Implement restore from seed logic

src/org/thoughtcrime/securesms/crypto/IdentityKeyUtil.java

@@ -24,12 +24,14 @@ import android.support.annotation.NonNull;
 
 import org.thoughtcrime.securesms.backup.BackupProtos;
 import org.thoughtcrime.securesms.util.Base64;
+import org.thoughtcrime.securesms.util.Hex;
 import org.whispersystems.libsignal.IdentityKey;
 import org.whispersystems.libsignal.IdentityKeyPair;
 import org.whispersystems.libsignal.InvalidKeyException;
 import org.whispersystems.libsignal.ecc.Curve;
 import org.whispersystems.libsignal.ecc.ECKeyPair;
 import org.whispersystems.libsignal.ecc.ECPrivateKey;
+import org.whispersystems.libsignal.logging.Log;
 
 import java.io.IOException;
 import java.util.LinkedList;
@@ -84,6 +86,18 @@ public class IdentityKeyUtil {
     }
   }
 
+  public static void generateIdentityKeyPair(Context context, String hexEncodedPrivateKey) {
+    try {
+      byte[] privateKey = Hex.fromStringCondensed(hexEncodedPrivateKey);
+      ECKeyPair keyPair = Curve.generateKeyPair(privateKey);
+      IdentityKey  publicKey = new IdentityKey(keyPair.getPublicKey());
+      save(context, IDENTITY_PUBLIC_KEY_PREF, Base64.encodeBytes(publicKey.serialize()));
+      save(context, IDENTITY_PRIVATE_KEY_PREF, Base64.encodeBytes(keyPair.getPrivateKey().serialize()));
+    } catch (Exception e) {
+      Log.d("Loki", "Couldn't restore key pair from seed due to error: " + e.getMessage());
+    }
+  }
+
   public static void generateIdentityKeys(Context context) {
     ECKeyPair    djbKeyPair     = Curve.generateKeyPair();
     IdentityKey  djbIdentityKey = new IdentityKey(djbKeyPair.getPublicKey());

src/org/thoughtcrime/securesms/loki/KeyPairActivity.kt

@@ -124,8 +124,18 @@ class KeyPairActivity : BaseActionBarActivity() {
     }
 
     private fun registerOrRestore() {
-        val publicKey = keyPair!!.publicKey
-        val hexEncodedPublicKey = keyPair!!.hexEncodedPublicKey
+        val keyPair: IdentityKeyPair
+        when (mode) {
+            Mode.Register -> keyPair = this.keyPair!!
+            Mode.Restore -> {
+                val mnemonic = mnemonicEditText.text.toString()
+                val hexEncodedPrivateKey = MnemonicCodec(languageFileDirectory).decode(mnemonic)
+                IdentityKeyUtil.generateIdentityKeyPair(this, hexEncodedPrivateKey)
+                keyPair = IdentityKeyUtil.getIdentityKeyPair(this)
+            }
+        }
+        val publicKey = keyPair.publicKey
+        val hexEncodedPublicKey = keyPair.hexEncodedPublicKey
         val registrationID = KeyHelper.generateRegistrationId(false)
         TextSecurePreferences.setLocalRegistrationId(this, registrationID)
         DatabaseFactory.getIdentityDatabase(this).saveIdentity(Address.fromSerialized(hexEncodedPublicKey), publicKey,