com.github.bloodshura.x.cryptography.impl.twoway.ByteSwitch Maven / Gradle / Ivy

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/*
 * Copyright (c) 2013-2018, João Vitor Verona Biazibetti - All Rights Reserved
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see .
 *
 * https://www.github.com/BloodShura
 */

package com.github.bloodshura.x.cryptography.impl.twoway;

import com.github.bloodshura.x.cryptography.Twoway;

import javax.annotation.Nonnull;

public class ByteSwitch implements Twoway {
	private int modifier;

	public ByteSwitch() {
		this(16);
	}

	public ByteSwitch(int modifier) {
		this.modifier = modifier;
	}

	@Nonnull
	@Override
	public byte[] decrypt(@Nonnull byte[] data) {
		byte[] result = new byte[data.length / 2];

		for (int i = data.length - 1; i >= 0; i -= 2) {
			int offset = i / 2;
			short s = (short) ((data[i - 1] << 8) + data[i]);
			byte bit;

			if (i == data.length - 1) {
				bit = (byte) (short) (s - getModifier());
			}
			else {
				bit = (byte) (short) (s - result[offset + 1] + getModifier());
			}

			result[offset] = bit;
		}

		return result;
	}

	@Nonnull
	@Override
	public byte[] encrypt(@Nonnull byte[] data) {
		byte[] result = new byte[data.length * 2];

		for (int i = 0; i < data.length; i++) {
			int offset = i * 2;
			short bit;

			if (i == data.length - 1) {
				bit = (short) (data[i] + getModifier());
			}
			else {
				bit = (short) (data[i] + data[i + 1] - getModifier());
			}

			result[offset] = (byte) ((bit >>> 8) & 0xFF);
			result[offset + 1] = (byte) (bit & 0xFF);
		}

		return result;
	}

	public int getModifier() {
		return modifier;
	}

	public boolean needsSalt() {
		return false;
	}

	public void setModifier(int modifier) {
		if ((Byte.MAX_VALUE * modifier) > Short.MAX_VALUE) {
			throw new IllegalArgumentException("Modifier out of Short bounds.");
		}

		this.modifier = modifier;
	}
}