EncryptDataHelper.java

/**
 * This class helps to encrypt passwords before saving and decrypt then
 * <p>
 * Created by Dmitriy V. Chernysh
 * <p>
 * https://instagr.am/mobiledevpro
 * <p>
 * #MobileDevPro
 */
public class EncryptDataHelper {
    //store this key in KeyStore
    private static final String KEY = "Q5~VAwarOiOwexZa53xy0v1|E~OHcWYcYSd*8ZUFD%8m39D2=UZIvC2ueh3";
    private static final String CHARSET_NAME = "UTF-8";
    private static EncryptDataHelper sHelper;

    private EncryptDataHelper() {

    }

    public static EncryptDataHelper getInstance() {
        if (sHelper == null) sHelper = new EncryptDataHelper();
        return sHelper;
    }

    public String encryptString(String str) {
        try {
            //convert key to SHA-256
            MessageDigest digest = MessageDigest.getInstance("SHA-256");

            byte[] keyBytes = digest.digest(KEY.getBytes(CHARSET_NAME));
            byte[] ivBytes = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};

            //encrypt string
            byte[] result = encrypt(ivBytes, keyBytes, str.getBytes(CHARSET_NAME));
            //convert result to Base64
            return Base64.encodeToString(result, Base64.DEFAULT).replace("\n", "");

        } catch (Exception e) {
            Log.e(Constants.LOG_TAG_ERROR, "EncryptDataHelper.encryptString: " + e.getLocalizedMessage(), e);
        }
        return str;
    }

    public String decryptString(String str) {
        try {
            byte[] encodedStr = Base64.decode(str, Base64.DEFAULT);
            //convert key to SHA-256
            MessageDigest digest = MessageDigest.getInstance("SHA-256");

            byte[] keyBytes = digest.digest(KEY.getBytes(CHARSET_NAME));
            byte[] ivBytes = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};

            byte[] result = decrypt(ivBytes, keyBytes, encodedStr);
            return new String(result, CHARSET_NAME);
        } catch (Exception e) {
            Log.e(Constants.LOG_TAG_ERROR, "EncryptDataHelper.decryptString: " + e.getLocalizedMessage(), e);
        }
        return str;
    }

    private byte[] encrypt(byte[] ivBytes, byte[] keyBytes, byte[] textBytes)
            throws UnsupportedEncodingException,
            NoSuchAlgorithmException,
            NoSuchPaddingException,
            InvalidKeyException,
            InvalidAlgorithmParameterException,
            IllegalBlockSizeException,
            BadPaddingException {

        AlgorithmParameterSpec ivSpec = new IvParameterSpec(ivBytes);
        SecretKeySpec newKey = new SecretKeySpec(keyBytes, "AES");
        Cipher cipher = null;
        cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        cipher.init(Cipher.ENCRYPT_MODE, newKey, ivSpec);
        return cipher.doFinal(textBytes);
    }

    private byte[] decrypt(byte[] ivBytes, byte[] keyBytes, byte[] textBytes)
            throws UnsupportedEncodingException,
            NoSuchAlgorithmException,
            NoSuchPaddingException,
            InvalidKeyException,
            InvalidAlgorithmParameterException,
            IllegalBlockSizeException,
            BadPaddingException {

        AlgorithmParameterSpec ivSpec = new IvParameterSpec(ivBytes);
        SecretKeySpec newKey = new SecretKeySpec(keyBytes, "AES");
        Cipher cipher = null;
        cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        cipher.init(Cipher.DECRYPT_MODE, newKey, ivSpec);
        return cipher.doFinal(textBytes);
    }
}