Show max AES key size

app/src/main/java/eu/faircode/email/FragmentOptionsPrivacy.java

@@ -55,6 +55,7 @@ import androidx.preference.PreferenceManager;
 
 import org.openintents.openpgp.util.OpenPgpApi;
 
+import java.security.NoSuchAlgorithmException;
 import java.util.ArrayList;
 import java.util.List;
 
@@ -70,6 +71,7 @@ public class FragmentOptionsPrivacy extends FragmentBase implements SharedPrefer
     private Button btnPin;
     private Spinner spBiometricsTimeout;
     private Button btnImportKey;
+    private TextView tvKeySize;
 
     private List<String> openPgpProvider = new ArrayList<>();
 
@@ -101,6 +103,7 @@ public class FragmentOptionsPrivacy extends FragmentBase implements SharedPrefer
         btnPin = view.findViewById(R.id.btnPin);
         spBiometricsTimeout = view.findViewById(R.id.spBiometricsTimeout);
         btnImportKey = view.findViewById(R.id.btnImportKey);
+        tvKeySize = view.findViewById(R.id.tvKeySize);
 
         Intent intent = new Intent(OpenPgpApi.SERVICE_INTENT_2);
         List<ResolveInfo> ris = getContext().getPackageManager().queryIntentServices(intent, 0);
@@ -232,6 +235,14 @@ public class FragmentOptionsPrivacy extends FragmentBase implements SharedPrefer
             }
         });
 
+        try {
+            int maxKeySize = javax.crypto.Cipher.getMaxAllowedKeyLength("AES");
+            tvKeySize.setText(getString(R.string.title_aes_key_size, maxKeySize));
+        } catch (NoSuchAlgorithmException ex) {
+            tvKeySize.setText(Helper.formatThrowable(ex));
+        }
+        tvKeySize.setVisibility(BuildConfig.DEBUG ? View.VISIBLE : View.GONE);
+
         PreferenceManager.getDefaultSharedPreferences(getContext()).registerOnSharedPreferenceChangeListener(this);
 
         return view;

app/src/main/res/layout/fragment_options_privacy.xml

@@ -218,5 +218,15 @@
             android:text="@string/title_import_encrypt_key"
             app:layout_constraintStart_toStartOf="parent"
             app:layout_constraintTop_toBottomOf="@id/spBiometricsTimeout" />
+
+        <TextView
+            android:id="@+id/tvKeySize"
+            android:layout_width="0dp"
+            android:layout_height="wrap_content"
+            android:text="@string/title_aes_key_size"
+            android:textAppearance="@style/TextAppearance.AppCompat.Small"
+            app:layout_constraintEnd_toEndOf="parent"
+            app:layout_constraintStart_toStartOf="parent"
+            app:layout_constraintTop_toBottomOf="@id/btnImportKey" />
     </androidx.constraintlayout.widget.ConstraintLayout>
 </ScrollView>

app/src/main/res/values/strings.xml

@@ -699,6 +699,7 @@
     <string name="title_not_encrypted">Message is not signed or encrypted</string>
     <string name="title_reset_sign_key">Reset sign key</string>
     <string name="title_import_encrypt_key">Import encryption key</string>
+    <string name="title_aes_key_size" translatable="false">Max AES key size: %1$d</string>
 
     <string name="title_signature_none">Message not signed</string>
     <string name="title_signature_valid">Message signature valid</string>