WIP make part of keyAgreement public, so it can be used for shard return

* 'social-backup-poc' of https://code.briarproject.org/briar/briar:
  Inject social backup eager singletons when Briar core is created.

bramble-api/src/main/java/org/briarproject/bramble/api/crypto/AuthenticatedCipher.java

@@ -1,12 +1,11 @@
-package org.briarproject.bramble.crypto;
+package org.briarproject.bramble.api.crypto;
 
-import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
 import java.security.GeneralSecurityException;
 
 @NotNullByDefault
-interface AuthenticatedCipher {
+public interface AuthenticatedCipher {
 
 	/**
 	 * Initializes this cipher for encryption or decryption with a key and an

bramble-api/src/main/java/org/briarproject/bramble/api/identity/IdentityManager.java

@@ -26,6 +26,11 @@ public interface IdentityManager {
 	 */
 	void registerIdentity(Identity i);
 
+	/**
+	 * Returns the cached local identity or loads it from the database.
+	 */
+	Identity getIdentity(Transaction txn) throws DbException;
+
 	/**
 	 * Returns the cached local identity or loads it from the database.
 	 */

bramble-api/src/main/java/org/briarproject/bramble/api/properties/TransportPropertyManager.java

@@ -74,6 +74,13 @@ public interface TransportPropertyManager {
 	TransportProperties getRemoteProperties(ContactId c, TransportId t)
 			throws DbException;
 
+	/**
+	 * Returns the remote transport properties for the given contact and
+	 * transport.
+	 */
+	TransportProperties getRemoteProperties(Transaction txn, ContactId c,
+			TransportId t) throws DbException;
+
 	/**
 	 * Merges the given properties with the existing local properties for the
 	 * given transport.

bramble-core/src/main/java/org/briarproject/bramble/crypto/CryptoComponentImpl.java

@@ -6,6 +6,7 @@ import net.i2p.crypto.eddsa.KeyPairGenerator;
 
 import org.briarproject.bramble.api.crypto.AgreementPrivateKey;
 import org.briarproject.bramble.api.crypto.AgreementPublicKey;
+import org.briarproject.bramble.api.crypto.AuthenticatedCipher;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.crypto.DecryptionException;
 import org.briarproject.bramble.api.crypto.KeyPair;

bramble-core/src/main/java/org/briarproject/bramble/crypto/CryptoModule.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.crypto;
 
+import org.briarproject.bramble.api.crypto.AuthenticatedCipher;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.crypto.KeyAgreementCrypto;
 import org.briarproject.bramble.api.crypto.PasswordStrengthEstimator;

bramble-core/src/main/java/org/briarproject/bramble/crypto/StreamDecrypterFactoryImpl.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.crypto;
 
+import org.briarproject.bramble.api.crypto.AuthenticatedCipher;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.crypto.StreamDecrypter;
 import org.briarproject.bramble.api.crypto.StreamDecrypterFactory;

bramble-core/src/main/java/org/briarproject/bramble/crypto/StreamDecrypterImpl.java

@@ -1,6 +1,7 @@
 package org.briarproject.bramble.crypto;
 
 import org.briarproject.bramble.api.FormatException;
+import org.briarproject.bramble.api.crypto.AuthenticatedCipher;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.crypto.StreamDecrypter;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;

bramble-core/src/main/java/org/briarproject/bramble/crypto/StreamEncrypterFactoryImpl.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.crypto;
 
+import org.briarproject.bramble.api.crypto.AuthenticatedCipher;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.crypto.StreamEncrypter;

bramble-core/src/main/java/org/briarproject/bramble/crypto/StreamEncrypterImpl.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.crypto;
 
+import org.briarproject.bramble.api.crypto.AuthenticatedCipher;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.crypto.StreamEncrypter;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;

bramble-core/src/main/java/org/briarproject/bramble/crypto/XSalsa20Poly1305AuthenticatedCipher.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.crypto;
 
+import org.briarproject.bramble.api.crypto.AuthenticatedCipher;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.spongycastle.crypto.DataLengthException;

bramble-core/src/main/java/org/briarproject/bramble/identity/IdentityManagerImpl.java

@@ -118,6 +118,11 @@ class IdentityManagerImpl implements IdentityManager, OpenDatabaseHook {
 		return cached.getLocalAuthor();
 	}
 
+	@Override
+	public Identity getIdentity(Transaction txn) throws DbException {
+		return getCachedIdentity(txn);
+	}
+
 	@Override
 	public LocalAuthor getLocalAuthor(Transaction txn) throws DbException {
 		return getCachedIdentity(txn).getLocalAuthor();

bramble-core/src/main/java/org/briarproject/bramble/properties/TransportPropertyManagerImpl.java

@@ -294,7 +294,13 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 	public TransportProperties getRemoteProperties(ContactId c, TransportId t)
 			throws DbException {
 		return db.transactionWithResult(true, txn ->
-				getRemoteProperties(txn, db.getContact(txn, c), t));
+				getRemoteProperties(txn, c, t));
+	}
+
+	@Override
+	public TransportProperties getRemoteProperties(Transaction txn,
+			ContactId c, TransportId t) throws DbException {
+		return getRemoteProperties(txn, db.getContact(txn, c), t);
 	}
 
 	@Override

bramble-core/src/test/java/org/briarproject/bramble/crypto/StreamDecrypterImplTest.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.crypto;
 
+import org.briarproject.bramble.api.crypto.AuthenticatedCipher;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.test.BrambleTestCase;
 import org.briarproject.bramble.test.TestUtils;

bramble-core/src/test/java/org/briarproject/bramble/crypto/StreamEncrypterImplTest.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.crypto;
 
+import org.briarproject.bramble.api.crypto.AuthenticatedCipher;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.test.BrambleTestCase;
 import org.briarproject.bramble.test.TestUtils;

bramble-core/src/test/java/org/briarproject/bramble/crypto/TestAuthenticatedCipher.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.crypto;
 
+import org.briarproject.bramble.api.crypto.AuthenticatedCipher;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 

bramble-core/src/test/java/org/briarproject/bramble/crypto/XSalsa20Poly1305AuthenticatedCipherTest.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.crypto;
 
+import org.briarproject.bramble.api.crypto.AuthenticatedCipher;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.test.BrambleTestCase;
 import org.briarproject.bramble.util.StringUtils;

briar-android/build.gradle

@@ -24,7 +24,7 @@ android {
 		targetSdkVersion 29
 		versionCode 10216
 		versionName "1.2.16"
-		applicationId "org.briarproject.briar.android"
+		applicationId "org.briarproject.briar.socialbackup"
 
 		vectorDrawables.useSupportLibrary = true
 		buildConfigField "String", "GitHash",
@@ -101,6 +101,7 @@ dependencies {
 	implementation 'androidx.constraintlayout:constraintlayout:2.0.4'
 	implementation 'com.google.android.material:material:1.2.1'
 	implementation 'androidx.recyclerview:recyclerview-selection:1.1.0-rc03'
+	implementation 'org.magmacollective.darkcrystal:dark-crystal-secret-sharing-wrapper:1.1.0'
 
 	implementation 'info.guardianproject.panic:panic:1.0'
 	implementation 'info.guardianproject.trustedintents:trustedintents:0.2'

briar-android/proguard-rules.txt

@@ -40,3 +40,5 @@
 
 # Dependency injection annotations, needed for UI tests on older API levels
 -keep class javax.inject.**
+
+-keep class com.sun.jna.** { *; }

briar-android/src/debug/res/values/strings.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
 <resources>
-	<string name="app_name" translatable="false">Briar Debug</string>
-	<string name="app_package" translatable="false">org.briarproject.briar.android.debug</string>
+	<string name="app_name" translatable="false">Briar SB Debug</string>
+	<string name="app_package" translatable="false">org.briarproject.briar.socialbackup.debug</string>
 </resources>

briar-android/src/main/AndroidManifest.xml

@@ -134,6 +134,42 @@
 			</intent-filter>
 		</activity>
 
+		<activity
+			android:name="org.briarproject.briar.android.account.NewOrRecoverActivity"
+			android:label="@string/activity_name_new_or_recover_account"
+			android:parentActivityName="org.briarproject.briar.android.login.StartupActivity">
+			<meta-data
+				android:name="android.support.PARENT_ACTIVITY"
+				android:value="org.briarproject.briar.android.login.StartupActivity" />
+		</activity>
+
+		<activity
+			android:name="org.briarproject.briar.android.socialbackup.DistributedBackupActivity"
+			android:label="@string/activity_name_distributed_backup"
+			android:parentActivityName="org.briarproject.briar.android.settings.SettingsActivity">
+			<meta-data
+				android:name="android.support.PARENT_ACTIVITY"
+				android:value="org.briarproject.briar.android.settings.SettingsActivity" />
+		</activity>
+
+		<activity
+			android:name="org.briarproject.briar.android.socialbackup.RecoverActivity"
+			android:label="@string/activity_name_recovery"
+			android:parentActivityName="org.briarproject.briar.android.account.NewOrRecoverActivity">
+			<meta-data
+				android:name="android.support.PARENT_ACTIVITY"
+				android:value="org.briarproject.briar.android.account.NewOrRecoverActivity" />
+		</activity>
+
+		<activity
+			android:name="org.briarproject.briar.android.socialbackup.CustodianHelpRecoverActivity"
+			android:label="@string/activity_name_custodian_help_recovery"
+			android:parentActivityName="org.briarproject.briar.android.conversation.ConversationActivity">
+			<meta-data
+				android:name="android.support.PARENT_ACTIVITY"
+				android:value="org.briarproject.briar.android.conversation.ConversationActivity" />
+		</activity>
+
 		<activity
 			android:name="org.briarproject.briar.android.conversation.ConversationActivity"
 			android:label="@string/app_name"

briar-android/src/main/java/org/briarproject/briar/android/AndroidComponent.java

@@ -13,6 +13,7 @@ import org.briarproject.bramble.api.contact.ContactExchangeManager;
 import org.briarproject.bramble.api.contact.ContactManager;
 import org.briarproject.bramble.api.crypto.CryptoExecutor;
 import org.briarproject.bramble.api.crypto.PasswordStrengthEstimator;
+import org.briarproject.bramble.api.db.DatabaseComponent;
 import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.TransactionManager;
 import org.briarproject.bramble.api.event.EventBus;
@@ -59,7 +60,9 @@ import org.briarproject.briar.api.privategroup.PrivateGroupFactory;
 import org.briarproject.briar.api.privategroup.PrivateGroupManager;
 import org.briarproject.briar.api.privategroup.invitation.GroupInvitationFactory;
 import org.briarproject.briar.api.privategroup.invitation.GroupInvitationManager;
+import org.briarproject.briar.api.socialbackup.SocialBackupManager;
 import org.briarproject.briar.api.test.TestDataCreator;
+import org.briarproject.briar.socialbackup.SocialBackupManagerImpl_Factory;
 
 import java.util.concurrent.Executor;
 
@@ -184,6 +187,10 @@ public interface AndroidComponent
 
 	Thread.UncaughtExceptionHandler exceptionHandler();
 
+	SocialBackupManager socialBackupManager();
+
+    DatabaseComponent databaseComponent();
+
 	void inject(SignInReminderReceiver briarService);
 
 	void inject(BriarService briarService);

briar-android/src/main/java/org/briarproject/briar/android/AppModule.java

@@ -48,6 +48,7 @@ import org.briarproject.briar.api.android.DozeWatchdog;
 import org.briarproject.briar.api.android.LockManager;
 import org.briarproject.briar.api.android.ScreenFilterMonitor;
 import org.briarproject.briar.api.test.TestAvatarCreator;
+import org.briarproject.briar.socialbackup.AndroidDarkCrystalModule;
 
 import java.io.File;
 import java.security.GeneralSecurityException;
@@ -82,6 +83,7 @@ import static org.briarproject.briar.android.TestingConstants.IS_DEBUG_BUILD;
 		SettingsModule.class,
 		DevReportModule.class,
 		ContactListModule.class,
+		AndroidDarkCrystalModule.class,
 		// below need to be within same scope as ViewModelProvider.Factory
 		ForumModule.class,
 		GroupListModule.class,

briar-android/src/main/java/org/briarproject/briar/android/account/NewOrRecoverActivity.java

@@ -0,0 +1,59 @@
+package org.briarproject.briar.android.account;
+
+import android.content.Intent;
+import android.os.Bundle;
+
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.activity.ActivityComponent;
+import org.briarproject.briar.android.activity.BaseActivity;
+import org.briarproject.briar.android.fragment.BaseFragment;
+import org.briarproject.briar.android.socialbackup.RecoverActivity;
+
+import static android.content.Intent.FLAG_ACTIVITY_CLEAR_TASK;
+import static android.content.Intent.FLAG_ACTIVITY_CLEAR_TOP;
+import static android.content.Intent.FLAG_ACTIVITY_NEW_TASK;
+import static android.content.Intent.FLAG_ACTIVITY_TASK_ON_HOME;
+
+public class NewOrRecoverActivity extends BaseActivity implements
+		BaseFragment.BaseFragmentListener, SetupNewAccountChosenListener,
+		RecoverAccountListener {
+
+	@Override
+	public void injectActivity(ActivityComponent component) {
+		component.inject(this);
+	}
+
+	@Override
+	public void onCreate(Bundle state) {
+		super.onCreate(state);
+		// fade-in after splash screen instead of default animation
+		overridePendingTransition(R.anim.fade_in, R.anim.fade_out);
+		setContentView(R.layout.activity_fragment_container);
+		NewOrRecoverFragment fragment = NewOrRecoverFragment.newInstance();
+		showInitialFragment(fragment);
+	}
+
+	@Override
+	public void setupNewAccountChosen() {
+		finish();
+		Intent i = new Intent(this, SetupActivity.class);
+		i.addFlags(FLAG_ACTIVITY_NEW_TASK | FLAG_ACTIVITY_CLEAR_TOP |
+				FLAG_ACTIVITY_CLEAR_TASK | FLAG_ACTIVITY_TASK_ON_HOME);
+		startActivity(i);
+	}
+
+	@Override
+	public void recoverAccountChosen() {
+		finish();
+		Intent i = new Intent(this, RecoverActivity.class);
+		i.addFlags(FLAG_ACTIVITY_NEW_TASK | FLAG_ACTIVITY_CLEAR_TOP |
+				FLAG_ACTIVITY_CLEAR_TASK | FLAG_ACTIVITY_TASK_ON_HOME);
+		startActivity(i);
+	}
+
+	@Override
+	@Deprecated
+	public void runOnDbThread(Runnable runnable) {
+		throw new RuntimeException("Don't use this deprecated method here.");
+	}
+}

briar-android/src/main/java/org/briarproject/briar/android/account/NewOrRecoverFragment.java

@@ -0,0 +1,70 @@
+package org.briarproject.briar.android.account;
+
+import android.content.Context;
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.Button;
+
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.activity.ActivityComponent;
+import org.briarproject.briar.android.fragment.BaseFragment;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
+public class NewOrRecoverFragment extends BaseFragment {
+
+	public static final String TAG = NewOrRecoverFragment.class.getName();
+
+	protected SetupNewAccountChosenListener setupNewAccountListener;
+	protected RecoverAccountListener recoverAccountListener;
+
+	public static NewOrRecoverFragment newInstance() {
+		Bundle bundle = new Bundle();
+		NewOrRecoverFragment fragment = new NewOrRecoverFragment();
+		fragment.setArguments(bundle);
+		return fragment;
+	}
+	@Override
+	public void onCreate(@Nullable Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+		requireActivity().setTitle(R.string.setup_title);
+	}
+
+	@Nullable
+	@Override
+	public View onCreateView(@NonNull LayoutInflater inflater, @Nullable
+			ViewGroup container, @Nullable Bundle savedInstanceState) {
+		View view = inflater.inflate(R.layout.fragment_new_or_recover,
+				container, false);
+		Button newAccountButton = view.findViewById(R.id.buttonSetupNewAccount);
+		newAccountButton.setOnClickListener(e -> {
+			setupNewAccountListener.setupNewAccountChosen();
+		});
+
+		Button recoverAccountButton = view.findViewById(R.id.buttonRestoreAccount);
+		recoverAccountButton.setOnClickListener(e -> {
+			recoverAccountListener.recoverAccountChosen();
+		});
+		return view;
+	}
+
+	@Override
+	public void onAttach(Context context) {
+		super.onAttach(context);
+		setupNewAccountListener = (SetupNewAccountChosenListener) context;
+		recoverAccountListener = (RecoverAccountListener) context;
+	}
+
+	@Override
+	public String getUniqueTag() {
+		return TAG;
+	}
+
+	@Override
+	public void injectFragment(ActivityComponent component) {
+		component.inject(this);
+	}
+}

briar-android/src/main/java/org/briarproject/briar/android/account/RecoverAccountListener.java

@@ -0,0 +1,8 @@
+package org.briarproject.briar.android.account;
+
+import androidx.annotation.UiThread;
+
+public interface RecoverAccountListener {
+	@UiThread
+	void recoverAccountChosen();
+}

briar-android/src/main/java/org/briarproject/briar/android/account/SetupNewAccountChosenListener.java

@@ -0,0 +1,8 @@
+package org.briarproject.briar.android.account;
+
+import androidx.annotation.UiThread;
+
+public interface SetupNewAccountChosenListener {
+	@UiThread
+	void setupNewAccountChosen();
+}

briar-android/src/main/java/org/briarproject/briar/android/activity/ActivityComponent.java

@@ -2,10 +2,13 @@ package org.briarproject.briar.android.activity;
 
 import android.app.Activity;
 
+import org.briarproject.bramble.api.db.DatabaseComponent;
 import org.briarproject.briar.android.AndroidComponent;
 import org.briarproject.briar.android.StartupFailureActivity;
 import org.briarproject.briar.android.account.AuthorNameFragment;
 import org.briarproject.briar.android.account.DozeFragment;
+import org.briarproject.briar.android.account.NewOrRecoverActivity;
+import org.briarproject.briar.android.account.NewOrRecoverFragment;
 import org.briarproject.briar.android.account.SetPasswordFragment;
 import org.briarproject.briar.android.account.SetupActivity;
 import org.briarproject.briar.android.account.UnlockActivity;
@@ -77,20 +80,32 @@ import org.briarproject.briar.android.sharing.ShareBlogFragment;
 import org.briarproject.briar.android.sharing.ShareForumActivity;
 import org.briarproject.briar.android.sharing.ShareForumFragment;
 import org.briarproject.briar.android.sharing.SharingModule;
+//import org.briarproject.briar.android.socialbackup.CustodianDisplayFragment;
+import org.briarproject.briar.android.socialbackup.CustodianHelpRecoverActivity;
+import org.briarproject.briar.android.socialbackup.CustodianSelectorFragment;
+import org.briarproject.briar.android.socialbackup.DistributedBackupActivity;
+import org.briarproject.briar.android.socialbackup.ExistingBackupFragment;
+import org.briarproject.briar.android.socialbackup.OwnerRecoveryModeExplainerFragment;
+import org.briarproject.briar.android.socialbackup.RecoverActivity;
+import org.briarproject.briar.android.socialbackup.ShardQrCodeFragment;
+import org.briarproject.briar.android.socialbackup.ShardsSentFragment;
+import org.briarproject.briar.android.socialbackup.ThresholdSelectorFragment;
+import org.briarproject.briar.android.socialbackup.creation.CreateBackupModule;
 import org.briarproject.briar.android.splash.SplashScreenActivity;
 import org.briarproject.briar.android.test.TestDataActivity;
 
 import dagger.Component;
 
 @ActivityScope
-@Component(modules = {
+@Component(modules ={
 		ActivityModule.class,
 		BlogModule.class,
 		CreateGroupModule.class,
 		GroupInvitationModule.class,
 		GroupMemberModule.class,
 		GroupRevealModule.class,
-		SharingModule.SharingLegacyModule.class
+		SharingModule.SharingLegacyModule.class,
+		CreateBackupModule.class
 }, dependencies = AndroidComponent.class)
 public interface ActivityComponent {
 
@@ -182,6 +197,10 @@ public interface ActivityComponent {
 
 	void inject(CrashReportActivity crashReportActivity);
 
+	void inject(NewOrRecoverActivity newOrRecoverActivity);
+
+	void inject(CustodianHelpRecoverActivity custodianHelpRecoverActivity);
+
 	// Fragments
 
 	void inject(AuthorNameFragment fragment);
@@ -238,4 +257,23 @@ public interface ActivityComponent {
 
 	void inject(ConfirmAvatarDialogFragment fragment);
 
+	void inject(ThresholdSelectorFragment thresholdSelectorFragment);
+
+	void inject(ShardQrCodeFragment shardQrCodeFragment);
+
+	void inject(DistributedBackupActivity distributedBackupActivity);
+
+	void inject(RecoverActivity recoverActivity);
+
+	void inject(DatabaseComponent databaseComponent);
+
+	void inject(CustodianSelectorFragment custodianSelectorFragment);
+
+	void inject(ShardsSentFragment shardsSentFragment);
+
+	void inject(OwnerRecoveryModeExplainerFragment ownerRecoveryModeExplainerFragment);
+
+	void inject(ExistingBackupFragment existingBackupFragment);
+
+	void inject(NewOrRecoverFragment newOrRecoverFragment);
 }

briar-android/src/main/java/org/briarproject/briar/android/contactselection/BaseContactSelectorFragment.java

@@ -56,8 +56,11 @@ public abstract class BaseContactSelectorFragment<I extends SelectableContactIte
 
 		Bundle args = requireArguments();
 		byte[] b = args.getByteArray(GROUP_ID);
-		if (b == null) throw new IllegalStateException("No GroupId");
-		groupId = new GroupId(b);
+//		if (b == null) throw new IllegalStateException("No GroupId");
+		// TODO find what the groupId should be when selecting custodians
+		if (b != null) {
+			groupId = new GroupId(b);
+		}
 	}
 
 	@Override

briar-android/src/main/java/org/briarproject/briar/android/contactselection/ContactSelectorFragment.java

@@ -18,7 +18,7 @@ public abstract class ContactSelectorFragment extends
 
 	public static final String TAG = ContactSelectorFragment.class.getName();
 
-	private Menu menu;
+	protected Menu menu;
 
 	@Override
 	protected ContactSelectorAdapter getAdapter(Context context,

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationActivity.java

@@ -52,6 +52,7 @@ import org.briarproject.briar.android.conversation.ConversationVisitor.TextCache
 import org.briarproject.briar.android.forum.ForumActivity;
 import org.briarproject.briar.android.introduction.IntroductionActivity;
 import org.briarproject.briar.android.privategroup.conversation.GroupActivity;
+import org.briarproject.briar.android.socialbackup.CustodianHelpRecoverActivity;
 import org.briarproject.briar.android.util.BriarSnackbarBuilder;
 import org.briarproject.briar.android.view.BriarRecyclerView;
 import org.briarproject.briar.android.view.ImagePreview;
@@ -396,6 +397,12 @@ public class ConversationActivity extends BriarActivity
 			case R.id.action_social_remove_person:
 				askToRemoveContact();
 				return true;
+			case R.id.action_help_recover_account:
+				if (contactId == null) return false;
+				Intent i = new Intent(this, CustodianHelpRecoverActivity.class);
+				i.putExtra(CONTACT_ID, contactId.getInt());
+				startActivity(i);
+				return true;
 			default:
 				return super.onOptionsItemSelected(item);
 		}

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationNoticeItem.java

@@ -3,6 +3,7 @@ package org.briarproject.briar.android.conversation;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.api.conversation.ConversationRequest;
 import org.briarproject.briar.api.conversation.ConversationResponse;
+import org.briarproject.briar.api.socialbackup.ShardMessageHeader;
 
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.NotThreadSafe;
@@ -30,6 +31,13 @@ class ConversationNoticeItem extends ConversationItem {
 		this.msgText = null;
 	}
 
+	ConversationNoticeItem(@LayoutRes int layoutRes, String text,
+			ShardMessageHeader r) {
+		super(layoutRes, r);
+		this.text = text;
+		this.msgText = null;
+	}
+
 	@Nullable
 	String getMsgText() {
 		return msgText;

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationVisitor.java

@@ -16,6 +16,7 @@ import org.briarproject.briar.api.introduction.IntroductionResponse;
 import org.briarproject.briar.api.messaging.PrivateMessageHeader;
 import org.briarproject.briar.api.privategroup.invitation.GroupInvitationRequest;
 import org.briarproject.briar.api.privategroup.invitation.GroupInvitationResponse;
+import org.briarproject.briar.api.socialbackup.ShardMessageHeader;
 
 import java.util.List;
 
@@ -292,6 +293,19 @@ class ConversationVisitor implements
 		}
 	}
 
+	@Override
+	public ConversationItem visitShardMessage(ShardMessageHeader r) {
+		if (r.isLocal()) {
+			String text = ctx.getString(R.string.social_backup_shard_sent);
+			return new ConversationNoticeItem(
+					R.layout.list_item_conversation_notice_out, text, r);
+		} else {
+			String text = ctx.getString(R.string.social_backup_shard_received);
+			return new ConversationNoticeItem(
+					R.layout.list_item_conversation_notice_in, text, r);
+		}
+	}
+
 	interface TextCache {
 		@Nullable
 		String getText(MessageId m);

briar-android/src/main/java/org/briarproject/briar/android/keyagreement/CameraException.java

@@ -2,7 +2,7 @@ package org.briarproject.briar.android.keyagreement;
 
 import java.io.IOException;
 
-class CameraException extends IOException {
+public class CameraException extends IOException {
 
 	CameraException(String message) {
 		super(message);

briar-android/src/main/java/org/briarproject/briar/android/keyagreement/QrCodeDecoder.java

@@ -30,7 +30,7 @@ import static java.util.logging.Level.WARNING;
 @SuppressWarnings("deprecation")
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
-class QrCodeDecoder implements PreviewConsumer, PreviewCallback {
+public class QrCodeDecoder implements PreviewConsumer, PreviewCallback {
 
 	private static final Logger LOG =
 			Logger.getLogger(QrCodeDecoder.class.getName());
@@ -41,7 +41,7 @@ class QrCodeDecoder implements PreviewConsumer, PreviewCallback {
 	private Camera camera = null;
 	private int cameraIndex = 0;
 
-	QrCodeDecoder(ResultCallback callback) {
+	public QrCodeDecoder(ResultCallback callback) {
 		this.callback = callback;
 	}
 
@@ -142,7 +142,7 @@ class QrCodeDecoder implements PreviewConsumer, PreviewCallback {
 	}
 
 	@NotNullByDefault
-	interface ResultCallback {
+	public interface ResultCallback {
 
 		void handleResult(Result result);
 	}

briar-android/src/main/java/org/briarproject/briar/android/keyagreement/QrCodeUtils.java

@@ -21,13 +21,13 @@ import static java.util.logging.Level.WARNING;
 import static org.briarproject.bramble.util.LogUtils.logException;
 
 @NotNullByDefault
-class QrCodeUtils {
+public class QrCodeUtils {
 
 	private static final Logger LOG =
 			Logger.getLogger(QrCodeUtils.class.getName());
 
 	@Nullable
-	static Bitmap createQrCode(DisplayMetrics dm, String input) {
+	public static Bitmap createQrCode(DisplayMetrics dm, String input) {
 		int smallestDimen = Math.min(dm.widthPixels, dm.heightPixels);
 		try {
 			// Generate QR code

briar-android/src/main/java/org/briarproject/briar/android/login/StartupActivity.java

@@ -7,6 +7,7 @@ import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.BriarService;
+import org.briarproject.briar.android.account.NewOrRecoverActivity;
 import org.briarproject.briar.android.account.SetupActivity;
 import org.briarproject.briar.android.activity.ActivityComponent;
 import org.briarproject.briar.android.activity.BaseActivity;
@@ -107,7 +108,7 @@ public class StartupActivity extends BaseActivity implements
 	private void onAccountDeleted() {
 		setResult(RESULT_CANCELED);
 		finish();
-		Intent i = new Intent(this, SetupActivity.class);
+		Intent i = new Intent(this, NewOrRecoverActivity.class);
 		i.addFlags(FLAG_ACTIVITY_NEW_TASK | FLAG_ACTIVITY_CLEAR_TOP |
 				FLAG_ACTIVITY_CLEAR_TASK | FLAG_ACTIVITY_TASK_ON_HOME);
 		startActivity(i);

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/CustodianHelpRecoverActivity.java

@@ -0,0 +1,67 @@
+package org.briarproject.briar.android.socialbackup;
+
+import android.content.Intent;
+import android.os.Bundle;
+import android.widget.Toast;
+
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.db.DatabaseComponent;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.activity.ActivityComponent;
+import org.briarproject.briar.android.activity.BriarActivity;
+import org.briarproject.briar.android.fragment.BaseFragment;
+import org.briarproject.briar.api.socialbackup.SocialBackupManager;
+
+import javax.inject.Inject;
+
+import static org.briarproject.briar.android.conversation.ConversationActivity.CONTACT_ID;
+
+public class CustodianHelpRecoverActivity extends BriarActivity implements
+		BaseFragment.BaseFragmentListener, CustodianScanQrButtonListener {
+	@Override
+	public void injectActivity(ActivityComponent component) {
+		component.inject(this);
+	}
+
+	@Inject
+	public SocialBackupManager socialBackupManager;
+
+	@Inject
+	public DatabaseComponent db;
+
+	@Override
+	public void onCreate(Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+		setContentView(R.layout.activity_recover); // TODO change this
+
+		Intent intent = getIntent();
+		int id = intent.getIntExtra(CONTACT_ID, -1);
+		if (id == -1) throw new IllegalStateException("No ContactId");
+		ContactId contactId = new ContactId(id);
+
+		// check if we have a shard for this secret owner
+		try {
+			db.transaction(false, txn -> {
+				if (!socialBackupManager.amCustodian(txn, contactId)) {
+					throw new DbException();
+				}
+				CustodianRecoveryModeExplainerFragment fragment =
+						new CustodianRecoveryModeExplainerFragment();
+				showInitialFragment(fragment);
+			});
+		} catch (DbException e) {
+			// TODO improve this
+			Toast.makeText(this,
+					"You do not hold a backup shard from this contact",
+					Toast.LENGTH_SHORT).show();
+			finish();
+		}
+	}
+
+	@Override
+	public void scanQrButtonClicked() {
+		// TODO scan qr code
+		finish();
+	}
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/CustodianRecoveryModeExplainerFragment.java

@@ -0,0 +1,51 @@
+package org.briarproject.briar.android.socialbackup;
+
+import android.content.Context;
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.Button;
+
+import org.briarproject.briar.android.fragment.BaseFragment;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import org.briarproject.briar.R;
+
+public class CustodianRecoveryModeExplainerFragment extends BaseFragment {
+
+	protected CustodianScanQrButtonListener listener;
+
+	public static final String TAG = CustodianRecoveryModeExplainerFragment.class.getName();
+
+	@Override
+	public void onCreate(@Nullable Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+		requireActivity().setTitle(R.string.title_help_recover);
+	}
+
+	@Nullable
+	@Override
+	public View onCreateView(@NonNull LayoutInflater inflater, @Nullable
+			ViewGroup container, @Nullable Bundle savedInstanceState) {
+		View view = inflater.inflate(R.layout.fragment_recovery_custodian_explainer,
+				container, false);
+
+		Button button = view.findViewById(R.id.button);
+		button.setOnClickListener(e -> listener.scanQrButtonClicked());
+		return view;
+	}
+
+	@Override
+	public void onAttach(Context context) {
+		super.onAttach(context);
+		listener = (CustodianScanQrButtonListener) context;
+	}
+
+	@Override
+	public String getUniqueTag() {
+		return TAG;
+	}
+}
+

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/CustodianScanQrButtonListener.java

@@ -0,0 +1,8 @@
+package org.briarproject.briar.android.socialbackup;
+
+import androidx.annotation.UiThread;
+
+public interface CustodianScanQrButtonListener {
+	@UiThread
+	void scanQrButtonClicked();
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/CustodianSelectorFragment.java

@@ -0,0 +1,93 @@
+package org.briarproject.briar.android.socialbackup;
+
+import android.os.Bundle;
+import android.view.MenuItem;
+import android.widget.Toast;
+
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+import org.briarproject.bramble.api.sync.GroupId;
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.activity.ActivityComponent;
+import org.briarproject.briar.android.socialbackup.creation.CreateBackupController;
+import org.briarproject.briar.android.contactselection.BaseContactSelectorAdapter;
+import org.briarproject.briar.android.contactselection.ContactSelectorController;
+import org.briarproject.briar.android.contactselection.ContactSelectorFragment;
+import org.briarproject.briar.android.contactselection.SelectableContactItem;
+import org.briarproject.briar.android.controller.handler.ResultExceptionHandler;
+
+import java.util.Collection;
+
+import javax.inject.Inject;
+
+import androidx.annotation.Nullable;
+
+import static java.util.Objects.requireNonNull;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class CustodianSelectorFragment extends ContactSelectorFragment {
+
+	public static final String TAG = CustodianSelectorFragment.class.getName();
+
+	@Inject
+	CreateBackupController controller;
+
+	public static CustodianSelectorFragment newInstance() {
+		Bundle args = new Bundle();
+
+		CustodianSelectorFragment fragment = new CustodianSelectorFragment();
+		fragment.setArguments(args);
+
+		return fragment;
+	}
+
+	@Override
+	public void injectFragment(ActivityComponent component) {
+		component.inject(this);
+	}
+
+	@Override
+	public void onCreate(@Nullable Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+
+		requireActivity().setTitle(R.string.title_select_custodians);
+	}
+
+	@Override
+	protected ContactSelectorController<SelectableContactItem> getController() {
+		return controller;
+	}
+
+	@Override
+	public String getUniqueTag() {
+		return TAG;
+	}
+
+	@Override
+	protected void onSelectionChanged() {
+		super.onSelectionChanged();
+		if (menu == null) return;
+		MenuItem item = menu.findItem(R.id.action_contacts_selected);
+		if (item == null) return;
+
+		BaseContactSelectorAdapter a = adapter;
+		selectedContacts = a.getSelectedContactIds();
+
+		int n = selectedContacts.size();
+		int min = 2;
+		boolean enough = n >= min;
+
+		item.setVisible(enough);
+		if (n == 0) {
+			Toast.makeText(getContext(), String.format(getString(R.string.select_at_least_n_contacts), min),
+					Toast.LENGTH_SHORT).show();
+		} else if (n < min) {
+			Toast.makeText(getContext(), String.format(getString(R.string.select_at_least_n_more_contacts), min - n),
+					Toast.LENGTH_SHORT).show();
+		}
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/DarkCrystalImpl.java

@@ -0,0 +1,56 @@
+package org.briarproject.briar.android.socialbackup;
+import org.briarproject.bramble.api.crypto.SecretKey;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.briar.api.socialbackup.Shard;
+import org.briarproject.briar.api.socialbackup.DarkCrystal;
+import org.magmacollective.darkcrystal.secretsharingwrapper.SecretSharingWrapper;
+
+import java.security.GeneralSecurityException;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Random;
+
+import javax.inject.Inject;
+
+import dagger.Provides;
+
+import static org.briarproject.briar.socialbackup.SocialBackupConstants.SECRET_ID_BYTES;
+
+@NotNullByDefault
+public class DarkCrystalImpl implements DarkCrystal {
+
+    @Inject
+	DarkCrystalImpl() {
+	}
+
+	@Override
+	public List<Shard> createShards(SecretKey secret, int numShards,
+			int threshold) {
+		Random random = new Random();
+		byte[] secretId = new byte[SECRET_ID_BYTES];
+		random.nextBytes(secretId);
+		List<byte[]> shardsBytes = SecretSharingWrapper.share(secret.getBytes(), numShards, threshold);
+		List<Shard> shards = new ArrayList<>(numShards);
+		for (byte[] shardBytes : shardsBytes) {
+			shards.add(new Shard(secretId, shardBytes));
+		}
+		return shards;
+	}
+
+	@Override
+	public SecretKey combineShards(List<Shard> shards) throws
+			GeneralSecurityException {
+		// Check each shard has the same secret Id
+		byte[] secretId = shards.get(0).getSecretId();
+		for (Shard shard : shards) {
+			if (!Arrays.equals(shard.getSecretId(), secretId)) throw new GeneralSecurityException();
+		}
+        List<byte[]> shardsBytes = new ArrayList<>(shards.size());
+		for (Shard shard : shards) {
+			shardsBytes.add(shard.getShard());
+		}
+		byte[] secretBytes = SecretSharingWrapper.combine(shardsBytes);
+		return new SecretKey(secretBytes);
+	}
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/DistributedBackupActivity.java

@@ -0,0 +1,91 @@
+package org.briarproject.briar.android.socialbackup;
+
+import android.os.Bundle;
+import android.widget.Toast;
+
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.db.DatabaseComponent;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.activity.ActivityComponent;
+import org.briarproject.briar.android.activity.BriarActivity;
+import org.briarproject.briar.android.contactselection.ContactSelectorListener;
+import org.briarproject.briar.android.fragment.BaseFragment;
+import org.briarproject.briar.api.socialbackup.BackupMetadata;
+import org.briarproject.briar.api.socialbackup.SocialBackupManager;
+
+import java.util.Collection;
+import java.util.List;
+
+import javax.inject.Inject;
+
+public class DistributedBackupActivity extends BriarActivity implements
+		BaseFragment.BaseFragmentListener, ContactSelectorListener,
+		ThresholdDefinedListener,
+		ShardsSentFragment.ShardsSentDismissedListener {
+
+	private Collection<ContactId> custodians;
+
+	@Inject
+	public SocialBackupManager socialBackupManager;
+
+	@Inject
+	public DatabaseComponent db;
+
+	@Override
+	public void injectActivity(ActivityComponent component) {
+		component.inject(this);
+	}
+
+	@Override
+	public void onCreate(Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+		setContentView(R.layout.activity_distributed_backup);
+
+		try {
+			db.transaction(false, txn -> {
+				BackupMetadata backupMetadata =
+						socialBackupManager.getBackupMetadata(txn);
+				if (backupMetadata == null) throw new DbException();
+				ExistingBackupFragment fragment =
+						ExistingBackupFragment.newInstance(backupMetadata);
+				showInitialFragment(fragment);
+			});
+		} catch (DbException e) {
+			CustodianSelectorFragment fragment =
+					CustodianSelectorFragment.newInstance();
+			showInitialFragment(fragment);
+		}
+	}
+
+	@Override
+	public void contactsSelected(Collection<ContactId> contacts) {
+		Toast.makeText(this,
+				String.format("selected %d contacts", contacts.size()),
+				Toast.LENGTH_SHORT).show();
+		custodians = contacts;
+		ThresholdSelectorFragment fragment =
+				ThresholdSelectorFragment.newInstance(contacts.size());
+		showNextFragment(fragment);
+	}
+
+	@Override
+	public void thresholdDefined(int threshold) {
+		try {
+			db.transaction(false, txn -> {
+				socialBackupManager
+						.createBackup(txn, (List<ContactId>) custodians,
+								threshold);
+				ShardsSentFragment fragment = new ShardsSentFragment();
+				showNextFragment(fragment);
+			});
+		} catch (DbException e) {
+			e.printStackTrace();
+		}
+	}
+
+	@Override
+	public void shardsSentDismissed() {
+		finish();
+	}
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/ExistingBackupFragment.java

@@ -0,0 +1,85 @@
+package org.briarproject.briar.android.socialbackup;
+
+import android.content.Context;
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.TextView;
+
+import org.briarproject.bramble.api.identity.Author;
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.activity.ActivityComponent;
+import org.briarproject.briar.android.fragment.BaseFragment;
+import org.briarproject.briar.api.socialbackup.BackupMetadata;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
+public class ExistingBackupFragment extends BaseFragment {
+
+	private static final String THRESHOLD = "threshold";
+	private static final String CUSTODIANS = "custodians";
+	public static final String TAG = ExistingBackupFragment.class.getName();
+
+	public static ExistingBackupFragment newInstance(
+			BackupMetadata backupMetadata) {
+		Bundle bundle = new Bundle();
+		List<Author> custodians = backupMetadata.getCustodians();
+		ArrayList custodianNames = new ArrayList();
+	    for (Author custodian : custodians) {
+	    	custodianNames.add(custodian.getName());
+	    }
+	    bundle.putStringArrayList(CUSTODIANS, custodianNames);
+		bundle.putInt(THRESHOLD, backupMetadata.getThreshold());
+		ExistingBackupFragment fragment = new ExistingBackupFragment();
+		fragment.setArguments(bundle);
+		return fragment;
+	}
+	@Override
+	public void onCreate(@Nullable Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+		requireActivity().setTitle(R.string.title_distributed_backup);
+
+	}
+
+	@Nullable
+	@Override
+	public View onCreateView(@NonNull LayoutInflater inflater, @Nullable
+			ViewGroup container, @Nullable Bundle savedInstanceState) {
+		View view = inflater.inflate(R.layout.fragment_existing_backup,
+				container, false);
+		Bundle args = requireArguments();
+        ArrayList<String> custodianNames = args.getStringArrayList(CUSTODIANS);
+        String custodianNamesString = "";
+        for (String custodianName : custodianNames) {
+          	custodianNamesString += custodianName + ", ";
+        }
+        TextView textViewThreshold = view.findViewById(R.id.textViewThreshold);
+        textViewThreshold.setText(String.format("%d of %d contacts needed to restore account", args.getInt(THRESHOLD), custodianNames.size()));
+        TextView textViewCustodians = view.findViewById(R.id.textViewCustodians);
+        textViewCustodians.setText(custodianNamesString);
+		return view;
+	}
+
+	@Override
+	public void onAttach(Context context) {
+		super.onAttach(context);
+//		listener = (ShardsSentDismissedListener) context;
+	}
+
+
+	@Override
+	public String getUniqueTag() {
+		return TAG;
+	}
+
+	@Override
+	public void injectFragment(ActivityComponent component) {
+		component.inject(this);
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/ExplainerDismissedListener.java

@@ -0,0 +1,8 @@
+package org.briarproject.briar.android.socialbackup;
+
+import androidx.annotation.UiThread;
+
+public interface ExplainerDismissedListener {
+	@UiThread
+	void explainerDismissed();
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/OwnerRecoveryModeExplainerFragment.java

@@ -0,0 +1,58 @@
+package org.briarproject.briar.android.socialbackup;
+
+import android.content.Context;
+import android.os.Bundle;
+
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.Button;
+
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.activity.ActivityComponent;
+import org.briarproject.briar.android.fragment.BaseFragment;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
+public class OwnerRecoveryModeExplainerFragment extends BaseFragment {
+
+	protected ExplainerDismissedListener listener;
+	public static final String TAG =
+			OwnerRecoveryModeExplainerFragment.class.getName();
+
+	@Override
+	public void onCreate(@Nullable Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+		requireActivity().setTitle(R.string.title_recovery_mode);
+	}
+
+	@Nullable
+	@Override
+	public View onCreateView(@NonNull LayoutInflater inflater,
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
+		View view = inflater.inflate(R.layout.fragment_recovery_owner_explainer,
+				container, false);
+		Button button = view.findViewById(R.id.beginButton);
+		button.setOnClickListener(e -> listener.explainerDismissed());
+
+		return view;
+	}
+
+	@Override
+	public void onAttach(Context context) {
+		super.onAttach(context);
+		listener = (ExplainerDismissedListener) context;
+	}
+
+	@Override
+	public void injectFragment(ActivityComponent component) {
+		component.inject(this);
+	}
+
+	@Override
+	public String getUniqueTag() {
+		return TAG;
+	}
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/OwnerRecoveryModeMainFragment.java

@@ -0,0 +1,73 @@
+package org.briarproject.briar.android.socialbackup;
+
+import android.content.Context;
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.Button;
+import android.widget.TextView;
+
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.fragment.BaseFragment;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
+public class OwnerRecoveryModeMainFragment extends BaseFragment {
+
+	protected ScanQrButtonListener listener;
+
+	public static final String NUM_RECOVERED = "num_recovered";
+
+	public static final String TAG =
+			OwnerRecoveryModeMainFragment.class.getName();
+
+	public static OwnerRecoveryModeMainFragment newInstance(int numRecovered) {
+		Bundle args = new Bundle();
+		args.putInt(NUM_RECOVERED, numRecovered);
+		OwnerRecoveryModeMainFragment fragment =
+				new OwnerRecoveryModeMainFragment();
+		fragment.setArguments(args);
+		return fragment;
+	}
+
+	private int numShards;
+
+	@Override
+	public String getUniqueTag() {
+		return TAG;
+	}
+
+	@Override
+	public void onCreate(@Nullable Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+		requireActivity().setTitle(R.string.title_recovery_mode);
+
+		Bundle args = requireArguments();
+		numShards = args.getInt(NUM_RECOVERED);
+	}
+
+	@Nullable
+	@Override
+	public View onCreateView(@NonNull LayoutInflater inflater,
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
+		View view = inflater.inflate(R.layout.fragment_recovery_owner_main,
+				container, false);
+
+		TextView textViewCount = view.findViewById(R.id.textViewShardCount);
+		textViewCount.setText(String.format("%d", numShards));
+
+		Button button = view.findViewById(R.id.button);
+		button.setOnClickListener(e -> listener.scanQrButtonClicked());
+		return view;
+	}
+
+	@Override
+	public void onAttach(Context context) {
+		super.onAttach(context);
+		listener = (ScanQrButtonListener) context;
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/RecoverActivity.java

@@ -0,0 +1,179 @@
+package org.briarproject.briar.android.socialbackup;
+
+import android.os.Bundle;
+import android.widget.Toast;
+
+import org.briarproject.bramble.api.keyagreement.KeyAgreementResult;
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.activity.ActivityComponent;
+import org.briarproject.briar.android.activity.BaseActivity;
+import org.briarproject.briar.android.fragment.BaseFragment;
+
+import javax.annotation.Nullable;
+
+import androidx.annotation.UiThread;
+import androidx.core.app.ActivityCompat;
+
+import static android.Manifest.permission.CAMERA;
+import static android.content.pm.PackageManager.PERMISSION_GRANTED;
+import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_PERMISSION_CAMERA_LOCATION;
+
+public class RecoverActivity extends BaseActivity implements
+		BaseFragment.BaseFragmentListener, ExplainerDismissedListener,
+		ScanQrButtonListener, ShardQrCodeFragment.ShardQrCodeEventListener {
+
+	@Override
+	public void keyAgreementFailed() {
+
+	}
+
+	@Nullable
+	@Override
+	public String keyAgreementWaiting() {
+		return null;
+	}
+
+	@Nullable
+	@Override
+	public String keyAgreementStarted() {
+		return null;
+	}
+
+	@Override
+	public void keyAgreementAborted(boolean remoteAborted) {
+
+	}
+
+	@Nullable
+	@Override
+	public String keyAgreementFinished(KeyAgreementResult result) {
+		return null;
+	}
+
+	private enum Permission {
+		UNKNOWN, GRANTED, SHOW_RATIONALE, PERMANENTLY_DENIED
+	}
+
+	private Permission cameraPermission = Permission.UNKNOWN;
+
+
+	private int numRecovered;
+
+	@Override
+	public void onCreate(Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+		setContentView(R.layout.activity_recover);
+
+		numRecovered = 0; // TODO - retrieve this from somewhere
+
+		// only show the explainer if we have no shards
+		if (numRecovered == 0) {
+			OwnerRecoveryModeExplainerFragment fragment =
+					new OwnerRecoveryModeExplainerFragment();
+			showInitialFragment(fragment);
+		} else {
+			OwnerRecoveryModeMainFragment fragment =
+					OwnerRecoveryModeMainFragment.newInstance(numRecovered);
+			showInitialFragment(fragment);
+		}
+	}
+
+	@Override
+	public void injectActivity(ActivityComponent component) {
+		component.inject(this);
+	}
+
+	@Override
+	public void explainerDismissed() {
+		OwnerRecoveryModeMainFragment fragment =
+				OwnerRecoveryModeMainFragment.newInstance(numRecovered);
+		showNextFragment(fragment);
+	}
+
+	@Override
+	public void scanQrButtonClicked() {
+		if (checkPermissions()) showQrCodeFragment();
+	}
+
+
+	private void showQrCodeFragment() {
+		ShardQrCodeFragment f = ShardQrCodeFragment.newInstance();
+		showNextFragment(f);
+	}
+
+	private void requestPermissions() {
+		String[] permissions = new String[] {CAMERA};
+		ActivityCompat.requestPermissions(this, permissions,
+				REQUEST_PERMISSION_CAMERA_LOCATION);
+	}
+
+	@Override
+	@UiThread
+	public void onRequestPermissionsResult(int requestCode,
+			String[] permissions, int[] grantResults) {
+		if (requestCode != REQUEST_PERMISSION_CAMERA_LOCATION)
+			throw new AssertionError();
+		if (gotPermission(CAMERA, permissions, grantResults)) {
+			cameraPermission = Permission.GRANTED;
+		} else if (shouldShowRationale(CAMERA)) {
+			cameraPermission = Permission.SHOW_RATIONALE;
+		} else {
+			cameraPermission = Permission.PERMANENTLY_DENIED;
+		}
+		// If a permission dialog has been shown, showing the QR code fragment
+		// on this call path would cause a crash due to
+		// https://code.google.com/p/android/issues/detail?id=190966.
+		// In that case the isResumed flag prevents the fragment from being
+		// shown here, and showQrCodeFragmentIfAllowed() will be called again
+		// from onPostResume().
+		if (checkPermissions()) showQrCodeFragment();
+	}
+
+	private boolean gotPermission(String permission, String[] permissions,
+			int[] grantResults) {
+		for (int i = 0; i < permissions.length; i++) {
+			if (permission.equals(permissions[i]))
+				return grantResults[i] == PERMISSION_GRANTED;
+		}
+		return false;
+	}
+
+	private boolean shouldShowRationale(String permission) {
+		return ActivityCompat.shouldShowRequestPermissionRationale(this,
+				permission);
+	}
+
+	private boolean checkPermissions() {
+		if (areEssentialPermissionsGranted()) return true;
+		// If an essential permission has been permanently denied, ask the
+		// user to change the setting
+		if (cameraPermission == Permission.PERMANENTLY_DENIED) {
+			Toast.makeText(this,
+					"camera permission is denied",
+					Toast.LENGTH_SHORT).show();
+//			showDenialDialog(R.string.permission_camera_title,
+//					R.string.permission_camera_denied_body);
+			return false;
+		}
+		if (cameraPermission == Permission.SHOW_RATIONALE) {
+//			showRationale(R.string.permission_camera_title,
+//					R.string.permission_camera_request_body);
+			Toast.makeText(this,
+					"camera permission - show rationale",
+					Toast.LENGTH_SHORT).show();
+		} else {
+			requestPermissions();
+		}
+		return false;
+	}
+
+	@Override
+	@Deprecated
+	public void runOnDbThread(Runnable runnable) {
+		throw new RuntimeException("Don't use this deprecated method here.");
+	}
+
+	private boolean areEssentialPermissionsGranted() {
+		return cameraPermission == Permission.GRANTED;
+	}
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/ScanQrButtonListener.java

@@ -0,0 +1,8 @@
+package org.briarproject.briar.android.socialbackup;
+
+import androidx.annotation.UiThread;
+
+public interface ScanQrButtonListener {
+	@UiThread
+	void scanQrButtonClicked();
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/ShardQrCodeFragment.java

@@ -0,0 +1,381 @@
+package org.briarproject.briar.android.socialbackup;
+
+import android.content.Context;
+import android.graphics.Bitmap;
+import android.os.Bundle;
+import android.util.DisplayMetrics;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.LinearLayout;
+import android.widget.TextView;
+import android.widget.Toast;
+
+import com.google.zxing.Result;
+
+import org.briarproject.bramble.api.UnsupportedVersionException;
+import org.briarproject.bramble.api.event.Event;
+import org.briarproject.bramble.api.event.EventBus;
+import org.briarproject.bramble.api.keyagreement.KeyAgreementResult;
+import org.briarproject.bramble.api.keyagreement.KeyAgreementTask;
+import org.briarproject.bramble.api.keyagreement.Payload;
+import org.briarproject.bramble.api.keyagreement.PayloadEncoder;
+import org.briarproject.bramble.api.keyagreement.PayloadParser;
+import org.briarproject.bramble.api.keyagreement.event.KeyAgreementAbortedEvent;
+import org.briarproject.bramble.api.keyagreement.event.KeyAgreementFailedEvent;
+import org.briarproject.bramble.api.keyagreement.event.KeyAgreementFinishedEvent;
+import org.briarproject.bramble.api.keyagreement.event.KeyAgreementListeningEvent;
+import org.briarproject.bramble.api.keyagreement.event.KeyAgreementStartedEvent;
+import org.briarproject.bramble.api.keyagreement.event.KeyAgreementWaitingEvent;
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.activity.ActivityComponent;
+import org.briarproject.briar.android.fragment.BaseEventFragment;
+import org.briarproject.briar.android.keyagreement.CameraException;
+import org.briarproject.briar.android.keyagreement.CameraView;
+import org.briarproject.briar.android.keyagreement.ContactExchangeErrorFragment;
+import org.briarproject.briar.android.keyagreement.QrCodeDecoder;
+import org.briarproject.briar.android.keyagreement.QrCodeUtils;
+import org.briarproject.briar.android.view.QrCodeView;
+
+import java.io.IOException;
+import java.nio.charset.Charset;
+import java.util.concurrent.Executor;
+import java.util.logging.Logger;
+
+import javax.annotation.Nullable;
+import javax.inject.Inject;
+import javax.inject.Provider;
+
+import androidx.annotation.UiThread;
+
+import static android.content.pm.ActivityInfo.SCREEN_ORIENTATION_NOSENSOR;
+import static android.view.View.INVISIBLE;
+import static android.view.View.VISIBLE;
+import static android.view.ViewGroup.LayoutParams.MATCH_PARENT;
+import static android.widget.LinearLayout.HORIZONTAL;
+import static android.widget.Toast.LENGTH_LONG;
+import static java.util.logging.Level.INFO;
+import static java.util.logging.Level.WARNING;
+import static org.briarproject.bramble.util.LogUtils.logException;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class ShardQrCodeFragment extends BaseEventFragment
+		implements QrCodeDecoder.ResultCallback, QrCodeView.FullscreenListener {
+
+	static final String TAG = org.briarproject.briar.android.keyagreement.KeyAgreementFragment.class.getName();
+
+	private static final Logger LOG = Logger.getLogger(TAG);
+	@SuppressWarnings("CharsetObjectCanBeUsed") // Requires minSdkVersion >= 19
+	private static final Charset ISO_8859_1 = Charset.forName("ISO-8859-1");
+
+	@Inject
+	Provider<KeyAgreementTask> keyAgreementTaskProvider;
+	@Inject
+	PayloadEncoder payloadEncoder;
+	@Inject
+	PayloadParser payloadParser;
+	@Inject
+	@IoExecutor
+	Executor ioExecutor;
+	@Inject
+	EventBus eventBus;
+
+	private CameraView cameraView;
+	private LinearLayout cameraOverlay;
+	private View statusView;
+	private QrCodeView qrCodeView;
+	private TextView status;
+
+	private boolean gotRemotePayload;
+	private volatile boolean gotLocalPayload;
+	private KeyAgreementTask task;
+	private ShardQrCodeEventListener
+			listener;
+
+	public static ShardQrCodeFragment newInstance() {
+		Bundle args = new Bundle();
+		ShardQrCodeFragment
+				fragment = new ShardQrCodeFragment();
+		fragment.setArguments(args);
+		return fragment;
+	}
+
+	@Override
+	public void onAttach(Context context) {
+		super.onAttach(context);
+		listener = (ShardQrCodeEventListener) context;
+	}
+
+	@Override
+	public void injectFragment(ActivityComponent component) {
+		component.inject(this);
+	}
+
+	@Override
+	public String getUniqueTag() {
+		return TAG;
+	}
+
+	@Nullable
+	@Override
+	public View onCreateView(LayoutInflater inflater,
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
+		return inflater.inflate(R.layout.fragment_keyagreement_qr, container,
+				false);
+	}
+
+	@Override
+	public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
+		super.onViewCreated(view, savedInstanceState);
+		cameraView = view.findViewById(R.id.camera_view);
+		cameraOverlay = view.findViewById(R.id.camera_overlay);
+		statusView = view.findViewById(R.id.status_container);
+		status = view.findViewById(R.id.connect_status);
+		qrCodeView = view.findViewById(R.id.qr_code_view);
+		qrCodeView.setFullscreenListener(this);
+	}
+
+	@Override
+	public void onActivityCreated(@Nullable Bundle savedInstanceState) {
+		super.onActivityCreated(savedInstanceState);
+		requireActivity().setRequestedOrientation(SCREEN_ORIENTATION_NOSENSOR);
+		cameraView.setPreviewConsumer(new QrCodeDecoder(this));
+	}
+
+	@Override
+	public void onStart() {
+		super.onStart();
+		try {
+			cameraView.start();
+		} catch (CameraException e) {
+			logCameraExceptionAndFinish(e);
+		}
+		startListening();
+	}
+
+	@Override
+	public void setFullscreen(boolean fullscreen) {
+		LinearLayout.LayoutParams statusParams, qrCodeParams;
+		if (fullscreen) {
+			// Grow the QR code view to fill its parent
+			statusParams = new LinearLayout.LayoutParams(0, 0, 0f);
+			qrCodeParams = new LinearLayout.LayoutParams(MATCH_PARENT, MATCH_PARENT, 1f);
+		} else {
+			// Shrink the QR code view to fill half its parent
+			if (cameraOverlay.getOrientation() == HORIZONTAL) {
+				statusParams = new LinearLayout.LayoutParams(0, MATCH_PARENT, 1f);
+				qrCodeParams = new LinearLayout.LayoutParams(0, MATCH_PARENT, 1f);
+			} else {
+				statusParams = new LinearLayout.LayoutParams(MATCH_PARENT, 0, 1f);
+				qrCodeParams = new LinearLayout.LayoutParams(MATCH_PARENT, 0, 1f);
+			}
+		}
+		statusView.setLayoutParams(statusParams);
+		qrCodeView.setLayoutParams(qrCodeParams);
+		cameraOverlay.invalidate();
+	}
+
+	@Override
+	public void onStop() {
+		super.onStop();
+		stopListening();
+		try {
+			cameraView.stop();
+		} catch (CameraException e) {
+			logCameraExceptionAndFinish(e);
+		}
+	}
+
+	@UiThread
+	private void logCameraExceptionAndFinish(CameraException e) {
+		logException(LOG, WARNING, e);
+		Toast.makeText(getActivity(), R.string.camera_error,
+				LENGTH_LONG).show();
+		finish();
+	}
+
+	@UiThread
+	private void startListening() {
+		KeyAgreementTask oldTask = task;
+		KeyAgreementTask newTask = keyAgreementTaskProvider.get();
+		task = newTask;
+		ioExecutor.execute(() -> {
+			if (oldTask != null) oldTask.stopListening();
+			newTask.listen();
+		});
+	}
+
+	@UiThread
+	private void stopListening() {
+		KeyAgreementTask oldTask = task;
+		ioExecutor.execute(() -> {
+			if (oldTask != null) oldTask.stopListening();
+		});
+	}
+
+	@UiThread
+	private void reset() {
+		// If we've stopped the camera view, restart it
+		if (gotRemotePayload) {
+			try {
+				cameraView.start();
+			} catch (CameraException e) {
+				logCameraExceptionAndFinish(e);
+				return;
+			}
+		}
+		statusView.setVisibility(INVISIBLE);
+		cameraView.setVisibility(VISIBLE);
+		gotRemotePayload = false;
+		gotLocalPayload = false;
+		startListening();
+	}
+
+	@UiThread
+	private void qrCodeScanned(String content) {
+		try {
+			byte[] payloadBytes = content.getBytes(ISO_8859_1);
+			if (LOG.isLoggable(INFO))
+				LOG.info("Remote payload is " + payloadBytes.length + " bytes");
+			Payload remotePayload = payloadParser.parse(payloadBytes);
+			gotRemotePayload = true;
+			cameraView.stop();
+			cameraView.setVisibility(INVISIBLE);
+			statusView.setVisibility(VISIBLE);
+			status.setText(R.string.connecting_to_device);
+			task.connectAndRunProtocol(remotePayload);
+		} catch (UnsupportedVersionException e) {
+			reset();
+			String msg;
+			if (e.isTooOld()) {
+				msg = getString(R.string.qr_code_too_old,
+						getString(R.string.app_name));
+			} else {
+				msg = getString(R.string.qr_code_too_new,
+						getString(R.string.app_name));
+			}
+			showNextFragment(ContactExchangeErrorFragment.newInstance(msg));
+		} catch (CameraException e) {
+			logCameraExceptionAndFinish(e);
+		} catch (IOException | IllegalArgumentException e) {
+			LOG.log(WARNING, "QR Code Invalid", e);
+			reset();
+			Toast.makeText(getActivity(), R.string.qr_code_invalid,
+					LENGTH_LONG).show();
+		}
+	}
+
+	@Override
+	public void eventOccurred(Event e) {
+		if (e instanceof KeyAgreementListeningEvent) {
+			KeyAgreementListeningEvent event = (KeyAgreementListeningEvent) e;
+			gotLocalPayload = true;
+			setQrCode(event.getLocalPayload());
+		} else if (e instanceof KeyAgreementFailedEvent) {
+			keyAgreementFailed();
+		} else if (e instanceof KeyAgreementWaitingEvent) {
+			keyAgreementWaiting();
+		} else if (e instanceof KeyAgreementStartedEvent) {
+			keyAgreementStarted();
+		} else if (e instanceof KeyAgreementAbortedEvent) {
+			KeyAgreementAbortedEvent event = (KeyAgreementAbortedEvent) e;
+			keyAgreementAborted(event.didRemoteAbort());
+		} else if (e instanceof KeyAgreementFinishedEvent) {
+			keyAgreementFinished(((KeyAgreementFinishedEvent) e).getResult());
+		}
+	}
+
+	@UiThread
+	private void keyAgreementFailed() {
+		reset();
+		listener.keyAgreementFailed();
+	}
+
+	@UiThread
+	private void keyAgreementWaiting() {
+		status.setText(listener.keyAgreementWaiting());
+	}
+
+	@UiThread
+	private void keyAgreementStarted() {
+		qrCodeView.setVisibility(INVISIBLE);
+		statusView.setVisibility(VISIBLE);
+		status.setText(listener.keyAgreementStarted());
+	}
+
+	@UiThread
+	private void keyAgreementAborted(boolean remoteAborted) {
+		reset();
+		listener.keyAgreementAborted(remoteAborted);
+	}
+
+	@UiThread
+	private void keyAgreementFinished(KeyAgreementResult result) {
+		statusView.setVisibility(VISIBLE);
+		status.setText(listener.keyAgreementFinished(result));
+	}
+
+	private void setQrCode(Payload localPayload) {
+		Context context = getContext();
+		if (context == null) return;
+		DisplayMetrics dm = context.getResources().getDisplayMetrics();
+		ioExecutor.execute(() -> {
+			byte[] payloadBytes = payloadEncoder.encode(localPayload);
+			if (LOG.isLoggable(INFO)) {
+				LOG.info("Local payload is " + payloadBytes.length
+						+ " bytes");
+			}
+			// Use ISO 8859-1 to encode bytes directly as a string
+			String content = new String(payloadBytes, ISO_8859_1);
+			Bitmap qrCode = QrCodeUtils.createQrCode(dm, content);
+			runOnUiThreadUnlessDestroyed(() -> qrCodeView.setQrCode(qrCode));
+		});
+	}
+
+	@Override
+	public void handleResult(Result result) {
+		runOnUiThreadUnlessDestroyed(() -> {
+			LOG.info("Got result from decoder");
+			// Ignore results until the KeyAgreementTask is ready
+			if (!gotLocalPayload) return;
+			if (!gotRemotePayload) qrCodeScanned(result.getText());
+		});
+	}
+
+	@Override
+	protected void finish() {
+		getActivity().getSupportFragmentManager().popBackStack();
+	}
+
+	@NotNullByDefault
+	interface ShardQrCodeEventListener {
+
+		@UiThread
+		void keyAgreementFailed();
+
+		// Should return a string to be displayed as status.
+		@UiThread
+		@Nullable
+		String keyAgreementWaiting();
+
+		// Should return a string to be displayed as status.
+		@UiThread
+		@Nullable
+		String keyAgreementStarted();
+
+		// Will show an error fragment.
+		@UiThread
+		void keyAgreementAborted(boolean remoteAborted);
+
+		// Should return a string to be displayed as status.
+		@UiThread
+		@Nullable
+		String keyAgreementFinished(KeyAgreementResult result);
+	}
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/ShardsSentFragment.java

@@ -0,0 +1,70 @@
+package org.briarproject.briar.android.socialbackup;
+
+import android.content.Context;
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.Button;
+
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.activity.ActivityComponent;
+import org.briarproject.briar.android.fragment.BaseFragment;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.annotation.UiThread;
+
+public class ShardsSentFragment extends BaseFragment {
+
+	public static final String TAG = ShardsSentFragment.class.getName();
+
+	interface ShardsSentDismissedListener {
+
+		@UiThread
+		void shardsSentDismissed();
+
+	}
+
+	protected ShardsSentDismissedListener listener;
+
+	@Override
+	public void onCreate(@Nullable Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+		requireActivity().setTitle(R.string.title_distributed_backup);
+	}
+
+	@Nullable
+	@Override
+	public View onCreateView(@NonNull LayoutInflater inflater,
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
+		View view = inflater.inflate(R.layout.fragment_shards_sent,
+				container, false);
+
+		Button button = view.findViewById(R.id.button);
+		button.setOnClickListener(e -> {
+			listener.shardsSentDismissed();
+		});
+
+		return view;
+	}
+
+	@Override
+	public void onAttach(Context context) {
+		super.onAttach(context);
+		listener = (ShardsSentDismissedListener) context;
+	}
+
+
+	@Override
+	public String getUniqueTag() {
+		return TAG;
+	}
+
+	@Override
+	public void injectFragment(ActivityComponent component) {
+		component.inject(this);
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/ThresholdDefinedListener.java

@@ -0,0 +1,12 @@
+package org.briarproject.briar.android.socialbackup;
+
+import org.briarproject.bramble.api.db.DbException;
+
+import androidx.annotation.UiThread;
+
+public interface ThresholdDefinedListener {
+
+	@UiThread
+	void thresholdDefined(int threshold) throws DbException;
+
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/ThresholdSelectorFragment.java

@@ -0,0 +1,182 @@
+package org.briarproject.briar.android.socialbackup;
+
+import android.content.Context;
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.Menu;
+import android.view.MenuInflater;
+import android.view.MenuItem;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.SeekBar;
+import android.widget.TextView;
+
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.activity.ActivityComponent;
+import org.briarproject.briar.android.fragment.BaseFragment;
+import org.magmacollective.darkcrystal.secretsharingwrapper.SecretSharingWrapper;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
+public class ThresholdSelectorFragment extends BaseFragment {
+
+	public static final String TAG = ThresholdSelectorFragment.class.getName();
+	private static final String NUMBER_CUSTODIANS = "numberCustodians";
+
+	protected ThresholdDefinedListener listener;
+
+	private int numberOfCustodians;
+	private int threshold;
+	private int recommendedThreshold;
+	private SeekBar seekBar;
+	private TextView thresholdRepresentation;
+	private TextView message;
+	private TextView mOfn;
+
+	public static ThresholdSelectorFragment newInstance(int numberCustodians) {
+		Bundle bundle = new Bundle();
+		bundle.putInt(NUMBER_CUSTODIANS, numberCustodians);
+		ThresholdSelectorFragment fragment = new ThresholdSelectorFragment();
+		fragment.setArguments(bundle);
+		return fragment;
+	}
+
+	@Override
+	public void onCreate(@Nullable Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+		requireActivity().setTitle(R.string.title_define_threshold);
+	}
+
+	@Nullable
+	@Override
+	public View onCreateView(@NonNull LayoutInflater inflater,
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
+		View view = inflater.inflate(R.layout.fragment_select_threshold,
+				container, false);
+		Bundle args = requireArguments();
+		numberOfCustodians = args.getInt(NUMBER_CUSTODIANS);
+		seekBar = view.findViewById(R.id.seekBar);
+		thresholdRepresentation =
+				view.findViewById(R.id.textViewThresholdRepresentation);
+		message = view.findViewById(R.id.textViewMessage);
+		mOfn = view.findViewById(R.id.textViewmOfn);
+
+		if (numberOfCustodians == 2) {
+			message.setText(R.string.threshold_too_few_custodians);
+		}
+		if (numberOfCustodians > 3) {
+			seekBar.setMax(numberOfCustodians -3);
+			seekBar.setProgress(threshold - 2);
+			seekBar.setOnSeekBarChangeListener(new SeekBarListener());
+			recommendedThreshold =
+					SecretSharingWrapper.defaultThreshold(numberOfCustodians);
+			threshold = recommendedThreshold;
+
+		} else {
+			seekBar.setEnabled(false);
+			threshold = 2;
+			seekBar.setMax(numberOfCustodians);
+			seekBar.setProgress(threshold);
+			TextView t = view.findViewById(R.id.title_threshold);
+			t.setText(R.string.threshold_disabled);
+		}
+		thresholdRepresentation.setText(buildThresholdRepresentationString());
+		setmOfnText();
+		return view;
+//        return super.onCreateView(inflater, container, savedInstanceState);
+	}
+
+	private void setmOfnText() {
+		mOfn.setText(String.format(
+				getString(R.string.threshold_m_of_n), threshold,
+				numberOfCustodians));
+	}
+
+	@Override
+	public void onAttach(Context context) {
+		super.onAttach(context);
+		listener = (ThresholdDefinedListener) context;
+	}
+
+
+	@Override
+	public String getUniqueTag() {
+		return TAG;
+	}
+
+	@Override
+	public void injectFragment(ActivityComponent component) {
+		component.inject(this);
+	}
+
+	@Override
+	public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
+		inflater.inflate(R.menu.define_threshold_actions, menu);
+		super.onCreateOptionsMenu(menu, inflater);
+	}
+
+	@Override
+	public boolean onOptionsItemSelected(MenuItem item) {
+		switch (item.getItemId()) {
+			case R.id.action_threshold_defined:
+				try {
+					listener.thresholdDefined(threshold);
+				} catch (DbException e) {
+					e.printStackTrace();
+				}
+				return true;
+			default:
+				return super.onOptionsItemSelected(item);
+		}
+	}
+
+	private String buildThresholdRepresentationString() {
+		String thresholdRepresentationText = "";
+		for (int i = 0; i < threshold; i++) {
+			thresholdRepresentationText += getString(R.string.filled_bullet);
+		}
+		for (int i = 0; i < (numberOfCustodians - threshold); i++) {
+			thresholdRepresentationText += getString(R.string.linear_bullet);
+		}
+		return thresholdRepresentationText;
+	}
+
+	private class SeekBarListener implements SeekBar.OnSeekBarChangeListener {
+
+		@Override
+		public void onProgressChanged(SeekBar seekBar, int progress,
+				boolean fromUser) {
+			threshold = progress + 2;
+
+			thresholdRepresentation.setText(
+					buildThresholdRepresentationString()
+			);
+			setmOfnText();
+
+			int sanityLevel = SecretSharingWrapper
+					.thresholdSanity(threshold, numberOfCustodians);
+			int text = R.string.threshold_secure;
+			if (threshold == recommendedThreshold)
+				text = R.string.threshold_recommended;
+			if (sanityLevel < -1) text = R.string.threshold_low_insecure;
+			if (sanityLevel > 0) text = R.string.threshold_high_insecure;
+			message.setText(text);
+			// TODO change colour of thresholdRepresentation to green/red based on sanityLevel
+		}
+
+		@Override
+		public void onStartTrackingTouch(SeekBar seekBar) {
+			// do nothing
+		}
+
+		@Override
+		public void onStopTrackingTouch(SeekBar seekBar) {
+			// do nothing
+		}
+
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/creation/CreateBackupController.java

@@ -0,0 +1,26 @@
+package org.briarproject.briar.android.socialbackup.creation;
+
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.GroupId;
+import org.briarproject.briar.android.contactselection.ContactSelectorController;
+import org.briarproject.briar.android.contactselection.SelectableContactItem;
+import org.briarproject.briar.android.controller.handler.ResultExceptionHandler;
+
+import java.util.Collection;
+
+import androidx.annotation.Nullable;
+
+@NotNullByDefault
+public interface CreateBackupController
+		extends ContactSelectorController<SelectableContactItem> {
+
+	void createGroup(String name,
+			ResultExceptionHandler<GroupId, DbException> result);
+
+	void sendInvitation(GroupId g, Collection<ContactId> contacts,
+			@Nullable String text,
+			ResultExceptionHandler<Void, DbException> result);
+
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/creation/CreateBackupControllerImpl.java

@@ -0,0 +1,206 @@
+package org.briarproject.briar.android.socialbackup.creation;
+
+import org.briarproject.bramble.api.contact.Contact;
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.contact.ContactManager;
+import org.briarproject.bramble.api.crypto.CryptoExecutor;
+import org.briarproject.bramble.api.db.DatabaseExecutor;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.db.NoSuchContactException;
+import org.briarproject.bramble.api.identity.IdentityManager;
+import org.briarproject.bramble.api.identity.LocalAuthor;
+import org.briarproject.bramble.api.lifecycle.LifecycleManager;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.GroupId;
+import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.briar.android.contactselection.ContactSelectorControllerImpl;
+import org.briarproject.briar.android.controller.handler.ResultExceptionHandler;
+import org.briarproject.briar.api.identity.AuthorManager;
+import org.briarproject.briar.api.privategroup.GroupMessage;
+import org.briarproject.briar.api.privategroup.GroupMessageFactory;
+import org.briarproject.briar.api.privategroup.PrivateGroup;
+import org.briarproject.briar.api.privategroup.PrivateGroupFactory;
+import org.briarproject.briar.api.privategroup.PrivateGroupManager;
+import org.briarproject.briar.api.privategroup.invitation.GroupInvitationFactory;
+import org.briarproject.briar.api.privategroup.invitation.GroupInvitationManager;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.concurrent.Executor;
+import java.util.logging.Logger;
+
+import javax.annotation.concurrent.Immutable;
+import javax.inject.Inject;
+
+import androidx.annotation.Nullable;
+
+import static java.util.logging.Level.WARNING;
+import static org.briarproject.bramble.util.LogUtils.logException;
+
+@Immutable
+@NotNullByDefault
+/**
+ * Derived from {@link org.briarproject.briar.android.privategroup.invitation.GroupInvitationControllerImpl}
+ */
+class CreateBackupControllerImpl extends ContactSelectorControllerImpl
+		implements CreateBackupController {
+
+	private static final Logger LOG =
+			Logger.getLogger(
+					CreateBackupControllerImpl.class.getName());
+
+	private final Executor cryptoExecutor;
+	private final ContactManager contactManager;
+	private final IdentityManager identityManager;
+	private final PrivateGroupFactory groupFactory;
+	private final GroupMessageFactory groupMessageFactory;
+	private final PrivateGroupManager groupManager;
+	private final GroupInvitationFactory groupInvitationFactory;
+	private final GroupInvitationManager groupInvitationManager;
+	private final Clock clock;
+
+	@Inject
+	CreateBackupControllerImpl(@DatabaseExecutor Executor dbExecutor,
+			@CryptoExecutor Executor cryptoExecutor,
+			LifecycleManager lifecycleManager, ContactManager contactManager,
+			IdentityManager identityManager, PrivateGroupFactory groupFactory,
+			GroupMessageFactory groupMessageFactory,
+			PrivateGroupManager groupManager,
+			GroupInvitationFactory groupInvitationFactory,
+			GroupInvitationManager groupInvitationManager, Clock clock, AuthorManager authorManager) {
+		super(dbExecutor, lifecycleManager, contactManager, authorManager);
+		this.cryptoExecutor = cryptoExecutor;
+		this.contactManager = contactManager;
+		this.identityManager = identityManager;
+		this.groupFactory = groupFactory;
+		this.groupMessageFactory = groupMessageFactory;
+		this.groupManager = groupManager;
+		this.groupInvitationFactory = groupInvitationFactory;
+		this.groupInvitationManager = groupInvitationManager;
+		this.clock = clock;
+	}
+
+	@Override
+	public void createGroup(String name,
+			ResultExceptionHandler<GroupId, DbException> handler) {
+		runOnDbThread(() -> {
+			try {
+				LocalAuthor author = identityManager.getLocalAuthor();
+				createGroupAndMessages(author, name, handler);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+				handler.onException(e);
+			}
+		});
+	}
+
+	private void createGroupAndMessages(LocalAuthor author, String name,
+			ResultExceptionHandler<GroupId, DbException> handler) {
+		cryptoExecutor.execute(() -> {
+			LOG.info("Creating group...");
+			PrivateGroup group =
+					groupFactory.createPrivateGroup(name, author);
+			LOG.info("Creating new join announcement...");
+			GroupMessage joinMsg =
+					groupMessageFactory.createJoinMessage(group.getId(),
+							clock.currentTimeMillis(), author);
+			storeGroup(group, joinMsg, handler);
+		});
+	}
+
+	private void storeGroup(PrivateGroup group, GroupMessage joinMsg,
+			ResultExceptionHandler<GroupId, DbException> handler) {
+		runOnDbThread(() -> {
+			LOG.info("Adding group to database...");
+			try {
+				groupManager.addPrivateGroup(group, joinMsg, true);
+				handler.onResult(group.getId());
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+				handler.onException(e);
+			}
+		});
+	}
+
+	@Override
+	protected boolean isDisabled(GroupId g, Contact c) {
+		return false;
+	}
+
+	@Override
+	public void sendInvitation(GroupId g, Collection<ContactId> contactIds,
+			@Nullable String text,
+			ResultExceptionHandler<Void, DbException> handler) {
+		runOnDbThread(() -> {
+			try {
+				LocalAuthor localAuthor = identityManager.getLocalAuthor();
+				List<Contact> contacts = new ArrayList<>();
+				for (ContactId c : contactIds) {
+					try {
+						contacts.add(contactManager.getContact(c));
+					} catch (NoSuchContactException e) {
+						// Continue
+					}
+				}
+				signInvitations(g, localAuthor, contacts, text, handler);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+				handler.onException(e);
+			}
+		});
+	}
+
+	private void signInvitations(GroupId g, LocalAuthor localAuthor,
+			Collection<Contact> contacts, @Nullable String text,
+			ResultExceptionHandler<Void, DbException> handler) {
+		cryptoExecutor.execute(() -> {
+			long timestamp = clock.currentTimeMillis();
+			List<InvitationContext> contexts = new ArrayList<>();
+			for (Contact c : contacts) {
+				byte[] signature = groupInvitationFactory.signInvitation(c, g,
+						timestamp, localAuthor.getPrivateKey());
+				contexts.add(new InvitationContext(c.getId(), timestamp,
+						signature));
+			}
+			sendInvitations(g, contexts, text, handler);
+		});
+	}
+
+	private void sendInvitations(GroupId g,
+			Collection<InvitationContext> contexts, @Nullable String text,
+			ResultExceptionHandler<Void, DbException> handler) {
+		runOnDbThread(() -> {
+			try {
+				for (InvitationContext context : contexts) {
+					try {
+						groupInvitationManager.sendInvitation(g,
+								context.contactId, text, context.timestamp,
+								context.signature);
+					} catch (NoSuchContactException e) {
+						// Continue
+					}
+				}
+				//noinspection ConstantConditions
+				handler.onResult(null);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+				handler.onException(e);
+			}
+		});
+	}
+
+	private static class InvitationContext {
+
+		private final ContactId contactId;
+		private final long timestamp;
+		private final byte[] signature;
+
+		private InvitationContext(ContactId contactId, long timestamp,
+				byte[] signature) {
+			this.contactId = contactId;
+			this.timestamp = timestamp;
+			this.signature = signature;
+		}
+	}
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/creation/CreateBackupModule.java

@@ -0,0 +1,18 @@
+package org.briarproject.briar.android.socialbackup.creation;
+
+import org.briarproject.briar.android.activity.ActivityScope;
+
+import dagger.Module;
+import dagger.Provides;
+
+@Module
+public class CreateBackupModule {
+
+	@ActivityScope
+	@Provides
+	CreateBackupController provideCreateGroupController(
+			CreateBackupControllerImpl createBackupController) {
+		return createBackupController;
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/socialbackup/AndroidDarkCrystalModule.java

@@ -0,0 +1,16 @@
+package org.briarproject.briar.socialbackup;
+
+import org.briarproject.briar.android.socialbackup.DarkCrystalImpl;
+import org.briarproject.briar.api.socialbackup.DarkCrystal;
+
+import dagger.Module;
+import dagger.Provides;
+
+@Module
+public class AndroidDarkCrystalModule {
+
+	@Provides
+	DarkCrystal darkCrystal(DarkCrystalImpl darkCrystal) {
+		return darkCrystal;
+	}
+}

briar-android/src/main/res/drawable/ic_baseline_done_outline_24.xml

@@ -0,0 +1,5 @@
+<vector android:height="24dp" android:tint="#29C400"
+    android:viewportHeight="24" android:viewportWidth="24"
+    android:width="24dp" xmlns:android="http://schemas.android.com/apk/res/android">
+    <path android:fillColor="@android:color/white" android:pathData="M19.77,5.03l1.4,1.4L8.43,19.17l-5.6,-5.6 1.4,-1.4 4.2,4.2L19.77,5.03m0,-2.83L8.43,13.54l-4.2,-4.2L0,13.57 8.43,22 24,6.43 19.77,2.2z"/>
+</vector>

briar-android/src/main/res/layout/activity_distributed_backup.xml

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/fragmentContainer"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+</androidx.constraintlayout.widget.ConstraintLayout>

briar-android/src/main/res/layout/activity_preview_recovery_custodian1.xml

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto"
+	android:layout_width="match_parent"
+	android:layout_height="match_parent"
+	android:fitsSystemWindows="true"
+	android:orientation="vertical">
+
+	<androidx.appcompat.widget.Toolbar
+		android:id="@+id/toolbar"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:background="?attr/colorPrimary"
+		android:minHeight="?attr/actionBarSize"
+		app:title="@string/title_help_recover"
+		app:titleTextColor="@android:color/white" />
+
+	<include layout="@layout/fragment_recovery_custodian_explainer" />
+
+</LinearLayout>

briar-android/src/main/res/layout/activity_preview_recovery_custodian2.xml

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto"
+	android:layout_width="match_parent"
+	android:layout_height="match_parent"
+	android:fitsSystemWindows="true"
+	android:orientation="vertical">
+
+	<androidx.appcompat.widget.Toolbar
+		android:id="@+id/toolbar"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:background="?attr/colorPrimary"
+		android:minHeight="?attr/actionBarSize"
+		app:title="@string/title_help_recover"
+		app:titleTextColor="@android:color/white" />
+
+	<include layout="@layout/fragment_recovery_custodian_error_explainer" />
+
+</LinearLayout>

briar-android/src/main/res/layout/activity_preview_recovery_owner1.xml

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto"
+	android:layout_width="match_parent"
+	android:layout_height="match_parent"
+	android:fitsSystemWindows="true"
+	android:orientation="vertical">
+
+	<androidx.appcompat.widget.Toolbar
+		android:id="@+id/toolbar"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:background="?attr/colorPrimary"
+		android:minHeight="?attr/actionBarSize"
+		app:title="@string/title_recovery_mode"
+		app:titleTextColor="@android:color/white" />
+
+	<include layout="@layout/fragment_recovery_owner_explainer" />
+
+</LinearLayout>

briar-android/src/main/res/layout/activity_preview_recovery_owner2.xml

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto"
+	android:layout_width="match_parent"
+	android:layout_height="match_parent"
+	android:fitsSystemWindows="true"
+	android:orientation="vertical">
+
+	<androidx.appcompat.widget.Toolbar
+		android:id="@+id/toolbar"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:background="?attr/colorPrimary"
+		android:minHeight="?attr/actionBarSize"
+		app:title="@string/title_recovery_mode"
+		app:titleTextColor="@android:color/white" />
+
+	<include layout="@layout/fragment_recovery_owner_error_explainer" />
+
+</LinearLayout>

briar-android/src/main/res/layout/activity_preview_recovery_owner3.xml

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto"
+	android:layout_width="match_parent"
+	android:layout_height="match_parent"
+	android:fitsSystemWindows="true"
+	android:orientation="vertical">
+
+	<androidx.appcompat.widget.Toolbar
+		android:id="@+id/toolbar"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:background="?attr/colorPrimary"
+		android:minHeight="?attr/actionBarSize"
+		app:title="@string/title_recovery_mode"
+		app:titleTextColor="@android:color/white" />
+
+	<include layout="@layout/fragment_recovery_owner_main" />
+
+</LinearLayout>

briar-android/src/main/res/layout/activity_preview_recovery_owner4.xml

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto"
+	android:layout_width="match_parent"
+	android:layout_height="match_parent"
+	android:fitsSystemWindows="true"
+	android:orientation="vertical">
+
+	<androidx.appcompat.widget.Toolbar
+		android:id="@+id/toolbar"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:background="?attr/colorPrimary"
+		android:minHeight="?attr/actionBarSize"
+		app:title="@string/title_recovery_mode"
+		app:titleTextColor="@android:color/white" />
+
+	<include layout="@layout/fragment_recovery_owner_recovering" />
+
+</LinearLayout>

briar-android/src/main/res/layout/activity_preview_welcome.xml

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto"
+	android:layout_width="match_parent"
+	android:layout_height="match_parent"
+	android:fitsSystemWindows="true"
+	android:orientation="vertical">
+
+	<androidx.appcompat.widget.Toolbar
+		android:id="@+id/toolbar"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:background="?attr/colorPrimary"
+		android:minHeight="?attr/actionBarSize"
+		app:title="@string/setup_title"
+		app:titleTextColor="@android:color/white" />
+
+	<include layout="@layout/fragment_start" />
+
+</LinearLayout>

briar-android/src/main/res/layout/activity_recover.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout
+	xmlns:android="http://schemas.android.com/apk/res/android"
+	android:id="@+id/fragmentContainer"
+	android:layout_width="match_parent"
+	android:layout_height="match_parent">
+
+</androidx.constraintlayout.widget.ConstraintLayout>

briar-android/src/main/res/layout/activity_welcome.xml

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto"
+	android:layout_width="match_parent"
+	android:layout_height="match_parent"
+	android:fitsSystemWindows="true"
+	android:orientation="vertical">
+
+	<androidx.appcompat.widget.Toolbar
+		android:id="@+id/toolbar"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:background="?attr/colorPrimary"
+		android:minHeight="?attr/actionBarSize"
+		app:title="@string/setup_title"
+		app:titleTextColor="@android:color/white" />
+
+</LinearLayout>

briar-android/src/main/res/layout/fragment_account_recovered.xml

@@ -0,0 +1,50 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:id="@+id/linearLayout"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:paddingLeft="@dimen/margin_large"
+    android:paddingTop="@dimen/margin_medium"
+    android:paddingRight="@dimen/margin_large"
+    android:paddingBottom="@dimen/margin_medium">
+
+    <Button
+        android:id="@+id/button"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_marginTop="32dp"
+        android:text="@string/backup_done_dismiss"
+        android:textSize="24sp"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/textView2" />
+
+    <TextView
+        android:id="@+id/textView2"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_marginTop="16dp"
+        android:gravity="center"
+        android:text="@string/recovery_account_recovered"
+        android:textSize="30sp"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/imageView2" />
+
+    <ImageView
+        android:id="@+id/imageView2"
+        android:layout_width="match_parent"
+        android:layout_height="0dp"
+        android:layout_marginStart="32dp"
+        android:layout_marginLeft="32dp"
+        android:layout_marginTop="8dp"
+        android:layout_marginEnd="32dp"
+        android:layout_marginRight="32dp"
+        app:layout_constraintDimensionRatio="1:1"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent"
+        app:srcCompat="@drawable/ic_baseline_done_outline_24" />
+</androidx.constraintlayout.widget.ConstraintLayout>

briar-android/src/main/res/layout/fragment_existing_backup.xml

@@ -0,0 +1,35 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout
+	xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:tools="http://schemas.android.com/tools"
+	xmlns:app="http://schemas.android.com/apk/res-auto"
+	android:layout_width="match_parent"
+
+	android:paddingLeft="@dimen/margin_large"
+	android:paddingTop="@dimen/margin_large"
+	android:paddingRight="@dimen/margin_large"
+	android:paddingBottom="@dimen/margin_medium"
+	android:layout_height="match_parent">
+
+	<TextView
+		android:id="@+id/textViewThreshold"
+		android:layout_width="wrap_content"
+		android:layout_height="wrap_content"
+		android:gravity="center"
+		android:text="placeholder threshold"
+		android:textSize="16sp"
+		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintStart_toStartOf="parent"
+		app:layout_constraintTop_toTopOf="parent" />
+
+	<TextView
+		android:id="@+id/textViewCustodians"
+		android:layout_width="wrap_content"
+		android:layout_height="wrap_content"
+		android:gravity="center"
+		android:text="@string/backup_done_info"
+		android:textSize="16sp"
+		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintStart_toStartOf="parent"
+		app:layout_constraintTop_toBottomOf="@+id/textViewThreshold" />
+</androidx.constraintlayout.widget.ConstraintLayout>

briar-android/src/main/res/layout/fragment_mockups.xml

@@ -0,0 +1,130 @@
+<?xml version="1.0" encoding="utf-8"?>
+<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto"
+	xmlns:tools="http://schemas.android.com/tools"
+	android:layout_width="match_parent"
+	android:layout_height="match_parent">
+
+	<LinearLayout
+		android:id="@+id/linearLayout"
+		android:layout_width="match_parent"
+		android:layout_height="match_parent"
+		android:orientation="vertical"
+		android:paddingLeft="@dimen/margin_large"
+		android:paddingTop="@dimen/margin_medium"
+		android:paddingRight="@dimen/margin_large"
+		android:paddingBottom="@dimen/margin_medium">
+
+		<TextView
+			android:layout_width="wrap_content"
+			android:layout_height="wrap_content"
+			android:text="Backup creation" />
+
+		<Button
+			android:id="@+id/buttonSelectThreshold"
+			android:layout_width="match_parent"
+			android:layout_height="wrap_content"
+			android:drawableLeft="@drawable/ic_security"
+			android:text="Select Threshold" />
+
+		<Button
+			android:id="@+id/buttonShardsSent"
+			android:layout_width="match_parent"
+			android:layout_height="wrap_content"
+			android:drawableLeft="@drawable/ic_security"
+			android:text="Shards sent" />
+
+		<TextView
+			android:layout_width="wrap_content"
+			android:layout_height="wrap_content"
+			android:text="Setup" />
+
+		<Button
+			android:id="@+id/buttonWelcome"
+			android:layout_width="match_parent"
+			android:layout_height="wrap_content"
+			android:drawableLeft="@drawable/ic_security"
+			android:text="Welcome" />
+
+		<TextView
+			android:layout_width="wrap_content"
+			android:layout_height="wrap_content"
+			android:text="Recovery from secrect owner's point of view" />
+
+		<Button
+			android:id="@+id/buttonOwnerRecoveryExplainer"
+			android:layout_width="match_parent"
+			android:layout_height="wrap_content"
+			android:drawableLeft="@drawable/ic_security"
+			android:text="Explainer" />
+
+		<Button
+			android:id="@+id/buttonOwnerRecoveryReceivedShard"
+			android:layout_width="match_parent"
+			android:layout_height="wrap_content"
+			android:drawableLeft="@drawable/ic_security"
+			android:text="Shard received" />
+
+		<Button
+			android:id="@+id/buttonOwnerRecoveryMain1"
+			android:layout_width="match_parent"
+			android:layout_height="wrap_content"
+			android:drawableLeft="@drawable/ic_security"
+			android:text="Main (0 shards)" />
+
+		<Button
+			android:id="@+id/buttonOwnerRecoveryMain2"
+			android:layout_width="match_parent"
+			android:layout_height="wrap_content"
+			android:drawableLeft="@drawable/ic_security"
+			android:text="Main (1 shard)" />
+
+		<Button
+			android:id="@+id/buttonOwnerRecoveryMain3"
+			android:layout_width="match_parent"
+			android:layout_height="wrap_content"
+			android:drawableLeft="@drawable/ic_security"
+			android:text="Recovering account…" />
+
+		<Button
+			android:id="@+id/buttonOwnerRecoveryAccountRecovered"
+			android:layout_width="match_parent"
+			android:layout_height="wrap_content"
+			android:drawableLeft="@drawable/ic_security"
+			android:text="Account recovered" />
+
+		<Button
+			android:id="@+id/buttonOwnerRecoveryErrorExplainer"
+			android:layout_width="match_parent"
+			android:layout_height="wrap_content"
+			android:drawableLeft="@drawable/ic_security"
+			android:text="Error" />
+
+		<TextView
+			android:layout_width="wrap_content"
+			android:layout_height="wrap_content"
+			android:text="Recovery from custodian's point of view" />
+
+		<Button
+			android:id="@+id/buttonCustodianRecoveryExplainer"
+			android:layout_width="match_parent"
+			android:layout_height="wrap_content"
+			android:drawableLeft="@drawable/ic_security"
+			android:text="Explainer" />
+
+		<Button
+			android:id="@+id/buttonCustodianRecoveryErrorExplainer"
+			android:layout_width="match_parent"
+			android:layout_height="wrap_content"
+			android:drawableLeft="@drawable/ic_security"
+			android:text="Error" />
+
+		<Button
+			android:id="@+id/buttonCustodianRecoveryDone"
+			android:layout_width="match_parent"
+			android:layout_height="wrap_content"
+			android:drawableLeft="@drawable/ic_security"
+			android:text="Done" />
+
+	</LinearLayout>
+</ScrollView>

briar-android/src/main/res/layout/fragment_new_or_recover.xml

@@ -0,0 +1,34 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto"
+	xmlns:tools="http://schemas.android.com/tools"
+	android:id="@+id/linearLayout"
+	android:layout_width="match_parent"
+	android:layout_height="match_parent"
+	android:paddingLeft="@dimen/margin_large"
+	android:paddingTop="@dimen/margin_medium"
+	android:paddingRight="@dimen/margin_large"
+	android:paddingBottom="@dimen/margin_medium"
+	tools:showIn="@layout/activity_preview_welcome">
+
+	<Button
+		android:id="@+id/buttonSetupNewAccount"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:drawableLeft="@drawable/ic_contacts"
+		android:text="@string/setup_new_account"
+		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintStart_toStartOf="parent"
+		app:layout_constraintTop_toTopOf="parent" />
+
+	<Button
+		android:id="@+id/buttonRestoreAccount"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:drawableLeft="@drawable/ic_repeat"
+		android:text="@string/setup_restore_account"
+		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintStart_toStartOf="parent"
+		app:layout_constraintTop_toBottomOf="@+id/buttonSetupNewAccount" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>

briar-android/src/main/res/layout/fragment_recovery_custodian_done.xml

@@ -0,0 +1,39 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto"
+	xmlns:tools="http://schemas.android.com/tools"
+	android:id="@+id/linearLayout"
+	android:layout_width="match_parent"
+	android:layout_height="match_parent"
+	android:paddingLeft="@dimen/margin_large"
+	android:paddingTop="@dimen/margin_medium"
+	android:paddingRight="@dimen/margin_large"
+	android:paddingBottom="@dimen/margin_medium">
+
+	<TextView
+		android:id="@+id/textView2"
+		android:layout_width="wrap_content"
+		android:layout_height="wrap_content"
+		android:layout_marginTop="16dp"
+		android:gravity="center"
+		android:text="@string/custodian_shard_sent"
+		android:textSize="30sp"
+		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintStart_toStartOf="parent"
+		app:layout_constraintTop_toBottomOf="@+id/imageView2" />
+
+	<ImageView
+		android:id="@+id/imageView2"
+		android:layout_width="match_parent"
+		android:layout_height="0dp"
+		android:layout_marginStart="32dp"
+		android:layout_marginLeft="32dp"
+		android:layout_marginTop="8dp"
+		android:layout_marginEnd="32dp"
+		android:layout_marginRight="32dp"
+		app:layout_constraintDimensionRatio="1:1"
+		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintStart_toStartOf="parent"
+		app:layout_constraintTop_toTopOf="parent"
+		app:srcCompat="@drawable/ic_baseline_done_outline_24" />
+</androidx.constraintlayout.widget.ConstraintLayout>

briar-android/src/main/res/layout/fragment_recovery_custodian_error_explainer.xml

@@ -0,0 +1,60 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto"
+	xmlns:tools="http://schemas.android.com/tools"
+	android:id="@+id/linearLayout"
+	android:layout_width="match_parent"
+	android:layout_height="match_parent"
+	android:paddingLeft="@dimen/margin_large"
+	android:paddingTop="@dimen/margin_medium"
+	android:paddingRight="@dimen/margin_large"
+	android:paddingBottom="@dimen/margin_medium"
+	tools:ignore="VectorDrawableCompat"
+	tools:showIn="@layout/activity_preview_recovery_custodian2">
+
+	<TextView
+		android:id="@+id/textView1"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:layout_marginTop="24dp"
+		android:gravity="center"
+		android:text="@string/custodian_recovery_failed_to_send"
+		android:textSize="24sp"
+		app:layout_constraintTop_toTopOf="parent"
+		tools:layout_editor_absoluteX="16dp" />
+
+	<ImageView
+		android:id="@+id/imageView"
+		android:layout_width="wrap_content"
+		android:layout_height="wrap_content"
+		android:layout_marginTop="24dp"
+		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintStart_toStartOf="parent"
+		app:layout_constraintTop_toBottomOf="@+id/textView1"
+		app:srcCompat="@drawable/qr_code_error" />
+
+	<TextView
+		android:id="@+id/textView2"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:layout_marginTop="24dp"
+		android:gravity="center"
+		android:text="@string/recovery_helpful_suggestions"
+		android:textSize="24sp"
+		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintHorizontal_bias="0.0"
+		app:layout_constraintStart_toStartOf="parent"
+		app:layout_constraintTop_toBottomOf="@+id/imageView" />
+
+	<Button
+		android:id="@+id/button"
+		android:layout_marginTop="24dp"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:text="@string/recovery_retry"
+		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintHorizontal_bias="0.0"
+		app:layout_constraintStart_toStartOf="parent"
+		app:layout_constraintTop_toBottomOf="@+id/textView2" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>

briar-android/src/main/res/layout/fragment_recovery_custodian_explainer.xml

@@ -0,0 +1,47 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto"
+	xmlns:tools="http://schemas.android.com/tools"
+	android:id="@+id/linearLayout"
+	android:layout_width="match_parent"
+	android:layout_height="match_parent"
+	android:paddingLeft="@dimen/margin_large"
+	android:paddingTop="@dimen/margin_medium"
+	android:paddingRight="@dimen/margin_large"
+	android:paddingBottom="@dimen/margin_medium"
+	tools:ignore="VectorDrawableCompat"
+	tools:showIn="@layout/activity_preview_recovery_custodian1">
+
+	<TextView
+		android:id="@+id/textView"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:layout_marginTop="24dp"
+		android:gravity="center"
+		android:text="@string/custodian_recovery_explainer"
+		android:textSize="24sp"
+		app:layout_constraintTop_toTopOf="parent"
+		tools:layout_editor_absoluteX="16dp" />
+
+	<ImageView
+		android:id="@+id/imageView"
+		android:layout_width="wrap_content"
+		android:layout_height="wrap_content"
+		android:layout_marginTop="24dp"
+		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintStart_toStartOf="parent"
+		app:layout_constraintTop_toBottomOf="@+id/textView"
+		app:srcCompat="@drawable/qr_code_intro" />
+
+	<Button
+		android:id="@+id/button"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:layout_marginTop="24dp"
+		android:text="@string/custodian_scan_code"
+		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintHorizontal_bias="0.0"
+		app:layout_constraintStart_toStartOf="parent"
+		app:layout_constraintTop_toBottomOf="@+id/imageView" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>

briar-android/src/main/res/layout/fragment_recovery_owner_error_explainer.xml

@@ -0,0 +1,59 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto"
+	xmlns:tools="http://schemas.android.com/tools"
+	android:id="@+id/linearLayout"
+	android:layout_width="match_parent"
+	android:layout_height="match_parent"
+	android:paddingLeft="@dimen/margin_large"
+	android:paddingTop="@dimen/margin_medium"
+	android:paddingRight="@dimen/margin_large"
+	android:paddingBottom="@dimen/margin_medium"
+	tools:ignore="VectorDrawableCompat"
+	tools:showIn="@layout/activity_preview_recovery_owner2">
+
+	<TextView
+		android:id="@+id/textView1"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:layout_marginTop="24dp"
+		android:gravity="center"
+		android:text="@string/recovery_failed_to_receive"
+		android:textSize="24sp"
+		app:layout_constraintTop_toTopOf="parent" />
+
+	<ImageView
+		android:id="@+id/imageView"
+		android:layout_width="wrap_content"
+		android:layout_height="wrap_content"
+		android:layout_marginTop="24dp"
+		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintStart_toStartOf="parent"
+		app:layout_constraintTop_toBottomOf="@+id/textView1"
+		app:srcCompat="@drawable/qr_code_error" />
+
+	<TextView
+		android:id="@+id/textView2"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:layout_marginTop="24dp"
+		android:gravity="center"
+		android:text="@string/recovery_helpful_suggestions"
+		android:textSize="24sp"
+		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintHorizontal_bias="0.0"
+		app:layout_constraintStart_toStartOf="parent"
+		app:layout_constraintTop_toBottomOf="@+id/imageView" />
+
+	<Button
+		android:id="@+id/button"
+		android:layout_marginTop="24dp"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:text="@string/recovery_retry"
+		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintHorizontal_bias="0.0"
+		app:layout_constraintStart_toStartOf="parent"
+		app:layout_constraintTop_toBottomOf="@+id/textView2" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>

briar-android/src/main/res/layout/fragment_recovery_owner_explainer.xml

@@ -0,0 +1,47 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto"
+	xmlns:tools="http://schemas.android.com/tools"
+	android:id="@+id/linearLayout"
+	android:layout_width="match_parent"
+	android:layout_height="match_parent"
+	android:paddingLeft="@dimen/margin_large"
+	android:paddingTop="@dimen/margin_medium"
+	android:paddingRight="@dimen/margin_large"
+	android:paddingBottom="@dimen/margin_medium"
+	tools:ignore="VectorDrawableCompat"
+	tools:showIn="@layout/activity_preview_recovery_owner1">
+
+	<TextView
+		android:id="@+id/textView"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:layout_marginTop="24dp"
+		android:gravity="center"
+		android:text="@string/recovery_explainer"
+		android:textSize="24sp"
+		app:layout_constraintTop_toTopOf="parent"
+		tools:layout_editor_absoluteX="16dp" />
+
+	<ImageView
+		android:id="@+id/imageView"
+		android:layout_width="wrap_content"
+		android:layout_height="wrap_content"
+		android:layout_marginTop="24dp"
+		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintStart_toStartOf="parent"
+		app:layout_constraintTop_toBottomOf="@+id/textView"
+		app:srcCompat="@drawable/qr_code_intro" />
+
+	<Button
+		android:id="@+id/beginButton"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:layout_marginTop="24dp"
+		android:text="@string/recovery_begin"
+		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintHorizontal_bias="0.0"
+		app:layout_constraintStart_toStartOf="parent"
+		app:layout_constraintTop_toBottomOf="@+id/imageView" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>

briar-android/src/main/res/layout/fragment_recovery_owner_main.xml

@@ -0,0 +1,47 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto"
+	xmlns:tools="http://schemas.android.com/tools"
+	android:id="@+id/linearLayout"
+	android:layout_width="match_parent"
+	android:layout_height="match_parent"
+	android:paddingLeft="@dimen/margin_large"
+	android:paddingTop="@dimen/margin_medium"
+	android:paddingRight="@dimen/margin_large"
+	android:paddingBottom="@dimen/margin_medium"
+	tools:ignore="VectorDrawableCompat"
+	tools:showIn="@layout/activity_preview_recovery_owner3">
+
+	<TextView
+		android:id="@+id/textView"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:layout_marginTop="24dp"
+		android:gravity="center"
+		android:text="@string/recovery_recovered_shards"
+		android:textSize="24sp"
+		app:layout_constraintTop_toTopOf="parent"
+		tools:layout_editor_absoluteX="16dp" />
+
+	<TextView
+		android:id="@+id/textViewShardCount"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:layout_marginTop="24dp"
+		android:gravity="center"
+		android:text="0"
+		android:textSize="24sp"
+		app:layout_constraintTop_toBottomOf="@+id/textView"
+		tools:layout_editor_absoluteX="16dp" />
+
+	<Button
+		android:id="@+id/button"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:text="@string/recovery_scan_qr_code"
+		app:layout_constraintBottom_toBottomOf="parent"
+		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintHorizontal_bias="0.0"
+		app:layout_constraintStart_toStartOf="parent" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>

briar-android/src/main/res/layout/fragment_recovery_owner_recovering.xml

@@ -0,0 +1,58 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto"
+	xmlns:tools="http://schemas.android.com/tools"
+	android:id="@+id/linearLayout"
+	android:layout_width="match_parent"
+	android:layout_height="match_parent"
+	android:paddingLeft="@dimen/margin_large"
+	android:paddingTop="@dimen/margin_medium"
+	android:paddingRight="@dimen/margin_large"
+	android:paddingBottom="@dimen/margin_medium"
+	tools:ignore="VectorDrawableCompat"
+	tools:showIn="@layout/activity_preview_recovery_owner4">
+
+	<TextView
+		android:id="@+id/textView"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:layout_marginTop="24dp"
+		android:gravity="center"
+		android:text="@string/recovery_recovered_shards"
+		android:textSize="24sp"
+		app:layout_constraintTop_toTopOf="parent"
+		tools:layout_editor_absoluteX="16dp" />
+
+	<TextView
+		android:id="@+id/textViewShardCount"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:layout_marginTop="24dp"
+		android:gravity="center"
+		android:text="3"
+		android:textSize="24sp"
+		app:layout_constraintTop_toBottomOf="@+id/textView"
+		tools:layout_editor_absoluteX="16dp" />
+
+	<ProgressBar
+		android:id="@+id/progressBar"
+		android:layout_width="wrap_content"
+		android:layout_height="wrap_content"
+		android:layout_gravity="center"
+		android:layout_marginTop="144dp"
+		android:indeterminate="true"
+		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintStart_toStartOf="parent"
+		app:layout_constraintTop_toBottomOf="@+id/textViewShardCount" />
+
+	<TextView
+		android:id="@+id/textView3"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:layout_marginTop="24dp"
+		android:gravity="center"
+		android:text="@string/recovery_recovering_account"
+		android:textSize="24sp"
+		app:layout_constraintTop_toBottomOf="@+id/progressBar" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>

briar-android/src/main/res/layout/fragment_select_threshold.xml

@@ -0,0 +1,69 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:id="@+id/linearLayout"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:paddingLeft="@dimen/margin_large"
+    android:paddingTop="@dimen/margin_medium"
+    android:paddingRight="@dimen/margin_large"
+    android:paddingBottom="@dimen/margin_medium">
+
+    <TextView
+        android:id="@+id/title_threshold"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:text="@string/threshold"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent" />
+
+    <SeekBar
+        android:id="@+id/seekBar"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_marginTop="8dp"
+        android:max="5"
+        android:paddingTop="10dp"
+        android:progress="3"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintHorizontal_bias="0.0"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/title_threshold" />
+
+
+    <TextView
+        android:id="@+id/textViewThresholdRepresentation"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_marginTop="24dp"
+        android:text="placeholder"
+        android:textSize="64dp"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/seekBar" />
+
+    <TextView
+        android:id="@+id/textViewmOfn"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_marginTop="24dp"
+        android:text="m of n contacts needed to recover your account"
+        android:textSize="16dp"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/textViewThresholdRepresentation" />
+
+    <TextView
+        android:id="@+id/textViewMessage"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_marginTop="24dp"
+        android:text="@string/threshold_secure"
+        android:textSize="16dp"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/textViewmOfn" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>

briar-android/src/main/res/layout/fragment_shards_received.xml

@@ -0,0 +1,50 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:id="@+id/linearLayout"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:paddingLeft="@dimen/margin_large"
+    android:paddingTop="@dimen/margin_medium"
+    android:paddingRight="@dimen/margin_large"
+    android:paddingBottom="@dimen/margin_medium">
+
+    <Button
+        android:id="@+id/button"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_marginTop="32dp"
+        android:text="@string/backup_done_dismiss"
+        android:textSize="24sp"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/textView2" />
+
+    <TextView
+        android:id="@+id/textView2"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_marginTop="16dp"
+        android:gravity="center"
+        android:text="@string/recovery_shard_received"
+        android:textSize="30sp"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/imageView2" />
+
+    <ImageView
+        android:id="@+id/imageView2"
+        android:layout_width="match_parent"
+        android:layout_height="0dp"
+        android:layout_marginStart="32dp"
+        android:layout_marginLeft="32dp"
+        android:layout_marginTop="8dp"
+        android:layout_marginEnd="32dp"
+        android:layout_marginRight="32dp"
+        app:layout_constraintDimensionRatio="1:1"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent"
+        app:srcCompat="@drawable/ic_baseline_done_outline_24" />
+</androidx.constraintlayout.widget.ConstraintLayout>

briar-android/src/main/res/layout/fragment_shards_sent.xml

@@ -0,0 +1,50 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:id="@+id/linearLayout"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:paddingLeft="@dimen/margin_large"
+    android:paddingTop="@dimen/margin_medium"
+    android:paddingRight="@dimen/margin_large"
+    android:paddingBottom="@dimen/margin_medium">
+
+    <Button
+        android:id="@+id/button"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_marginTop="32dp"
+        android:text="@string/backup_done_dismiss"
+        android:textSize="24sp"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/textView2" />
+
+    <TextView
+        android:id="@+id/textView2"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_marginTop="16dp"
+        android:text="@string/backup_done_info"
+        android:gravity="center"
+        android:textSize="30sp"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/imageView2" />
+
+    <ImageView
+        android:id="@+id/imageView2"
+        android:layout_width="match_parent"
+        android:layout_height="0dp"
+        android:layout_marginStart="32dp"
+        android:layout_marginLeft="32dp"
+        android:layout_marginTop="8dp"
+        android:layout_marginEnd="32dp"
+        android:layout_marginRight="32dp"
+        app:layout_constraintDimensionRatio="1:1"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent"
+        app:srcCompat="@drawable/ic_baseline_done_outline_24" />
+</androidx.constraintlayout.widget.ConstraintLayout>

briar-android/src/main/res/layout/fragment_start.xml

@@ -0,0 +1,34 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto"
+	xmlns:tools="http://schemas.android.com/tools"
+	android:id="@+id/linearLayout"
+	android:layout_width="match_parent"
+	android:layout_height="match_parent"
+	android:paddingLeft="@dimen/margin_large"
+	android:paddingTop="@dimen/margin_medium"
+	android:paddingRight="@dimen/margin_large"
+	android:paddingBottom="@dimen/margin_medium"
+	tools:showIn="@layout/activity_preview_welcome">
+
+	<Button
+		android:id="@+id/buttonSelectThreshold"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:drawableLeft="@drawable/ic_contacts"
+		android:text="@string/setup_new_account"
+		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintStart_toStartOf="parent"
+		app:layout_constraintTop_toTopOf="parent" />
+
+	<Button
+		android:id="@+id/buttonShardsSent"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:drawableLeft="@drawable/ic_repeat"
+		android:text="@string/setup_restore_account"
+		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintStart_toStartOf="parent"
+		app:layout_constraintTop_toBottomOf="@+id/buttonSelectThreshold" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>

briar-android/src/main/res/layout/item_custodian.xml

@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    xmlns:tools="http://schemas.android.com/tools">
+
+    <CheckBox
+        android:id="@+id/checkBox"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="Bob"
+        tools:text="@sample/names.json/names/short_names/name" />
+
+</LinearLayout>

briar-android/src/main/res/menu/conversation_actions.xml

@@ -27,4 +27,9 @@
 		android:title="@string/delete_contact"
 		app:showAsAction="never"/>
 
+	<item
+		android:id="@+id/action_help_recover_account"
+		android:icon="@drawable/introduction_white"
+		android:title="@string/help_recover_account"
+		app:showAsAction="never"/>
 </menu>

briar-android/src/main/res/menu/define_threshold_actions.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<menu
+	xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto">
+
+	<item
+		android:id="@+id/action_threshold_defined"
+		android:icon="@drawable/ic_check_white"
+		android:title="@string/threshold_defined"
+		app:showAsAction="always"/>
+
+</menu>

briar-android/src/main/res/values/strings.xml

@@ -1,8 +1,8 @@
 <?xml version="1.0" encoding="utf-8"?>
 <resources xmlns:tools="http://schemas.android.com/tools" tools:ignore="MissingTranslation">
 
-	<string name="app_name" translatable="false">Briar</string>
-	<string name="app_package" translatable="false">org.briarproject.briar.android</string>
+	<string name="app_name" translatable="false">Briar SB</string>
+	<string name="app_package" translatable="false">org.briarproject.briar.socialbackup</string>
 
 	<!-- Setup -->
 	<string name="setup_title">Welcome to Briar</string>
@@ -638,4 +638,88 @@
 	<!-- This is a message to be used in screenshots. -->
 	<string name="screenshot_message_3">No problem, hope you like it 😀</string>
 
+	<!-- social backup -->
+
+	<!-- settings -->
+
+	<string name="pref_distributed_backup_title">Social backup</string>
+	<string name="pref_distributed_backup_summary">Backup your account using trusted contacts</string>
+
+	<string name="pref_distributed_old_backup_title">Existing Social backup</string>
+	<string name="pref_distributed_old_backup_summary">Information about your most recent social backup</string>
+
+	<!-- social backup procedure -->
+
+	<string name="select_custodians">Select Trusted Contacts:</string>
+
+	<string name="select_at_least_n_contacts">Please select at least %d contacts</string>
+	<string name="select_at_least_n_more_contacts">Please select at least %d more contacts</string>
+
+	<string name="threshold">Choose the minimum number of trusted contacts needed to restore your account</string>
+	<string name="threshold_disabled">Two trusted contacts will be needed to restore your account</string>
+	<string name="threshold_secure">Secure</string>
+	<string name="threshold_recommended">Secure - recommended threshold</string>
+	<string name="threshold_low_insecure">Insecure – higher threshold recommended</string>
+	<string name="threshold_high_insecure">Danger of loss – lower threshold recommended</string>
+	<string name="threshold_too_few_custodians">Danger of loss - more contacts recommended</string>
+	<string name="threshold_defined">Choose Threshold</string>
+	<string name="threshold_m_of_n">%d of %d contacts needed to recover your account</string>
+
+	<string name="backup_done_info">Backup pieces sent to trusted contacts</string>
+	<string name="backup_done_dismiss">Got it</string>
+
+	<string name="backup_created">Backup created 1/6/2020</string>
+
+	<!-- recovery from the secret owner's POV -->
+
+	<string name="recovery_explainer">You need to meet your trusted contacts in-person to receive pieces by scanning QR codes</string>
+	<string name="recovery_begin">Begin</string>
+	<string name="recovery_failed_to_receive">Failed to receive backup piece</string>
+	<string name="recovery_helpful_suggestions">Please check that bluetooth is swtiched on and that no-one but your trusted contact is able to scan the QR code</string>
+	<string name="recovery_retry">Retry</string>
+	<string name="recovery_recovered_shards">Recovered backup pieces:</string>
+	<string name="recovery_scan_qr_code">Scan QR code</string>
+	<string name="recovery_recovering_account">Recovering account…</string>
+	<string name="recovery_shard_received">Account backup piece received</string>
+	<string name="recovery_account_recovered">Account recovered</string>
+
+	<!-- recovery from the custodian's POV -->
+
+	<string name="custodian_recovery_explainer">You need to meet in-person to transfer backup piece</string>
+	<string name="custodian_recovery_failed_to_send">Failed to send backup piece</string>
+	<string name="custodian_scan_code">Scan code</string>
+	<string name="custodian_shard_sent">Account backup piece transmitted</string>
+
+	<!-- titles for the app bar -->
+
+	<string name="title_distributed_backup">Social Backup</string>
+	<string name="title_select_custodians">Select Trusted Contacts</string>
+	<string name="title_define_threshold">Threshold</string>
+	<string name="title_recovery_mode">Recovery Mode</string>
+	<string name="title_help_recover">Help recover account</string>
+
+	<!-- conversation action for custodian -->
+
+	<string name="help_recover_account">Help recover account</string>
+
+	<!-- setup screen -->
+
+	<string name="setup_new_account">Create new account</string>
+	<string name="setup_restore_account">Restore account from backup</string>
+
+	<!-- Symbols for visualising threshold values for social backup -->
+	<string name="filled_bullet">\u25CF</string>
+	<string name="linear_bullet">\u25CB</string>
+
+	<!-- activity names -->
+	<string name="activity_name_distributed_backup">Social Backup</string>
+	<string name="activity_name_old_distributed_backup">Old Social Backup</string>
+
+	<!-- conversation -->
+	<string name="social_backup_shard_received">You have received a social backup shard.</string>
+	<string name="social_backup_shard_sent">You have sent a social backup shard.</string>
+
+	<string name="activity_name_new_or_recover_account">Create new account or recover existing account</string>
+	<string name="activity_name_recovery">Recover Account</string>
+	<string name="activity_name_custodian_help_recovery">Help recover account</string>
 </resources>

briar-android/src/main/res/xml/settings.xml

@@ -90,6 +90,17 @@
 		android:layout="@layout/preferences_category"
 		android:title="@string/security_settings_title">
 
+		<Preference
+			android:summary="@string/pref_distributed_backup_summary"
+			android:title="@string/pref_distributed_backup_title"
+			app:iconSpaceReserved="false">
+
+			<intent
+				android:targetClass="org.briarproject.briar.android.socialbackup.DistributedBackupActivity"
+				android:targetPackage="@string/app_package" />
+
+		</Preference>
+
 		<SwitchPreference
 			android:enabled="false"
 			android:key="pref_key_lock"

briar-android/witness.gradle

@@ -110,28 +110,32 @@ dependencyVerification {
         'com.google.auto:auto-common:0.8:auto-common-0.8.jar:97db1709f57b91b32edacb596ef4641872f227b7d99ad90e467f0d77f5ba134a',
         'com.google.code.findbugs:jsr305:3.0.2:jsr305-3.0.2.jar:766ad2a0783f2687962c8ad74ceecc38a28b9f72a2d085ee438b7813e928d0c7',
         'com.google.code.gson:gson:2.8.5:gson-2.8.5.jar:233a0149fc365c9f6edbd683cfe266b19bdc773be98eabdaf6b3c924b48e7d81',
+        'com.google.code.gson:gson:2.8.6:gson-2.8.6.jar:c8fb4839054d280b3033f800d1f5a97de2f028eb8ba2eb458ad287e536f3f25f',
         'com.google.dagger:dagger-compiler:2.24:dagger-compiler-2.24.jar:3c5afb955fb188da485cb2c048eff37dce0e1530b9780a0f2f7187d16d1ccc1f',
         'com.google.dagger:dagger-producers:2.24:dagger-producers-2.24.jar:f10f45b95191954d5d6b043fca9e62fb621d21bf70634b8f8476c7988b504c3a',
         'com.google.dagger:dagger-spi:2.24:dagger-spi-2.24.jar:c038445d14dbcb4054e61bf49e05009edf26fce4fdc7ec1a9db544784f68e718',
         'com.google.dagger:dagger:2.24:dagger-2.24.jar:550a6e46a6dfcdf1d764887b6090cea94f783327e50e5c73754f18facfc70b64',
         'com.google.errorprone:error_prone_annotations:2.2.0:error_prone_annotations-2.2.0.jar:6ebd22ca1b9d8ec06d41de8d64e0596981d9607b42035f9ed374f9de271a481a',
         'com.google.errorprone:error_prone_annotations:2.3.2:error_prone_annotations-2.3.2.jar:357cd6cfb067c969226c442451502aee13800a24e950fdfde77bcdb4565a668d',
+        'com.google.errorprone:error_prone_annotations:2.3.4:error_prone_annotations-2.3.4.jar:baf7d6ea97ce606c53e11b6854ba5f2ce7ef5c24dddf0afa18d1260bd25b002c',
         'com.google.errorprone:javac-shaded:9-dev-r4023-3:javac-shaded-9-dev-r4023-3.jar:65bfccf60986c47fbc17c9ebab0be626afc41741e0a6ec7109e0768817a36f30',
         'com.google.googlejavaformat:google-java-format:1.5:google-java-format-1.5.jar:aa19ad7850fb85178aa22f2fddb163b84d6ce4d0035872f30d4408195ca1144e',
         'com.google.guava:failureaccess:1.0.1:failureaccess-1.0.1.jar:a171ee4c734dd2da837e4b16be9df4661afab72a41adaf31eb84dfdaf936ca26',
-        'com.google.guava:guava:27.0.1-jre:guava-27.0.1-jre.jar:e1c814fd04492a27c38e0317eabeaa1b3e950ec8010239e400fe90ad6c9107b4',
         'com.google.guava:guava:27.1-jre:guava-27.1-jre.jar:4a5aa70cc968a4d137e599ad37553e5cfeed2265e8c193476d7119036c536fe7',
+        'com.google.guava:guava:28.1-android:guava-28.1-android.jar:e112ce92c0f0733965eede73d94589c59a72128b06b08bba5ebe2f9ea672ef60',
         'com.google.guava:guava:28.1-jre:guava-28.1-jre.jar:30beb8b8527bd07c6e747e77f1a92122c2f29d57ce347461a4a55eb26e382da4',
         'com.google.guava:listenablefuture:9999.0-empty-to-avoid-conflict-with-guava:listenablefuture-9999.0-empty-to-avoid-conflict-with-guava.jar:b372a037d4230aa57fbeffdef30fd6123f9c0c2db85d0aced00c91b974f33f99',
         'com.google.j2objc:j2objc-annotations:1.1:j2objc-annotations-1.1.jar:2994a7eb78f2710bd3d3bfb639b2c94e219cedac0d4d084d516e78c16dddecf6',
         'com.google.j2objc:j2objc-annotations:1.3:j2objc-annotations-1.3.jar:21af30c92267bd6122c0e0b4d20cccb6641a37eaf956c6540ec471d584e64a7b',
         'com.google.jimfs:jimfs:1.1:jimfs-1.1.jar:c4828e28d7c0a930af9387510b3bada7daa5c04d7c25a75c7b8b081f1c257ddd',
-        'com.google.protobuf:protobuf-java:2.6.1:protobuf-java-2.6.1.jar:55aa554843983f431df5616112cf688d38aa17c132357afd1c109435bfdac4e6',
+        'com.google.protobuf:protobuf-java-util:3.11.4:protobuf-java-util-3.11.4.jar:29aacfff1cc455102627d4cfe6f319e4864ea7ce1a4e9d03b4c7bb01fc8255b0',
         'com.google.protobuf:protobuf-java:3.10.0:protobuf-java-3.10.0.jar:161d7d61a8cb3970891c299578702fd079646e032329d6c2cabf998d191437c9',
+        'com.google.protobuf:protobuf-java:3.11.4:protobuf-java-3.11.4.jar:42e98f58f53d1a49fd734c2dd193880f2dfec3436a2993a00d06b8800a22a3f2',
         'com.google.zxing:core:3.3.3:core-3.3.3.jar:5820f81e943e4bce0329306621e2d6255d2930b0a6ce934c5c23c0d6d3f20599',
         'com.googlecode.json-simple:json-simple:1.1:json-simple-1.1.jar:2d9484f4c649f708f47f9a479465fc729770ee65617dca3011836602264f6439',
         'com.ibm.icu:icu4j:53.1:icu4j-53.1.jar:e37a4467bac5cdeb02c5c4b8e5063d2f4e67b69e3c7df6d6b610f13185572bab',
         'com.jraska:falcon:2.1.1:falcon-2.1.1.aar:827f06556b7fa599f29a48a5277df39ca3dce5080d4ea6f9ea1f9c7b6b78bb7a',
+        'com.madgag.spongycastle:core:1.58.0.0:core-1.58.0.0.jar:199617dd5698c5a9312b898c0a4cec7ce9dd8649d07f65d91629f58229d72728',
         'com.squareup:javapoet:1.11.1:javapoet-1.11.1.jar:9cbf2107be499ec6e95afd36b58e3ca122a24166cdd375732e51267d64058e90',
         'com.squareup:javawriter:2.1.1:javawriter-2.1.1.jar:f699823d0081f69cbb676c1845ea222e0ada79bc88a53e5d22d8bd02d328f57e',
         'com.squareup:javawriter:2.5.0:javawriter-2.5.0.jar:fcfb09fb0ea0aa97d3cfe7ea792398081348e468f126b3603cb3803f240197f0',
@@ -156,6 +160,8 @@ dependencyVerification {
         'nekohtml:xercesMinimal:1.9.6.2:xercesMinimal-1.9.6.2.jar:95b8b357d19f63797dd7d67622fd3f18374d64acbc6584faba1c7759a31e8438',
         'net.bytebuddy:byte-buddy-agent:1.9.10:byte-buddy-agent-1.9.10.jar:8ed739d29132103250d307d2e8e3c95f07588ef0543ab11d2881d00768a5e182',
         'net.bytebuddy:byte-buddy:1.9.10:byte-buddy-1.9.10.jar:2936debc4d7b6c534848d361412e2d0f8bd06f7f27a6f4e728a20e97648d2bf3',
+        'net.i2p.crypto:eddsa:0.2.0:eddsa-0.2.0.jar:a7cb1b85c16e2f0730b9204106929a1d9aaae1df728adc7041a8b8b605692140',
+        'net.java.dev.jna:jna:5.5.0:jna-5.5.0.aar:12ef4a3c2ea685c9c816caa6a77ae8f17bb7727d8460f249925409acda270101',
         'net.ltgt.gradle.incap:incap:0.2:incap-0.2.jar:b625b9806b0f1e4bc7a2e3457119488de3cd57ea20feedd513db070a573a4ffd',
         'net.sf.jopt-simple:jopt-simple:4.9:jopt-simple-4.9.jar:26c5856e954b5f864db76f13b86919b59c6eecf9fd930b96baa8884626baf2f5',
         'net.sf.kxml:kxml2:2.3.0:kxml2-2.3.0.jar:f264dd9f79a1fde10ce5ecc53221eff24be4c9331c830b7d52f2f08a7b633de2',
@@ -184,6 +190,7 @@ dependencyVerification {
         'org.bouncycastle:bcprov-jdk15on:1.52:bcprov-jdk15on-1.52.jar:0dc4d181e4d347893c2ddbd2e6cd5d7287fc651c03648fa64b2341c7366b1773',
         'org.bouncycastle:bcprov-jdk15on:1.56:bcprov-jdk15on-1.56.jar:963e1ee14f808ffb99897d848ddcdb28fa91ddda867eb18d303e82728f878349',
         'org.checkerframework:checker-compat-qual:2.5.3:checker-compat-qual-2.5.3.jar:d76b9afea61c7c082908023f0cbc1427fab9abd2df915c8b8a3e7a509bccbc6d',
+        'org.checkerframework:checker-compat-qual:2.5.5:checker-compat-qual-2.5.5.jar:11d134b245e9cacc474514d2d66b5b8618f8039a1465cdc55bbc0b34e0008b7a',
         'org.checkerframework:checker-qual:2.5.2:checker-qual-2.5.2.jar:64b02691c8b9d4e7700f8ee2e742dce7ea2c6e81e662b7522c9ee3bf568c040a',
         'org.checkerframework:checker-qual:2.8.1:checker-qual-2.8.1.jar:9103499008bcecd4e948da29b17864abb64304e15706444ae209d17ebe0575df',
         'org.codehaus.groovy:groovy-all:2.4.15:groovy-all-2.4.15.jar:51d6c4e71782e85674239189499854359d380fb75e1a703756e3aaa5b98a5af0',
@@ -213,6 +220,9 @@ dependencyVerification {
         'org.jmock:jmock-testjar:2.8.2:jmock-testjar-2.8.2.jar:8900860f72c474e027cf97fe78dcbf154a1aa7fc62b6845c5fb4e4f3c7bc8760',
         'org.jmock:jmock:2.8.2:jmock-2.8.2.jar:6c73cb4a2e6dbfb61fd99c9a768539c170ab6568e57846bd60dbf19596b65b16',
         'org.jvnet.staxex:stax-ex:1.8:stax-ex-1.8.jar:95b05d9590af4154c6513b9c5dc1fb2e55b539972ba0a9ef28e9a0c01d83ad77',
+        'org.magmacollective.darkcrystal:dark-crystal-key-backup-crypto:1.0.0:dark-crystal-key-backup-crypto-1.0.0.jar:7c808f30314f7bc0c715b53415b07bd7e9a6bbcc55e5f672a296e5298d335f78',
+        'org.magmacollective.darkcrystal:dark-crystal-secret-sharing-wrapper:1.1.0:dark-crystal-secret-sharing-wrapper-1.1.0.aar:b8cac2348b9e652de413fa587168e9bb6ff36f6eea4bd1c72d3ecd56fc186e09',
+        'org.magmacollective.darkcrystal:shamir-secret-sharing-jna:1.0.0:shamir-secret-sharing-jna-1.0.0.aar:cdccfaf74dc1fcf30799a45d034c406315ce8507a8f4382eee118a66fb229ced',
         'org.mockito:mockito-core:3.1.0:mockito-core-3.1.0.jar:89b09e518e04f5c35f5ccf7abe45e72f594070a53d95cc2579001bd392c5afa6',
         'org.objenesis:objenesis:2.6:objenesis-2.6.jar:5e168368fbc250af3c79aa5fef0c3467a2d64e5a7bd74005f25d8399aeb0708d',
         'org.ow2.asm:asm-analysis:7.0:asm-analysis-7.0.jar:e981f8f650c4d900bb033650b18e122fa6b161eadd5f88978d08751f72ee8474',
@@ -231,6 +241,7 @@ dependencyVerification {
         'org.robolectric:shadows-framework:4.3.1:shadows-framework-4.3.1.jar:9c69db134cdd79be751856a148020fd9b32b086bb491846eedc0a1106fcadd5e',
         'org.robolectric:utils-reflector:4.3.1:utils-reflector-4.3.1.jar:9d7bf2557947d44d6f3ed76ec5231e8b72e33eb61c65ac9e149ad307b0eb936c',
         'org.robolectric:utils:4.3.1:utils-4.3.1.jar:6f9e406cd667019a5450e473c4e2d372bff9c9ab6ef55aafcbc9843109cb1519',
+        'org.whispersystems:curve25519-java:0.5.0:curve25519-java-0.5.0.jar:0aadd43cf01d11e9b58f867b3c4f25c3194e8b0623d1953d32dfbfbee009e38d',
         'tools.fastlane:screengrab:2.0.0:screengrab-2.0.0.aar:15ac15eb7c371db05e721be8d466567c2b7274b767d91478e781b6d89ee5d3d0',
         'uk.co.samuelwall:material-tap-target-prompt:3.0.0:material-tap-target-prompt-3.0.0.aar:e4d3c472b2d378e39a6535b7788e6c790fc9dde2d7659974e006ed8c7260911d',
     ]

briar-api/src/main/java/org/briarproject/briar/api/conversation/ConversationMessageVisitor.java

@@ -10,6 +10,7 @@ import org.briarproject.briar.api.introduction.IntroductionResponse;
 import org.briarproject.briar.api.messaging.PrivateMessageHeader;
 import org.briarproject.briar.api.privategroup.invitation.GroupInvitationRequest;
 import org.briarproject.briar.api.privategroup.invitation.GroupInvitationResponse;
+import org.briarproject.briar.api.socialbackup.ShardMessageHeader;
 
 @NotNullByDefault
 public interface ConversationMessageVisitor<T> {
@@ -31,4 +32,6 @@ public interface ConversationMessageVisitor<T> {
 	T visitIntroductionRequest(IntroductionRequest r);
 
 	T visitIntroductionResponse(IntroductionResponse r);
+
+	T visitShardMessage(ShardMessageHeader r);
 }

briar-api/src/main/java/org/briarproject/briar/api/keyagreement/KeyAgreementUtils.java

@@ -0,0 +1,35 @@
+package org.briarproject.briar.api.keyagreement;
+
+public class KeyAgreementUtils {
+
+	public enum BluetoothDecision {
+		/**
+		 * We haven't asked the user about Bluetooth discoverability.
+		 */
+		UNKNOWN,
+
+		/**
+		 * The device doesn't have a Bluetooth adapter.
+		 */
+		NO_ADAPTER,
+
+		/**
+		 * We're waiting for the user to accept or refuse discoverability.
+		 */
+		WAITING,
+
+		/**
+		 * The user has accepted discoverability.
+		 */
+		ACCEPTED,
+
+		/**
+		 * The user has refused discoverability.
+		 */
+		REFUSED
+	}
+
+	public enum Permission {
+		UNKNOWN, GRANTED, SHOW_RATIONALE, PERMANENTLY_DENIED
+	}
+}

briar-api/src/main/java/org/briarproject/briar/api/socialbackup/BackupExistsException.java

@@ -0,0 +1,11 @@
+package org.briarproject.briar.api.socialbackup;
+
+import org.briarproject.bramble.api.db.DbException;
+
+/**
+ * Thrown when an attempt is made to create a social account backup but a
+ * backup already exists. This exception may occur due to concurrent updates
+ * and does not indicate a database error.
+ */
+public class BackupExistsException extends DbException {
+}

briar-api/src/main/java/org/briarproject/briar/api/socialbackup/BackupMetadata.java

@@ -0,0 +1,42 @@
+package org.briarproject.briar.api.socialbackup;
+
+import org.briarproject.bramble.api.crypto.SecretKey;
+import org.briarproject.bramble.api.identity.Author;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import java.util.List;
+
+import javax.annotation.concurrent.Immutable;
+
+@Immutable
+@NotNullByDefault
+public class BackupMetadata {
+
+	private final SecretKey secret;
+	private final List<Author> custodians;
+	private final int threshold, version;
+
+	public BackupMetadata(SecretKey secret, List<Author> custodians,
+			int threshold, int version) {
+		this.secret = secret;
+		this.custodians = custodians;
+		this.threshold = threshold;
+		this.version = version;
+	}
+
+	public SecretKey getSecret() {
+		return secret;
+	}
+
+	public List<Author> getCustodians() {
+		return custodians;
+	}
+
+	public int getThreshold() {
+		return threshold;
+	}
+
+	public int getVersion() {
+		return version;
+	}
+}

briar-api/src/main/java/org/briarproject/briar/api/socialbackup/DarkCrystal.java

@@ -0,0 +1,15 @@
+package org.briarproject.briar.api.socialbackup;
+
+import org.briarproject.bramble.api.crypto.SecretKey;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import java.security.GeneralSecurityException;
+import java.util.List;
+
+@NotNullByDefault
+public
+interface DarkCrystal {
+
+	List<Shard> createShards(SecretKey secret, int shards, int threshold);
+	SecretKey combineShards(List<Shard> shards) throws GeneralSecurityException;
+}

briar-api/src/main/java/org/briarproject/briar/api/socialbackup/Shard.java

@@ -0,0 +1,25 @@
+package org.briarproject.briar.api.socialbackup;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import javax.annotation.concurrent.Immutable;
+
+@Immutable
+@NotNullByDefault
+public class Shard {
+
+	private final byte[] secretId, shard;
+
+	public Shard(byte[] secretId, byte[] shard) {
+		this.secretId = secretId;
+		this.shard = shard;
+	}
+
+	public byte[] getSecretId() {
+		return secretId;
+	}
+
+	public byte[] getShard() {
+		return shard;
+	}
+}

briar-api/src/main/java/org/briarproject/briar/api/socialbackup/ShardMessageHeader.java

@@ -0,0 +1,36 @@
+package org.briarproject.briar.api.socialbackup;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.GroupId;
+import org.briarproject.bramble.api.sync.MessageId;
+import org.briarproject.briar.api.attachment.AttachmentHeader;
+import org.briarproject.briar.api.conversation.ConversationMessageHeader;
+import org.briarproject.briar.api.conversation.ConversationMessageVisitor;
+
+import java.util.List;
+
+import javax.annotation.concurrent.Immutable;
+
+@Immutable
+@NotNullByDefault
+public class ShardMessageHeader extends ConversationMessageHeader {
+
+	private final List<AttachmentHeader> attachmentHeaders;
+
+	public ShardMessageHeader(MessageId id, GroupId groupId, long timestamp,
+			boolean local, boolean read, boolean sent, boolean seen,
+			List<AttachmentHeader> headers) {
+		super(id, groupId, timestamp, local, read, sent, seen);
+		this.attachmentHeaders = headers;
+	}
+
+	public List<AttachmentHeader> getAttachmentHeaders() {
+		return attachmentHeaders;
+	}
+
+	@Override
+	public <T> T accept(ConversationMessageVisitor<T> v) {
+		return v.visitShardMessage(this);
+	}
+
+}

briar-api/src/main/java/org/briarproject/briar/api/socialbackup/ShardReceivedEvent.java

@@ -0,0 +1,19 @@
+package org.briarproject.briar.api.socialbackup;
+
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.briar.api.conversation.event.ConversationMessageReceivedEvent;
+
+import jdk.nashorn.internal.ir.annotations.Immutable;
+
+@Immutable
+@NotNullByDefault
+public class ShardReceivedEvent
+		extends ConversationMessageReceivedEvent<ShardMessageHeader> {
+
+	public ShardReceivedEvent(ShardMessageHeader shardMessageHeader,
+			ContactId contactId) {
+		super(shardMessageHeader, contactId);
+	}
+
+}

briar-api/src/main/java/org/briarproject/briar/api/socialbackup/SocialBackupManager.java

@@ -0,0 +1,58 @@
+package org.briarproject.briar.api.socialbackup;
+
+import org.briarproject.bramble.api.contact.Contact;
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.db.Transaction;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.ClientId;
+import org.briarproject.briar.api.conversation.ConversationManager;
+import org.briarproject.briar.api.conversation.ConversationMessageHeader;
+
+import java.util.Collection;
+import java.util.List;
+
+import javax.annotation.Nullable;
+
+@NotNullByDefault
+public interface SocialBackupManager extends
+		ConversationManager.ConversationClient {
+
+	/**
+	 * The unique ID of the social backup client.
+	 */
+	ClientId CLIENT_ID = new ClientId("pw.darkcrystal.backup");
+
+	/**
+	 * The current major version of the social backup client.
+	 */
+	int MAJOR_VERSION = 0;
+
+	/**
+	 * The current minor version of the social backup client.
+	 */
+	int MINOR_VERSION = 0;
+
+	/**
+	 * Returns the metadata for this device's backup, or null if no backup has
+	 * been created.
+	 */
+	@Nullable
+	BackupMetadata getBackupMetadata(Transaction txn) throws DbException;
+
+	/**
+	 * Creates a backup for this device using the given custodians and
+	 * threshold. The encrypted backup and a shard of the backup key will be
+	 * sent to each custodian.
+	 *
+	 * @throws BackupExistsException If a backup already exists
+	 */
+	void createBackup(Transaction txn, List<ContactId> custodianIds,
+			int threshold) throws DbException;
+
+	@Override
+	Collection<ConversationMessageHeader> getMessageHeaders(
+			Transaction txn, ContactId contactId) throws DbException;
+
+	boolean amCustodian(Transaction txn, ContactId contactId);
+}

briar-core/src/main/java/org/briarproject/briar/BriarCoreEagerSingletons.java

@@ -10,6 +10,8 @@ import org.briarproject.briar.messaging.MessagingModule;
 import org.briarproject.briar.privategroup.PrivateGroupModule;
 import org.briarproject.briar.privategroup.invitation.GroupInvitationModule;
 import org.briarproject.briar.sharing.SharingModule;
+import org.briarproject.briar.socialbackup.SocialBackupModule;
+//import org.briarproject.briar.socialbackup.DefaultSocialBackupModule;
 
 public interface BriarCoreEagerSingletons {
 
@@ -33,6 +35,8 @@ public interface BriarCoreEagerSingletons {
 
 	void inject(SharingModule.EagerSingletons init);
 
+	void inject(SocialBackupModule.EagerSingletons init);
+
 	class Helper {
 
 		public static void injectEagerSingletons(BriarCoreEagerSingletons c) {
@@ -46,6 +50,7 @@ public interface BriarCoreEagerSingletons {
 			c.inject(new SharingModule.EagerSingletons());
 			c.inject(new IdentityModule.EagerSingletons());
 			c.inject(new IntroductionModule.EagerSingletons());
+			c.inject(new SocialBackupModule.EagerSingletons());
 		}
 	}
 }

briar-core/src/main/java/org/briarproject/briar/BriarCoreModule.java

@@ -13,6 +13,7 @@ import org.briarproject.briar.messaging.MessagingModule;
 import org.briarproject.briar.privategroup.PrivateGroupModule;
 import org.briarproject.briar.privategroup.invitation.GroupInvitationModule;
 import org.briarproject.briar.sharing.SharingModule;
+import org.briarproject.briar.socialbackup.SocialBackupModule;
 import org.briarproject.briar.test.TestModule;
 
 import dagger.Module;
@@ -31,6 +32,7 @@ import dagger.Module;
 		MessagingModule.class,
 		PrivateGroupModule.class,
 		SharingModule.class,
+		SocialBackupModule.class,
 		TestModule.class
 })
 public class BriarCoreModule {

briar-core/src/main/java/org/briarproject/briar/socialbackup/BackupMetadataEncoder.java

@@ -0,0 +1,11 @@
+package org.briarproject.briar.socialbackup;
+
+import org.briarproject.bramble.api.data.BdfDictionary;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.briar.api.socialbackup.BackupMetadata;
+
+@NotNullByDefault
+interface BackupMetadataEncoder {
+
+	BdfDictionary encodeBackupMetadata(BackupMetadata backupMetadata);
+}