AES Encryption Decryption in Android

This is the easiest way of implementing AES Encryption and Decryption in Android.

import javax.crypto.Cipher;
 import javax.crypto.SecretKey;
 import javax.crypto.spec.SecretKeySpec;

public class AESEncryptionDecryption {

private static final byte[] keyValue =
        new byte[]{'c', 'o', 'd', 'i', 'n', 'g', 'a', 'f', 'f', 'a', 'i', 'r', 's', 'c', 'o', 'm'};


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

public static String decrypt(String encrypted)
        throws Exception {

    byte[] enc = toByte(encrypted);
    byte[] result = decrypt(enc);
    return new String(result);
}

private static byte[] getRawKey() throws Exception {
    SecretKey key = new SecretKeySpec(keyValue, "AES");
    byte[] raw = key.getEncoded();
    return raw;
}

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

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));
}

String encrypted = "";
try {
    encrypted = AESEncryptionDecryption.encrypt(plain_text);
    Log.d(Constants.firebase_app, "encrypted:" + encrypted);
} catch (Exception e) {
    e.printStackTrace();
}
*********************************************************************
String decrypted = "";
try {
    decrypted = AESEncryptionDecryption.decrypt(encrypted);
    Log.d(Constants.firebase_app, "decrypted:" + decrypted);
} catch (Exception e) {
    e.printStackTrace();
}

Author:

Hammad Tariq

Android Developer

Allatori obfuscator android mapping file location

If you are using Allatori for obfuscation and want to get non obfuscated stack track in crash reporting or your app logs than use mapping files generataed by Allatori during obfuscation.


From following address

Project\AppName\build\intermediates\classes\allatori-log-debug.xml
Project\AppName\app\build\intermediates\classes\allatori-log-release.xml


Use stack trace utility and stack trace and mapping file from above location
to get non obfuscated stack trace. so that you can fix issues :)




Author:
Hammad Tariq

Android Developer

How to Convert Drawable to Bitmap in Android

In this tutorial I will explain how to read Drawable from resources as Bitmap and than I will write down some common techniques for processing Bitmaps.


public final static Integer[] imageResIds = new Integer[]{
R.drawable.a, R.drawable.b, R.drawable.c,
R.drawable.d, R.drawable.e, R.drawable.f,
R.drawable.k, R.drawable.l, R.drawable.m};


loadBitmap(imageResIds[index], mImageView);


public void loadBitmap(int resId, ImageView imageView) {
 //Now we have bitmap object from drawable resource. we can scale this bitmap
 //according to device screen density.
    Bitmap bitmap = BitmapFactory.decodeResource(getResources(), data);

}

Note: This method can cause out of memory error.
- If you want to avoid this exception use scaled down version of bitmap in memory.
- Process Bitmaps Off the UI thread (Use Async Task).




Author:
Hammad Tariq
Android Developer