EncryptionUtils.java

/*
 * Copyright (C) 2015 AChep@xda <artemchep@gmail.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 * MA  02110-1301, USA.
 */
package com.achep.base.utils;

import android.support.annotation.NonNull;
import android.util.Base64;

/**
 * @author Artem Chepurnoy
 */
public class EncryptionUtils {

    /**
     * Method deciphers previously ciphered message
     *
     * @param message ciphered message
     * @param salt    salt which was used for ciphering
     * @return deciphered message
     */
    @NonNull
    public static String fromX(@NonNull String message, @NonNull String salt)
            throws IllegalArgumentException {
        return x(new String(Base64.decode(message, Base64.URL_SAFE)), salt);
    }

    /**
     * Symmetric algorithm used for ciphering/deciphering.
     *
     * @param message message
     * @param salt    salt
     * @return ciphered/deciphered message
     */
    @NonNull
    public static String x(@NonNull String message, @NonNull String salt) {
        final char[] m = message.toCharArray();
        final char[] s = salt.toCharArray();

        final int ml = m.length;
        final int sl = s.length;
        final char[] result = new char[ml];

        for (int i = 0; i < ml; i++) {
            result[i] = (char) (m[i] ^ s[i % sl]);
        }
        return new String(result);
    }

}