Hi friends today I made very simple Encryption Decryption Example in Android for you. where we use simple text file as example which we Encrypt it on Encrypt Btn click and Decrypt on decrypt button click
and save on sd card. but be sure to put file name as
sampleFile.
PS. we can also use Mp3 and videos file.
MainActivity.java
package
com.example.encryptdecrypt;
import java.io.File;
import
java.io.FileInputStream;
import
java.io.FileOutputStream;
import java.io.IOException;
import
java.security.InvalidKeyException;
import
java.security.NoSuchAlgorithmException;
import javax.crypto.Cipher;
import
javax.crypto.CipherInputStream;
import
javax.crypto.CipherOutputStream;
import
javax.crypto.NoSuchPaddingException;
import
javax.crypto.spec.SecretKeySpec;
import
android.app.Activity;
import android.os.Bundle;
import
android.os.Environment;
import android.view.View;
import
android.view.View.OnClickListener;
import
android.widget.Button;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle
savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button
encryptButton = (Button) findViewById(R.id.button1);
Button
DecryptButton = (Button) findViewById(R.id.button2);
encryptButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated
method stub
try {
encrypt();
}
catch (InvalidKeyException
e) {
// TODO Auto-generated
catch block
e.printStackTrace();
}
catch
(NoSuchAlgorithmException e) {
// TODO Auto-generated
catch block
e.printStackTrace();
}
catch
(NoSuchPaddingException e) {
// TODO Auto-generated
catch block
e.printStackTrace();
}
catch (IOException e) {
// TODO Auto-generated
catch block
e.printStackTrace();
}
}
});
DecryptButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated
method stub
try {
decrypt();
}
catch (InvalidKeyException
e) {
// TODO Auto-generated
catch block
e.printStackTrace();
}
catch
(NoSuchAlgorithmException e) {
// TODO Auto-generated
catch block
e.printStackTrace();
}
catch
(NoSuchPaddingException e) {
// TODO Auto-generated
catch block
e.printStackTrace();
}
catch (IOException e) {
// TODO Auto-generated
catch block
e.printStackTrace();
}
}
});
}
/**
* Here is Both function for encrypt and decrypt
file in Sdcard folder. we
* can not lock folder but we can encrypt file
using AES in Android, it may
* help you.
*
* @throws IOException
* @throws NoSuchAlgorithmException
* @throws NoSuchPaddingException
* @throws InvalidKeyException
*/
static void encrypt() throws IOException,
NoSuchAlgorithmException,
NoSuchPaddingException,
InvalidKeyException {
// Here you read
the cleartext.
File
extStore = Environment.getExternalStorageDirectory();
FileInputStream
fis = new
FileInputStream(extStore + "/sampleFile");
// This stream
write the encrypted text. This stream will be wrapped by
// another stream.
FileOutputStream
fos = new
FileOutputStream(extStore + "/encrypted");
// Length is 16
byte
SecretKeySpec
sks = new SecretKeySpec("MyDifficultPassw".getBytes(),
"AES");
// Create cipher
Cipher
cipher = Cipher.getInstance("AES");
cipher.init(Cipher.ENCRYPT_MODE, sks);
// Wrap the output
stream
CipherOutputStream
cos = new
CipherOutputStream(fos, cipher);
// Write bytes
int b;
byte[] d = new byte[8];
while ((b = fis.read(d))
!= -1) {
cos.write(d,
0, b);
}
// Flush and close
streams.
cos.flush();
cos.close();
fis.close();
}
static void decrypt() throws IOException,
NoSuchAlgorithmException,
NoSuchPaddingException,
InvalidKeyException {
File
extStore = Environment.getExternalStorageDirectory();
FileInputStream
fis = new FileInputStream(extStore
+ "/encrypted");
FileOutputStream
fos = new
FileOutputStream(extStore + "/decrypted");
SecretKeySpec
sks = new SecretKeySpec("MyDifficultPassw".getBytes(),
"AES");
Cipher
cipher = Cipher.getInstance("AES");
cipher.init(Cipher.DECRYPT_MODE, sks);
CipherInputStream
cis = new
CipherInputStream(fis, cipher);
int b;
byte[] d = new byte[8];
while ((b = cis.read(d))
!= -1) {
fos.write(d,
0, b);
}
fos.flush();
fos.close();
cis.close();
}
Xml file
Activity_main.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:layout_marginTop="147dp"
android:text="Encrypt" />
<Button
android:id="@+id/button2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignRight="@+id/button1"
android:layout_centerVertical="true"
android:text="Decrypt" />
</RelativeLayout>
and Android manifest.xml requires WriteExternal_Storage permition
<?xml version="1.0"
encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.encryptdecrypt"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="17" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.example.encryptdecrypt.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN"
/>
<category android:name="android.intent.category.LAUNCHER"
/>
</intent-filter>
</activity>
</application>
</manifest>
you can download complete example from here
