How to save database to be extracted from android app

Question

I was just looking that even when you apply proguard in your app , still one can use your database (dataset , lets suppose of quiz data) by extracting/break your app , like if you have quiz app , one can easily extract your quiz database (dataset) through your apk , how we can save it , so no one can extract or can get it , one way I found is put our app database online so one can use it through net like from server , if he/she turn off the internet app should stop working. But how can we save our database if we make it to play offline too.

Answer 1

The best option is using SQLCipher: http://sqlcipher.net/sqlcipher-for-android/

I have succesfully used it, and it work great.

I'll copy their example for you, so you can see how simple it is:

package com.demo.sqlcipher;

import java.io.File;
import net.sqlcipher.database.SQLiteDatabase;
import android.app.Activity;
import android.os.Bundle;

public class HelloSQLCipherActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        InitializeSQLCipher();
    }

    private void InitializeSQLCipher() {
        SQLiteDatabase.loadLibs(this);
        File databaseFile = getDatabasePath("demo.db");
        databaseFile.mkdirs();
        databaseFile.delete();
        SQLiteDatabase database = SQLiteDatabase.openOrCreateDatabase(databaseFile, "test123", null);
        database.execSQL("create table t1(a, b)");
        database.execSQL("insert into t1(a, b) values(?, ?)", new Object[]{"one for the money",
                                                                        "two for the show"});
    }
}

Answer 2

You want to look at database encryption.

A simple way to do it is to create a method that "encrypts" your message before saving them to the database. The method should easily be reversible.

A simple example is to XOR the bits to save. The very nice thing about XOR is that by reapplying the same method on the data would decrypt the message. But instead of reinventing the wheel, you can look at this answer for some implementation examples in java.

This Stack Overflow answer seems to have a lot of useful information about it if you want to use a database. If you prefer using a file, like an XML file, have a look at this answer.