/*

 * Copyright (c) 1997, 2007, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package com.sun.crypto.provider;

import java.security.InvalidKeyException;

/**

 * This class implements the Triple DES algorithm (DES encryption, followed by

 * DES decryption, followed by DES encryption) on a byte array of size

 * <code>DES_BLOCK_SIZE</code>. Each DES operation has its own key.

 *

 * @author Gigi Ankeny

 * @author Jan Luehe

 *

 *

 * @see DESConstants

 * @see DESCipher

 */

final class DESedeCrypt extends DESCrypt implements DESConstants {

    /*

     * the expanded key used in encrypt/decrypt/encrypt phase

     */

    private byte[] key1 = null;

    private byte[] key2 = null;

    private byte[] key3 = null;

    private byte[] buf1, buf2;

    /*

     * constructor

     */

    DESedeCrypt() {

        buf1 = new byte[DES_BLOCK_SIZE];

        buf2 = new byte[DES_BLOCK_SIZE];

    }

    void init(boolean decrypting, String algorithm, byte[] keys)

            throws InvalidKeyException {

        if (!algorithm.equalsIgnoreCase("DESede")

                    && !algorithm.equalsIgnoreCase("TripleDES")) {

            throw new InvalidKeyException

                ("Wrong algorithm: DESede or TripleDES required");

        }

        if (keys.length != DES_BLOCK_SIZE * 3) {

            throw new InvalidKeyException("Wrong key size");

        }

        byte[] keybuf = new byte[DES_BLOCK_SIZE];

        // retrieve the first key

        key1 = new byte[128];

        System.arraycopy(keys, 0, keybuf, 0, DES_BLOCK_SIZE);

        expandKey(keybuf);

        System.arraycopy(expandedKey, 0, key1, 0, 128);

        // check if the third key is the same

        if (keyEquals(keybuf, 0, keys, DES_BLOCK_SIZE*2, DES_BLOCK_SIZE)) {

            key3 = key1;

        } else {

            key3 = new byte[128];

            System.arraycopy(keys, DES_BLOCK_SIZE*2, keybuf, 0,

                             DES_BLOCK_SIZE);

            expandKey(keybuf);

            System.arraycopy(expandedKey, 0, key3, 0, 128);

        }

        // retrieve the second key

        key2 = new byte[128];

        System.arraycopy(keys, DES_BLOCK_SIZE, keybuf, 0, DES_BLOCK_SIZE);

        expandKey(keybuf);

        System.arraycopy(expandedKey, 0, key2, 0, 128);

    }

    /**

     * Performs encryption operation.

     *

     * <p>The input plain text <code>plain</code>, starting at

     * <code>plainOffset</code> and ending at

     * <code>(plainOffset + blockSize - 1)</code>, is encrypted.

     * The result is stored in <code>cipher</code>, starting at

     * <code>cipherOffset</code>.

     *

     * @param plain the buffer with the input data to be encrypted

     * @param plainOffset the offset in <code>plain</code>

     * @param cipher the buffer for the result

     * @param cipherOffset the offset in <code>cipher</code>

     */

    void encryptBlock(byte[] plain, int plainOffset,

                 byte[] cipher, int cipherOffset)

    {

        expandedKey = key1;

        decrypting = false;

        cipherBlock(plain, plainOffset, buf1, 0);

        expandedKey = key2;

        decrypting = true;

        cipherBlock(buf1, 0, buf2, 0);

        expandedKey = key3;

        decrypting = false;

        cipherBlock(buf2, 0, cipher, cipherOffset);

    }

    /**

     * Performs decryption operation.

     *

     * <p>The input cipher text <code>cipher</code>, starting at

     * <code>cipherOffset</code> and ending at

     * <code>(cipherOffset + blockSize - 1)</code>, is decrypted.

     * The result is stored in <code>plain</code>, starting at

     * <code>plainOffset</code>.

     *

     * @param cipher the buffer with the input data to be decrypted

     * @param cipherOffset the offset in <code>cipherOffset</code>

     * @param plain the buffer for the result

     * @param plainOffset the offset in <code>plain</code>

     */

    void decryptBlock(byte[] cipher, int cipherOffset,

                 byte[] plain, int plainOffset)

    {

        expandedKey = key3;

        decrypting = true;

        cipherBlock(cipher, cipherOffset, buf1, 0);

        expandedKey = key2;

        decrypting = false;

        cipherBlock(buf1, 0, buf2, 0);

        expandedKey = key1;

        decrypting = true;

        cipherBlock(buf2, 0, plain, plainOffset);

    }

    private boolean keyEquals(byte[] key1, int off1,

                              byte[] key2, int off2, int len) {

        for (int i=0; i<len; i++) {

            if (key1[i+off1] != key2[i+off2])

                return false;

        }

        return true;

    }

}