Implementing EncryptedSharedPreferences with XML UI

Step 4: Implement Saving and Retrieving Data in Your Activity or Fragment

Now, use the helper class in your activities or fragments to save and retrieve data.

Create the necessary UI components in your activity_main.xml file. For simplicity, let's use an EditText and a Button to save a string and a TextView to display the retrieved string.

Then, implement the logic in your MainActivity to handle the UI interaction and secure data storage.

import android.os.Bundle
import android.widget.Button
import android.widget.EditText
import android.widget.TextView
import androidx.appcompat.app.AppCompatActivity

class MainActivity : AppCompatActivity() {

    private lateinit var editTextData: EditText
    private lateinit var buttonSave: Button
    private lateinit var textViewRetrievedData: TextView

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        editTextData = findViewById(R.id.editTextData)
        buttonSave = findViewById(R.id.buttonSave)
        textViewRetrievedData = findViewById(R.id.textViewRetrievedData)

        buttonSave.setOnClickListener {
            saveData()
        }

        retrieveData() // Retrieve and display the data when the activity is created
    }

    private fun saveData() {
        val dataToSave = editTextData.text.toString()
        val sharedPreferences = SecureStorageManager.getSharedPreferences()
        val editor = sharedPreferences.edit()
        editor.putString("sensitive_data", dataToSave)
        editor.apply()

        // Optionally, clear the EditText after saving
        editTextData.text.clear()

        //Update UI
        retrieveData()
    }

    private fun retrieveData() {
        val sharedPreferences = SecureStorageManager.getSharedPreferences()
        val retrievedData = sharedPreferences.getString("sensitive_data", "No data saved")
        textViewRetrievedData.text = "Retrieved Data: $retrievedData"
    }
}

Step 5: Testing Your Implementation

Run your application, enter some data into the EditText, and click the save button. Verify that the data is saved and retrieved correctly. You can also check the shared_prefs directory using Android Studio's Device File Explorer to confirm that the preference file is encrypted (the contents will be unreadable without decryption).

Best Practices and Considerations

• Handle Exceptions: Always wrap the EncryptedSharedPreferences initialization in a try-catch block to handle potential exceptions.
• Data Sensitivity: Only store truly sensitive data using this method. Overusing encryption can impact performance.
• Key Rotation: Consider implementing key rotation strategies for enhanced security.
• Regularly Update Dependencies: Keep the security-crypto dependency updated to benefit from the latest security patches and improvements.

Advanced Tips

• Clearing all data you can implement the Clear option:

      fun clear() {
           encryptedSharedPreferences?.edit()?.clear()?.apply()
      }
  

  And calling that from any place that has access to that Helper class:

   SecureStorageManager.clear()
  

• Key Derivation: Use robust key derivation functions (KDFs) if you derive encryption keys from user passwords or other secrets.
• Secure Backup: When using Android's backup service, exclude EncryptedSharedPreferences to prevent keys from being backed up insecurely.

Conclusion

Implementing EncryptedSharedPreferences in an XML UI-based Android application provides a straightforward way to secure sensitive data. By following these steps and best practices, you can enhance your app's security posture and protect user data effectively. The combination of enhanced security and relative ease of implementation makes it a valuable tool in any Android developer’s arsenal.