.KEY)).getBytes());
+			} catch (IOException e ) {
+				throw new AssertionError(e);
+			}
+		}
+		cursor.close();
+		return record;
+	}
+
+	public List<SignedPreKeyRecord> loadSignedPreKeys(Account account) {
+		List<SignedPreKeyRecord> prekeys = new ArrayList<>();
+		SQLiteDatabase db = this.getReadableDatabase();
+		String[] columns = {AxolotlService.SQLiteAxolotlStore.KEY};
+		String[] selectionArgs = {account.getUuid()};
+		Cursor cursor = db.query(AxolotlService.SQLiteAxolotlStore.SIGNED_PREKEY_TABLENAME,
+				columns,
+				AxolotlService.SQLiteAxolotlStore.ACCOUNT + "=?",
+				selectionArgs,
+				null, null, null);
+
+		while(cursor.moveToNext()) {
+			try {
+				prekeys.add(new SignedPreKeyRecord(cursor.getString(cursor.getColumnIndex(AxolotlService.SQLiteAxolotlStore.KEY)).getBytes()));
+			} catch (IOException ignored) {
+			}
+		}
+		return prekeys;
+	}
+
+	public boolean containsSignedPreKey(Account account, int signedPreKeyId) {
+		Cursor cursor = getCursorForPreKey(account, signedPreKeyId);
+		int count = cursor.getCount();
+		cursor.close();
+		return count != 0;
+	}
+
+	public void storeSignedPreKey(Account account, SignedPreKeyRecord record) {
+		SQLiteDatabase db = this.getWritableDatabase();
+		ContentValues values = new ContentValues();
+		values.put(AxolotlService.SQLiteAxolotlStore.ID, record.getId());
+		values.put(AxolotlService.SQLiteAxolotlStore.KEY, record.serialize());
+		values.put(AxolotlService.SQLiteAxolotlStore.ACCOUNT, account.getUuid());
+		db.insert(AxolotlService.SQLiteAxolotlStore.SIGNED_PREKEY_TABLENAME, null, values);
+	}
+
+	public void deleteSignedPreKey(Account account, int signedPreKeyId) {
+		SQLiteDatabase db = this.getWritableDatabase();
+		String[] args = {account.getUuid(), Integer.toString(signedPreKeyId)};
+		db.delete(AxolotlService.SQLiteAxolotlStore.SIGNED_PREKEY_TABLENAME,
+				AxolotlService.SQLiteAxolotlStore.ACCOUNT + "=? AND "
+						+ AxolotlService.SQLiteAxolotlStore.ID + "=?",
+				args);
+	}
 }