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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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).
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 * 2 along with this work; if not, write to the Free Software Foundation,
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package sun.security.provider;

import java.security.*;
import java.util.Arrays;

import static sun.security.provider.ByteArrayAccess.*;

The MD4 class is used to compute an MD4 message digest over a given
buffer of bytes. It is an implementation of the RSA Data Security Inc
MD4 algorithim as described in internet RFC 1320.
The MD4 algorithm is very weak and should not be used unless it is
unavoidable. Therefore, it is not registered in our standard providers. To
obtain an implementation, call the static getInstance() method in this
class.
Author:
     Andreas Sterbenz/**
 * The MD4 class is used to compute an MD4 message digest over a given
 * buffer of bytes. It is an implementation of the RSA Data Security Inc
 * MD4 algorithim as described in internet RFC 1320.
 *
 * <p>The MD4 algorithm is very weak and should not be used unless it is
 * unavoidable. Therefore, it is not registered in our standard providers. To
 * obtain an implementation, call the static getInstance() method in this
 * class.
 *
 * @author      Andreas Sterbenz
 */
public final class MD4 extends DigestBase {

    // state of this object
    private int[] state;
    // temporary buffer, used by implCompress()
    private int[] x;

    // rotation constants
    private static final int S11 = 3;
    private static final int S12 = 7;
    private static final int S13 = 11;
    private static final int S14 = 19;
    private static final int S21 = 3;
    private static final int S22 = 5;
    private static final int S23 = 9;
    private static final int S24 = 13;
    private static final int S31 = 3;
    private static final int S32 = 9;
    private static final int S33 = 11;
    private static final int S34 = 15;

    private final static Provider md4Provider;

    static {
        md4Provider = new Provider("MD4Provider", 1.8d, "MD4 MessageDigest") {
            private static final long serialVersionUID = -8850464997518327965L;
        };
        AccessController.doPrivileged(new PrivilegedAction<Void>() {
            public Void run() {
                md4Provider.put("MessageDigest.MD4", "sun.security.provider.MD4");
                return null;
            }
        });
    }

    public static MessageDigest getInstance() {
        try {
            return MessageDigest.getInstance("MD4", md4Provider);
        } catch (NoSuchAlgorithmException e) {
            // should never occur
            throw new ProviderException(e);
        }
    }

    // Standard constructor, creates a new MD4 instance.
    public MD4() {
        super("MD4", 16, 64);
        state = new int[4];
        x = new int[16];
        resetHashes();
    }

    // clone this object
    public Object clone() throws CloneNotSupportedException {
        MD4 copy = (MD4) super.clone();
        copy.state = copy.state.clone();
        copy.x = new int[16];
        return copy;
    }

    
Reset the state of this object.
/**
     * Reset the state of this object.
     */
    void implReset() {
        // Load magic initialization constants.
        resetHashes();
        // clear out old data
        Arrays.fill(x, 0);
    }

    private void resetHashes() {
        state[0] = 0x67452301;
        state[1] = 0xefcdab89;
        state[2] = 0x98badcfe;
        state[3] = 0x10325476;
    }

    
Perform the final computations, any buffered bytes are added
to the digest, the count is added to the digest, and the resulting
digest is stored.
/**
     * Perform the final computations, any buffered bytes are added
     * to the digest, the count is added to the digest, and the resulting
     * digest is stored.
     */
    void implDigest(byte[] out, int ofs) {
        long bitsProcessed = bytesProcessed << 3;

        int index = (int)bytesProcessed & 0x3f;
        int padLen = (index < 56) ? (56 - index) : (120 - index);
        engineUpdate(padding, 0, padLen);

        i2bLittle4((int)bitsProcessed, buffer, 56);
        i2bLittle4((int)(bitsProcessed >>> 32), buffer, 60);
        implCompress(buffer, 0);

        i2bLittle(state, 0, out, ofs, 16);
    }

    private static int FF(int a, int b, int c, int d, int x, int s) {
        a += ((b & c) | ((~b) & d)) + x;
        return ((a << s) | (a >>> (32 - s)));
    }

    private static int GG(int a, int b, int c, int d, int x, int s) {
        a += ((b & c) | (b & d) | (c & d)) + x + 0x5a827999;
        return ((a << s) | (a >>> (32 - s)));
    }

    private static int HH(int a, int b, int c, int d, int x, int s) {
        a += ((b ^ c) ^ d) + x + 0x6ed9eba1;
        return ((a << s) | (a >>> (32 - s)));
    }

    
This is where the functions come together as the generic MD4
transformation operation. It consumes sixteen
bytes from the buffer, beginning at the specified offset.
/**
     * This is where the functions come together as the generic MD4
     * transformation operation. It consumes sixteen
     * bytes from the buffer, beginning at the specified offset.
     */
    void implCompress(byte[] buf, int ofs) {
        b2iLittle64(buf, ofs, x);

        int a = state[0];
        int b = state[1];
        int c = state[2];
        int d = state[3];

        /* Round 1 */
        a = FF (a, b, c, d, x[ 0], S11); /* 1 */
        d = FF (d, a, b, c, x[ 1], S12); /* 2 */
        c = FF (c, d, a, b, x[ 2], S13); /* 3 */
        b = FF (b, c, d, a, x[ 3], S14); /* 4 */
        a = FF (a, b, c, d, x[ 4], S11); /* 5 */
        d = FF (d, a, b, c, x[ 5], S12); /* 6 */
        c = FF (c, d, a, b, x[ 6], S13); /* 7 */
        b = FF (b, c, d, a, x[ 7], S14); /* 8 */
        a = FF (a, b, c, d, x[ 8], S11); /* 9 */
        d = FF (d, a, b, c, x[ 9], S12); /* 10 */
        c = FF (c, d, a, b, x[10], S13); /* 11 */
        b = FF (b, c, d, a, x[11], S14); /* 12 */
        a = FF (a, b, c, d, x[12], S11); /* 13 */
        d = FF (d, a, b, c, x[13], S12); /* 14 */
        c = FF (c, d, a, b, x[14], S13); /* 15 */
        b = FF (b, c, d, a, x[15], S14); /* 16 */

        /* Round 2 */
        a = GG (a, b, c, d, x[ 0], S21); /* 17 */
        d = GG (d, a, b, c, x[ 4], S22); /* 18 */
        c = GG (c, d, a, b, x[ 8], S23); /* 19 */
        b = GG (b, c, d, a, x[12], S24); /* 20 */
        a = GG (a, b, c, d, x[ 1], S21); /* 21 */
        d = GG (d, a, b, c, x[ 5], S22); /* 22 */
        c = GG (c, d, a, b, x[ 9], S23); /* 23 */
        b = GG (b, c, d, a, x[13], S24); /* 24 */
        a = GG (a, b, c, d, x[ 2], S21); /* 25 */
        d = GG (d, a, b, c, x[ 6], S22); /* 26 */
        c = GG (c, d, a, b, x[10], S23); /* 27 */
        b = GG (b, c, d, a, x[14], S24); /* 28 */
        a = GG (a, b, c, d, x[ 3], S21); /* 29 */
        d = GG (d, a, b, c, x[ 7], S22); /* 30 */
        c = GG (c, d, a, b, x[11], S23); /* 31 */
        b = GG (b, c, d, a, x[15], S24); /* 32 */

        /* Round 3 */
        a = HH (a, b, c, d, x[ 0], S31); /* 33 */
        d = HH (d, a, b, c, x[ 8], S32); /* 34 */
        c = HH (c, d, a, b, x[ 4], S33); /* 35 */
        b = HH (b, c, d, a, x[12], S34); /* 36 */
        a = HH (a, b, c, d, x[ 2], S31); /* 37 */
        d = HH (d, a, b, c, x[10], S32); /* 38 */
        c = HH (c, d, a, b, x[ 6], S33); /* 39 */
        b = HH (b, c, d, a, x[14], S34); /* 40 */
        a = HH (a, b, c, d, x[ 1], S31); /* 41 */
        d = HH (d, a, b, c, x[ 9], S32); /* 42 */
        c = HH (c, d, a, b, x[ 5], S33); /* 43 */
        b = HH (b, c, d, a, x[13], S34); /* 44 */
        a = HH (a, b, c, d, x[ 3], S31); /* 45 */
        d = HH (d, a, b, c, x[11], S32); /* 46 */
        c = HH (c, d, a, b, x[ 7], S33); /* 47 */
        b = HH (b, c, d, a, x[15], S34); /* 48 */

        state[0] += a;
        state[1] += b;
        state[2] += c;
        state[3] += d;
    }

}