AES (Advanced Encryption Standard) Encryption / Decryption of 'Strings' in Android using Cipher Cryptography in Java

Encrypt / Decrypt String Flush Encrypted String to External Storage

Download APK

Source Github

	package com.blogspot.dbh4ck.aes_encrypt_decrypt_android;
	import android.os.Build;
	import android.os.Bundle;
	import android.os.Environment;
	import android.support.design.widget.FloatingActionButton;
	import android.support.design.widget.Snackbar;
	import android.util.Base64;
	import android.view.View;
	import android.support.design.widget.NavigationView;
	import android.support.v4.view.GravityCompat;
	import android.support.v4.widget.DrawerLayout;
	import android.support.v7.app.ActionBarDrawerToggle;
	import android.support.v7.app.AppCompatActivity;
	import android.support.v7.widget.Toolbar;
	import android.view.Menu;
	import android.view.MenuItem;
	import android.view.Window;
	import android.view.WindowManager;
	import android.widget.Button;
	import android.widget.EditText;
	import android.widget.TextView;
	import android.widget.Toast;
	import java.io.BufferedWriter;
	import java.io.File;
	import java.io.FileInputStream;
	import java.io.FileOutputStream;
	import java.io.FileWriter;
	import java.io.IOException;
	import java.security.InvalidKeyException;
	import java.security.NoSuchAlgorithmException;
	import javax.crypto.BadPaddingException;
	import javax.crypto.Cipher;
	import javax.crypto.CipherInputStream;
	import javax.crypto.CipherOutputStream;
	import javax.crypto.IllegalBlockSizeException;
	import javax.crypto.NoSuchPaddingException;
	import javax.crypto.spec.SecretKeySpec;
	public class Nav_AES_Android extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener, View.OnClickListener {
	EditText input_aes, file_name;
	Button btn_aes_enc, btn_aes_dec, btn_write_file;
	TextView result_aes, dec_Txt;
	String output= "";
	String plainText;
	AboutAesDialog aboutAesDialog;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
	super.onCreate(savedInstanceState);
	setContentView(R.layout.activity_nav__aes__android);
	Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
	setSupportActionBar(toolbar);
	Window window = getWindow();
	window.clearFlags(WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS);
	window.addFlags(WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS);
	if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
	window.setStatusBarColor(getResources().getColor(android.R.color.holo_blue_light));
	}
	input_aes = (EditText) findViewById(R.id.txtInput);
	file_name = (EditText) findViewById(R.id.txtFileName);
	btn_aes_enc = (Button) findViewById(R.id.btnEncrypt);
	btn_aes_enc.setOnClickListener(this);
	btn_aes_dec = (Button) findViewById(R.id.btnDecrypt);
	btn_aes_dec.setOnClickListener(this);
	btn_write_file = (Button) findViewById(R.id.btnSaveEncryptFile);
	btn_write_file.setOnClickListener(this);
	result_aes = (TextView) findViewById(R.id.txtOutput);
	dec_Txt = (TextView) findViewById(R.id.txtOriginal);
	DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
	ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
	drawer.setDrawerListener(toggle);
	toggle.syncState();
	NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
	navigationView.setNavigationItemSelectedListener(this);
	}
	@Override
	public void onBackPressed() {
	DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
	if (drawer.isDrawerOpen(GravityCompat.START)) {
	drawer.closeDrawer(GravityCompat.START);
	} else {
	super.onBackPressed();
	}
	}
	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
	// Inflate the menu; this adds items to the action bar if it is present.
	getMenuInflater().inflate(R.menu.nav__aes__android, menu);
	return true;
	}
	@Override
	public boolean onOptionsItemSelected(MenuItem item) {
	// Handle action bar item clicks here. The action bar will
	// automatically handle clicks on the Home/Up button, so long
	// as you specify a parent activity in AndroidManifest.xml.
	int id = item.getItemId();
	//noinspection SimplifiableIfStatement
	if (id == R.id.action_exit) {
	System.exit(0);
	return true;
	}
	return super.onOptionsItemSelected(item);
	}
	@SuppressWarnings("StatementWithEmptyBody")
	@Override
	public boolean onNavigationItemSelected(MenuItem item) {
	// Handle navigation view item clicks here.
	int id = item.getItemId();
	if (id == R.id.nav_home) {
	// Handle the camera action
	}else if (id == R.id.nav_blog) {
	dbBlog();
	} else if (id == R.id.nav_about) {
	About();
	} else if (id == R.id.nav_exit) {
	System.exit(0);
	}
	DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
	drawer.closeDrawer(GravityCompat.START);
	return true;
	}
	private void About() {
	aboutAesDialog = new AboutAesDialog(this);
	aboutAesDialog.show();
	aboutAesDialog.setCanceledOnTouchOutside(false);
	}
	private void dbBlog() {
	}
	@Override
	public void onClick(View view) {
	switch (view.getId()){
	case R.id.btnEncrypt:
	String strInput = input_aes.getText().toString();
	if (strInput.trim().equals("")) {
	Toast.makeText(getApplicationContext(), "Input must not be blank!", Toast.LENGTH_SHORT).show();
	return;
	}
	else{
	Encryption();
	}
	break;
	case R.id.btnDecrypt:
	Decryption();
	break;
	case R.id.btnSaveEncryptFile:
	try {
	String strName = file_name.getText().toString();
	if (strName.trim().equals("")) {
	Toast.makeText(getApplicationContext(), "File name is required!", Toast.LENGTH_SHORT).show();
	return;
	}
	else{
	if(strName.matches("^[a-zA-Z0-9_+-]*$")){
	String data = input_aes.getText().toString();
	writeToFile(data);
	return;
	}
	Toast.makeText(getApplicationContext(), "File name should contain only a-z A-Z 0-9 +-_ and no spaces.", Toast.LENGTH_SHORT).show();
	}
	} catch (IOException | NoSuchPaddingException | NoSuchAlgorithmException | InvalidKeyException e) {
	e.printStackTrace();
	}
	break;
	}
	}
	private void writeToFile(String data) throws IOException, NoSuchPaddingException, NoSuchAlgorithmException, InvalidKeyException {
	File dir = new File(Environment.getExternalStorageDirectory().getAbsolutePath() + "/AES-Android-Example");
	dir.mkdir();
	File newFrm = new File(dir + File.separator);
	File file = new File(newFrm, file_name.getText() +".txt");
	try {
	BufferedWriter bw = new BufferedWriter(new FileWriter(file));
	bw.write(data);
	bw.close();
	} catch (Exception e) {
	e.printStackTrace();
	}
	File outfile = new File(file+".enc.txt");
	FileInputStream fis = new FileInputStream(file);
	FileOutputStream fos = new FileOutputStream(outfile);
	Cipher encipher = Cipher.getInstance("AES");
	SecretKeySpec sks = new SecretKeySpec("MyDifficultPassw".getBytes(), "AES");
	encipher.init(Cipher.ENCRYPT_MODE, sks);
	CipherInputStream cis = new CipherInputStream(fis, encipher);
	CipherOutputStream cos = new CipherOutputStream(fos, encipher);
	byte[] bArr = new byte[8];
	Toast.makeText(getApplicationContext(), "File is Ecrypted and Saved!", Toast.LENGTH_SHORT).show();
	while (true) {
	int read = fis.read(bArr);
	if (read != -1) {
	cos.write(bArr, 0, read);
	} else {
	cos.close();
	fis.close();
	return;
	}
	}
	}
	private void Decryption() {
	try {
	Cipher decipher = Cipher.getInstance("AES");
	SecretKeySpec sks = new SecretKeySpec("MyDifficultPassw".getBytes(), "AES");
	decipher.init(Cipher.DECRYPT_MODE, sks);
	byte[] decodedValue = Base64.decode(output.getBytes(), Base64.DEFAULT);
	byte[] decryptedVal = decipher.doFinal(decodedValue); // Finish
	output = new String(decryptedVal);
	dec_Txt.setText(output);
	} catch (NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException | BadPaddingException | IllegalBlockSizeException e) {
	e.printStackTrace();
	}
	}
	private void Encryption() {
	try {
	plainText = input_aes.getText().toString();
	Cipher encipher = Cipher.getInstance("AES");
	SecretKeySpec sks = new SecretKeySpec("MyDifficultPassw".getBytes(), "AES");
	encipher.init(Cipher.ENCRYPT_MODE, sks);
	byte[] results = encipher.doFinal(plainText.getBytes("UTF-8"));
	output = Base64.encodeToString(results, Base64.DEFAULT);
	result_aes.setText(output);
	} catch (Exception e) {
	// TODO Auto-generated catch block
	e.printStackTrace();
	}
	}
	}

view raw Nav_AES_Android.java hosted with ❤ by GitHub

	package com.blogspot.dbh4ck.aes_encrypt_decrypt_android;
	import android.app.Dialog;
	import android.content.Context;
	import android.view.View;
	import android.widget.Button;
	/**
	* Created by DB on 18-02-2017.
	*/
	public class AboutAesDialog extends Dialog implements View.OnClickListener {
	Button OkBtn;
	public AboutAesDialog(Context context) {
	super(context);
	}
	public AboutAesDialog(Context context, int themeResId) {
	super(context, themeResId);
	}
	protected AboutAesDialog(Context context, boolean cancelable, OnCancelListener cancelListener) {
	super(context, cancelable, cancelListener);
	}
	protected void onStart() {
	super.onStart();
	setContentView(R.layout.about_aes);
	getWindow().setFlags(4,4);
	setTitle("About AES");
	OkBtn = (Button) findViewById(R.id.OkBtn);
	OkBtn.setOnClickListener(this);
	}
	@Override
	public void onClick(View view) {
	this.dismiss();
	}
	}

view raw AboutAesDialog.java hosted with ❤ by GitHub