package com.aes_encrypt;

import java.security.NoSuchAlgorithmException;

import java.security.SecureRandom;

import javax.crypto.Cipher;

import javax.crypto.KeyGenerator;

import javax.crypto.SecretKey;

import javax.crypto.spec.SecretKeySpec;

import android.app.Activity;

import android.os.Bundle;

import android.util.Base64;

import android.widget.TextView;

public class Main extends Activity {

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

String s = "This is my data I want to keep safe.";

String encryptedText = encrypt(s);

String clearText = decrypt(encryptedText);

((TextView)findViewById(R.id.encrypted_text)).setText(encryptedText);

((TextView)findViewById(R.id.clear_text)).setText(clearText);

}

private byte[] getKey() {

byte[] seed = "here_is_your_aes_key".getBytes();

KeyGenerator kg;

try {

kg = KeyGenerator.getInstance("AES");

} catch (NoSuchAlgorithmException e) {

return null;

}

SecureRandom sr;

try {

sr = SecureRandom.getInstance("SHA1PRNG");

} catch (NoSuchAlgorithmException e) {

return null;

}

sr.setSeed(seed);

kg.init(128, sr);

SecretKey sk = kg.generateKey();

byte[] key = sk.getEncoded();

return key;

}

private String encrypt(String clearText) {

byte[] encryptedText = null;

try {

SecretKeySpec ks = new SecretKeySpec(getKey(), "AES");

Cipher c = Cipher.getInstance("AES");

c.init(Cipher.ENCRYPT_MODE, ks);

encryptedText = c.doFinal(clearText.getBytes("UTF-8"));

return Base64.encodeToString(encryptedText, Base64.DEFAULT);

} catch (Exception e) {

return null;

}

}

private String decrypt (String encryptedText) {

byte[] clearText = null;

try {

SecretKeySpec ks = new SecretKeySpec(getKey(), "AES");

Cipher c = Cipher.getInstance("AES");

c.init(Cipher.DECRYPT_MODE, ks);

clearText = c.doFinal(Base64.decode(encryptedText, Base64.DEFAULT));

return new String(clearText, "UTF-8");

} catch (Exception e) {

return null;

}

}

}