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/*
 * Copyright 2022 Siisise Net.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package net.siisise.security.mode;

import net.siisise.security.block.Block;

/**
 * Propagating Cipher Block Chaning (PCBC).
 * Wikipediaより
 * BlockModeのみ
 * ブロックの前後差し替えが可能なので利用されない。
 */
public class PCBC extends BlockMode {

    byte[] vector;

    public PCBC(Block b) {
        super(b);
    }

    @Override
    public void init(byte[]... key) {
        byte[][] nkey = new byte[key.length - 1][];
        System.arraycopy(key,0,nkey,0,key.length - 1);
        super.init(nkey);
        byte[] iv = key[key.length - 1];
        vector = new byte[block.getBlockLength() / 8];
        System.arraycopy(iv, 0, vector, 0, vector.length > iv.length ? iv.length : vector.length);
    }

    @Override
    public byte[] encrypt(byte[] src, int offset) {
        for (int i = 0; i < vector.length; i++) {
            vector[i] ^= src[offset + i];
        }
        byte[] ret = block.encrypt(vector, 0);
        for (int i = 0; i < vector.length; i++) {
            vector[i] = (byte) (src[offset + i] ^ ret[i]);
        }
        return ret;
    }

    @Override
    public byte[] decrypt(byte[] src, int offset) {
        byte[] ret = block.decrypt(src, offset);
        for (int i = 0; i < vector.length; i++) {
            ret[i] ^= vector[i];
        }
        for (int i = 0; i < vector.length; i++) {
            vector[i] = (byte) (ret[i] ^ src[offset + i]);
        }
        return ret;
    }

    @Override
    public int[] encrypt(int[] src, int offset) {
        throw new UnsupportedOperationException("Not supported yet.");
    }

    @Override
    public int[] decrypt(int[] src, int offset) {
        throw new UnsupportedOperationException("Not supported yet.");
    }

}