/*

 * Copyright (c) 2003, 2012, 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 sun.security.provider;

import java.util.Arrays;

/**

 * Implementation for the MD2 algorithm, see RFC1319. It is very slow and

 * not particular secure. It is only supported to be able to verify

 * RSA/Verisign root certificates signed using MD2withRSA. It should not

 * be used for anything else.

 *

 * @since   1.5

 * @author  Andreas Sterbenz

 */

public final class MD2 extends DigestBase {

    // state, 48 ints

    private int[] X;

    // checksum, 16 ints. they are really bytes, but byte arithmetic in

    // the JVM is much slower that int arithmetic.

    private int[] C;

    // temporary store for checksum C during final digest

    private byte[] cBytes;

    /**

     * Create a new MD2 digest. Called by the JCA framework

     */

    public MD2() {

        super("MD2", 16, 16);

        X = new int[48];

        C = new int[16];

        cBytes = new byte[16];

    }

    public Object clone() throws CloneNotSupportedException {

        MD2 copy = (MD2) super.clone();

        copy.X = copy.X.clone();

        copy.C = copy.C.clone();

        copy.cBytes = new byte[16];

        return copy;

    }

    // reset state and checksum

    void implReset() {

        Arrays.fill(X, 0);

        Arrays.fill(C, 0);

    }

    // finish the digest

    void implDigest(byte[] out, int ofs) {

        int padValue = 16 - ((int)bytesProcessed & 15);

        engineUpdate(PADDING[padValue], 0, padValue);

        for (int i = 0; i < 16; i++) {

            cBytes[i] = (byte)C[i];

        }

        implCompress(cBytes, 0);

        for (int i = 0; i < 16; i++) {

            out[ofs + i] = (byte)X[i];

        }

    }

    // one iteration of the compression function

    void implCompress(byte[] b, int ofs) {

        for (int i = 0; i < 16; i++) {

            int k = b[ofs + i] & 0xff;

            X[16 + i] = k;

            X[32 + i] = k ^ X[i];

        }

        // update the checksum

        int t = C[15];

        for (int i = 0; i < 16; i++) {

            t = (C[i] ^= S[X[16 + i] ^ t]);

        }

        t = 0;

        for (int i = 0; i < 18; i++) {

            for (int j = 0; j < 48; j++) {

                t = (X[j] ^= S[t]);

            }

            t = (t + i) & 0xff;

        }

    }

    // substitution table derived from Pi. Copied from the RFC.

        41, 46, 67, 201, 162, 216, 124, 1, 61, 54, 84, 161, 236, 240, 6,

        19, 98, 167, 5, 243, 192, 199, 115, 140, 152, 147, 43, 217, 188,

        76, 130, 202, 30, 155, 87, 60, 253, 212, 224, 22, 103, 66, 111, 24,

        138, 23, 229, 18, 190, 78, 196, 214, 218, 158, 222, 73, 160, 251,

        245, 142, 187, 47, 238, 122, 169, 104, 121, 145, 21, 178, 7, 63,

        148, 194, 16, 137, 11, 34, 95, 33, 128, 127, 93, 154, 90, 144, 50,

        39, 53, 62, 204, 231, 191, 247, 151, 3, 255, 25, 48, 179, 72, 165,

        181, 209, 215, 94, 146, 42, 172, 86, 170, 198, 79, 184, 56, 210,

        150, 164, 125, 182, 118, 252, 107, 226, 156, 116, 4, 241, 69, 157,

        112, 89, 100, 113, 135, 32, 134, 91, 207, 101, 230, 45, 168, 2, 27,

        96, 37, 173, 174, 176, 185, 246, 28, 70, 97, 105, 52, 64, 126, 15,

        85, 71, 163, 35, 221, 81, 175, 58, 195, 92, 249, 206, 186, 197,

        234, 38, 44, 83, 13, 110, 133, 40, 132, 9, 211, 223, 205, 244, 65,

        129, 77, 82, 106, 220, 55, 200, 108, 193, 171, 250, 36, 225, 123,

        8, 12, 189, 177, 74, 120, 136, 149, 139, 227, 99, 232, 109, 233,

        203, 213, 254, 59, 0, 29, 57, 242, 239, 183, 14, 102, 88, 208, 228,

        166, 119, 114, 248, 235, 117, 75, 10, 49, 68, 80, 180, 143, 237,

        31, 26, 219, 153, 141, 51, 159, 17, 131, 20,

    };

    // digest padding. 17 element array.

    // padding[0] is null

    // padding[i] is an array of i time the byte value i (i = 1..16)

    static {

        PADDING = new byte[17][];

        for (int i = 1; i < 17; i++) {

            byte[] b = new byte[i];

            Arrays.fill(b, (byte)i);

            PADDING[i] = b;

        }

    }

}