Android - การจัดเก็บคีย์ส่วนตัวในที่เก็บคีย์

ฉันจะจัดเก็บคีย์ส่วนตัวของฉัน (รหัสผ่าน, ชื่อผู้ใช้, Sha1) ไว้ใน Keystore เพื่อให้ปลอดภัยได้อย่างไร ฉันลองใช้โค้ดด้านล่างแล้ว แต่ก็ไม่มีโชค

private Context ctx;

public MainActivity(Context ctx) {
    this.ctx = ctx;
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    try {
        genKey();
    } catch (Exception e) {

        e.printStackTrace();
        Log.d("warning", "m in catch");
    }

}

public void genKey() throws Exception {
    SecretKey key = KeyGenerator.getInstance("AES").generateKey();

    KeyStore ks = KeyStore.getInstance(KeyStore.getDefaultType());
    ks.load(null, "clavedekey".toCharArray());

    PasswordProtection pass = new PasswordProtection(
            "fedsgjk".toCharArray());
    KeyStore.SecretKeyEntry skEntry = new KeyStore.SecretKeyEntry(key);
    ks.setEntry("secretKeyAlias", skEntry, pass);

    FileOutputStream fos = ctx.openFileOutput("bs.keystore",
            Context.MODE_PRIVATE);
    ks.store(fos, "clavedekey".toCharArray());
    fos.close();
}

นี่คือบันทึกข้อผิดพลาดที่ฉันได้รับ

06-13 14:04:11.829: E/AndroidRuntime(6248): FATAL EXCEPTION: main
06-13 14:04:11.829: E/AndroidRuntime(6248): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.demo_keystore/com.demo_keystore.MainActivity}: java.lang.InstantiationException: can't instantiate class com.demo_keystore.MainActivity; no empty constructor
06-13 14:04:11.829: E/AndroidRuntime(6248):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2045)
06-13 14:04:11.829: E/AndroidRuntime(6248):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2146)
06-13 14:04:11.829: E/AndroidRuntime(6248):     at android.app.ActivityThread.access$700(ActivityThread.java:140)
06-13 14:04:11.829: E/AndroidRuntime(6248):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1238)
06-13 14:04:11.829: E/AndroidRuntime(6248):     at android.os.Handler.dispatchMessage(Handler.java:99)
06-13 14:04:11.829: E/AndroidRuntime(6248):     at android.os.Looper.loop(Looper.java:177)
06-13 14:04:11.829: E/AndroidRuntime(6248):     at android.app.ActivityThread.main(ActivityThread.java:4947)
06-13 14:04:11.829: E/AndroidRuntime(6248):     at java.lang.reflect.Method.invokeNative(Native Method)
06-13 14:04:11.829: E/AndroidRuntime(6248):     at java.lang.reflect.Method.invoke(Method.java:511)
06-13 14:04:11.829: E/AndroidRuntime(6248):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1038)
06-13 14:04:11.829: E/AndroidRuntime(6248):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:805)
06-13 14:04:11.829: E/AndroidRuntime(6248):     at dalvik.system.NativeStart.main(Native Method)
06-13 14:04:11.829: E/AndroidRuntime(6248): Caused by: java.lang.InstantiationException: can't instantiate class com.demo_keystore.MainActivity; no empty constructor
06-13 14:04:11.829: E/AndroidRuntime(6248):     at java.lang.Class.newInstanceImpl(Native Method)
06-13 14:04:11.829: E/AndroidRuntime(6248):     at java.lang.Class.newInstance(Class.java:1319)
06-13 14:04:11.829: E/AndroidRuntime(6248):     at android.app.Instrumentation.newActivity(Instrumentation.java:1068)
06-13 14:04:11.829: E/AndroidRuntime(6248):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2036)
06-13 14:04:11.829: E/AndroidRuntime(6248):     ... 11 more