Easy way to Encrypt/Decrypt string in Android

Question

My question is how to encrypt a String:

String AndroidId;

@Override
public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.download_movie_activity);

  cancel = (Button)findViewById(R.id.img_cancle);

  linear= (LinearLayout)findViewById(R.id.progress);
  linear.setVisibility(View.GONE);

  String encrypted = "MzIyNTE2" + "OTQNzM4NTQ=";

  Log.e("Encrypt", encrypted);

  WifiManager wifiManager = (WifiManager) getSystemService(Context.WIFI_SERVICE);
  WifiInfo wInfo = wifiManager.getConnectionInfo();
  AndroidId = wInfo.getMacAddress();

  AndroidId=encrypted;

How do i encrypt my AndroidId in which I storing a MAC address.

Answer 1

You can use Cipher for this.

This class provides the functionality of a cryptographic cipher for encryption and decryption. It forms the core of the Java Cryptographic Extension (JCE) framework.

Sample of encryption and decryption:

public static SecretKey generateKey() 
    throws NoSuchAlgorithmException, InvalidKeySpecException 
{ 
    return secret = new SecretKeySpec(password.getBytes(), "AES"); 
}

public static byte[] encryptMsg(String message, SecretKey secret)
    throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, InvalidParameterSpecException, IllegalBlockSizeException, BadPaddingException, UnsupportedEncodingException 
{ 
   /* Encrypt the message. */
   Cipher cipher = null; 
   cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
   cipher.init(Cipher.ENCRYPT_MODE, secret); 
   byte[] cipherText = cipher.doFinal(message.getBytes("UTF-8")); 
   return cipherText; 
}

public static String decryptMsg(byte[] cipherText, SecretKey secret) 
    throws NoSuchPaddingException, NoSuchAlgorithmException, InvalidParameterSpecException, InvalidAlgorithmParameterException, InvalidKeyException, BadPaddingException, IllegalBlockSizeException, UnsupportedEncodingException 
{
    /* Decrypt the message, given derived encContentValues and initialization vector. */
    Cipher cipher = null;
    cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
    cipher.init(Cipher.DECRYPT_MODE, secret); 
    String decryptString = new String(cipher.doFinal(cipherText), "UTF-8");
    return decryptString; 
}

To encrypt:

SecretKey secret = generateKey();
EncUtil.encryptMsg(String toEncrypt, secret))

To decrypt:

EncUtil.decryptMsg(byte[] toDecrypt, secret))

Answer 2

Using these helper class you can encrypt and decrypt string in android simple way, but this will work only for below Android 7.0, for Android 8.0 and above you can find from here

import java.security.SecureRandom;
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

public class AESHelper {

public static String encrypt(String seed, String cleartext) throws Exception {
    byte[] rawKey = getRawKey(seed.getBytes());
    byte[] result = encrypt(rawKey, cleartext.getBytes());
    return toHex(result);
}

public static String decrypt(String seed, String encrypted) throws Exception {
    byte[] rawKey = getRawKey(seed.getBytes());
    byte[] enc = toByte(encrypted);
    byte[] result = decrypt(rawKey, enc);
    return new String(result);
}

private static byte[] getRawKey(byte[] seed) throws Exception {
    KeyGenerator kgen = KeyGenerator.getInstance("AES");
    SecureRandom sr = SecureRandom.getInstance("SHA1PRNG","Crypto");
    sr.setSeed(seed);
    kgen.init(128, sr); // 192 and 256 bits may not be available
    SecretKey skey = kgen.generateKey();
    byte[] raw = skey.getEncoded();
    return raw;
}


private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception {
    SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
    Cipher cipher = Cipher.getInstance("AES");
    cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
    byte[] encrypted = cipher.doFinal(clear);
    return encrypted;
}

private static byte[] decrypt(byte[] raw, byte[] encrypted) throws Exception {
    SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
    Cipher cipher = Cipher.getInstance("AES");
    cipher.init(Cipher.DECRYPT_MODE, skeySpec);
    byte[] decrypted = cipher.doFinal(encrypted);
    return decrypted;
}

public static String toHex(String txt) {
    return toHex(txt.getBytes());
}
public static String fromHex(String hex) {
    return new String(toByte(hex));
}

public static byte[] toByte(String hexString) {
    int len = hexString.length()/2;
    byte[] result = new byte[len];
    for (int i = 0; i < len; i++)
        result[i] = Integer.valueOf(hexString.substring(2*i, 2*i+2), 16).byteValue();
    return result;
}

public static String toHex(byte[] buf) {
    if (buf == null)
        return "";
    StringBuffer result = new StringBuffer(2*buf.length);
    for (int i = 0; i < buf.length; i++) {
        appendHex(result, buf[i]);
    }
    return result.toString();
}
private final static String HEX = "0123456789ABCDEF";
private static void appendHex(StringBuffer sb, byte b) {
    sb.append(HEX.charAt((b>>4)&0x0f)).append(HEX.charAt(b&0x0f));
}
}

below is your method for encryption and decryption for string,

public String encryption(String strNormalText){
    String seedValue = "YourSecKey";
    String normalTextEnc="";
    try {
        normalTextEnc = AESHelper.encrypt(seedValue, strNormalText);
    } catch (Exception e) {
        e.printStackTrace();
    }
    return normalTextEnc;
}
public String decryption(String strEncryptedText){
    String seedValue = "YourSecKey";
    String strDecryptedText="";
    try {
        strDecryptedText = AESHelper.decrypt(seedValue, strEncryptedText);
    } catch (Exception e) {
        e.printStackTrace();
    }
    return strDecryptedText;
}

finally you can use like as:

String encryptedString = encryption("Input Normal String");
String decryptedString = decryption("Input Encrypted String");

Answer 3

Actually Saravanan Ee's answer is the correct one. But there are several logic and syntax errors. Here is a correct code snippet of his approach.

private String SECRET_KEY = "aesEncryptionKey";
private String INIT_VECTOR = "encryptionIntVec";

public static String encrypt(String value) {
    try {
        IvParameterSpec iv = new IvParameterSpec(INIT_VECTOR.getBytes("UTF-8"));
        SecretKeySpec skeySpec = new SecretKeySpec(SECRET_KEY.getBytes("UTF-8"), "AES");
     
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING");
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec, iv);
     
        byte[] encrypted = cipher.doFinal(value.getBytes());
        return Base64.encodeToString(encrypted, Base64.DEFAULT);
    } catch (Exception ex) {
        ex.printStackTrace();
    }
    return null;
}

public static String decrypt(String value) {
    try {
        IvParameterSpec iv = new IvParameterSpec(INIT_VECTOR.getBytes("UTF-8"));
        SecretKeySpec skeySpec = new SecretKeySpec(SECRET_KEY.getBytes("UTF-8"), "AES");
     
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING");
        cipher.init(Cipher.DECRYPT_MODE, skeySpec, iv);
        byte[] original = cipher.doFinal(Base64.decode(value, Base64.DEFAULT));
     
        return new String(original);
    } catch (Exception ex) {
        ex.printStackTrace();
    }
     
    return null;
}

USAGE:

Encryption:

String textForEncryption = "This my text that will be encrypted!";
String encryptedString;
encryptedString = encrypt(textForEncryption);
//Result: BItjtWPNKXjdHZ6clbtXWAzUwJAbMpIaP294eRB9+7BR0g+gJ9jZv4AZt+8epG36

Decryption:

String encryptedText = "BItjtWPNKXjdHZ6clbtXWAzUwJAbMpIaP294eRB9+7BR0g+gJ9jZv4AZt+8epG36";
String decryptedString;
decryptedString = decrypt(encryptedText);
//Result: This my text that will be encrypted!

Answer 4

Using BlueFish algorithm you can simple encrypt & decrypt any string. Blowfish with key size of 128-bit up to 448-bit, its considered as a better faster algorithm. Try as follows

public class CryptUtil {
private static final String ALGORITHM = "Blowfish";
private static final String MODE = "Blowfish/CBC/PKCS5Padding";
private static final String IV = "abcdefgh";
private static final String KEY= "MyKey";

public static  String encrypt(String value ) throws NoSuchPaddingException, NoSuchAlgorithmException, InvalidAlgorithmParameterException, InvalidKeyException, BadPaddingException, IllegalBlockSizeException {
    SecretKeySpec secretKeySpec = new SecretKeySpec(KEY.getBytes(), ALGORITHM);
    Cipher cipher = Cipher.getInstance(MODE);
    cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, new IvParameterSpec(IV.getBytes()));
    byte[] values = cipher.doFinal(value.getBytes());
    return Base64.encodeToString(values, Base64.DEFAULT);
}

public static  String decrypt(String value) throws NoSuchPaddingException, NoSuchAlgorithmException, InvalidAlgorithmParameterException, InvalidKeyException, BadPaddingException, IllegalBlockSizeException {
    byte[] values = Base64.decode(value, Base64.DEFAULT);
    SecretKeySpec secretKeySpec = new SecretKeySpec(KEY.getBytes(), ALGORITHM);
    Cipher cipher = Cipher.getInstance(MODE);
    cipher.init(Cipher.DECRYPT_MODE, secretKeySpec, new IvParameterSpec(IV.getBytes()));
    return new String(cipher.doFinal(values));
  }

}