Hands-on Lab Practice

This hands-on lab practice is intended to help students develop a better understanding of encryption for data at rest and the consequences of not having encryption.

Create a new Android Studio project and name it “Encrypt” with company domain of "android.encrypt" and click on Next.

Place all the following codes under each file

//Copy and paste the following code into "EncryptActivity.java".

//EncryptActivity.java

package encrypt.android.encrypt;

import android.os.Bundle;

import androidx.appcompat.app.AppCompatActivity;

import android.view.Menu;

import android.view.MenuItem;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.EditText;

import java.security.KeyPair;

import java.security.KeyPairGenerator;

import java.security.PrivateKey;

import java.security.PublicKey;

import java.security.SecureRandom;

import javax.crypto.Cipher;

public class EncryptActivity extends AppCompatActivity {

@Override

protected void onCreate(Bundle savedInstanceState) {

try {

generateKey();

} catch (Exception e1) {

// TODO Auto-generated catch block

e1.printStackTrace();

}

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_encrypt);

final Button enButton = (Button) findViewById(R.id.enbutton);

final Button deButton = (Button) findViewById(R.id.debutton);

final EditText input = (EditText) findViewById(R.id.Input);

final EditText Raw = (EditText) findViewById(R.id.raw);

final EditText output = (EditText) findViewById(R.id.OriginText);

enButton.setOnClickListener(new OnClickListener() {

public void onClick(View v) {

try {

Raw.setText(encrypt(input.getText().toString()));

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

};

});

deButton.setOnClickListener(new OnClickListener() {

public void onClick(View v) {

try {

output.setText(String.valueOf(decrypt(Raw.getText().toString())));

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

});

}

private final static String RSA = "RSA";

public static PublicKey uk;

public static PrivateKey rk;

public static void generateKey() throws Exception {

KeyPairGenerator gen = KeyPairGenerator.getInstance(RSA);

gen.initialize(512, new SecureRandom());

KeyPair keyPair = gen.generateKeyPair();

uk = keyPair.getPublic();

rk = keyPair.getPrivate();

}

private static byte[] encrypt(String text, PublicKey pubRSA)

throws Exception {

Cipher cipher = Cipher.getInstance(RSA);

cipher.init(Cipher.ENCRYPT_MODE, pubRSA);

return cipher.doFinal(text.getBytes());

}

public final static String encrypt(String text) {

try {

return byte2hex(encrypt(text, uk));

} catch (Exception e) {

e.printStackTrace();

}

return null;

}

public final static String decrypt(String data) {

try {

return new String(decrypt(hex2byte(data.getBytes())));

} catch (Exception e) {

e.printStackTrace();

}

return null;

}

private static byte[] decrypt(byte[] src) throws Exception {

Cipher cipher = Cipher.getInstance(RSA);

cipher.init(Cipher.DECRYPT_MODE, rk);

return cipher.doFinal(src);

}

public static String byte2hex(byte[] b) {

String hs = "";

String stmp = "";

for (int n = 0; n < b.length; n++) {

stmp = Integer.toHexString(b[n] & 0xFF);

if (stmp.length() == 1)

hs += ("0" + stmp);

else

hs += stmp;

}

return hs.toUpperCase();

}

public static byte[] hex2byte(byte[] b) {

if ((b.length % 2) != 0)

throw new IllegalArgumentException("hello");

byte[] b2 = new byte[b.length / 2];

for (int n = 0; n < b.length; n += 2) {

String item = new String(b, n, 2);

b2[n / 2] = (byte) Integer.parseInt(item, 16);

}

return b2;

}

@Override

public boolean onCreateOptionsMenu(Menu menu) {

// Inflate the menu; this adds items to the action bar if it is present.

getMenuInflater().inflate(R.menu.menu_encrypt, 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();

if (id == R.id.action_settings) {

return true;

}

return super.onOptionsItemSelected(item);

}

}

//Copy and paste the following code into "activity_encrypt.xml".

//activity_encrypt.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:paddingLeft="16dp"

android:paddingRight="16dp"

android:orientation="vertical" >

<TextView android:id="@+id/text"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:text="Hello World, EncryptActivity!" />

<EditText

android:id="@+id/Input"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:hint="Input Message" />

<Button

android:id="@+id/enbutton"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_gravity="left"

android:text="Encrypt it by PublicKey" />

<EditText

android:id="@+id/raw"

android:layout_width="match_parent"

android:layout_height="0dp"

android:layout_weight="1"

android:text="Encrypted Message" />

<Button

android:id="@+id/debutton"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_gravity="left"

android:text="Decrypt it by PrivateKey" />

<EditText

android:id="@+id/OriginText"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:text="Original Message" />

</LinearLayout>

//Copy and paste the following code into the newly created "menu_encrypt.xml".

//menu_encrypt.xml

<menu xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:app="http://schemas.android.com/apk/res-auto"

xmlns:tools="http://schemas.android.com/tools" tools:context=".EncryptActivity">

<item android:id="@+id/action_settings" android:title="@string/action_settings"

android:orderInCategory="100" app:showAsAction="never" />

</menu>

//Copy and paste the following code into "AndroidManifest.xml". It can be located in the manifest folder in the project sidebar.

//AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

package="encrypt.android.encrypt" >

<application

android:allowBackup="true"

android:icon="@mipmap/ic_launcher"

android:label="@string/app_name"

android:theme="@style/Theme.Encrypt" >

<activity

android:name=".EncryptActivity"

android:exported="true"

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>

Save your project and run it on the AVD.

OUTPUT INTERFACES

DOWNLOAD LINK FOR ENcrypt FILE